I have Chevy Small Block L05 factory roller engine from a Buick Roadmaster 1992, that I'm going to modify this winter.

The Swirl Port heads on the L05 engine have 65,3 cc combustion chambers and (the factory roller blocks) an advertised compression of 9,6:1.

I'm planning to put on a set of Vortec heads and was adviced to use the ,015 thick head gasket.
The Vortec heads combustion chambers are 64 cc.

Is it correct the this will result in compression of 9,99:1? Or is my math wrong?
Will it be too much? Should I switch to a ,026 head gasket instead?

This is not a race car.
I'm going to change the cam as well, and have rebuilt the heads.
But will it be too much compression?

 

Any idea what your piston 2 deck height Is? Really you want arround .030-.040 of quench. So the p2d height plus the compression thickness of the gasket. So if you are using a .015 gasket then hopefully your p2d height is roughly .025

As for the compression of you are running 91 or 93 octane I would just try and keep it below 10.5:1 static but its also dependent on how big your cam is. you may run up to 11:1 compression without issues with a larger cam(intake closes event...abdc). But without knowing your cam, it's hard to say your dynamic comp, as even if you have say 10.5:1 compression but have a baby overlap cam, you may have a high dynamic compression of 8.8:1..9.0:1...exc personally I've never had issues with 7.5:1-8.5:1 dynamic compression with 93 octane. Both alum or iron heads but alum will help slightly and let you run a bit more without knock.

But if you only have 10:1 static compression i dont see any issues if you run 91 or 93 octane no matter the cam.

 

I'm planning to use this cam. In combination with 1.6:1 rocker arms:

Howards Stock #: 183215-14
Camshaft Type: Hydraulic Roller
Duration Exhaust: 278
Duration Intake: 270
Duration at 050 Exhaust: 225
Duration at 050 Intake: 217
Engine: 305/350
Firing Order: 1-8-4-3-6-5-7-2
Intake Centerline: 110
Lobe Separation: 114
Engine Manufacturer: Chevrolet
RPM Range: 1300 to 5500
Valve Lift Exhaust: .500

But I haven't bought it yet. I will buy the cam when the heads are taken off, just to be 100% sure that the engine has the flat top pistons it is supposed to have.
And then I can measure the piston to deck hight.

 

10:1 with Vortec heads will be perfect for that cam.

 

I would strongly recommend against the .015" (steel-shim) head gasket.

Those require meticulous block & head surface preparation to provide a good seal. If you are not doing that, for example if you're taking a used short block and putting a used set of heads on it without any machine work to anything, there is a very high probability of failure.

Use the standard .039" composition type instead.

A stock short block will usually have anywhere from .025" to .035" of deck clearance (piston is that far below the deck @ TDC). Most often, toward the high end of that range. Factory "spec" for compression assumes the "ideal" value of .025" which is not realistic in the reality found in the real world.

Vortec heads are usually a bit smaller than 64cc according to many people who have measured many of them. Usually 62 - 63cc. The chamber can get larger however, depending on how much the valve seats have worn and many valve jobs have been done; or smaller, if they've been decked.

A 350 with 62.5cc heads, .035" deck clearance, and .039" gasket, 6cc valve reliefs in the pistons, works out to about 9.5 - 9.6:1 compression. (it's ridiculous to quote this to 2 decimal places, given the tolerances and slop in everything, and the variation among cylinders which is always quite high... it's tough enough to guess it to even within ONE decimal place) About right for a good street motor.

I wouldn't worry about "quench" if you're not doing any machine work. It's basically outside your control, if all you're doing is just putting a bunch of parts together ("assembling" as opposed to "building"). It is totally insignificant with dished pistons and only starts to become significant as the compression increases. At the compression you'll have, with those heads, it's not really a factor. Not worth compromising your gasket choice to "optimize" it, for sure.

 

I don't know where you get 65.3cc on the stock LO5 head but it should be a direct swap with the 64cc vortec heads. Maybe you measured 65.3cc yourself but having recently measured my LT1 heads no way I could be more accurate than 1/2cc w/o expensive special equipment so I have to assume that you read that 65.3cc number somewhere. Beware of your information sources on the internet.

Next the advertised c.r. for the LO5 is 9.25 so I don't know where you that 9.6 number either. Vortec head for swirl port head is a direct swap - don't make it harder than it is.

Go with that steel shim 0.015" gasket. That's what it was designed and made for - iron head on iron block. That gasket (FelPro) is what I have on my 74 corvette 350 and it works great. It's alot cheaper to.

Last that 270 duration is an excellent choice for that vortec head 350 to. IMHO I think you have it nailed. Put it together and don't look back.

 

Thanks for your answers!

Cardo0, here's where i found the L05 roller block information:
http://paceperformance.com/i-5133946...-brougham.html

 

Doesn't too much matter where you found it.

It's probably "accurate", to the extent that any such thing ever is; but just wait until you measure it.

