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Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
The car is an 84 Trans Am. 100,000 miles on a 305 that runs very well but naturally lacks power. Car never sees snow and just before parking for the winter we broke something in the auto trans. Son's car and he decided the time had come for some changes.
While home on leave my son pulled a 350 out of the JY. It appears to be a GM crate motor which apparently was a replacement shortly before the vehicle found its way to the JY. The 350 appears to be low mileage. There is no cylinder ridge and cross hatching is still visible. The engine appears to be an L31 Vortech (062 heads) with two bolt mains. Roller cam.
The engine is currently at the speed shop for cleaning and checking. We want to make sure there are no cracks in the block or heads.
The goal is to get the HP up to not less than 400 at the crank. 450 would be better. I'm old school and more comfortable with carbed motors. He's paying the bills and prefers fuel injection cause it's more modern. He is interested in going port fuel injection and turocharged. Once we get the block back a decision will have to be made about what direction the project will take so that the correct pistons can be ordered. Dished vs domed.
I have an ASE master mechanic to do the technical side. He is well versed in fuel injection. Not well versed in turbo. But he's smart as a whip.
I'm tossing this out for the wisdom of the board. Looking for discussion of what makes the most sense. My son would also like to make a move from the 700R4 to a T56. But that's another day.
One of the main questions is what can we get with out turbo and what with turbo. And we need to make a decision on new camshaft. Not interested in talking LS unless this block is trash. Once we decide on a course of action I can spend more time on the relevant sections of the forum.
Thank is advance for advice and opinions. I may not follow it but I'll sure appreciate it.
Well, you certainly didn't experience the "typical" junkyard truck 350 find.
It's fairly easy to get 400 GFWHP out of a carb'd Vortec-headed 350. The heads will do it with a good cam and valve spring upgrades (and the usual "hot rod" stuff like headers and good-flowing exhaust). The 062 (and 906) Vortec heads are the best production heads for Gen I SBC out there.
Not that they aren't without their flaws, like huge valve guide OD that limits valve spring choices, and exhaust ports that don't live up to the intake port potential. Some say crack-prone as well, but I've seen more Vortec engines with rod bearing issues than cracked heads.
He really needs to decide which direction he wants to go, NA or power adder, as that affects every part of the build. Personally, for a street car, NA makes more sense to me, and it'll have plenty of power to get you in trouble.
If it were me, my NA build would look something like clean up the exhaust ports (the intake ports are fine, leave them alone), cut the exhaust seats for 1.60" valves (the 1.94" intakes are fine), cut the tops of the valve guides for positive-type valve stem seals, good springs like Comp 918s (at a minimum), Manley valves. Replacing the press-in rocker studs with screw-in is also a good idea.
Flat top pistons with valve reliefs would yield a pump-gas-friendly compression ratio of around 10.5:1. I'd keep the roller lifter cam, although word is LS7 lifters are the best factory-type roller lifter available. There are all sorts of good cams out there, but your best bet is probably give Bullet Cams a call after you have all of your other details figured out and buy whatever cam they suggest.
Carb would be simpler and less expensive in this case, but I understand why he'd want EFI.
If he decides to go turbo, then a lot of the above will still apply, but like you said, dished pistons would be in order. Going to the Power Adder forum for advice on the build would be wise (we can handle the nuts & bolts issues of swapping engines here, but that forum would be the best for all of the turbo details).
One thing he should be aware of is the stock rear end will not be up to the task, especially if he goes T56. The Strange S60 is the strongest choice for a 3rd gen, even though it is also the heaviest. There are also 9" and 12-bolt options available, but he shouldn't even consider keeping the 10-bolt.
It'll be fun watching how this project progresses.
five7kid,
Thanks for the reply and info. We agree that the whole drive train will need upgrading to match the horsepower increase. (BTW I didn't recognize the acronym GFWHP, can you clarify?) My thought process is to try to not change too many things at once. The transmission will be longer, which changes the driveshaft length, so that means the rearend should be changed at that time. So I'm thinking we should see if the auto trans is a simple repair and get the engine in and running with the present drivetrain. Once that works we can tackle the drivetrain.
I appreciate the engine build suggestions. Hopefully the block will be clean this week and I can discuss these suggestions with the shop. A little more research for me, so I can speak halfway intelligently about these.
I'm planning to paint the block with a POR engine kit.
Is a standard Chevy oil pan a good choice for this project?
It's not too hard to get 450 HP from a vortec headed 355, but 380 to 415 hp is the common avg. hp from mild street builds.
Turbo... Well your budget and fab skills are the only limits. I seen many 600-800 HP "mild" boosted engines running high boost levels.
You need to pick your path now as NA and turbo builds are completely night and day apart from each other.
No, do not run a std oil pan on any performance build IMO. There is a good 10 to 20 HP hiding in that oil control system. Use a 6 or 7 qt pan with kicked out sump, and trap door baffling. Install a rear main baffle, install a windage screen (screen works better than tray).
