loopy

iTrader: (1)

Sorry had a busy day and hadn't read that paper when I posted the question

Ok. The head CC'd at 63 (ish) the ish because I used a syringe from a vet and plug installed and wasn't ideal circumstances but that will be fairly close. Will try again tomorrow in daylight.

loopy

iTrader: (1)

I still intend to disassemble the block to install some ARP rod bolts and get the shop to resize the rods and check bearing clearances.

skinny z

Without knowing the cc of the piston we're flying blind. I'll see if I can't find the spec on-line somewhere.
Using what we do know and assuming a dish of 12cc then you get a SCR of 9.5:1 using a .015" gasket. That gasket will get you to a .040" quench to take advantage of the small quench that's on the piston.
With a 22 cc dish, that SCR drops to 8.7:1.
Using a Comp XR276HR cam, (which is the one I ran with my 2nd Vortec 353), your DCR comes in a 7.7:1 and 7.0:1 respectively.
To put that in perspective, Agent 87 had a DCR of 7.18:1 (or thereabouts). They ran a smaller 268 cam.
My guess is that a DCR of 7.0:1 will run on regular grade fuel regardless of the piston type used.

Incidentally, my old engine combination had a SCR of 9.8:1, DCR of 8.0:1, full timing curve, needed premium fuel and pushed my 3700 lb IROC into the 12's at 106+ mph.

RamIt

I believe the vortec crate uses powdered metal rods which are cracked apart instead of machined on the big end. I am not sure how shops resize these rods. Maybe they hone the bore and use oversized outside diameter bearings?

loopy

iTrader: (1)

Is a DCR of 7:1 high enough Kevin? How will this affect low rpm drive ability? I don't have a problem with running the bigger cam but don't want to lose the vortecs low down torque.

loopy

iTrader: (1)

I'm going to have to find out. The engine shop told me I would probably need to resize rods after installing ARP bolts

Fast355

iTrader: (2)

The F-car LT1 cammed 350 vortec in my brothers 1999 Suburban is in the 7.5:1 ballpark DCR. Running a S10 converter that flash stalls about 2,700-2,800 rpm and 3.42 gears the big suburban jumps off the line and gets up and goes.

skinny z

Is it splitting hairs to say 7.5 is ok and 7 isn't? We'd have to go through some back to back engine dyno testing to see how much the horsepower drops but if your objective is to run regular grade fuel, then you'll have to sacrifice some performance. Compression pressure is what builds torque. Premium fuel allows more of it.
One build I have to go on (and I keep coming back to it ) is Agent 87. About 7.2:1 DCR with a little 268 cam and yet the (magazine) dyno numbers say 390 hp. That doesn't seem unreasonable although that 390 hp is undoubtedly with all the testing goodies like no accessory drives, well matched headers, etc. Still, even if you could manage 1 hp/cubic inch, with the right converter and gearing (see Fast355's comment), you car will perform. Keep in mind that the tendency for detonation in a LT1 engine is reduced due to the better cylinder head cooling. Fast doesn't say what fuel he's running.
The variable we're not able to determine is at what point will you reach the cut-off for regular fuel? I suppose, if you build too much compression pressure, you could pull a few degrees of timing out of it as temporary fix. You know how I feel about timing though. Or make the switch to a premium fuel. It's been argued that engines with higher compression and a need for higher octane deliver better fuel economy so the trade off is more or less square.
Ultimately it's your dollars we're dealing with. It seems to me there's money to be saved by using the stock short block as is, with the pistons as delivered. Upgrade the rod bolts, zero in the on a cam keeping in mind that you'll still want to keep the piston to head clearence close to .040", and shoot for a DCR that's close to that of Agent 87.
I'm going to start a thread about the regular fuel question. Maybe someone has some insights.

skinny z

Maybe this will yield some results.

https://www.thirdgen.org/forums/tech...c-regular.html

Feel free to chime in with whatever.

loopy

iTrader: (1)

Awesome advice.

The local fuel pod has 91 RON octane. If I have to put enough in to get to town to fill up with 96, well that's OK too.

