[Joshua Paul]

I recently got a decent deal on a 455 that was built a year ago and just sat in the corner of a garage. It has the 4X 1H heads (I believe 114 cc) and a comp cams XE250H-10 cam shaft. Motor was never ran. I intend to replace the head gaskets as the owner had pulled one off for pictures. I will also pull the cam to re-lube as it sat for over a year.

Questions or guidance:
1. I have a set of #16 75 cc heads currently on my tired 400. Rebuilt built them years ago and probably only have a thousand miles on them. Which would you use?

2. The xe 250 seems a bit small. Recommendations.

Currently have a slightly above stock stall on the torque converter, TH350 transmission, and 2.73 rear gears.

[i82much]

are the pistons dished and how much are they below the deck? assume stock stroke and rod length?

[Joshua Paul]

From what I know, stock rebuild bored 30 over.

[Stan Weiss]

Originally Posted by Joshua Paul

I recently got a decent deal on a 455 that was built a year ago and just sat in the corner of a garage. It has the 4X 1H heads (I believe 114 cc) and a comp cams XE250H-10 cam shaft. Motor was never ran. I intend to replace the head gaskets as the owner had pulled one off for pictures. I will also pull the cam to re-lube as it sat for over a year.

Questions or guidance:
1. I have a set of #16 75 cc heads currently on my tired 400. Rebuilt built them years ago and probably only have a thousand miles on them. Which would you use?

2. The xe 250 seems a bit small. Recommendations.

Currently have a slightly above stock stall on the torque converter, TH350 transmission, and 2.73 rear gears.

Without really knowing very much about this engine. That cam is to small!

You need to figure out what you CR is now and what cc the current heads are. If you have a 114 cc head and around 7.75:1 CR then the 75 cc heads will be around 10.3:1 with only changing the heads.

Stan

[Joshua Paul]

Thank you. Sounds like the #16 heads are the way to go. I guess next question is about the cam or which one to go to.

[25stevem]

Well not so fast here!
Those 16 heads are the way to go only if you get the compression down to 9.5 by means of dishing those pistons, or if not then running a mixture of pump and race gas, or otherwise stuffing in a very big unstreetable Cam to deal with that 10.3 or so compression.

Dishing the pistons means a rebalance job also.

[Joshua Paul]

I'm not opposed to mixing gas. Unfortunately have not been able to find race gas on the East side of Tampa, Florida. Which is surprising, because I live within 10 miles of East Bay Raceway. Even checked out Sunoco's website and their stations. What about off the shelf octane booster? This car is not a daily driver by any means.

[67Fbird]

10.3 comp isn't that dramatic with iron heads. That was the number I was shooting for with my street build....ended up at 10.1

[zippy]

I'm 10.6 Been that for years. 455HO bored and stroked to 470 with 87cc #64 HO heads

[Jay S]

A 455 with 75 cc heads is going to be just over 11:1 with factory type pistons.

[Sirrotica]

Originally Posted by Jay S

A 455 with 75 cc heads is going to be just over 11:1 with factory type pistons.

Since I have done that swap before with 48 heads, (1977) I was fairly certain that the 10.3 number was low. Putting small chamber 400 heads on a 455, and trying to run it on the street with pump gas is going to be a real PITA, IMO.

After trying this combo many years ago when the feds were implementing the unleaded fuel and there was no premium fuel available, only octane booster, I proceeded to blow holes in the pistons of 1, 455, and a 428 with pop up pistons. Upon talking with Nunzi, he told me to look for a set of early 70s 400 heads which relaxed the compression ratio back to a reasonable ratio. I found a set of 96 heads which have advertised 96 CC chamber volume, and could safely run those on a 455 race engine. (69 GP dirt track car in my signature pictures).

From then on, I've tried to keep compression down to keep my 455 and 428 combos happy. The reduction in compression can be made up with port work, and careful cam selection. If you get somewhere that you can't buy good fuel, you can trash the engine quicker than you think. Build for easily available fuel, would be my suggestion. Pontiac was able to pull some pretty good numbers with round port low compression engines, namely the 455 HOs, and the 455 SD combos.

I have run 455 HO heads on the street, and the afore mentioned 96s, as well as a set of 5C heads on a 455 short block. These combos aren't octane sensitive when set up properly, will run on 93 fuel, or less. The 5c heads have a fair amount of port work done, and run quite well in a 76 T/A with 3.23 gears, T400.

Round port aluminum heads would be another choice, they flow better than most ported cast iron heads out of the box, and are more octane tolerant.