I do agree with five7kid on the added mods to vortec heads, but at some point you have to look at the price points. I love vortec heads. I have them on my 355 in my S10, but I look at them as a budget heads only.
If you do all the mods that he mentioned which are correct, you will end up with a ton of money in a so so head. That is about $700 worth of parts and machining on those vortec heads.
For $500 more you can have a brand new pair of alum pro filer or brodix IK heads that will make a good 35+ HP more than the vortecs and support a lot more power in the future
BTW I didn't recognize the acronym GFWHP, can you clarify?
"Gross FlyWheel Horse Power". As opposed to "net flywheel HP", usually only called "net horsepower", which the factory uses for their ratings; or "rear wheel HP" (aka "wheel HP") which people tend to use without knowing what they're talking about.
GFWHP is what is typically used to make the number seem bigger; e.g. for crate engine sales or bench racing. It was also used by the factory until the early 70's for the same reason. This is typically tested with the engine on a dyno, an optimized induction system, optimized exhaust, no accessories powered by the engine, and measured at the flywheel. Obviously, this isn't very "real-world".
The switch to net HP came about around 1972, which required the engine to be rated as it would be as installed in the vehicle: same induction system including the air cleaner, same full exhaust, the engine powering accessories such as water pump, alternator, fuel pump, cooling fan, etc. (but not air conditioning or other optional engine-powered systems) as the vehicle used; but it is still an engine dyno and measured at the flywheel. This is much more "real-world", and the numbers will drop vs. a gross flywheel measurement. For example, the 1984 Trans Am LG4 305 was rated at 150 net horsepower - put that engine on an engine dyno, use a facility-powered water pump and fuel pump, headers, Edelbrock intake and Holley carb with velocity stack instead of the factory air cleaner, and tune it carefully, and you'll easily get 250 HP out of it - with no internal engine changes.
Rear wheel HP is used because chassis dynos are often used for tuning purposes. While it may seem more "real world", because you're measuring through the drivetrain (transmission, rear end) as well, there is actually more variation from dyno-to-dyno than there is with engine dynos. Consider a chassis dyno as a tuning aid only, not as a way to measure the power output of the engine. Chassis dyno numbers are typically around 15% lower than net HP numbers due to powertrain losses.
Well we have some small progress. The shop called and the engine block checks out and is finished with the cleaning process. Picking it up tomorrow. The cylinder heads aren't finished yet. The decision has been made to build this normally aspirated. Still undecided about carb or fuel injection.
Today's question is what oil pan? Want to get one with a windage tray. It would seem to be foolish not to pick up the horsepower gains that this can provide. But it has to fit into the 84 TA. Don't want to have anything that hangs lower if at all possible.
Any specific recommendations for a manufacturer and model?
This is the infamous son chiming in. We have made some moves since this thread was last active. Right now we have officially decided to go NA with an EFI. We got flat top pistons with valve reliefs, and now we are deciding the heart and soul of the engine, the cam.
For the EFI, we have been looking into the Edelbrock Pro Flo 3 which is set to release sometime this month. One of the issues we have run into is that after talking it over, we have decided that we want torque above all else.
With that decision being made, we have dictated where we want to go relative to the cam. However, some of the more aggressive cams (comp 280HR or XR 276) have lobe separations at 110. Edelbrock says not to go below 112 for their EFI systems.
I am wondering if that is a hard fast rule, i.e. go beneath 112 and your engine is now an oversized paperweight, or going under 112 just means you will have to work the tuning more because it is outside of the self learning/pre-programmed setup of the pro flo 3. Any advice on this is most welcome.
"We are what we repeatedly do, excellence, therefore, is not an act but a habit"
-Aristotle
Its all bs. The wide lobe center is for those who cant tune efi with big cams. Also it can fool computers who try to maintain a certain o2 sensor target. Overlap in the cam leads to excess fresh air in exhaust which can skew o2 readings. But tune open loop and its fine.
The pro flo 3 comes with a victor E-tec manifold (or at least as far as I can tell), however that intake is "rated" for 2500 to 8000 rpm.
We are aiming for a broad torque curve with access to high torque levels at low RPM ranges. So will the E-tec manifold restrict our torque production off the line/in lower rpm bands because of its higher rpm rating?
Or since we are using multi port, will the manifold will play less of a factor since it is ferrying just air down until it reaches the injector vice an air fuel mixture like a carb or tbi would?
The manifold will flow more air (~1000 CFM) than the engine will even draw at max rpm (600 to 660 CFM, assuming around 85 to 90% VE), so is all this concern irrelevant, or should we look at a single plane intake with a lower RPM rating?