When you have the heads off, measure the deck clearance on all 8. You'll see what I mean. When you have the heads in your hand, cc them. Then calculate the compression on each individual cylinder.

If I was the betting kind (I'm not), I'd bet that there will be a variation of AT LEAST 0.2 in the REAL TRUE ACTUAL MEASURED compression ratio among all cyls. Which makes all that 2 decimal place kind of stuff, ... sorta moot.

I would STRONGLY recommend that you NOT use a steel shim gasket. Every single one I've ever taken apart - now granted, I've only been doing this for 45 years so far, so I could run into one that's different almost any day now - but so far in my young budding hot-rod career, EVERY SINGLE ENGINE I've ever torn down that had those gaskets in it, they had failed. EVERY ONE without exception. Not the odds I'd want for my personal build. The tiny increase in compression, and whatever other "benefits" are projected, isn't worth putting something together that has to come right back apart again.

 

Is a shim gasket different than an MLS gasket?

 

Yes.

MLS = multi-layer steel... generally 2 layers of thin steel with composition of some sort between them

Steel-shim = one sheet of shim stock material with some shapes stamped into it around various holes

Very very different.

Most modern engines come from their factories with MLS type gaskets. LSx for example. They're popular and available for older engines like small-block Chevy as well. They're typically about the same .040"ish thickness as the usual compostion such as FelPro HS-7733PT-x or 1010, sometimes a bit more.

 

Yes, this is why I was asking if you mean shim=MLS. I wasn't sure if you meant MLS because they work very well.

 

The heads are resurfaced.

 

I always use mls gaskets.. the shims.. I haven't had any experience with then bit have been told to stay away many times. Mls gaskets can be found in almost any thickness for a build. I personally have . 027 compression thickness mls head gaskets on my sbc. Sure I had to wait longer as it got shipped directly from the manufacturer. Normally I buy my stuff from summit and it's here in a day. These gaskets took 2 weeks.

Granted you won't find a .015 mls head gasket bit you probly will fine some arround .021. 023 .025 .027 exc and that will give you some better numbers. I just figure if you can get good quench......why not take advantage of it.

I totally understand in most cases quench doent mean crap unless you are really modifying your engine alot. But here is the thing. Why not get it as close to where you want to be.

So I would personally check your piston to deck clearance and verify it, as alot of blocks have been decked multiple times so who knows what they are currently at, then go though summit and filter though to fine the gasket of the proper thickness to get you .030-.050 quench. I garentee you'll find one thst gets you in those numbers.

Keep it under 10.5 with that cam and heads, and you won't have any detonation issues.

 

As for static compression, I'm running the "Vortec-like" heads and 58cc chambers netting 10.8:1, as built, on pump gas in a daily driver. Of course, it's running on a knock sensor, PCM spark control with 58° total advance, and SFI, not a carburetor and Mallory distributor. Drop a few compression points if you don't use modern fuel and ignition systems.

 

58 degrees of timing??? Btdc? Wow. That's alot

 

A short update on this.
Engine runs nice so far.

Went down from 1.6 to 1.5 rockers after app 50 miles, because the rockers turned blue from strong heat.
Didn't find out if the blueing is normal for the Comp Cams Chrome Moly roller tip rockers, or not. Some said it is.

After double checking the clearances, I decided to change to 1,5 ratio rockers as well, to be on the safe side. But none of the push rods were bent after using the 1,6 ones.
Changed to full rollers while I was at it. PRW stainless steel.

Despite some of the advices, I decided to use the ,015 head gaskets, since I already had ordered them. Also got the heads resurfaced.
There are no signs of any leaks. Oil and cooling water looks normal, engine runs nice. Have adjusted it to 800 rpm's at idle.
Haven't had any race testing yet, but the engine pulls much better through the complete rpm range, and is much quicker to increase rpm.

Still have some ignition and carb tuning to do, but I guess a fuel consumption of 24 miles pr gallon with the 670 cfm Holley double pumper indicates that It can't be that far off.

Again, thank you to all of you for your inputs!

 

As long as it is a cast iron block that has a deck in good shape and a cast iron head that is also straight and true, you will not have an issue with the 0.16" stamped steel gaskets. The OEM shim style gaskets lasted more 200K miles and nearly 20 years on my 1983 G20 van. I have also used several other sets and had no issues with them on those applications. One went atleast 100K miles in 7 years and the other has gone 75K in the past 12 years. The first one I had to tear down for other lower end issues unrelated to the head gaskets and no signs of any head gasket leakage or failure. The engine in my signature is still together, in a different vehicle, still runs great and still has the same set of steel shim gaskets I installed on it when I built it.

For my aluminum head setups I have had great luck using the GM Performance Parts MLS 0.028 compressed gaskets.

 

It's all about the deck and head surface prep. For the SLS (single layer shim) gaskets, you want a surface RA of around 25 or less. For reference, you can get there with about a 320 grit, or a 220 grit that's been used and brought down it's high spots a touch. I resurface heads frequently and bought an RA meter for checking my process.

GD