I got my hands on an L31 long block (was pulled from a 1998 Van by the guy I got it from) that I intend to build up over time for my 84 TA. As may have been said before, I set myself a goal for 450 horses on pump gas spinning to at least 6000 rpms. That said, this should be easy. I know there are a billion ways to do it, but I just want something streetable as this is my fun car. I've brought this up before but at the time I had nothing to work with. Now however, I do have an engine to work with and now really need to see about the shopping list.

So far, the 84 has been built with a 97 Z28 spec T56, Konis and Eibach Pro Kit springs, UMI suspension for control arms and panhard bar. Rear brakes have been upgraded to PBR rears, fronts with LS1 fronts. 1LE prop valve. Rear is your standard 7.5 inch 10 bolt rear 3.73 gears. Moser axles.

What I had in mind here was to punch the L31 out to 383 cubes, an RPM performer intake, the heads need to be rebuilt anyway, so I'll get LS6 or LS1 beehive springs, 2.02/1.6 valves, looking at 1.6 roller rockers. I've read that should use at least the LT4 retainers if upping the lift. I'll get a 650 carb from a guy I know locally for this motor since I don't really need anything bigger than that for this motor.

The questions come up with this, the balancer on the front of the vortec is the 8 incher, can this be reused with your typical T56 flywheel? I never can seem to find anything about manual cars and balancing, its all flexplates and balancers.....what the hell?

What cam should I run with this? Roller cam naturally but which one?
I'm wondering about the comp 274 and LT4 Hot Cam among others.

What would be the best rod and piston combo for this setup? Need an opinion on using the stock rods (I believe they're 5.7 inches). Flat tops or dished pistons?

Finally what do I realistically need to do machine work wise on the heads? I know they would need port work and cut to use the bigger valves. What else?

I'm sure there will be other questions. I'm used to working with stock parts, this is the first time I'm truly trying to piece together several aftermarket compoents. I rebuilt a 350 TPI with success sofar, (that particular motor started on the first try literally) so the process of assembly is not new but piecing it together is.

I apologize for the novel, thanks for input. There are hundreds of ways to do this, I just want to narrow down my shopping list so I can buy parts and get moving on this build.

 

Balance required for a particular comb is the same regardless of flywheel or flexplate
Vortec is std 1 pce RMS ; takes any size neutral balance SBC balancer
Bear in mind ;
balancer type will be determined by your stroker crank choice
If you buy one of the cheaper cranks ( or stroker kits) they are often based on a 400 crank so you will need a
external balance 400 balancer
Ditto the flywheel / flexplate ;
Vortec is std 1 pce RMS type, if you go to a 400 style stroker crank then you will need a 400 ( Ext ) balance flywheel

 

Check out my video's in my signature. I got alex's springs vortec springs, and got them up to .550" of lift, but i also had my guides cut and i have screw in studs. And I run 11.91 at 112.56 mph. I still have 1.94 valves and no port work done. I have an L31 block as well.

 

http://www.nastyz28.com/forum/showpo...72&postcount=7
http://www.nastyz28.com/forum/showpo...90&postcount=9

 

you better lower your goals a little bit- 400hp is easy for a streetable 350" small block with no power adders, but 450 is really pushing it and will require that the engine be built to make power way up high in the power band. the vortec heads are also pretty much maxed out at around 400hp in unmodified form.

i have to ask this- do you have any idea what 400hp is like? it's way more power than you need to get yourself in over your head on the street.

 

Oh yes I do know what it feels like, I've driven cars with that power. And I'm shooting high so when I miss I'm not disappointed; so if I miss, instead of having a car that runs 11.5s when have traction, I'll be running mid to high 12s. And I'm stroking it, I just stated I had an L31 long block because I do. I'm not trying 450 with the stock 350 layout, I'm trying for 450 with a stroked out L31.

