Street 455 build suggestions
 

Hello Have been reading A LOT. Wanted to ask, since most advice here seems to be for guys going to 5000+ rpm. I have no interest in ever spinning that high. Max shift point will be at 4500, but realistically 4000 MAX.

1973 Grand Prix 455 with a TKX .68 trans, full weight. XL code, which I believe means 8:1 compressionand an 067 cam, and a wideband o2. Idle is around 18" vacuum with vac advance through manifold, and timing set st 35 at 3k rpm. More than 1/3 throttle and Im at 10-11 afr, and WOT its in the 9s. Holly 4780 carb, and an edelbrock intake (unsure which one)

Goals:
Runs on 89 octane
Daily driver, low maintenance
Powerband idle-4500rpm

Ive read a lot into different cams like xe274 and crowers and such, wirh 10.5+ compression shifted at 5200-5400 - this is not the goal, that will give me poor street performance because I will never see such high rpm.

Heads: kre? Not looking for high cfm porting, 10:1 comp max I would guess for 89? what cc would I need? under 240cfm ?
Cam: 068 seems to have what I would want?
Carb: probably sniper efi
exhaust: currently headers with crush bent 2.25", but wanting to get RA manifolds with mandrel 2.5

Appreciate the advice. I will not be drag racing the car, will not be in high RPMs, and do not want to pull the motor our for pistin or rod work. Not interested in a big cam.

Thank you!

Everything you’re telling us about to me makes me say that you want a stock 1973 455 but with fuel injection and RA exh manifolds .

Rebuild your 4x heads top to bottom if they pass a crack detection test and put in a new timing chain & gears and go have fun driving .

Isnt 8:1 pretty low on the compression?

If you are going to run a smaller camshaft, I'm not sure that KRE heads are really needed. A good set of 6X's should do everything that you want to do. An 068 cam or a Summit 2801 would work well, idle smooth and pull hard to 4,500 rpm nicely.

It sounds like you're wanting to do the top end only. Based on your stated goals, even the out of box KRE and Edelbrock D ports may produce more top-end power than you're looking for. However, that doesn't necessarily mean you have to use it and it also doesn't mean that the engine is going to lack anything in the lower rpm range. My previous engine was a +0.030 455 with a set of as cast KRE D ports, a smallish roller cam and a torker ii manifold topped with a FiTech system. It made power to about 5500 rpm and I never wanted for torque anywhere.

I would be inclined to run Butler's "744" hydraulic roller in this engine with a set of 1.6 ratio rockers. In the bigger cube 455 with a Performer RPM intake and a set of out of the box KRE D-ports, you probably make peak power in the mid to upper 4000rpm range.

https://butlerperformance.com/i-3164...tegory:1459689

The 068 hydraulic roller would pull that down even further, maybe too much based on the cubes.

The RA manifolds with a 2.5" mandrel bent system with a cross-over (H or X) would be good here I think as well. If you're definitely planning on a throttle body injection system, whatever you end up doing, make sure the exhaust cross-over is removed. The throttle body systems don't like, or need the heat from the cross-over.

You need a bigger cam, even though you think you do not.

Thanks! Main reason for kre or edelbrock heads are, the prices on 6x heads are pretty high up. Butler wants 2300 for two 6x heads, at that price why not go with an unmodofied aluminum casting, that was my thinking. Lighter, better design, screw in studs.

Agreed, at that price point, there's not much reason NOT to go with a KRE or Edelbrock D port.

Especially with these heads though, a smaller cam doesn't always do what you think it's going to. From your original post it sounds like you want to maximize power within a shorter operating range.

In these builds it's not necessarily that going to a smaller cam will create more torque sooner. In many cases, going to a somewhat larger profile cam will not only create the same amount of early rpm torque, but carry that torque further. 455 cubic inches is a lot; the engines soak up a lot of cam duration and are simply happier with more cam in them.

You didn't say if you were set on flat tappet or roller cams. My personal opinion is you need to shoot for @0.050" durations around 230-234 on the intake and need your gross valve lift with the KRE head between .525 and .550. You'll make over 500 ft lbs and it'll be basically available everywhere.

I would run a set of KRE heads at 10.5 compression and stick to a mild cam and you will get 20mpg plus.

Go with the KRE,am disappointed with the E dports I just bought.Tom

That is the highest price I have ever heard of for a 6X head. Maybe look around before you give up on them.

I paid $200 for the 6X head on my car a few years ago (2020), and they came with a 400. I see them frequently on marketplace for $200 to $600. Sometime even freshly rebuild. Doesn’t sound like aluminum heads are offering much if you only want to rev the engine to 4500.

I have not looked at FB marketplace, but ebay they are going for 1500/set. Theres usually nothing poncho related on craigslist, but FB may be worth a try. Also afraid to buy a used head that turns out to be cracked.

Look up Phillips Muscle car parts. They ship and have a set 6X-4 for $600. 6X are not easy to crack, it is the toughest head Pontiac ever made. As far as I know anyway :) 4X is the heads that like to crack.

https://www.facebook.com/share/1AdTZ...ibextid=wwXIfr

https://www.facebook.com/share/1AjD7...ibextid=wwXIfr

https://www.facebook.com/share/1DMw9...ibextid=wwXIfr

Unfortunately $2300 is the going rate for a set of done heads through a quality builder, I’m not at all surprised by that number. If someone were to buy a set of 6X’s for the typical used price of $500 then send it to a machine shop & add rebuild cost it works out the same, there’s no free lunch anymore unless you have a buddy at a machine shop.

Is the bottom and of this rebuilt? If not, I would save up for a rebuild top to bottom.
If it is in known sound condition, I’d pull the heads and have the rebuilt and take some determined amount off of them to gain a little compression. If HFT cam, run the 068 cam, some Hylift Johnson lifters and the 2.5 exhaust and enjoy.

$2300 for 6x heads??? Is that ported from Butler? Seems extremely high for stock rebuilt 6x heads.

6x-4 cores are $250/pr all day long, 6x-8 are even less at ~$100-150/pr. A good 3 angle valve job even with new guides & valves does not cost anywhere near $2000, at most shops in the midwest a set of pontiac heads can be rebuilt for basic street use for well under $1000.

For the OP's stated purpose of low rpm & low compression use, rebuilt 6x or 5C (same basic head) heads would be fine and save a lot of $$ over KRE or E-heads that the extra flow isnt really needed for this purpose.
I had unported 6x-4 heads on a 455 back in the 90's that ran great with lots of power, a mild comp 280 magnum cam, 2000 stall, could smoke the tires at will and ran in the upper 12's, but also drove around town as a daily driver almost like a stock engine, very tame idle, and decent MPG for that size engine.

For the stated use, just keep it simple & save some money to put towards other things on the car, a good set of iron heads will do everything you mentioned you want. IMO.

I think at one of my friends places there should be a set of small valve 98cc 4X/4c 1973 heads someplace here. Would be a nice head for a mild 455 pump gas engine that spends its life below 4000 rpm. I could drop them off at my friends machine shop and have them mag’d, freshened up with new valves, positive seals, surfaced, and they probably wouldn’t even be a grand shipped back to you for everything. The shop is called the Horsepower Genie out of Falls City, NE. He does engines projects from all over the country.

Stock heads rebuilt by Butler $2295

https://butlerperformance.com/i-3164...tegory:1234782

I bet that helps sell Aluminum heads.

If you end up with KRE heads , be advised you will need to helicoil all the fastener holes. For some reason, they don't use them at all in any location. I do the intake and exhaust manifold holes, rocker arm studs, valve cover rail and the front accessory attachment holes. Other than that, they are nice heads.