"we are what we repeatedly do, excellence, therefore, is not an act but a habit"
-Aristotle
Correct, its not like the carb world. Intake is just carrying air and wont hurt torque production near as bad as it would in a carb car.
Torque is about airspeed and runner lengths, and although the intake is abit larger than needed, it still will produce good broad power. It has decent runner length, longer than some of the alternatives like miniram or possibly proflo xt type intake.
Back to Dad now. The block is an 880 Vortec but it is one of those that has all the bolt holes drilled for a timing cover. So it appears we can use an old school cover rather than the plastic Vortec one with the crank sensor. The Pro Flo 3 does not use a crank sensor so we can eliminate that. The heads are getting 3/8 studs.
This weeks big question is the cam choice. Here are the finalists in no particular order.
Bullet CHS 284/292 218 226 .492 .492 LSA 113 In C/L 108
Comp XR276 224 230 .502 .510 LSA 110 In C/L 106
Lunati 2008-0721 219 227 .515 .530 112
Summit/Comp 08-412-8 212 218 .487 .498 LSA 110 In C/L 106
Edelbrock 2209 212 222 .462 .479 LSA 112 In C/L 107
Rockers will be 1.5
Keep in mind that the goal is strong street acceleration with no strip work. We are thinking the HP will fall in the 360 to 380 range with a broad torque curve near 400 ft lbs.
The speed shop we are working with thinks the Edelbrock 2209 is a good choice.
Interested in hearing opinions from those that know more than me. (That should be just about all of you.)
The screw in studs are being done. A lot of what I've read says that lifts above .480 don't help with Vortec heads. Consensus seems to be that their strength is lower than that and that additional lift is not useable. Am I missing a key point? Trust me, it's taken me a long time just to get conversational with terms let alone theory. I'm the worlds oldest rookie.
The Vortecs are known for their low and mid lift flow on the intake. The exhaust port, not so much. Flow numbers suggest that intake port "stalls" approaching .500" lift so the idea is to keep lift in that range. Because of the poor intake to exhaust relationship, a dual pattern cam is often suggested (but not always used).
When making a choice between cams, a good street rule of thumb is to go with the most lift for a given duration. If you target .500", then, generally the cam with the least duration at that lift value will give the most satisfying results in a street car. The shorter duration will promote low engine speed torque and that's what you'll feel as you accelerate from the stop light or enter the highway.
For what it's worth, I ran the Comp XR276 in my Vortec headed 350. With 9.8:1 compression, cranking pressure was about 190 psi, performance was excellent (it put my 3700 lb Camaro into the 12's) and highway mileage was in the 20 mpg range with a carb.
I neglected to ask. You say the heads are in the shop getting screw in studs. Is that the limit of your modifications?
If so you'll be limited on valve lift before the intakes run out of air. Max lift is arguably between .450" to .480" in the OEM configuration. Seal to retainer clearance is the issue. Add to that the stock springs won't handle much cam. Witness my bent valves with the Vortecs and a .454 218 cam. I moved up to better springs, larger rocker studs and roller rockers. That handled the 276 easily.
The springs are being changed. The shop owner runs a Vortec head himself and says he has an appropriate spring. I'm not sure of the particulars of the new springs. The rockers will be upgraded as well.
We had discussed the valve clearance issues as well as the need for new valve springs to allow us more lift. The speed shop we are working sells a spring that should meet our requirements for lift with out modification to the head itself.
That being said, I also read about the bee hive springs that comp sells, and was curious to see if you had any experience, good or bad, with those springs?
Also based on what you are saying, most lift with the shortest duration at .50, the lunati would be our best option with:
Am I correct with this assessment, or am I misunderstanding the concept? A lot of this is all very new to me and I am picking it up as fast as I can. Thanks again
The springs are being changed. The shop owner runs a Vortec head himself and says he has an appropriate spring. I'm not sure of the particulars of the new springs. The rockers will be upgraded as well.
I trust your machinist will inform you of the choices in rocker arms and guide plates. There are decisions to be made regarding keeping the pushrod where it belongs. That is, self guiding rocker arms or conventional rocker arms with guide plates. One thing leads to the next.
Originally Posted by Hammer's Bird
We had discussed the valve clearance issues as well as the need for new valve springs to allow us more lift. The speed shop we are working sells a spring that should meet our requirements for lift with out modification to the head itself.
That being said, I also read about the bee hive springs that comp sells, and was curious to see if you had any experience, good or bad, with those springs?
Also based on what you are saying, most lift with the shortest duration at .50, the lunati would be our best option with:
Am I correct with this assessment, or am I misunderstanding the concept? A lot of this is all very new to me and I am picking it up as fast as I can. Thanks again
There are any number of choices for a "drop in" spring. If your shop has something they prefer and guarantee, I can't argue.