 

Stroker kits for later one pice RMS engines typically use a stock flexplate or flywheel. The "balance" on stock unts have an issue with terminology. They are not neutral balanced- they clearly have a SLIGHT couter-weight on them but they are often referred to as being "neutral balanced". And the counter weight is not anything like the one on an old 2 piece RMS 400/383 stroker flywheel/flexplate. It's it's own thing and only applies to those later 1 piece RMS engines.

I think it was Five7kid on this board who said it best when he said something like "stop trying to call it neutral balanced or counter-weighted. It only gets everyone confused. Use the term "stock" or "not stock" when talking with stroker kit manufacturers about their stroker assemblies and what flywheel or flexplate is required with it."

Heads.... Find a shop that knows what they are doing with installing larger valves and doing the port work required to make those bigger valves work. Larger valves by themselves are worthless, possibly even counter-productive, on Vortec heads without doing the port and chamber work necessary to work with them. Agreed with above that stock Vortecs are maxed out around 400-425 HP in stock form no matter how big a mill you put under them. Only the torque curve changes.

 

I found this combo in an old thread I started and forgot about over a year ago. Had this combination in it that I found and people liked.

1pc RMS block from JY- $100
Scat crank PN 910526- $188
Scat Comp 5.7 I beam rods PN 25700716- $315
SRP Forged Pistons PN 139628- $508
TFS 215cc AL head. PN TFS-32400006- $1,350
Comp XR282HR cam PN 08-432-8- $289
Edelbrock RPM Air Gap PN EDL-7501- $220

The only difference I can find between that combo and what I'm trying to do is I want to use the RPM Performer intake as there is really no noticeable difference on the street between that and the air gap. And I won't use those heads. This combo made a reported 486 horses and 500 ft lbs. I likely won't lose that much power with the intake change. But the heads are another story.

I spoke with the machinist regarding the headwork, he looked at a couple head options I found and suggested that I just get new heads. His reasoning is the price would have come close to the cost of new heads anyway. Either the Scoggin RA2 Vortecss that can handle .600 lift at 400 each, or the BowTie Vortecs which I found a bit pricy. I also found these heads which slide between those two with bigger valves and 200cc vs Vortecs 170cc.

http://www.summitracing.com/parts/DRT-127322/

But I don't know what to make of those.

 

Agreed on the cost analysis of working stock castings vs. buying new.

The Dart SHP heads are a quality product from what I've heard from others who have used them (I have not, personally). Probably easily capable of 450HP right out of the box. Made in America, too, not China.

If you want to step up to a really good set of heads (AFR, for instance) you're looking at about another $500-600. But you'll use them over and over again on many different combos. I have an older set of AFR 190s (out of production at least 5 years now) and they have been swapped onto different combos 3 times so far. They flow enough to support 500HP easily (probably still better than those new Dart SHP heads, but not as good as the current generation of AFR "Eliminator" heads) and the quality is excellent. Other than spring changes to suit different cams I haven't had to change out ANYTHING on them. Same valves, guides, seals, seats, etc. as the day they came out of the box. And when I sell them I'll still get a reasonable percentage of my purchase price back.

If you can't tell, I'm a believer in buying the best heads you can afford and looking at it as long term inestment in my hobby. I typically spend more than half my budget on the heads (well in excess of the 33% normally reommended by most old timers). But for that money I get greater logevity and make more power that I would have with lesser heads the whole time I own them. Like buying a new computer it's usually more cost effective in the long run to pay a few bucks more and get a good computer you can use for 5 years than the "bargain basement" model that will need replacement in only 3 years.

Still, investing in a set of Dart SHP heads is probably money well spent vs. reworking stock heads. Less hassle for the same end result and you'll have a set of heads you can use again and again. Or something worth decent money if you decide to sell them later. Nobody is going to pay you a nickel more for a set of worked Vortecs than they would for an equivalent set of stockers.

 

Oh, and BTW, it might be easier to start with the 72cc version of those heads to keep compression at a reasonable ~10:1 with flattop pistons in a bigger cube motor like a 383. 64cc heads will be up around 11:1 with flattops in a 383.