[Dragncar]

With that cam its going to be a ping monster and beat out the rod bearings. 11-1 is aluminum head territory. Even with the perfect cam I would not do it.
Heck Butler used to sell their 455s with aluminum head set at 9.9 CR to avoid the customer hurting things.

[Dragncar]

Originally Posted by Sirrotica

Since I have done that swap before with 48 heads, (1977) I was fairly certain that the 10.3 number was low. Putting small chamber 400 heads on a 455, and trying to run it on the street with pump gas is going to be a real PITA, IMO.

After trying this combo many years ago when the feds were implementing the unleaded fuel and there was no premium fuel available, only octane booster, I proceeded to blow holes in the pistons of 1, 455, and a 428 with pop up pistons. Upon talking with Nunzi, he told me to look for a set of early 70s 400 heads which relaxed the compression ratio back to a reasonable ratio. I found a set of 96 heads which have advertised 96 CC chamber volume, and could safely run those on a 455 race engine. (69 GP dirt track car in my signature pictures).

From then on, I've tried to keep compression down to keep my 455 and 428 combos happy. The reduction in compression can be made up with port work, and careful cam selection. If you get somewhere that you can't buy good fuel, you can trash the engine quicker than you think. Build for easily available fuel, would be my suggestion. Pontiac was able to pull some pretty good numbers with round port low compression engines, namely the 455 HOs, and the 455 SD combos.

I have run 455 HO heads on the street, and the afore mentioned 96s, as well as a set of 5C heads on a 455 short block. These combos aren't octane sensitive when set up properly, will run on 93 fuel, or less. The 5c heads have a fair amount of port work done, and run quite well in a 76 T/A with 3.23 gears, T400.

Round port aluminum heads would be another choice, they flow better than most ported cast iron heads out of the box, and are more octane tolerant.

Exactly, spot on post.
I have a 9.3 455 in the 10s. Do it with the right port work and cam.
My 1970 455 HO engine, well Pontiac called it a HO but its not really one besides the block is a beast. I have the 64 heads and at 10-1 Dan Whitmore told me not to use them . He was a dealership mechanic in the 70s and those engines had a lot of comebacks due to people running regular or a bad batch of gas. Blew holes through he pistons just like you said.
He found me a set of "real" 71 HO heads and ported them.
64s are a great street head in a 400. I have ran as cast 96s on my 455 and got it down to 12 flat.
My brother has a entire 71 400 Firbird engine for a future build that we have never had apart. A Chevy guy just gave it to him to stuff a BBC in it for his criminal act.

[PunchT37]

Been there, done that. 62 heads on a flat top trw piston 455. 230 cam. 225 to 230 on cranking compression. Ping monster. Busted #5 piston, fixed that, got drunk and raced a 71 442. Busted #7 on that episode. Swapped to 6x head. All was well.

[67Fbird]

^^^^ on a set of flat tops....yeah..thats around 11.2+ comp. I'm currently with #62 on a 455 zero deck with -18 cc dish...in at 10.08

[i82much]

Originally Posted by PunchT37

Been there, done that. 62 heads on a flat top trw piston 455. 230 cam. 225 to 230 on cranking compression. Ping monster. Busted #5 piston, fixed that, got drunk and raced a 71 442. Busted #7 on that episode. Swapped to 6x head. All was well.

maybe the OP came here because he wants to get drunk and race oldsmobiles!

[hurryinhoosier62]

Originally Posted by Joshua Paul

I recently got a decent deal on a 455 that was built a year ago and just sat in the corner of a garage. It has the 4X 1H heads (I believe 114 cc) and a comp cams XE250H-10 cam shaft. Motor was never ran. I intend to replace the head gaskets as the owner had pulled one off for pictures. I will also pull the cam to re-lube as it sat for over a year.

Questions or guidance:
1. I have a set of #16 75 cc heads currently on my tired 400. Rebuilt built them years ago and probably only have a thousand miles on them. Which would you use?

2. The xe 250 seems a bit small. Recommendations.

Currently have a slightly above stock stall on the torque converter, TH350 transmission, and 2.73 rear gears.

If it is truly a “stock” rebuild the pistons are .015-.020 “in the hole”. With the 4X heads you’ll be lucky to have a 8:1 c/r. A time tested combination would be 6X-4 heads milled .040-.045( 85-87 cc) with the 041 or comparable camshaft along with Rhodes lifters. You will probably get an honest 400+ hp/500 ft-lbs at the flywheel and a more manageable engine that will run all day on 91-93 octane fuel.

[PunchT37]

Originally Posted by i82much

maybe the OP came here because he wants to get drunk and race oldsmobiles!

True story.