[REFORMULATED]

My 6X-8's will need to be completely rebuild, new valves, guides, springs, keepers, and at least 6 seats probably all of them are toast. Some genius ground at least 6 seats too low and cut the valves down to far to compensate, throwing my valve train geometry off, see link to my post that has all the sad details. When you add it all up with the machining costs, my time, it's not much less than buying a brand new set of KRE aluminum heads. My 70 Formula with .030 over 73 455 block has a standard flat top pistons, Crower 60918 cam (see specs below) Ram Air D Port Repop Exhaust Manifolds, Repop Two Piece Ram Air IV intake Manifold, M20 with 3:08s and a Cliff build Quadrajet. This car is a driver, not a track car. I'm leaning towards buying a fresh set 85cc heads from KRE rather than finding another set of 6Xs or rebuilding mine. Would rather buy from Ken and Jeff than Edelbrock. While I know you can run a higher CR with aluminum heads, with 101 vs 85cc chambers will my CR be too high to run crap CA gas? I'm thinking it will be in the low 10:1 range? Any other issues other than maybe adding an electric choke I should be aware of ? My old, fused, back and neck sure are in favor of ditching the old iron heads.

All input welcome.

Cam specs are:

288/298 Adv. Duration
444/467 Gross Lift
112 LC

http://forums.maxperformanceinc.com/...d.php?t=788247

[Will]

If you don't mind spending the extra dough, that's a great choice. They will give you a definite performance improvement.

You should be fine up to 10.5:1 or thereabouts. Aluminum heads can go about one more point of compression higher than iron, and in fact you need more compression with an aluminum head to make the same power as an iron head (if all else was equal). In other words, if you could run 9.5:1 with iron heads, you'll be fine at 10.5:1 with aluminum. Throw in the KRE head's superior chamber design and the much better flow and you should get a very nice performance bump.

Do you already have the cam? Seems pretty small in a 455 to me. You could easily tack on another 6-10 degrees intake duration and maintain a tame idle and good vacuum.

[blykins]

+1 on the KRE heads. I love old factory iron stuff, but at some point, it's just cost effective to go another route.

If you know your piston specs, how far they are below deck, etc., then we could get a more accurate measurement of what your compression ratio would be.

The extra flow will make it easier for the existing camshaft to make horsepower. With no change in duration, the engine should peak higher. With a 3.08 gear I don't think I'd get too carried away with the camshaft. I'd probably leave the camshaft alone.

[nas t eh]

If you get the KRE heads maybe have them set up for/with 1.65 rockers as well. Lift would be 488/513

[pontibeast]

Just had my 6X-8 heads completely redone....ported to 250/220, exhaust valves from 1.66 to 1.77, milled to give 9.7 SCR, new exhaust seats all around, new Viton seals and with Ferrea valves, comp spring setup for .650 list and all machining and labor was 1400, including the port work. I used Marty Warden and he was great to deal with. If you are interested PM me and I will give you his number.

[panhead59]

X3 on the KRE heads. I, like Pontibeast, have just had a set of 6x heads redone completely for a 455, for a total cost of around $14-1500. That was including $400 for the heads themselves, which had SOME of the work already done. So if you are interested in performance, as it looks like you are, and don't mind an extra $5-700, then I would go with the KRE's. I wish I would've. You are gaining what 40-50 HP and NEW heads. Even if the 6x's are completely redone, they are still 40 something years old. Just my opinion.

[71 T/A]

I was faced with the same decision and chose to keep my original 62s on my 69 GTO. Had Dave at SD port the iron heads to flow 268/223 @.600, which is real close to out of the box KREs and maybe a bit more. The cost was 1600-1700. It was going to be like 2800 for the KREs and new bolts. Plus my car looks all stock if you care about that stealth look.

[Chicagogoat]

If you go for the KRE D's then you may as well select a higher lift cam. SD performance seems to build great cnc'd KRE's and they have a cam program to match the range of power you're looking for.

