[Firebob]

Anybody know what the deck height is on a stock 455 block?(centerline of crank to top of deck)
If I have the block decked .025(to get to .005) and have the heads milled .010 will I have to have the intake trimmed for proper fit?

Robert

[WDCreech]

Don't mill the intake. Mill the intake side of the heads an equal amount to what was taken off of the block and heads. That way you can change intakes without milling it. Deck hieght of all Pontiacs, except for the 301 and the short deck RA Vs, is 10.23".

[gtofreek]

The intake probably won't fit. And yes, milling of the intake or heads will be necessary.If you do the heads, you will have to pull the water outlet out and cut both heads the same amount that was decked off of the block and heads combined. Same goes for the intake if you decide to cut it instead. People will say not to cut the intake and just cut the heads instead so you can try different intakes, well the same can hold true for the heads if you cut them. Then they are only good for decked blocks and you will have fitment issues if trying to use them on standard deck blocks. Guess it boils down to which part will be swapped around more. I like cutting the intakes myself since they are a lot cheaper than heads, but that's just me. If I was planning on trying several different manifolds, then I would consider cutting the heads. If I was going to upgrade heads, or try different heads, I would cut the intake.

The .010" cut on the heads isn't a problem as much as the .025" off the deck as far as head swapping is concerned. In other words, what I mean is, simply changing the head deck by .010" isn't going to cause any intake fitment issues that weren't present before. .025", now that's a different story.

[Dick Boneske]

A total of .035" off the heads and deck is really a minor amount to deal with regarding intake fit. The intake ports in the head and manifold are not often matched very closely unless porting is done. It was common practice in the '60's to mill the heads .060" or more both on the block surface and intake surface.

The .010" you're taking off the block is probably within factory tolerances for the machining operation.
s

[440GP69]

10.24 is stock

[PLAY400]

The stock deck height on my 1972/3 YC 455 measured from .006 to .024 at the 4 corners. Suggest you assemble and take your own measurements. I zero decked my 400 and just had the intake face of the heads cut so I could interchange intakes

[gtofreek]

I have seen stock decks heights range from 10.220"-10.240". Mid 70's have seemed to have shorter decks.

[Firebob]

Ok so with a set of trws@1.497 comp height and 6.625 rods and 2.105(1/2 of stroke), I get .013 with 10.24 and .003 with 10.23 deck height.

.003 I can live with. At .013 I would only have to cut, at most, .010 off the deck. Even .013 is liveable.
Sound right?

Robert

[antique69lemans]

Originally Posted by PLAY400

The stock deck height on my 1972/3 YC 455 measured from .006 to .024 at the 4 corners. Suggest you assemble and take your own measurements. I zero decked my 400 and just had the intake face of the heads cut so I could interchange intakes

FWIW the 455 I had "zero decked" took about .015" with my setup.It supposedly had
.012" variance from front to back cylinder.It was original motor so either the factory was sloppy,there was core shift problem,or ? . You must trust your machinist to help make calls like this IMO. From what I have seen regard all the book dimensions as reference numbers only.

[opnwide]

Just decked my all original 76 455. Measured all bores, and was 018-022 in. Somewhat square, but I really thought I'd have to deck more. 015 was all I did (average) and I wound up with .005-.007 in the hole. Not bad.

[firechicken]

Back in my lazy engine building days, I just had .020 milled off the low end of my 400 block and ended up .005 out of the hole with stock crank/rods and TRWs.
That engine has made hundreds of passes N/A, nitroused, boosted to 15 psi with turbos and is now sitting on a stand ready to run.
Good ol' Pontiacs...

[WDCreech]

Originally Posted by Firebob

Ok so with a set of trws@1.497 comp height and 6.625 rods and 2.105(1/2 of stroke), I get .013 with 10.24 and .003 with 10.23 deck height.

.003 I can live with. At .013 I would only have to cut, at most, .010 off the deck. Even .013 is liveable.
Sound right?

Robert,
Have our deck squared. The intake will still fit. Then have both, the block side and the intake side of the head, milled to get the combustion chamber to the size that you want.
For a little extra horsepower, I would then port match both the intake and the head to an intake gasket. If you want to squeeze even more out of that engine, Get hold of the H-O Racing Specialties book "PONTIAC HIGH PERFORMANCE Engine Design & Blueprint Assembly", by Craig Hendrickson & Kern Osterstock. It has some very helpful information and illustrations on porting Pontiac heads. If I had to pick a single book that has helped me with building Pontiac engines, over the years, that would be it!

[Firebob]

Thanks Bill and everyone else. I'll look into getting that book. I'm about half way thru Jim Hands book now. I guess the best way is to drop the crank in mount a piston on all four corners and get a exact measurement.

If I only have to mill the block .010 and the heads .010, I shouldn't have to mill off the int side of the heads, right? I can port match them when I them back home.

Can I use my stock 400 harm balancer on this 455?

Robert

[WDCreech]

Originally Posted by Firebob

If I only have to mill the block .010 and the heads .010, I shouldn't have to mill off the int side of the heads, right? I can port match them when I them back home.

Can I use my stock 400 harm balancer on this 455?

Mill the intake side the same amount that you mill from the head surface.

You can use the 400 balancer, but I would buy an aftermarket SFI one.