Thing is, I see this build as my best chance to have what I have always wanted and if I get it wrong I doubt wife or finances will let me do it again. I would rather spend more now and have it right .

If running g 96 gives better fuel economy due to better compression as well as more power maybe that's what I should do

loopy

iTrader: (1)

I found this article Kevin

http://www.hotrod.com/events/coverag...ression-ratio/



It deals with it in a rule of thumb kind of a way.

Fast355

iTrader: (2)

With a 180*F thermostat I was running 87 octane. Being in a 5,200 lbs brick of a suburban I was running 12* timing at 800 rpm, 24* @ 2,000, 30* @ 2,800 and up to 32* at 4,800.

Same engine in my 97 Express with the stock cam would not tolerate more than 24* total on 87 octane. Had a DCR of over 8:1.

skinny z

Seems to me you may have answered your own question. What I'm trying to take into consideration (as you are I'm sure) is whether it's worth the added expense to swap out the pistons for the sake of a better combustion chamber design (thereby staving of detonation to some degree). If premium fuel isn't a real compromise to your driving experience then perhaps you can save some money and forgo the piston swap and build a typical L98/stock Vortec build with a better cam.

This I'll have to look in to.

Interesting fact.

loopy

iTrader: (1)

So, Kevin

What I get from the fuel vs DCR is that anything from say 7.5-8.0 is what I am looking for (safe) with our 91 octane. (I am still assuming 12cc dish but will CC piston +deck).

Do you agree?

I'm pretty keen to pull the trigger on the cam now.

My thoughts re. 270 vs 276

1. I have std stall better suited to 270
2. if go with 276 I can deck block .010" to keep DCR higher (only if necessary) Block will be disassembled anyways.
3. Prefer the idle of 276 (definitely )
4. 276 has much more power 427TQ vs 415 and 373HP vs 342

So far the 276 has it, but with standard stall will it be a dog at 50-60mph open road
and will it be sufficiently in its power band to maximise economy ? (3.73 gears 700r4)

What are your thoughts?

Still quite prepared to run 96 if but from what I have read it may not be necessary

EDIT we were posting at the same time. I'm thinking piston swap not necessary at this point

loopy

iTrader: (1)

Do you have any suggestions for CAI?

Nothing available here in NZ will have to ship it from the states

loopy

iTrader: (1)

I have just CC'd the block.

I did it twice, 1st time 22cc 2nd time 20cc. This is the piston dish plus deck and piston gap volume. I wasn't able to CC piston dish alone.

I assume the inconsistencies are mine.

Using the Pat Kelley calculator I get 7.5 DCR with xr270HR and 7.34 for the 276. (this was averaging CC's at 21)

I guess either cam will be acceptable but neither will be optimised

Your thought welcome.
.

skinny z

What variables did you use to arrive at 7.34 DCR for the 276 cam?

skinny z

I think you can skip the piston swap and any engine machining with the direction this build is going. It will be like any other L98 or L31 hot rod engine.
You SCR should fall in the 8.75:1 range. That's with the deck height you measured, the piston dish and head cc as measured also and using a .015" gasket. Combined with your .025" deck, you get what quench that's available at .040".
I get a DCR of slightly more than 7:1 using the 276 cam. Moving to the XR270HR will yield a slightly higher DCR of 7.2:1.
I've heard it argued many times that when there's a choice of camshaft to be made, choose the smaller of the two. That might prove to be a useful arguement here.
I fully expect either engine would run of regular grade fuel. The 270 should provide a slightly better seat of the pants feels at lower engine revs too.

loopy

iTrader: (1)

I used 0 for piston to deck

84cc chamber

0 dish

4.166 gasket

Every thing else is as you have it. Basically I added deck/piston CC's to chamber volume (85cc) and entered block as 0 deck height.

skinny z

Somehow the math doesn't jive.
I'm inclined to use my own method, inserting the variables as they are.
That said, does what I have listed make sense? Either of those cams would work well. The SCR is less than 9:1 which seems to be the target for low octane. The smaller of the two cams may provide a little more "pep" while giving up some on the top end.

loopy

iTrader: (1)

Yeah mate.

They make perfect sense.