What I can say is I've run the Comps Beehive spring (PN 26915, 26918). It's also a drop in and will accommodate the lift you're working with (and more). I can't give you the lift value when installed over the stock valve guide seal (although I believe it's .550", something I'd have to verify) but I can say it's +/- .600" when the guides have been cut a traditional positive style valve stem seal. I ran .575" with no clearance issues.
As for the cam choice, yes the concept for an engine that's going need a RPM range that includes off idle response, the lift target with the least duration will give results that I've found most people like. If you find a couple of cams with similar .050" numbers, look to advertised value. A quicker lobe profile (which is desirable) will have a smaller adv. value for a given .050" number.
However, this is all tied into static compression ratio. Have you worked out what that will be? If you select a cam that's too "short" and your CR is high, it becomes an issue with spark knock and ignition timing. I can't say I know offhand what a stock L31 had for a CR and what head gasket was used. Something else I'd have to look up.
Last edited by skinny z; 05-10-2016 at 05:16 PM.
Reason: Punctuation is important too.
"One thing leads to the next". Truer words were never spoken. LOL
The shop did mention the need for guiding.
We ordered the pistons through him and he says they should yield 10.25 to 1.
You mentioned a cam that is too "short". I'm a bit lost there. Do you mean low lift numbers?
The guiding will be either by guide plates or the right rocker arms. Either/or really for your goal.
The final CR is important regarding your choice of cam. To get 10.25:1 out of a stock Vortec block and heads takes some effort. This is something you'll need to measure to confirm or your cam choice could be a bust. Perhaps your machine shop can provide: PN's for pistons, head gasket and whether they intend to deck the block. Then you can work out your own CR and be sure. My stock Chevy block with flat top pistons, Vortec heads and a .026" head gasket yielded 9.8:1.
That leads to the term "short" cam. That refers to amount of time the intake valve is open (basically speaking ). A cam with short duration traps more air in the cylinder (for a given cylinder head and compression ratio) and builds more pressure. That equates to more compression pressure on ignition and more torque. Too much pressure caused by too high a CR and too short of a cam leads to detonation.(or engine death).
Want an interesting read? This paper refers to what we've been taking about.
If you talked to Bullet's tech line, told them all you had and what you wanted, and they said to use that cam, that's the cam I'd use. I've never heard of anyone getting a bad cam recommendation from them.
I know there are people putting beehive valve springs on Vortec heads to get around the large OD and height of the valve guide, but in my opinion, it makes more sense to cut the guide so you can use better springs and seals. The heads are off and apart now; now is the time to do it right.
I know there are people putting beehive valve springs on Vortec heads to get around the large OD and height of the valve guide, but in my opinion, it makes more sense to cut the guide so you can use better springs and seals. The heads are off and apart now; now is the time to do it right.
The inference here is that the beehive is not a good spring. I don't believe that's the case and I'm not sure if that's what your intention was. While there are many "beehive" or conical springs out there, all are not created equal. While I'm somewhat suspect of the Alex spring (manufacturer and origin unknown), the Comp 26918 with it's reduced mass (including retainer) will have, at seat (about 5%) and open (about 17%) pressure less than a Comp 987 and outperform it in terms of valvetrain control vs RPM. The General thinks the conical spring is good idea too.
I didn't want the OP to get the wrong impression should he be faced with making that decision. I don't believe that was your intent but I think it can be construed that way.
Really interesting article, it makes a lot of sense but it is something I never thought of.
Based on what you said about the compression ratio we took a step back and are rechecking that fact. However, we are running into issues with calculating it ourselves because we do not know some of the information they are asking. Mainly, deck clearance, compressed gasket thickness, and effective dome volume. We put 0 for effective dome volume because we are using flat topped pistons but we are unsure how to account for the possible change in compression due to the valve reliefs. Here is a link to the page we are using if you would like to see.
The numbers we are getting are much higher than we believe they should be. So we are pretty sure we do not have proper constants for our engine. (a lot of people on the internet have been saying different numbers for deck clearance)
Now, correct me if I am wrong, but what I gathered was we should be shooting for a cam that opens the intake nice and wide but does so quickly, i.e. short duration, with a good amount of advance (4 or 5 degrees). This is how we can decrease the amount of time the valve spends open while the piston is in compression. Thus increasing our DCR without physically changing the SCR by boring over or stroking.
Now as I understand it increasing our DCR is good for torque but could lead to early detonation with a low octane fuel. Is there a number to fear in terms of DCR in which we should really start using higher octane fuel? Not opposed to the idea, and won't change the build just so I can operate on lower octane fuel, but I would like to know so we don't screw something up.
The best calculator I've found is the one that's attached to the end of that article. It's generally referred to as Pat Kelly's DCR calculator but it has an excellent static compression ratio calculator as well.
