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.

That’s a bunch of work/expense tapping for all of those different sizes of Heli-Coils and installing inserts.

One wonders why they don’t offer that as an extra cost option. It wouldn’t really cost them much more to just use the correct insert taps and then tap all the holes for inserts on the CNC during the machining process. Then give you the option of having them install the inserts or let you handle it.

I just paid $1213 for a complete rebuild of my #12 heads...clean & mag heads, resurfacing deck and exhaust surfaces, install brass liners, cut for seals, hi-perf street valve job, new Ferrea 1-pc SS valves (16), new CC dual valve springs, retainers, & locks, two separate washes, and assembly at a very competent shop. This price includes 6% sales tax too.

Dennis

That sounds far more like it !

That Butler price of 2300 includes the iron heads not just rebuilding a set.

It seems like the stock engine already hits your targets. Since you have the 5 speed overdrive, why not just put in new rear gears? At least 4.11, maybe even 4.56.

What is the issue with fastner holes?? I cant say Ive heard this mentioned. Not a small project.

Thanks for the lwad on the 6x heads

I put OD not to be at crazy high rpm on the highway, gear like that would put me back up there ??

I do wish I went with the 3.27/.72 version tho, for anyone considering the tkx.

I had a friend with a 455 powered 1965 GTO convertible. He had a 200-4R transmission in it with a 4.11 rear end.

First gear was useless, couldn’t get traction.

After switching to a 3.08 rear end gear the car was much more driveable and enjoyable.

Still seems priced extremely high... so if a good 3 angle head rebuild is $1000-1300, that still means they are charging $1000 for a set of iron 6x-8 heads. :eek: No thanks. For a few hundred dollars more you can buy an assembled pair of edelbrock D port aluminum heads from summit.

There is not a direct issue with any of the fastener holes. However, if running spring pressures over 150 lbs. on the seat and 300 Lbs open, pulling aluminum stud threads out is pretty common. When using stainless steel fasteners such as ARP, the bolts will often gall and pull out of the intake/exhaust/accessory bolt holes. Using a liberal coating of anti-sieze will help some. When fitting headers, it is common to have a little trouble starting some of the bolts. Aluminum threads are much easier to cross thread or strip than a heli-coil. Accessory bolt holes tend to pull out over time with all the load on the brackets going into aluminum threads and heads. When spending over $2000.00 for a set of heads, it would be a nice touch to have fastener holes that can hold up to several installations/removals without everything being stripped out. It's just part of making a quality product IMO. I like the KRE heads, but feel this wasn't the best place to cut corners. Even the cheapest of the cheap Speedmaster heads have some heli-coils factory installed. (rocker stud and exhaust holes).

My quick math of typical parts prices comes up with right at $700.00 worth of parts alone! That's at discounted Summit type prices. If they are doing all that shop work for only $500.00, their shop labor rate must be about $75.00 an hour. That's one heck of a deal. No idea how they stay in business at that rate in this economy. Around here, the parts and work you describe would be at least $1600.00-1800.00.

While I do think helicoils would be nice. I want to point out that my experience with the KRE D-ports has not suffered by not having helicoiled fastener holes.

I've had the heads for 10 years at this point and haven't had a single issue at all with the heads as supplied by KRE. Spring pressures around 145 on the seat.

Mike, parts were $522, labor at $691.

Dennis

Smoking deal on the parts, and a very good deal on the labor. I am a warehouse distributor for Ferrea and I can't buy that stuff for those prices!! Fantastic!

My .030" over 455 with 068 cam, '96' heads, 1.6 rockers, Rochester, 1 5/8" headers, cast iron intake, turbo 400 and 2.73 rear is a lot of fun to drive and gets about 12 mpg cruising at 67-70 with the air conditioning on. It also pings a lot on 93. I'm still dialing it in and need to play with the timing and add some sort of cold air system too. The idle is super smooth and I think I could of gone bigger in the cam department.

Paul (GTOFreek) has previously advised on here of the threads pulling out on KRE heads.

Oh and the my combo made 367hp and 524 torque. The power plateaued at 4400 and began gradually falling off after 4500. The torque was 524 at the beginning of the pull at 3000 and gradually fell off gradually.

great info!!!

I daily drive a Bonneville with a 455. Heavier than your GP, but close. This car tickles 4,000 RPM maybe once or twice a week thanks to the super tall gears in the back. I think I should chime in.

I put a Comp XE cam in it when I built it 4-5 years ago and I hated it. Switched to a Summit 2802 and it's been a blast. Good idle vacuum, runs the A/C just fine, and the TH400 doesn't complain too much. With a manual it would be perfect, maybe with some 3.23 gears for a nice cruising RPM. I get about 11-12 MPG with the A/C on with 87 octane.