I am inclined to go with the 276 on account of the meaty idle ( I love the sound) if for no other reason.

DCR difference between the two is negligible. As this is at the end of the day, my toy,

driveability at low RPM can be adjusted by going down in gear.

That's my thoughts on it.

Just a quick note on the methodology used for determining the DCR.............

The measured deck + dish + skirt volume is 21cc.

You accounted for some of that with piston-deck measurement of .025"

I'm thinking that by also entering dish volume as 21cc you in effect re-entered some of it for the 2nd time.

If I new how to determine the volume of 4"x.025" I figure I could work out the actual
dish + piston to block volume.

Do you see where I am coming from with this?

So, if we use the following variables to check my theory:

Chamber 63
gasket .015
Gasket bore 4.166
Deck 0
Dish 21 ( allows for the measured block piston CC's)

I get a DCR of 7.41 for the 276 cam.

Am I correct with what I am saying about using some of the piston deck volume twice?

Thanks for helping me out with this

skinny z

Yes. You're correct in that I'm incorrect. I missed on the "dish volume" including the piston below deck value.
So..
Bore: 4.00
Stroke: 3.48
Chamber volume: 63cc
Gasket: .015" x 4.100" (FelPro)
Piston to deck clearence. 0.00"
Piston dish. 21cc
DCR with the 270: 7.58:1
DCR with the 276: 7.42:1

loopy

iTrader: (1)

Sweet!!

Those are good numbers are they not

I'm gonna order the 276.

Now I've read about cam buttons. Will I need one?

The timing cover say replace once removed so I guess I need a timing cover and maybe a timing chain set?

What did you use for these?

skinny z

I had a non-roller block so I ordered a retro-roller cam and a Cloyes cast aluminum timing cover with a built in cam button. That won't apply to you as you have an OEM roller block with a cam retaining ring. The cams are different .
http://www.summitracing.com/parts/clo-9-221
I aslo picked up the Cloyes Hex-Adjust timing chain. This allowed me to experiment with cam timing using the aforementioned timing cover.
http://www.summitracing.com/int/part...100a/overview/

Neither piece you may be interested in.
I would think that any resonably priced timing cover would fit the bill for you. As for a timing gear set, it depends on what you have. If it has nylon teeth, the conventional thinking is to toss it away. What you would be looking for is a 'double roller". Again that's a bit of a mis-nomer because they're all not created equal.
Do you have this book? If not I highly recommend it. Lots of great budget orientated tips in there. Including your timing chain question.
I've recently moved (across the country) and don't have access to my library. Perhaps Thirdgen.org can come to the rescue here.

skinny z

PS. You'll like the 276. It's even better with a higher stall converter. While not the most popular, the TCI 10" with lock-up has been an excellent street performer for me. It really wakes up the launch. Not the best for drag racing as it lacks a little something in the ultimate performance end of things. Perhaps the money you're saving on pistons and machine work can be funneled towards a new converter....

loopy

iTrader: (1)

I'm sure I'll love it ! LOL After the 305 and all

If the overtime at work keeps up a higher stall converter is a definite possibility, but not until the engine is reassembled and ready to run.

I'll probably ask you about the TQ converter later .

In the mean time I'll get the cam under way.

Just on a side note, I removed the press-in rocker studs to day so in the next week or so I'll get the heads into the shop to install the screw in studs and guide plates. When the cam arrives I'll get the block into the shop as well.

skinny z

Just to be sure, it IS a factory roller block isn't it?
As for head gaskets, I'm not sure what you've thought about. I haven't used a shim gasket as I've always liked the Victor Reinz/Cometic 5746.
I found these shim gaskets however another inquirey at ThirdGen may yield something as good or better.
http://www.summitracing.com/int/part...make/chevrolet
The knock against a shim gasket is that it needs a true surface to seal against. With your new block and heads, I imagine you'll be ok. With your deck, the thinnest gasket you can use would be a .015".

loopy

iTrader: (1)

Yep its a roller block.