 

Alright, I'm gonna see if I can start accumulating parts for this one. I would go with AFRs if it weren't for price. I know I may be buying them twice but if I want to drive it then perhaps those darts are the way to go. I didn't want to spend over a grand for what was basically a vortec head when looking at the BowTie Vortecs. Seeing as the Darts are only 50 bucks more per side or so it doesn't make sense to go with the Scoggin RA2s. I wanted to talk to the machinist before I did anything bec you never know. But now I know what the deal is, new heads it is. If I were just refurbishing them it would be a done deal, but because I want power it doesn't make sense. Using the Darts and that same cam I'm guessing would work nicely.

 

Oh thanks for catching that. I didn't want to go higher than 10.5 compression. I presume you mean the flattop with valve reliefs right? I'll make sure they are the 72 cc chambers when I order.

 

Want to add to this "a deal" is priced low for reasons.So as stated above buy quality parts in the first place.

 

A cam with the duration required to make 450+ Hp is going to bleed that CR off;
ie ,lower the DCR that is a better indicator of engine knock potential

"It appears that most gas engines make the best power with a DCR between 7.5 and 8.5 on 91 or better octane."
http://members.uia.net/pkelley2/DynamicCR.html

 

Not that easy ,
you need to know everything in the engine; piston dish volume , head gasket thickness, cam duration ,
head chamber size , block height , etc
and do the calculations to see what projected CR will be.
A slight change of one item can have major effect on the CR
Read the DCR link I posted above
Very hard to get the compression back if you start with too large a chamber size and then find the DCR of the finished engine is too low

FWIW ,
current thinking is to run as small a chamber size as possible ( gives better quench)
Read
https://www.thirdgen.org/forums/powe...ce-vs-dcr.html
http://racingarticles.com/article_racing-10.html
http://www.camaros.net/forums/showthread.php?t=124935

and use dished pistons ( if you have to ) to adjust CR ( after taking into account items mentioned above)

 

I would be content with a compression ratio that would run on pump gas. I just didn't want anything too wild. Most of the pistons I've looked at were good for 9.7-10.1 compression with 64cc heads. Which is why I put the 64cc head link in there. If the bigger chambers work better then so be it. What would be the best way guessimate the gasket thickness and block height? I seem to be better off using the dart SHP heads as opposed to the Vortecs of any kind. The XE282HR cam has .510/.520 lift with 1.5 rockers, 230/236 duration at .050 lift, 282/288 total duration, 110LSA.

 

There is nothing wrong with you buying say 72cc heads and cutting to the chamber volume you want like 67cc.Stock design deck is 9.025.Head gaskets is .040.Standard decking is normally .010 down or at 0.I like the cam because it does lean more towards the exhaust side,but the LSA at 110 is making a move more towards the higher RPM range and something in the area of a 112 would be better spreading the curve.If you measured and found you have the room for a 0 interference,you might be able to advance the cam say 2 or 4 degrees to lower when the curve starts. Degreeing stock GM cam timing sets you'll find GM build them with a 2 degree retard in them. Checking many of the aftermarket cams you will find they are not built straight on 0 either. There are some cheap power gains to be had by degree'ing in a cam where you can somewhat tailor the curve to your combo.

 

Download and install this CR calculator
http://cochise.uia.net/pkelley2/dcrvb6.zip

Allows you to change engine spec numbers and see the result on the CR
If you have the full cam specs ( need Adv intake duration , not @ 50 duration )
you can input cam details and see the affect of different cam durations on the DCR

 

1Gary, what about something closer to this.

http://www.summitracing.com/parts/NAL-19244485/

 

I put in numbers, want to be sure I did this correct.

Cylinders 8
bore 4.030
stroke 3.75
chamber vol. 72
pistons were flattops with 6cc reliefs
gasket thickness .040 <-- from Gary's number above
gasket bore 4.030 <-- I'm sure its different, not sure how much though
Piston to deck is 0

Came out with
383 inches (Duh)
quench distance of 0.04
and static compression of 10.1 to one.

Sound about right?