Certain values you have to measure to know for sure. Deck height (or more precisely, piston to deck distance) is one of them. In my experience I've seen factory piston below deck numbers ranging from .036" to .025" and that's on the same shortblock. My decked block is an even .014". The only way to know for certain is to measure. The go-to number people tend to use if the value isn't measured or can't be (because the engine is assembled) is .025". I haven't heard of any stock factory block having a value greater than that so any error would be on the safe side. This isn't to say those blocks don't exist though.
As for piston volume, flat top valve reliefs in the few pistons I've worked with range from 5cc to 7cc. If you enter zero for the piston dome volume/relief, that'll inflate your result. That probably what you're seeing. Most catalogues will list the valve relief volume.
The gasket thickness is something you'll select once you've zeroed in your approximate compression ratio. You can work with different thickness' to see how things stack up. When going for an ultimate build, often the piston to deck clearance is predetermined (.040" is a safe minimum) the block decked to a certain number (.014" in my case) and a suitable gasket used to reach that target. I use a .026" gasket to work with the .014" deck to get .040" clearance.
Make sense?
As for the magic DCR value and pump gas. Well I can tell with certainty that my experiment with a DCR of 8.5 (from a CR of 10.4:1 and a 274 cam) didn't work all that well with my iron heads (very similar to Vortecs). Dropping the CR to about 9.9:1 lowered the DCR to less than 8:1 and I could put a full timing curve to it. Before that it had significant detonation problems. I've learned that the CR isn't the big deal inasmuch as the proper timing is. Just my experience there. As for regular pump gas, I'll go out on a limb and say that if your DCR is around 7.5:1, then I doubt you'll an issue. There's an interesting article in Chevy High Performance that combined the Vortec heads and a GM spec cam to build a regular fuel hotrod engine. I'll have to look that up to see what the specs of the cam were.
FYI:
I found the 87 octane engine build.
SCR of 8.7:1 with a Vortec head, a 21 cc D dish piston and .045" piston deck height. CompsXE268H cam 268/280 adv, 224/230 @ .050" by my calculator nets a 7.2:1 DCR.
By way of comparison, a premium fuel build might have a 10.2 compression ratio and with a larger cam like the 276 (from the list above) nets a DCR of 8.2:1.
That's getting up there but workable. That engine would probably have about 190 psi cranking pressure. Both engines have about a .045" piston/head clearance.
Using the calc you suggested I am getting much better numbers (around 9.9:1). So I am happy with that, but working some of the cam numbers I am starting to be concerned about losing Volumetric Efficiency due to a mach index of .60.
Is this a valid concern to be having? It seems that even if I choose the most valve lift, i.e. the lunati, I would still run a mach index of .60. Now I know that is more of a concern at the higher rpm ranges, but is this something I should be thinking about?
To be perfectly honest with you Hammer, I've never considered the mach value (or port velocity) in my cam selection as it's more a function of the intake system as a whole. This would also include the exhaust port and header seeing as during overlap, there is (or should be) a negative pressure applied to the intake valve. For the velocity to be changed in any meaningful way, other than cam specs, the port has to be modified. This includes the intake manifold as well. Keep in my too that too much port speed causes other problems. Sonic choke being one of them.
I'm curious. Where are you pulling that number from? I'm using the PipeMax program to work out my VE% as it pertains to intake port CFM (and all the rest that determine CFM). Specific port velocities are mentioned and their effects although it's not described as "mach value". That could be determined mathematically of course.
At any rate, I think anyone here will tell you (from their experiences) that the plan is to build to an appropriate compression ratio with the cam selected and you'll get satisfying results.
Last edited by skinny z; 05-11-2016 at 08:02 PM.
Reason: Additional information
Well I will defer to your expertise on this one. As far as the figures go I was trying to get more clarification on ATDC and BBDC and that stuff so I went to this site:
At the bottom is talks about valve lift considerations regarding mach value. I had no clue how mach would apply to this so I did more research and got the gist of it. Then I started looking into calculators for this and found this site:
So that is where I got all that from. I did see that everyone recommended the pipemax program for calculating this stuff, so I am thinking you are right. No surprise there! haha
I did have a question about overlap. I understand what overlap is and I have calculated what all the cams overlap numbers are but I do not understand what that gives me in terms of output from the engine. Nor do I understan if i should be looking for more or less overlap, positive or negative, and so on.
Cannot express how grateful we are for all your help!
Little is said of overlap as most everyone refers to duration however it's the amount of overlap that'll give an engine it's characteristics. In general terms , and relating to our Gen 1 small block Chevys, small amounts of overlap will assist in low engine speed torque. This is for a given duration and is determined by the LSA. The vacuum is higher than the same duration cam with more overlap and cylinder filling is better as a result. Now the reverse is true at higher RPMs. Overlap is needed to help assist the intake charge into the cylinder by way of exhaust scavenging. It's gets really complex as the engine approaches the "race" category but in a nutshell, that's about it.
