Buford T Justice -- the full tour

[andy30thz]

Well that sucks you can't find the shim gaskets... I figured any of the chain stores could have them next day. I think they are original equipment on 1971 350 c10 trucks. But I don't know if they'd be rubber coated. I think that is important.
I think your giving up quite a bit just from the quench side of things, not just the compression increase. Such a cheap easy fix too and you're right there!
I thought the same thing when I built our 460 and didn't deck the block...that it was close enough...I was wrong.

BUT! I totally hear you on getting this thing buttoned up!! Sitting out for a few days with the heads off is a uncomfortable feeling!! Not to mention the fear of the shim gaskets leaking and having to tear it all back down.

I found this old CHP article and thought there was some interesting similarities...

http://www.chevyhiperformance.com/techarticles/46370_gm_350_crate_engine_build_v/viewall.html

VERY cool you found some guys that totally GET this project!! Most of the machine shops local to me either don't do high performance work, or don't understand what a "budget" build is.

[Monk]

Well that sucks you can't find the shim gaskets... I figured any of the chain stores could have them next day. I think they are original equipment on 1971 350 c10 trucks. But I don't know if they'd be rubber coated. I think that is important.
I think your giving up quite a bit just from the quench side of things, not just the compression increase. Such a cheap easy fix too and you're right there!
I thought the same thing when I built our 460 and didn't deck the block...that it was close enough...I was wrong.

BUT! I totally hear you on getting this thing buttoned up!! Sitting out for a few days with the heads off is a uncomfortable feeling!! Not to mention the fear of the shim gaskets leaking and having to tear it all back down.

I found this old CHP article and thought there was some interesting similarities...

http://www.chevyhiperformance.com/techarticles/46370_gm_350_crate_engine_build_v/viewall.html

VERY cool you found some guys that totally GET this project!! Most of the machine shops local to me either don't do high performance work, or don't understand what a "budget" build is.

That's a great article..........good info on the Borla mufflers.

[Brian Lohnes]

Andy, a quick scan of that story indicates to me that the engine they were using was damned similar to mine. The cylinder heads on my car are the same ones used on the old 300hp crate motor GM Performance used to sell. Pretty sure the crate engine had flat tops in it but my hopes are buoyed by their success!

It gnaws at me a little not the grab the thinner gaskets, but I feel like I am going to sleep better with stock thickness pieces in their for sealing. I do realize that I am leaving some umph on the table.

[Scott Liggett]

Pistons down in the holes is the bigger problem. Amazingly my 454 had the pistons nearly at zero deck from new. My machinist said the 454's in 1970 were hand assembled and balanced. It explained the check marks stamped on the pad above the oil filter.

[Deaf Bob]

Andy, a quick scan of that story indicates to me that the engine they were using was damned similar to mine. The cylinder heads on my car are the same ones used on the old 300hp crate motor GM Performance used to sell. Pretty sure the crate engine had flat tops in it but my hopes are buoyed by their success!

It gnaws at me a little not the grab the thinner gaskets, but I feel like I am going to sleep better with stock thickness pieces in their for sealing. I do realize that I am leaving some umph on the table.

You worry too much!
I used the stock bottom end on my flatbed.. 77 Chev 350.. Stock heads just cleaned up and reinstalled, Performer intake, Holley 600, and the 280H cam.. I could chirp the dualies going into 3rd empty.. Rode many sports cars' asses in the twisties.. It didn't work that great under 1500 rpms but it worked.. Since my bottom end had hi miles, I never went over 5 grand if I could help it..
I think you will have so much fun, the big block will be further down the road than you are thinking now..

[andy30thz]

Pistons down in the holes is the bigger problem. Amazingly my 454 had the pistons nearly at zero deck from new. My machinist said the 454's in 1970 were hand assembled and balanced. It explained the check marks stamped on the pad above the oil filter.

Yep, the pistons down in the hole is the problem... I was VERY impressed how your 454 runs and I truly believe the tight quench distance plays a role.
I really messed up and didn't deck the block on the 460 we built, I didn't understand the importance of quench. With my rebuilder speed pro flat tops 0.035 in the hole plus a 0.041 gasket...it really dulls the edge off that engine. And if you believe in the "for every 0.010" tighter piston to head distance = 10ftlbs" rule, I left 35ftlbs on the table. Thats a lot in a heavy car!

In this particular case, the comp XR276HR is pretty big for a heavy auto trans car...so the more compression & free torque the better. But as we discussed, pulling it all back apart because the shim gaskets leak...totally blows. I've been there done than. Yanking iron heads, in car, is painful.

Brian, did you ever measure the piston to deck height? Even just back stabbing a vernier caliper from the deck to piston in four positions, side to side with the wrist pin and top to bottom to account for piston rock at TDC, would give you a rough idea.