And how about this cam as opposed to the first choice, has a wider band which I'd prefer.
http://www.summitracing.com/parts/NAL-19244485/

 

I'm looking for the intake closing angle. No go so I can't put numbers in on the DCR calculator. Can't find total duration for the GM 19244485 cam either.

 

Got to watch the duration and compression ratio.The two work hand and fist.Too big duration on a lower compression engine it is forcing much of the air/fuel charge back into the intake.Try for .010 down down in the deck and see what the SCR works out to be.

I am going to say this out front. These decisions are not easy ones. You know that one of the keys to power output is compression and yet your limited by today's gas. After banging your head against the wall to "try" to come up with a compromise for a combo,it is almost drives to want to build a race only car and say the hell with it.

I really mean this:BUT DEEP DOWN IN YOUR HEART,YOU KNOW YOU HAVE FIGURED ONE OUT JUST LIKE SO MANY OTHER GUYS ON TODAY'S GAS BY PAYING ATTENTION TO EVERY LAST LITTLE DETAIL TO RING OUT A TAILORED POWER CURVE JUST FOR YOU!!!!. That is the essence of what I think hot rodding is. And for those that go through that process,I am in aw of them. Well,rant over. I'll get back on topic.

 

I suggest you be mindful of the heavy wt of the car and would want a broad torque band. A 112 would help you with that. It compounds the stroker effect as well.

 

So the GMPP 19244485 cam would be the better choice with this combo due to the wider band correct?

This can get frustrating. Funny when guys can build an engine and make it work, but it requires a degree from MIT to get the cam choice right.... I would hate to choose to small of a cam and have a dog of a motor. Especially when everything else works. Its the cam that changes everything. That setup should work beautifully with the right cam.

The SCR when I put in .010 deck height came down to 9.861 blah blah blah, so effectively its a 9.9 to one compression. I know my friend is running 10.4 to one or so with his 406 on premium fuel. So I think as far as the SCR goes I should be alright.

 

This one may work as well. http://www.summitracing.com/parts/EDL-2201/

 

Comp XR282HR Specs
http://www.compcams.com/Technical/Dy...2HR-10_001.asp

GM '847 cam
http://www.cranecams.com/product/car...detail&p=24209

 

Once again the DCR ,not the static CR is the determining factor
My 383 has 12:1 CR, the '847 cam mentioned above and has a DCR of 8.7( slightly over the recommended range )
Dynoed 410 RWHP with a loose non lockup converter and doesn't knock @ WOT on 91 at 200F

 

9.9 CR on a 383 with the GMPP # 19244485 cam gives a DCR of 6.7

Re-read the DCR link so you understand the importance of DCR vs CR

 

All this means you understand what your buying and not that you are designing a cam for yourself. I'm going to sleep on this and need to go to bed for a early day. I'll try to post something for you in the morning.

 

Sounds exactly right.

Combine with a cam like the Comp XE284 flat tappet (244/252* @ .050 on a 110* LSA) along with the usual go-fast goodies (appropriate intake, headers, etc.) and you have 450HP pretty much in the bag. Blueprint and tune it sharp and ~475 comes up. No problems running pump gas, either.

My point of reference for those estimates:

That combo in my buddy's old 72 Chevelle (all steel) using older Dart Pro1 heads (probably similar in capability to the Dart SHPs) with a 3000 stall converter, 3.73 rear gears and DRs ran bottom 12s @ 113 on 1.8 60 foot times that you could set your watch by. It dyno'ed just under 400 at the rear wheels.

With all due respect, I am not a big fan of running high compression ratios on the street. It's way too easy to step over the line into detonation. And it doesnt happen when the motor is fresh. It happens after you roll a few thousand miles under the tires when the piston faces and chambers get some carbon buildup on them. THEN the detonation problems begin. Remember that you will make more power with a slightly conservative compression ratio and optimized ignition advance than you will with too much compression and retarding the timing below optimum to keep out of detonation.

On a race-only car this doesn't matter because the engine is not running for long enough periods to build up much crud in the chambers. But a street engine lives a different life.