What your engine needs by way of overlap is determined by what you want the engine for. Your tow vehicle will want less as you need it produce torque at low RPM. Your drag racing engine needs more as it spends more of it's time at higher RPM. What you need is a bit of a juggling act. (And we're referring to 350's here. Larger engines have different requirements than smaller ones.) Typically the ticket for a hot street 350 was to tighten up the LSA a little and increase the overlap that way. It's tends to make for a power curve that is more acute. That is, it tends to have more of a peak to it's profile and more peak power as well. With a broader LSA, and therefore less overlap, the power curve tends to be broader albeit with less peak power. That's pretty simplified but accurate. The great thing about today's LS engines are the hugely efficient cylinder heads. The need for overlap isn't as pronounced as it is for these old school small blocks. You tend to see broader LSAs with the LS cams.
Safe to say, and this is verified by countless engine builds, that your 350 with a 108 degree LSA will make more peak power but somewhat less torque than if you ran an LSA of 112. This is for a given intake and exhaust duration. Most have settled in the middle (as I have with 110) as I want a little of the "have cake and eat it too". Peak power yes but not at the loss of low RPM torque. If you were building a drag racer and had the right converter, one which allows the engine to stay within a specific RPM range, then tighten up the LSA and let the engine build more peak power. You'll never be in the lower RPM register for it to make a difference. My street car however has to pull away from stop signs and such and is often cruising about at less than 2500 RPM. That helps on the highway too.
As for "deferring to my expertise", please don't. Use it as part of your research but don't let it stop there. What I'm spouting here is nothing new to the guys here who have spent a lot of time and money building hotrods. And I have to say, better hotrods than mine....so far.
I finally got all the numbers worked up after many miscalculations from not understanding the inputs needed. I have included the spec sheet that I have spun up for our options. We were more or less sold on the bullet but after seeing that it yielded the lowest DCR of any cam I was a little unsure.
Anyway, all of these calculations are accurate as far as I can tell. The few measurements we do not know for certain yet are the piston to deck clearance as well as the gasket thickness, and gasket bore. We are aiming for .04 quench distance so we made those numbers equal that. Luckily, as far as I understand it, those numbers wont affect the dynamic stroke length, thus any changes to those constants would have proportional shifts in DCR for all the cams.
lastly we just split the difference for piston valve relief volume and went for 6cc. I think they are 6.88 but not sure.
Do any of these stick out to you as a clear winner? We liked everything about the bullet, but seeing the 7.7 DCR is making me wonder about power.
My next thought then was, well if I am gunna foot the bill for higher end petro, why would I not run it up to the the lunati's 8.34 DCR or the XR264's 8.5. Would that be a bad leap to make?
I finally got all the numbers worked up after many miscalculations from not understanding the inputs needed. I have included the spec sheet that I have spun up for our options. We were more or less sold on the bullet but after seeing that it yielded the lowest DCR of any cam I was a little unsure.
Anyway, all of these calculations are accurate as far as I can tell. The few measurements we do not know for certain yet are the piston to deck clearance as well as the gasket thickness, and gasket bore. We are aiming for .04 quench distance so we made those numbers equal that. Luckily, as far as I understand it, those numbers wont affect the dynamic stroke length, thus any changes to those constants would have proportional shifts in DCR for all the cams.
lastly we just split the difference for piston valve relief volume and went for 6cc. I think they are 6.88 but not sure.
Do any of these stick out to you as a clear winner? We liked everything about the bullet, but seeing the 7.7 DCR is making me wonder about power.
My next thought then was, well if I am gunna foot the bill for higher end petro, why would I not run it up to the the lunati's 8.34 DCR or the XR264's 8.5. Would that be a bad leap to make?
Great chart.
One thing I can say, although it's a target of an engine build, is not to get too hung up on DCR. Use it as a tool or guideline. Or SCR for that matter. And I'm not saying to ignore, just keep it in perspective. It's far more important in terms of engine performance to have the correct timing curve than it is to have compression. Consider that for an engine of this output level, a full point in SCR might yield 4% greater torque, but if you have to pull back the timing because you're on the edge of detonation, then the losses quickly start to exceed any gains you may have made.
Looking at your chart, (and I haven't confirmed the accuracy by running the numbers myself), and specifically looking at the Bullet's LSA and ICL, I can't say I like it much. Not sure of the application but I would think torque will be reduced across the board and I can't say what might happen to peak power output. The DCR supports that line of reasoning.
Now from my experience, you'll be hard pressed to get your iron headed engine to work well with a DCR approaching 8.5. I know for a fact how difficult is it was keep mine from rattling. Especially at cruise when I'm close to having 50 degrees of spark advance. Because of that I'm satisfied with DCRs closer to 8:1. Looking at the Comp 276 and it looks better suited. For what it's worth, I ran that same cam in my Vortec 350 (same engine spec as yours, flat tops, Air Gap, etc) and it was a stellar performer for what it was. Seeing as you live in Wisconsin, it's basically across the lakes from where I was in central Ontario, cranking compression should be about the same. 190 psi, which is good result.