As for the deck being true, I had the impression while scraping the old gasket that the bolt holes and water holes had ever so slightly raised edges. I cant confirm that, just a feeling I had at the time.

skinny z

It's standard building practice to, in addition to chasing all the bolt holes with the proper tooling, to also chamfer the holes slightly as well. This may be something you'll want to do. Of course your machine shop could do it but it's certainly not a difficult task. If you were to do it yourself, I'd do it before the block is delivered to the shop. That way all of the debris will be cleaned up (or hopefully so).

loopy

iTrader: (1)

Do I do it with abrasive cone or steel type tooling?

Is 08-423-8 the correct part number for the cam for my engine?

It comes up as XR276HR-10 on Ebay

skinny z

It could be. I'm not entirely sure what you've got for an engine. I believe the Comp Cams website says it's for:
Chevrolet 305-350 c.i. V8 1987-2002 (Except LT1/LT4)
As for the tooling to use for de-burring the bolt holes, tool steel all the way.

loopy

iTrader: (1)

Cool

I just brought the cam I asked you about.

As I understand it, 87-2002 was the years the L31 vortecs were used in Chevy trucks and later on heavy vans so I hope its correct lol. It did say for OE roller blocks which is what I've got.

Heres the link to the ebay auction, not that it makes any difference, its paid for

http://www.ebay.com/itm/COMP-Cams-08-423-8-XTREME-ENERGY-SB-Chevy-Hydraulic-Roller-1900-5600-Camshaft-/181376671987?pt=Motors_Car_Truck_Parts_Accessories&hash=item2a3ae460f3&vxp=mtr

skinny z

I ran the Vortec flow numbers and the 276 specs through my Dyno Sim program.
I used the following:
350 c.i.d.
9.2:1 SCR
680 cfm carb
RPM Air Gap manifold
Vortec heads
XR276HR cam
Small tube headers with mufflers
Peak HP:376 @ 5500
Peak TQ:413 @ 4000
The headers really choke the performance when used in the program however it's a real world situation. If an open exhaust is inputed then the power goes up to 394 hp. TQ climbs to 430.

When this same engine ( with a 10:1 SCR) was installed in my 3700 lb IROC-Z, with a 700 trans and 3.73 gearing, I clicked off a 12.9x at about 106. Not sure, but that might have had a stall converter to help my 60 foot time.

loopy

iTrader: (1)

The headers are hedman 1-5/8" shorties.

I knew when I brought them that there was a price to pay in terms of loss of TQ
and the moving of the power band up higher in the RPM range.

From what I had read, long tube headers were a no go due to the extra expense involved with x members and dual exhaust.

Just reading the chart though, while at RPM below 1500 its a bit of a dog, from there up its the equal of the 305 to 2000 then comes on strong to 2 or more times the power right through to about 5500 where it drops slowly,

I can live with that. Its more than I expected to get when I started this exercise.

I can see a higher stall converter sometime in the future will unleash the beast lol

I'm also thinking to get an ignition module so I can put a rev limiter on it as I love the sound of a hard reving V8 and will likely push it too hard and break it unless I limit it to less than 6K

skinny z

Despite allof the rhetoric surrounding long tube vs short tube headers and such, (there are plenty of posts here and elsewhere regarding the debate) I can make this unequivocal statment.
An exhaust system will make or break an otherwise strong engine combination.
Originally I had the same Hedman short headers as you have. It's not so much the headers that kill performance but the poorly designed y-pipe that chokes cfm. Then I "stepped up" to Hedman mid-length headers with a very well made y-pipe (pics attached). That was connected to a typical Flowmaster cat-back arrangement with a single 40 series muffler in the stock location. This is still a poor design.
Here's the rule. Headers notwithstanding, an exhaust system must be capable of flowing 2.2 cfm/HP before the resulting backpressure starts to limit power production.
Case in point. My own current arrangement gained 2/10ths and a couple mph simply by opening up the cutout located just ahead of my single muffler. While it's not so much a restriction at cruise, much like too small a carb isn't, it certainly has an impact at WOT approaching maximum engine rpms.
Bottom line, when you can, don't skimp on the exhaust.
I'll be modifying the y-pipe in the attached pictures by placing cut-outs at an appropriate distance from the collectors. This should allow me to tune for open header performance.

loopy

iTrader: (1)

Yeah I can see what your saying.

