[bignate]

I just picked up this set of ‘71 455 HO heads and trying to decipher what I’m looking at. They do not have an external date code. I have not cc’d the chambers yet but will soon, and I’ll report back here with my findings.

If you look at the pictures the spark plug placement in the chamber looks like RAIV and obviously the chambers are much shallower than most 191/7 heads. They don’t appear to have been excessively milled either.

Thanks, Nate

[Mike Kasparian,Sr.]

Untouched #197 heads should cc approximately 110 cc . If you can post a picture of the chamber edge opposite the spark plug might be able to tell . Hard to tell from picture but they do look a little shallow there .

[74SDformula]

Very interesting for sure. Maybe post a few more photos when time allows. Intake ports look like they have definitely had some work done on them.

[Joe's Garage]

Possibly they've been milled to bump the compression.

I'm not sure how to check that, other than CCing a chamber.

I'd do a sonic-check to get the deck surface thickness and compare it to non-modified heads.

[Mike Kasparian,Sr.]

Maybe somebody angle milled the heads

[bignate]

They for sure have had a bunch of work done… I was told by the previous owner it was done by Diamond-Elkins in the late ‘70s.

Just going by a measurement off the lower accessory hole (I know it’s not super accurate) compared to a untouched head, they may have been milled .050”.

What has me puzzled is the spark plug location in relation to the chamber floor. There is a large space between the spark plug and the intake valve seat on a normal HO head, and these are just as close as a RAIV head.

I’ll attach another angle of the shallow side of mine and a picture of a normal HO chamber.

Nate

[Mike Kasparian,Sr.]

Looks like somebody did some chamber work , smoothing out the sharp ridges and if you look close unshrouding the spark plug . Maybe that's why it looks so close .

[JSuchma]

A classmate of mine got a pair of 197's from H.B. Bailey in the late 70's , [H.B. raced on the nascar circuit for Pontiac in the early 70's]. They had RAIV chambers with extensive port work and Pontiac experimental stampings on them. Wish I had gotten pictures of them!

[bignate]

Originally Posted by JSuchma

A classmate of mine got a pair of 197's from H.B. Bailey in the late 70's , [H.B. raced on the nascar circuit for Pontiac in the early 70's]. They had RAIV chambers with extensive port work and Pontiac experimental stampings on them. Wish I had gotten pictures of them!

Do you remember where the stampings were? There is a # starting with ES stamped on the center exhaust ports on these.

Nate

[JSuchma]

Sure don't. I will try and contact him for some pics.

[25stevem]

I agree, those would seem to be a experimental casting with the 1969 to 70 size chamber.

I believe Pontiac engineering did cast up such during the LS2 testing program.

I don't even think you could angle mill a 197 or 7F6 round port 455 head enough to get that shallow of a lip on the non spark plug side!

The push rod holes have been sleeved I see

Too bad the chamber eye brows have been far too rounded over, that will now effect re-atomization of wet flow on the Intake side which effect burn rate and in turn the chambers knock resistance .

The valves are pretty darn sunk also.
Not so much I big deal for the Exh, but its murder to Intake flow numbers.

Those heads are now a good candidate for custom 2.14" Intake valves!

Have you CC'ed any of the Intake ports to see how much larger they are now then the stock 174?

[74SDformula]

bignate, I have a pair of 614 casting heads that have a DS number stamped on the center exhaust port close to the gasket surface. Are your heads stamped in the same place?

[bignate]

Originally Posted by 74SDformula

bignate, I have a pair of 614 casting heads that have a DS number stamped on the center exhaust port close to the gasket surface. Are your heads stamped in the same place?

Yes right on the ledge at the gasket surface. I thought maybe it was done by whom ever did the port work.

Nate

[Skip Fix]

The guy I bought my RAIV heads from here in Houston in the late 80s had a 79 TA he street raced with a 455 with some round port HO heads. He also said they had small chambers. He worked at a Pontiac dealership.. Some of the other local guys that knew him said my RAIV heads might have gone "out the back door". New SR 614s bare.

[JSuchma]

Hey Skip, thats the guy I am refering to. I went to high school with him and his parents were loaded! He bought whatever he wanted, infact when he bought that 79 TA he loaded it on a trailer at the dealership and stopped by our house on the way home. Had the sticker still on the drivers window. When he left he went straight home and yanked the original, no miles motor out!!! He never worked at a Pontiac dealership! He got them from H.B.

['ol Pinion head]

Originally Posted by bignate

Yes right on the ledge at the gasket surface. I thought maybe it was done by whom ever did the port work.

Nate

Hope you can CC a few chambers. Need a bunch of pics & measurements of virgin, never surfaced 197's, let me know. Would be interesting to know if your 197's had been angle milled or just surfaced a bunch.

Originally, Pontiac Engineering was to release the 71 455 HO engine with round port heads w/ advertised C/R of 10.25-1. As the '71 Pontiac Performance engine lineup had been in the works for well over a year, it would not surprise me that these heads are truly Developmental Series 197's. That will def be the case, lets say, the chambers CC in the mid to upper 70's range, that wouuld equate to a high 80's cc chamber heads that had been cut .050.

Due to corporate edict on dropping compression ratios, I'll dig out the sheet for the date,but believe it was late in Feb 1970 when the '71 usage 10.25 CR 455 HO LS5 was cancelled.

[Skip Fix]

I got it Jeff , some one told me he worked at a dealer.I picked up the heads at his house-nice garage.

With the Holley, Warrior intake, sticky Hoosier dirt track tires it was a bad ass street racer. Heard the windshield popped out on one launch.

[JSuchma]

Originally Posted by Skip Fix

I got it Jeff , some one told me he worked at a dealer.I picked up the heads at his house-nice garage.

With the Holley, Warrior intake, sticky Hoosier dirt track tires it was a bad ass street racer. Heard the windshield popped out on one launch.

It was running mid 11's in the late 70's with a big hydraulic flat tappet and stall conv. I tried to buy those heads about a year ago, but he would'nt let go of them!

[25stevem]

If the head bolt pads are no longer perpendicular to the deck then that would be a definitive sign that the heads where angle milled , at least to some degree.

[Skip Fix]

He also had a 12 bolt under it with the 79 rear discs.