It's a premium fuel engine but then again, it's a performance engine too. You know the saying, "if you want to play, you have to pay".
Im no expert ....but if your going for sheer torque imo the Comp 2 6 4 grind sticks out to me as being the best torque grind of all of those .
I wouldn't doubt that the 264 would make lots of torque. The problem is, with all that compression pressure (due to the early intake valve closing and the high(ish) SCR), it would be difficult to keep that engine out of spark knock.
I tried to get an 8.4:1 DCR iron head 350 to work, and I never could keep the right amount of timing in it. That's with a 10.4:1 SCR a tight piston to head clearance (quench) of .040", cool running engine and 94 octane fuel.
Based on all we have learned here we are heavily leaning toward the 276. So much so that at this point I believe it is safe to say that that will be the cam we go with.
Now correct me if i am wrong, but since we have already installed larger studs, if we get new springs and rockers we should not run into any issues with bending any valves with that cam.
For setting the timing, I saw this snip-it in an article and I feel it pretty succinctly describes the results of messing with the timing chain. The question is, is this an accurate depiction?
Retard
delays intake event
opens intake valve later
builds more high-end power
increases piston-to-intake-valve clearance
decreases piston-to-exhaust-valve clearance
Now for the purposes of our build, should we be thinking about advancing the timing chain at all to move the torque band down to lower RPM? Here is a snip from the comp cams camquest page for our build with a 276.
As you can see, according to this, we should build torque very quickly, reaching 335 ft/lbs at 2000 RPM. But we are still only at 281 ft/lbs at 1500, and all of these figures are failing to include losses throughout the drive train. So we are curious if we should think about some timing advance, in order to compensate for losses, or just leave it alone?
Those are good numbers as is imo ...putting it in advanced isnt going to be a huuuge difference ....from years ago I seem to recall comps 268h had the best mix of higher tq and hp in a miilder grind with a very slight lope ...it was a huge seller for them and very popular among modders fwiw.....
I installed my 276 "straight up" using a degree wheel and dial indicator. I think you'll find that the torque you produce will be enough in that position as well. Consider also that even the "stockest" of torque converters is going to get the RPMs past 1500 in a hurry. Your cruising RPM with a lock-up OD trans and 3.23 is going to be higher than that too (unless you cruise at 40 mph).
The chart describes the valve events and results accurately.
You should have no trouble with piston to valve clearance. Always measure.
I can't really comment on your rockers, springs and studs or any interference you might have. Not knowing what you have for seals (OEM or aftermarket), or any other hardware makes it impossible for me to say. At the very least you'll have to measure the O.D. of your seal and the I.D. of the spring seat and determine what spring will fit and is capable of handling your hydraulic roller cam. I can say that the Comp "Beehive" 26918 or 26915 provides additional room between the valve guide seal and the spring retainer. I had these (26918) springs on my Vortecs with the 276 although my guides were cut for a positive type seal (Comp 529-16). My understanding is that those springs are a drop-in replacement regardless of the seal you have but again you'll have to confirm.
Sootie is right about the advance not making a huge difference. I've done a ton of simulations and the a 4 degree advance amounts to a few percent increased torque and the same amount lost in peak power. It would be tough to measure in the real world although there are plenty of builders who make that choice (to advance or retard) all the time.
Interestingly, in this latest build of mine, the 288 cam is so big (to me anyway) that I intend to move it ahead a couple of degrees in an attempt to compensate. I can't use the top end it would provide as I have a small tube header and a dual plane intake. Both limiting factors for high RPM (7000) use.
Yes, the 268H was the cam of choice back in the day. But these days, there are more modern profiles available and once the OEMs released factory roller cams, the game really changed.
We absolutely plan to measure it all out. We have spent plenty of time thinking it out that we would be remiss to not be as thoughtful on the install.
Based on what I've read and what you are saying I am thinking we are gunna try to avoid playing with some ACME TNT, in the form of timing chain advance. I think for us first timers, that might be a bridge too far on this build. We can save that for the next one lol!
We are more or less settled on the 276 despite the anticipated drop in DCR due to piston valve relief volume, albeit small (8.16 down to 8.08). Really should not matter all that much to be honest.
That leads me to the question of gearing. We have discussed a 9in rear end with 3.73 to 4.10 gearing. However, I have seen a lot discussing come about that mentions lesser gearing in most scenarios. I am looking for that line acceleration and based on our planned 6 speed manual (ideally t-56, but price may dictate different) I feel the 4.10 is the gearing I am looking for. I am not terribly worried about fuel economy since I will have that splendid 6th gear for any hwy driving, and my Colorado to handle to everyday driver needs. So am I missing a piece here?