I intended to run 3" from the collectors all the way around the RHS and joining just before the muffler with a custom Y into a larger bore muffler. I read somewhere that the exhaust will perform a lot better if muffler isn't the restriction. You achieve that by getting one that flows greater than the maximum CFM expected from the engine.
I assume that means either 3.5 or 4" muffler. I want twin 3" out from the muffler and all mandrel bends.

It'll be a while before I do anything there as theres lots to buy before that becomes a priority, and probably even longer before the car ever see's a strip or track.

In the meantime I'll do what I can to minimise losses as cheaply as possible.

That system of yours is very nice. Do you have any problems with it hitting the ground or speed humps etc?



EDIT I just noticed your emphasis on "appropriate " distance, Could you expand on that?

Night rider327

iTrader: (13)

The shim head gaskets are great to use. I use fel pro 1094 on at least 60% of the builds I do.

In the last 10 years I would guess I have put 1094's on 200+ engines and only had a couple of probs and that was 'user error' spraying too much nitrous or turning boost up too high. I do not recommend nitrous or boost at all on the 1094's but they can take small doses (75-100 HP shot, or 3-5 psi boost)

Yes the decks needs to be true but it's not as bad as you will read online. They do not have to be spot on, dead perfect to seal up just fine.

loopy

iTrader: (1)

That's good to know. you hear all sorts of stories online.

Thing with my build is, I need to use them to get my SCR high enough.

Night rider327

iTrader: (13)

Yeah they should work fine for you. Clean the decks good and lay a straightedge across the decks and look for any high or real low spots. If you have any high spots you can knock em' down with a file. If the decks are flat the 1094's will seal.

I ran them on an engine with 218 psi cyl pressure, I run them on mine now with 10.34:1 SCR.

My dad used them on his Twin T3 turbo'ed 327 and they worked fine with his low 5 psi and under boost for 6 mo.. Then he dialed up the boost to 10 psi and blew the head gasket 1st time he boosted.

loopy

iTrader: (1)

Mine will get about 9.2:1 so all good there.

Twin turbo 327 must have been a monster. What car was it in?

skinny z

That's what I needed to hear.
Yes, the .015" gasket combined with loopy's .025" piston deck will get him to the .040" quench distance (what there is of it with his dished piston anyway) and get his SCR up a little.

skinny z

Exhaust systems and in particular headers, can (should) be tuned for length. When running open headers, having a certain length collector (different lengths for different engines) will produce a pulse as the exhaust gas exits the collector into the open atmosphere. This pulse has a corresponding low pressure component that is reflected back up the primaries and when arriving at an exhaust valve that is open during the overlap event (when intake and exhaust valves are both open for a number of degrees) will provide a suction on the open intake port and initiate the induction flow. On a well tuned system, and something that's not easily achievable on a street car ,this suction is far greater than that which is created when the piston initially starts back down the bore on the intake stroke. I say "street car" because while this exhaust tuning exercise is something that is a must for a race orietated vehicle that can run open headers during cometition, it's not something that is easily achievable for a vehicle in street trim, (ie, full exhaust).
There are computer programs available, I use "PipeMax", and these will determine what length the collector needs to be to tune for a given combination so as to create the ideal pulse event.
If you haven't read Vizard's book, the one I provided a link to, (Max SBCs on a Budget), I strongly suggest you should. There an excellent section on this subject.
In my case, along the length of the stainless y-pipe you see in the pics, I'll cut in a collector stub with either caps or an electric cut-out. That cut-out will be along a predetermined distance from where the primaries join the secondary. The PipeMax program suggests something along the lines 16-18" for my given engine combination. When I'm at the track, I pop the caps, (just like I do to by-pass my muffler in my current arrangement) and hopefully, even though I have a relatively small overlap event, I will reap some benefit from having an exhaust system that will replicate an open header arrangement as much as is possible. The greater the overlap, the greater the result from exhaust pressure wave tuning.
If you've ever heard stories about how people run their engines with nothing attached to the short collector and comment on how the engine is gutless, it's exactly for this reason. The short collector produces a pulse which is inappropriate for the engine and consequently, volumetric efficiency, particularly at low engine speeds, is crippled. Result, no low engine speed torque production.
In our case, the best we can do if we choose to run an OEM exhaust system arrangement, is to maximize the size of the pipes and ensure that the muffler is capable of flowing at or near the requisite 2.2 cfm/hp spec. About the only mufflers I've come across that will flow 800 cfm are the racing bullets like Borlas or some of the Magnaflows.