Oh, if you take a quick look at the piston pic in the CHP article.... I bet they look a lot like yours!

http://www.chevyhiperformance.com/techarticles/46370_gm_350_crate_engine_build_v/photo_04.html

Man, also looking at that shim gasket in the picture...it is embossed so it WOULD have some compression for imperfections. Plus a rubberized sealing coat....maybe its worth waiting and giving them a shot?
They would DEFINITELY seal better than the dead flat copper gaskets I tried in my 460 and leaked.
It would only make sense I guess. If you're replacing a factory shim gasket in a shop, you sure as hell don't want them to leak. The manufactures know that and hopefully addressed it.
Tough call for sure!!

[andy30thz]

One last thing and I'll drop this for today, I promise!!
This is a thread of guys that have used the 0.015 thick felpro 1094 gasket and their results. Everything I read was positive reviews.

http://www.thirdgen.org/techboard/tech-general-engine/282447-anyone-use-fel-pro.html

$34 bucks from Summit.

http://www.summitracing.com/parts/fel-1094/overview/

[Brian Lohnes]

Andy, have you ever seen the movie 12 Angry Men? You are doing a damned good job of playing Jack Lemmon's character (and that is a good thing!).

I am going to steal my father in law's caliper tomorrow and give it a check. Maybe it will surprise us, but I am betting we'll see 25 or close to it in the hole.

With the 12-thou shaved off the bottom of the heads and the thin 15 gaskets, I am trying to figure out where to tweak the calculators to get an ideal of compression. Using the 6-thou = 1cc, if I take the chamber volume to 62 cc the calculator says 9.7:1 -- That's cool with me. My only other worry is piston to valve clearance with the new camshaft with a little over a half inch of lift. Thougts on that?

Edit..upon further thought, there shouldn't be any interference issues.

[Huskinhano]

What, no rocker studs, guide plates and roller rockers? Only kidding. I think the rebuilt heads are going to make a nice difference from about mid range up. It's good to revisit working over stock castings. In general, while close to aftermarket aluminum heads in cost, it'll still be cheaper and probably be plenty for most peoples needs on a street car. Great post!

While it's great to have the piston not down the hole, what can you do about it? Nothing, it is what it is and not worth worrying about at this point because fixing it if it's off is not in the scope of the project at this point. Yes it's nice to know for the heck of it.

[andy30thz]

Yep, I doubt with your dish and valve reliefs (you're still using stock the valve size, right?) you would have any piston to valve issues.

It will be interesting what you see for piston to deck height. The average seems to be 20-30, but its hard to tell. If it happens to be at the extreme end of a tolerance...the pistons might not be as deep as we think, or they might be deeper!

9.7:1 should make the cam even happier and maybe a premium pump gas motor. The great thing about tight quench is detonation resistance AND more compression!
I have a feeling that this thing might surprise you a little when you get it back together...and that's a good thing!

Although tuning will play a big role too. You'll need to scare up a wide band O2 sensor. You might want to weld the bung in the header collector now while they are sitting on the floor....
Wide band makes EVERYthing easier!

[Scott Liggett]

A 6-71 will fix all your ills.

[Scott Liggett]

Here are the pistons in the 383 after I polished them to get rid of hot spots that cause detonation.

[Mr4Speed]

I've used steel shims on old junk several times with no problems. I've used both spray Copper Coat and silver paint on them with no sealing issues.

[STINEY]

Here are the pistons in the 383 after I polished them to get rid of hot spots that cause detonation.

Scott is in the know here........crisp sharp edges are detonation about to happen, not to mention run-on. A few minutes spent smoothing everything is time WELL spent.

In other words, a sneaky builder can get away with a LOT more compression if he pays attention to details like this and cam specs. I can run pump gas in my 11.8-1 aircooled VW sandrail engine with no detonation. I don't like to do it - I see racing fuel as cheap insurance (and it stores better to boot), but I can in a pinch with no ill effects.

And be assured, you do NOT miss detonation in an engine with no water jackets to deaden the sound. Imagine a dozen little men in side beating on it with sledgehammers and you will have an idea of what I mean. Its just not something you can not notice.

[Brian Lohnes]

PLOT TWIST -

So I borrowed a caliper and also a really nice depth gauge from my father in law. I was checking #1 piston at TDC and getting weirdo numbers, like over .050 in the hole with the caliper. So I was sitting there and kind of staring at stuff wondering what in the hell I was doing wrong when all over a sudden...."Hey, is that a 0 stamped into the top of the piston?" It was and there was a 4 next to it...and the same was true on all of the other pistons. This thing has been rebuilt and bored 40 over! 357ci.

I made a couple of calls and it turns out that rebuilder pistons often use shorter compression heights to keep the compression in line with stock when and engine is over-bored. So those numbers in the 50s were accurate because the pistons are like 25 shorter than stock. I plugged all numbers in the Summit calculator, adding the increased bore and using the newly acquired piston depth and it came back at 8.5:1 -- factory stock spec.

The end result of all this is that I am definitely going to run the 15 thou shim gasket and it should get me about 9.2:1, not nearly as good as if the things had been at stock height, but now I know.