I've settled for a combination that's sort of middle of the road. That's the 700R4 and it's very low 1st gear at 3.06 and a rear gear of 3.73. I'm seeing an overall drive ratio of 11.41. With my limited suspension modifications, traction is difficult enough but I put a large part of that down to my old and ancient ET Streets. (New tires are on order this year).
Now having said that, the T56 has a couple of choices for gear ratios. The most popular looks to be 2.66:1 for 1st gear. There are also a 2.97 and even a 3.36 1st gears. With the 2.66 gear, the 4.10 nets a 10.9 final ratio. Very workable in my opinion but I'll point out, the manual shift set-up isn't my thing. I went the auto route years ago to help with my young (but 2nd time around) drag racing aspirations.
You may want to start another thread to get the expert opinion on the T56 and what works with it.
This is the old man back in the thread. Since my son has now passed me in understanding cams (that's a good thing), I thought I'd try my hand at posting pictures. These are (hopefully) a couple of pics of painting the block.
Taping off prior to paint.
Painted POR 15 black first and this is first coat of the orange. I'm not an orange guy, but my son is and since it's his car and it's a Chevy motor, it's orange.
Now that I've figured out how to post a picture it's time for the next question. With the cam decision about to be final we need to select a timing chain and cover. Apparently a few 880 blocks were made with the all the timing cover holes drilled. It appears we have one of those. Since the plan is to install an Edelbrock EFI system that does not use a crank position sensor it would seem that we can use any kind of timing cover. Since we've decided that advancing the cam over the advance built into the cam is pushing the boundaries of our competency we shouldn't need a hex adjust chain set or anything trick. Is there something out there in timing chains and covers that makes this an easy decision?
This pic shows that the block has the full complement of timing cover holes. Two for locating and the rest threaded.
I can't exactly tell you what to buy but I can offer advice on what to avoid.
Seeing as you don't need the adjustability of the Cloyes cover and timing set I use (that's the HexAjust deal you referred to) or the built in cam thrust button that it has (seeing as you have an OEM roller block) then the choices are pared down somewhat. What I can say is to avoid the cheapest copies available. Poor production tolerances have led to more than few people complaining of front crankshaft seal leaks. Seems the problem is related to hole in the timing cover (for the crank snout) being off-centre some amount. It wouldn't be something you could see but the results speak for themselves.
You would think that something over the counter from GM would have at least some degree of consistency with respect to the manufacturing.
I'm sure there's more than one opinion here on what constitutes a suitable cover.
You are correct on the electric fuel pump. The decision has been made to go EFI so a redone fuel system is in our future. We are looking closely at the Edelbrock Pro Flo 3 which is supposed to be available this month. I've looked at the work done by 3rd genners in the EFI forums and that kind of building and modifying fuel injection is beyond our abilities. Heck I have trouble reading their posts. LOL
Any suggestions for harmonic balancers? We cannot use the old one since we are not using the Crank pos sensor.
We have been looking at the different types of balancers but we are not totally sure if there is a specific style to lean toward or avoid. I am trying to understand the charts provided and I am finding myself lacking the information needed to make the decision.
Not looking for anything crazy fancy, we do not plan to rev that high. Something simple that will do the job for our torque engine.
Last edited by Hammer's Bird; 05-19-2016 at 06:07 PM.
Be aware Chevy used different timing marks & tabs configurations. If the "zero" TDC mark is just about in line with the crank keyway, you have a "2 o'clock" style damper (more like 1:30, but let's not split hairs). If the TDC mark is counterclockwise to the keyway, you have a "12 o'clock" damper. Then there were different diameter dampers from the factory (I tend toward larger is better). Use a front cover with the corresponding timing tab. Or get an aftermarket, bolt-on timing tab. I'd recommend getting a piston stop while you're at it to nail down where TDC is on the timing tab (you can get adjustable timing tabs for that purpose).
And, for the record, I hate the term "harmonic balancer", even though "everybody" uses it. It's function is to dampen harmonics in the crank, and therefore it is a "harmonic damper". It doesn't "balance" "harmonics", and the only configurations that use it to "balance" are long-stroke, "externally balanced" engines like 400 SBC and 454 SBC (and variants). It's primary function is still to dampen harmonics - balancing is a tag-on function for convenience.
Thanks five7, those ones seem to fit the bill perfectly.
As for fuel pumps, I am looking at three different styles of pumps that meet the requirements for our EFI system. And they are, for all intents and purposes, the same price.
One is a universal sump which would use a mech pump to pump into sump.
The next is a new in line electric pump, with a pressure reg and return line.
The last is an in tank pump with a return as well as a baffet to prevent vapor lock and slosh issues.
Has anyone had bad experiences with any of these systems? Or highly recommends another?
Last edited by Hammer's Bird; 05-20-2016 at 05:25 PM.
01-17-2016, 11:02 PM