skinny z

Yes. I've mashed the section of the y-pipe immediately behind the collector a few times. I'm running close to 2" drop and that does pose a few problems now and again. Clearence is about the diameter of a 355 ml /12 oz. beer can
when the vehicle isn't loaded with a driver or passengers.
The stock cross member was notched and reinforced to provide as much tucked up clearence as possible.

Night rider327

iTrader: (13)

Yeah it's a pretty darn fun car. It's my dad's 1982 firebird. One of those works in progress deals that's never done.

Started as a large journal N/A 327 bored .060", 305 HO heads, etc wanted more so we made up a backyard twin turbo system using junkyard and Ebay parts. Worked great with low boost, up the boost, blew head gaskets. Replaced with the thick blue fel pros, blew those at 12 psi boost.

He decided he wanted alot more out of the car so upgraded to brodix IK 180 heads, cometic MLS gaskets. Boosted 15 psi

Then had detonation probs and blew the engine. Broke a forged trw piston and cracked the block.

So took a 350 block had it machined, new lower compression pistons, bigger cam, intercooler, better blow off valve, boost timing retard, etc and got boost up to 18 psi.

Night rider327

iTrader: (13)

Oh yeah, need to mention on those fel pro 1094 gaskets. It's not needed per say but I always spray both sides of gaskets with copper spray sealant before I install them.

This does help to fill any voids in the deck surfaces.

skinny z

Yeah. It seems the hot rod community is split 50/50 when it comes to spraying them. I believe the instructions say if the deck and /or block surface is 60RMS (Roughness Mean Surface) or worse , then a copper coat is recommended. I can't comment beyond that as I've never used them. Up until recently it's always been the .026" 5746 by Victor Reinz. Having had what I perceived to be a too high a SCR/DCR issue, I've swapped to a thicker .040" Fel Pro. The heads will have to come off for service next season and I may switch back though.
Interestingly I think I'm on that cusp where the slight increase in compression ratio and the possible risk of detonation will be offset by the improved quench value. Something we've discussed here for Geoff's (Loopy) build. His compression values shouldn't present much of detonation risk. Even on regular fuel. The .015" gasket won't leave enough piston to head clearence in my case as the block's been decked for a .014" piston deck height. Loopy won't have a problem that way.

loopy

iTrader: (1)

I'm pretty impressed with the underside of your car Kevin. For a vehicle that gets regular use its a credit to you.


Good thing you're skinny_z. .....If you were fatty_z you would squash that can of beer. Can't have that!!LOL!

skinny z

I'll have to admit that those pictures were during the early stages of the build. That Sport Coupe was a roller I picked up in the southern U.S., stripped it to the bare chassis, sandblasted and painted the whole works. (or almost all of it).
It's probably got about 50 000 kms on it since then although I will say it's easy to keep clean.
As for the y-pipe, it had been on the car exactly one day when I loaded it up with luggage and golf clubs for two, picked up my buddy and promptly drove over a culvert that was the high spot in the road. Had to break it in one day. Might as well have been right away.

loopy

iTrader: (1)

LOL.....that's my kinda luck!

By the way, I have just found an online bookseller here in NZ who has that David Vizard book.

By a stroke of luck he lives near the same town-ship I do (who would have thought! in the middle of nowhere) so maybe I'll get to pick it up tonight.

I'm getting pretty excited about my build now, not much left to buy so will be getting the work done on the engine very soon

spurgeon76

The XE268H cam would work well with your motor and plans. Chevy Hi Performance made nearly 400hp with a low compression Goodwrench motor using that cam back in 1999. http://www.corvettefaq.com/c3/goodwrench/gm3508.htm