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Deck height of a 235?
#67350 Thu Oct 19 2006 04:05 AM
Joined: Aug 2004
Posts: 1,068
H
Shop Shark
Quick question. Anyone know what the deck height above the piston is at TDC on the Chevy 235?
If it matters, it's a 1959 engine.

I'm assuming 0.025", which is typical for Chevy V8's, but the stovebolt may vary from this.

I had to have my head shaved to get rid of a warp and the machinist knocked the maximum amount off, bringing combustion chamber volume to 69cc's. (I cc'd the chambers tonight). I had 84cc's previously. Assuming 0.025" deck height and 0.039" head gasket thickness, that gives me 9.10:1 compression. That's an improvement.

Anyway, anyone know the deck height above TDC?
Thanks


52 GMC 3/4 ton pickup
68 Big Block Vette
68 455 Firebird
Re: Deck height of a 235?
#67351 Thu Oct 19 2006 07:38 PM
Joined: Feb 2000
Posts: 770
L
Shop Shark
If the head is off you can measure the deck height with a straight edge and feeler gages.

Re: Deck height of a 235?
#67352 Fri Oct 20 2006 11:52 AM
Joined: Jan 2000
Posts: 1,609
T
Extreme Gabster
From my experience with about four 235 and several 261 engines,the deck height with standard size original GM pistons is around .010-.015.Replacement original type aftermarket oversize pistons usually have the deck height at .025-.040 to allow for block and head milling I suppose.

Re: Deck height of a 235?
#67353 Thu Oct 26 2006 04:42 AM
Joined: Aug 2004
Posts: 1,068
H
Shop Shark
Yeah, that's what I show too. They're 0.040" overbored pistons, which makes it about 241 cubic inches. And with the shaved heads, I have about 9.25:1 compression now.

It's a modest increase, but that sets the stage for a few other modifications to improve how this 235 runs, such as headers and dual exhaust.

I guess I won't turbocharge this particular motor, since my compression is up this high. Maybe I'll worry about that on a future stovebolt.

The head's back on though. Hopefully now it'll run a lot better.


52 GMC 3/4 ton pickup
68 Big Block Vette
68 455 Firebird
Re: Deck height of a 235?
#67354 Tue Oct 31 2006 01:50 AM
Joined: Aug 2004
Posts: 1,068
H
Shop Shark
Well I got the 235 back together and started it. Initially, it ran well. I drove it for about 5 miles until it warmed up. Once water temp came up and the pressure built up, I started smoking like a steam locomotive again.

Well, this time it's not the head. Water is definitely getting into the combustion somehow. I don't know if it's a hairline crack that I can't see that only sprays when my water pressure is up to 16 psi (yes, modern radiator), or if it's getting into the oil and the watery oil is getting past the rings. One way or another, I think I've eliminated every possibility but the block.

And you know what? An increase to 9.25:1 made absolutely NO difference that I could feel in the seat of the pants. Still a weak, stupid boat anchor of an engine.

I admire those who endeavor to keep these beautiful trucks original, but if I'm going to stay with a stovebolt engine, it's gonna need to be somewhere around or near 300 cubic inches, and possibly even with forced induction.
Trying to get a 3/4 ton down the road on a little over 100 horsepower is horse dookey.

frown


52 GMC 3/4 ton pickup
68 Big Block Vette
68 455 Firebird
Re: Deck height of a 235?
#67355 Tue Oct 31 2006 02:37 AM
Joined: Feb 2006
Posts: 112
D
Member
you sure the heads not cracked, could be inside head where you can't see it. did you have it magna fluxed when it was off.

Re: Deck height of a 235?
#67356 Thu Nov 02 2006 01:56 AM
Joined: Aug 2004
Posts: 1,068
H
Shop Shark
Nope. And I'm not going to either. At some point I have to draw the line. I am sure the head and block could be magnafluxed, and the block could even be re-sleeved. But at the end of the day, I still have a 235 cubic inch engine making a bit over 100 hp, for the same amount of work and money it would take to rebuild a larger engine.

I found a website that sells rebuilt 292's for about $1200 bucks. GMPP sells brand new 4-bolt 350 engines starting at $1700 bucks. Either engine would make loads more power than a 235 for about the same money it would cost to rebuilt it.
I have no problem parking the truck for a couple of months while I build up the cash I need.


52 GMC 3/4 ton pickup
68 Big Block Vette
68 455 Firebird

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