~10:1 is just dandy for the cam you will need to make about 450HP, in my experience. I should also metion that I use conservative HP estimates. My brain is calibrated more like factory HP numbers, not "magazine" HP numbers.

 

Ok, I constantly hear SCRs in relation to whether or not can run them on pump gas, generally an 11:1 motor is not considered streetable. I guess there is more involved than it seems. I can't input the Dynamic stroke because I don't have an intake closing angle. Also I need a intake lobe centerline. Til those numbers are input I can't get a DCR using that calculator. I suck at math these days, the quench came up at .05 with the deck at .010. Quench came up at .04 with the deck at 0. But that doesn't mean anything bec according to the calculator you need to use the Dyanamic stroke in the stroke figure on the compression calculator.

I'm not trying to tick people off here, I just want to figure out the cam specs I would need to make that engine work the way I want it to. Considering the sheer number of people running 500 horse strokers there has to be one that works like I want. This is 450 at the crank not at the wheels. Someone said I would need a 240 duration range cam to pull it off. Hence the cams I've suggested. They were on the shorter side of the duration. I will go back and read it again, on DCR. Perhaps I missed something.

My reference point was my friend's 406. Hes running a 10.4:1 compression. With Vortecs and a custom grind cam. I will have to look up his specs (he told me) but its a solid roller lifter at around .560 lift maybe? turned 477 horses at the flywheel. Hes running preminum gas. His best was a 12.4 at maybe 116? Hell its an 82 TA. Auto with a stall and 3.42 gears. I'm shooting for a lower power figure so I know I don't need a sky high compression. But my old motor and the GTA ran 9.3 and 9.5 compression running on regular gas. I didn't see a reason to go much higher than that. Like I said, when it comes to cams its like you need a degree from MIT.....


Damon, I need a roller cam. Its a roller block. Flat tappets are out for me.

 

DCR is not the be-all end-all any more that SCR is. The idea is you need to build enough cylinder pressure to make good power. The bigger the cam (the later the intake valve closes) the more SCR you need to keep the cylinder pressure in a good power producing range. Too low and it's a pig. Too high and you have detonation problems.

Don't over-think this stuff. Most cam manufacturers have a suggested comprssion ratio range listed for their cams. When in doubt, FOLLOW THE RECIPE. Don't go way out on a limb unless you know exactly why you are going out on that limb.

Sorry, forgot you have a roller block there. Look into one of the aftermarket cams designed to work with FACTORY roller gear- not the stuff that's designed to retrofit a roller into an earlier block. A well chosen roller cam will make more power than the flat tappet example I posted above (or you could use a milder one and make the same power). I think something like the popular LT4 HotCam (218/228* @ .050 on a 112* LSA) is going to be a bit too mild to hit the power level you are shooting for. I think you're going to need to go a bit more aggressive than that.

 

Don't worry about forgetting I was running a roller block. With all the talk and numbers someone was going to forget. I looked at the Hot Cam and thought it was gonna be too small. I will probably need something in the 230 @ .050 with 112. Someone said Gary I believe, said to run with the 112 LSA cams because it would be more stable at idle. Makes sense for a mainly street motor. I only put in 1/4 times as a performance benchmark. No means going to the strip every friday. I think I had the right idea, but got too caught up in the it must be right cam deal. So a 112 LSA is probably what I want, but the duration is up in the air. Perhaps I should get hold of comp cams and find out what they say?

 

Probably a good idea. The specs you just listed were right in the range of what I was going to suggest.

LSA is a subject unto itself because it affects EVERYTHING including "overlap" and when the intake valve closes. So it's important to realize that.

Generally speaking, wider LSA will give a smoother idle (less overlap), reduce DCR and give a broader but less peaky torque curve. These things are typically welcome in a street driven car, but at the expense of some peak power. The bigger the engine and the better flowing the heads the less you need a lot of "overlap" in the cam so it's not going to be a very big compromise to widen the LSA into the 112* range from the commonly mentioned 108-110* LSA performance cams.