There's users in this thread that are a lot smarter than me that can give you a better opinion, but I'm really not sure aluminum heads are what you want for what you're going to use this car for. For a street car on 89 octane, aluminum heads are total overkill IMO. You're not trying to win any races, 4x heads are great. Keep the CR around 8.5:1 and the 2802 will love it. Definitely start asking around some machine shops near you for some prices to get those heads worked on, you might be surprised. I may be biased but I find it a lot more satisfying to keep old iron in use than replacing it.

I have to agree that you don’t need aluminum heads to make good low-end power with a 455…and keep it affordable. You can get great power from the cheap and readily available 6X-8 heads. As mentioned previously, you need more cam, like the Summit 2802 at a minimum. The only place a factory 067 cam makes more power than a 2802 is from idle to 1500 rpm.

Here’s an actual dyno comparison of two 455’s using the same short block and cam (Summit 2802 & lifters) with different top ends…the first is with the original 1970 small valve 455 #15 heads and log manifolds (the standard 1970 Bonneville engine 360hp/500 lb-ft). The untouched #15 small valve heads had 90 cc’s finished (9.94 to 1 compression) with 195/145 cfm approximate flow. It dyno’d at 390 hp at 4600 rpm and 512 lb-ft torque at 3400 rpm.

I later switched over to ’71 455HO heads/intake/carb/RA exhaust manifolds. The 455HO #197 heads were also untouched originals with 108 cc chambers finished (8.60 to 1 compression) with 225/175 cfm port runner flow. I was surprised it made a bunch more power with a 1.4 drop in compression, but better flowing heads and exhaust. It made 431 hp at 5000 rpm and 535 lb-ft torque at 3500 rpm. It made a little more torque down low than with the small valve higher compression heads. Both combinations had the Felpro 1016 head gaskets (0.039” crushed thickness) to provide 0.040” quench.

The same engine with stock 6X-8 heads (more common and cheaper than the 6X-4 heads) would wind up somewhere in between power-wise, or around 410 hp at 4800 rpm and 525 lb-ft torque at 3500 rpm. The 6X-8’s have 100-102 cc chambers uncut, and after a truing cut gets them down to 98-99 cc’s netting roughly 9.25 to 1 compression on a 455 that is zero-decked.

Dennis

The way I would approach the question regarding the cam is to ask what is the biggest cam I could use and not need a stall converter. Maybe that's what you have now, maybe a little bigger, I don't know. Seems like a cam such as that would also have plenty of vacuum and would given you the best possible mid range power.

its a 5 speed tkx trans

Sorry. Don't know why I thought it was an auto. In that case, I'd still go with a bigger cam. :)

I agree with the 6X head option. have been very happy with the 6X-4 heads on my stroked 350/413. Only mod was port match on the Torker-I intake. Comp XE276 cam with 224/230 @ .050 with .502/.510 lift on 1.5 rockers. Compression came out around 9.3 to 1 with pistons at zero deck. No issues with 92 octane fuel and 442 Lb Ft@4300, 453HP@5600. TCI Breakaway converter with 2200-2600 stall and 3.23 axle. Running Hedman long tubes with Pypes 2.5" X system.

My motor is pretty basic, some specs in the signature below. 455, unported "66" heads with pressed-in studs (I've recently drilled/pinned them) with non adjustable valvetrain.

The dyno graph shows my motor at 7.8:1, and then again after changing pistons to bump it to around 8.3-.4. All runs were done on 87 octane.

Throttle response is instant. Motor stays around 175 degrees unless it is really hot outside. I have a FAST XFI Sportsman EFI system. If you go Holley, I'd suggest going Terminator with the matching distributor.

I may have some stock 6x Butler heads if you’re still looking. New in the box, only brought down to 91cc by Butler. I’m going to a ported Kauffman head. Let me know if you’re interested.

hi, anymore info? 6x what? screw in or pressed studs? valves or bare? price?

Thanks!

Am I understanding right that you got about 30hp/tq just by going from 7.8 to 8.3-8.4??

There's a lot of variables at play, but anywhere from 3-7% power increase for a full point of compression. The returns diminish though, so you wouldn't necessarily expect 10-20% for going from 7.5 to 10.5 for example.

However, you you achieve the the compression increase also matters. What if the head design gets more efficient through a modern head? What if the pistons are lighter, maybe coated, or have a thinner ring pack?

All of those things work in your favor. But if the compression was increased through something like milling of the head and no other changes were made, those small increases in power could be realistic.

Percent of power gain or loss.

All 6X and 6S heads have screw in rocker studs as does all the previous 5 serise of heads.

They are Butler 6x heads, screw in studs , ferrea valves etc… resurfaced to 91 cc by Butler. $1400 plus the ride…. Still in butler boxes…. Was going to get them ported but Butler is 6 months out and 2-3k to fully port them