[72blackbird]

Ported iron heads with the right cam can get 475-500 hp from a 455- pretty much what a set of out of the box KRE heads can do. Other than the weight reduction, the main advantage of going with aluminum heads is the potential for increased flow even exceeding heavily ported iron heads. I went with 325 cfm CNC ported e-heads from SD Performance, but SD and other well known Pontiac parts vendors offer 295, 305 and 315 cfm CNC ported KRE heads that can push the power level into the 550-575 hp range.You may not need that much power, but anyone who does sure is enjoying it.

Geno

[besserspat]

I was in a similar bath last year, being Canadian the price of the SD 295 KRE was a bit much to swallow around 2400$ US back then , which is about 3150 $ in Canadian pesos these days...

while going back and forth with the idea of shelling that kind of money in heads only ( You still need rockers, pushrods, lifters, cam, timing chain etc etc ) I stumbled on a set on SD performance CNC ported 46 heads, flowing 257 cfm and a very few miles on them for 800$. It was a no brainer for me.

There are good deals on properly ported iorn stuff out there,,,but its your decision its YOUR car.

As much as Id like to have another 50 hp and 46 pounds less off the nose, Im running nitrous and that will make up for it, for the weight , It would have been great , but the car has been lightened in the nose by a fair amount.

One think that very important for me is the period correctness or at least from the first look, of the parts on my old cars...I like the feel, the smell and look of my old time machines... when I install a tach I try to find an old Sun or Stewart Warner tach ,when I put a bar I make it 60s style...

Maybe I refuse to evolve or outdated but I love the time travel when my old toys offer me....

Peter

[Scarebird]

I bought my KRE's for the modern combustion chamber - cannot reshape the archaic iron head's chambers.

[Sprocket]

This is a no-brainer to me. KRE's all the way. If I were you, I would take the opportunity to move one step up in camshaft and get the Crower 60916 (assuming you want to stick with Crower), it has 221/229 @ 0.050", .455"/.470", 112LSA. Will idle smoothly, give you power throughout the whole 455 engine rev range, and allow the engine to really make use of the KRE's.

[tom s]

Dave thinks that 10.25 is good with the KRE Dports and our 91 gas.I would go even a little more with the cam though.232-236ish at 50.In mine I liked 236-242 with 3.55s and a M20.Tom

[ta man]

I routinely run 87 octane in mine at 10.25

[hurryinhoosier62]

Originally Posted by blykins

+1 on the KRE heads. I love old factory iron stuff, but at some point, it's just cost effective to go another route.

If you know your piston specs, how far they are below deck, etc., then we could get a more accurate measurement of what your compression ratio would be.

The extra flow will make it easier for the existing camshaft to make horsepower. With no change in duration, the engine should peak higher. With a 3.08 gear I don't think I'd get too carried away with the camshaft. I'd probably leave the camshaft alone.

X 2, Brent.

[Skip Fix]

To help choose -go pick up that 6X-then go pick up an aluminum head!. Why my ported 6Xs are on the shelf and I'm using aluminum heads on the new 455 for the 81.

[i82much]

C'mon guys. This guy needs tiger heads, a billet crank, a victor with a dominator and a lenco STAT.

[pontibeast]

Sounds good to me too, as soon as I win the lottery it's what I would go with.

[Jim Doran]

When you add it all up with the machining costs, my time, it's not much less than buying a brand new set of KRE aluminum heads.

No brainer on which performs better, but don't kid yourself they are close in price, especially when you add up all the bits and pieces on top

sdperformance.com

CNC Ported 255-265cfm D-port cast iron heads pair $ 1525.00


KRE 295cfm CNC Ported D-port head each $ 1385.00

[REFORMULATED]

Jim, You hit the nail on the head, while on the surface they appear close, but when you consider shipping, head bolts+studs+other items needed, it's a lot more. Going with #96's from a Forum Member, then will be ported-built by Marty Waldren. Should run pretty well and will still look correct. However he is less than all the quotes from my area (Northern CA). Will post pictures and results soon, Thank you everyone for all the help :thanx

Originally Posted by Jim Doran

No brainer on which performs better, but don't kid yourself they are close in price, especially when you add up all the bits and pieces on top

sdperformance.com

CNC Ported 255-265cfm D-port cast iron heads pair $ 1525.00


KRE 295cfm CNC Ported D-port head each $ 1385.00