[punkin]

Hello all,

I picked up a really clean set of #13 heads a few weeks ago. The price was too good to pass up. I really don't know much about them except they do have screw in studs. It appears as though there has been some mild bowl and runner work on them but nothing really aggressive.

Any thoughts on using these on a performance street built 455 (462)?


Thanks,

[Lee]

You'll need dished pistons. I've cc'ed 3 sets in my life, all were around 77cc's. Very good for compression on a 400, but WAY too high for a 455 with typical flat-top pistons (unless you are going to run E85).

[PunchT37]

Yep. I ran 62 heads on a 455. Had to run 100LL gas in it. 13's and 62's are basically the same thing.

[punkin]

Thanks a bunch guys.

[steve25]

13s flow better then the casting 64s that came on the first 455s in 1970 and they have a bit more Intake port volume also which helps with the 455.

[Cliff R]

Excellent head for a 389 or 400 build, but not for a 455. The 13's will have larger chambers like the 62's did. Most I've cc'd here were closer to 78cc than 72cc. Different story for their #12 counterparts used on the manual transmission 400's that year. Those have much smaller chambers.

In any case I'm not a big fan of using a huge dished piston to lower the compression on a 455 build just to use the early small chamber heads on them. Far better to use a flat top piston and larger chamber, then take steps to establish very tight squish instead........Cliff

[Lee]

FWIW, the 455 in my old '67 Firebird (in signature) had Speed Pro pistons with a rather large dish machined into them, so that I could run pump gas with the 72cc "16" D-ports.

I was worried about the pistons being so much thinner. I used very fine sandpaper to smooth over the sharp edges, then applied a thermal barrier coating to the tops of those pistons. Although I sold the car 12 years ago, the new owner and I have a mutual friend whom I talk to about once a year, and last he mentioned it was still running!

That said, I agree with Cliff, and would rather use a flat top and heads with a proper chamber size. But I had limited options when I built that motor, ~20 years ago.

[Formulajones]

Yep, I've machined dishes in these things before, works fine that way.

This little pure stock 400 with 12's and 3.31 gear has a mild dish to keep compression friendly, has no trouble making enough power to push the bird (@ 3,840 lbs) to bottom 13's on a warm day. Pass corrects to a 12.78 @ 106. Just need the weather to cooperate.

https://youtu.be/er1z7PpqsnY

[Cliff R]

"at said, I agree with Cliff, and would rather use a flat top and heads with a proper chamber size. But I had limited options when I built that motor, ~20 years ago."

The ONLY 455 engine built/dyno'd here that came up short on power for the combination of parts used dished pistons and small chamber heads. Everything else was in place, tight squish, etc, but it just didn't make the grade on the dyno compared to nearly identical engines we had done previously. Even with that said it made good power, but with all the stops out and our best tuning efforts came up about 30hp/45ft lbs short of where it should have been.........FWIW.......Cliff

[Formulajones]

I don't think I'm giving up anything when compared to other factory stock RAIII's that are actually running more gear than I am, and most likely more compression.

Matter of fact, I'm pretty confident that with more gear in the car, I'd be right on par with the quickest of the RAIII's that are currently competing.

[Squidward]

Go get a pair of 6x's for your 462. Put the #13's on a 350, and put it in a truck.

['ol Pinion head]

Originally Posted by Formulajones

I don't think I'm giving up anything when compared to other factory stock RAIII's that are actually running more gear than I am, and most likely more compression.

Matter of fact, I'm pretty confident that with more gear in the car, I'd be right on par with the quickest of the RAIII's that are currently competing.

Jones, can you relate what cam you are running in your '70 RAIII Formula?

[Formulajones]

Originally Posted by Squidward

Go get a pair of 6x's for your 462. Put the #13's on a 350, and put it in a truck.

funny chit!!

[Formulajones]

Originally Posted by 'ol Pinion head

Jones, can you relate what cam you are running in your '70 RAIII Formula?

I'm running the stock blue print 068 cam from Melling here....

https://www.summitracing.com/parts/m...w/make/Pontiac

[Skip Fix]

HO Racing even sold TRWs with a dish machined for using smaller chamber heads.

"The ONLY 455 engine built/dyno'd here that came up short on power for the combination of parts used dished pistons and small chamber heads. Everything else was in place, tight squish, etc, but it just didn't make the grade on the dyno compared to nearly identical engines we had done previously. Even with that said it made good power, but with all the stops out and our best tuning efforts came up about 30hp/45ft lbs short of where it should have been.........FWIW.......Cliff "

I think we can have a wide variability of factors that can do the same thing. Look at all the guys that have tried to copy Jim Hand's motor same cam heads etc. that were way off performance.

When I built my first 455 using fairly stock RAIV heads we dropped the piston down almost .100 to kill compression-still needed some race gas in it. UD 288/296 HFT, HO intake, Q jet 2" Hookers. It ran so well on a very conservative dyno the machinist built a very similar 455 with ported 6X heads, 0 deck, same cam, an HO intake and Q jet that was 30 HP off mine so go figure-no quench at .100 down, head flow probably a little better with the RAIVs and the rest the same made more HP.

[Skip Fix]

That 455 made enough HP to run 117-118 mph weighing 3900 lbs.

[steve25]

I don't think there's anything cut in stone with regards to how factors / things are intertwined with the 455 and it's fast piston speed due to its Bore to stroke Ratio and how it makes the cylinder pressure rise with different Cams!
Your example of having the Pistons .100" down in the hole and the relation of how air flow balances against compression makes it clear that the 4.210" stroke makes the 455 demand high levels of air flow to make great power more then it's needs for compression!

[Skip Fix]

It was a rattling fool in the summer if I did not have enough race gas in it! Autocrossed the heck out of it and then ran in in the old NMCA Modified stock class until they dropped it and I could not run RAIV heads on a 455 and switched to a 400 short block.

[slowbird]

From my personal experience small chmber and dish piston was the way to go. Made huge power. Every engine is different though

[Formulajones]

While we're on the subject, Tony had these dish pistons made for dads combo, in conjunction with the old bathtub combustion chamber Edelbrocks that he opened up to 89cc.

Compression is a pump gas friendly 10.84:1 and it only wanted 34 degrees of timing for best power.