 

^^^ is probably exactly what I need. I knew the LT4 Hot Cam was on the table with a 350 but 383s like to breathe. So that one was out. I didn't mind all the tech talk as its good information and you learn something, but peak power is not what I'm after. The broad power band of the 845 cam mentioned or 847 cam is probably right in where I need to be. But if someone has a better suggestion I'll listen to it. Since I'm def getting new heads I'm probably sticking with the Dart SHPs. I just need to be sure I get the right chamber size.

 

I worked out the DCR on a 9.9 CR engine with a 19244485 cam for you in post # 28

 

I saw, thanks, 6.7 is on the lower side of the scale according to that link you posted and what you've said. With that said, would I need to go bigger or smaller on the cam? Or does something else need to be changed?

 

Your call
Reduce the cam duration or increase static CR to bring DCR back up
Comp 08-467-8 230/236 cam is a popular 383 cam
Takes your 9.9

 

Well I "had" a really strong post I started and I left it to go back to it later.I lost it and it kind of ticked me off some.I won't get a chance to re-post it to later today. Might want to hold off on any serious choices.

 

LOL I'm not buying anything right now. As I said in the first one, this is a shopping list. The whole point of the majority of the discussion was the cam. I'm mainly trying to narrow down my options on the cam, or find a rough set of viable options just because the numbers are using the 485 GM cam doesn't mean thats the final choice. I look forward to that strong post.

 

Be very sure of the specs when using a GM cam vs. what specs any particular DCR calculator needs. Some do .050 at the cam for the closing point (and then estimate the real closing point some number of degrees after that), some use .015 at the valve, some want to do it all the way down to when the valve actually hits the seat (zero or close to it). GM is a little wishy-washy on how they calculate advertised duration and what list measurement is used for the valve opening and closing events.

Just be sure exactly what measurement points you are using. Otherwise it's a "GIGO" scenario (garbage in/garbage out).

 

Well we'll try this again. My approach to SCR VS DCR is different than what I have been reading here. The use of DCR is for calculating a given spec the loss or lack of it. I don't see the value in using it as a tool to bleed off compression and somewhat a band-aid repair to,well for the lack of a better term,poor parts choices in the first place. It isn't logical to build a compression ratio that needs a DCR to run correctly because in effect what you are doing is lowering that ratio that you should have built in the first place. My bottom line is I don't like using DCR's as a tool to bleed off compression. But I am a strong believer in it's use to determine if a cam choice is the wrong one in losses.

The main reason for you to know about these formulas,is for you to decipher what a cam company is suggesting to you after you provided them with your info. There is a hell of a difference between that and being directly involved in the design of a custom ground cam. So the MIT degree not so much. Just make sure you have all your figures and facts in hand before you call a tech line. And aside from all the formulas worked out about the engine,the wt of the car,T/C,rear end gear ratio,and tire size all come into play. A big one is your clear expectations.

One thing we didn't touch on is once you get into the 500's in a cam,wither or not your going to need a small base circle cam for rod bolt clearance. Some of that is related to you choices of rods. For me I bought stroker clearance Scat ARP press fit pin 5.7 rods. I think they are a big bang for your buck. In one hand,I say you build the longest rod engine you can and in the other hand I am saying because 6" rods require ring spacers,I don't recommend them for long mileage engine deals.

The other thing we didn't touch on is if you want in a cam choice to do the 4/7 firing order swap. It smooths out the idle and again does alittle to the torque band. It is one of those things in itself isn't sufficient,but along with playing close attention to the small details all adds up big.

Ok lets get to three cam tech lines for you to shop and then post what they suggest for us to discuss.

First one is Earson and they where the ones who found and developed the 4/7 swap:

http://www.pbmperformance.com/contact-us.php

Competition Products have always good a good job for me. There tech line isn't some Jojo just answering the phone during normal business hrs.

http://www.competitionproducts.com/


And of course Comp Cams tech line is strong as well.

Want to add company choices for cams are as varied as choices of oil and oil filters.