[spawn_x]

its a 5 speed tkx trans

[jhein]

Originally Posted by spawn_x

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.

[srmmmm]

Originally Posted by SD455DJ

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

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.

[Lee]

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.

[7D4 TA]

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.

[spawn_x]

Originally Posted by 7D4 TA

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!

[spawn_x]

Originally Posted by Lee

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.

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

[JLMounce]

Originally Posted by spawn_x

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.

[steve25]

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.

[7D4 TA]

Originally Posted by spawn_x

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

Thanks!

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

[Jay S]

When the engine is over cammed for the compression there can be pretty large gains in power from a small step in compression. That is the dilemma when engines have small cams and try to put all the power in at lower RPMs. Low RPM naturally aspirated pump gas engines that use small cams usually are stuck to a small increases (around 2%) in power for a point increase in compression. On a small cam combination a stock iron d port making max power by around 4000 RPM, the out of the box Aluminum d port is able to run about .8 higher compression for the same octane of the iron head.

So instead of the 10% gain in power for a half of a point from Lee’s example with a bigger cam, even after the Aluminum head swap, the small cam it ends up being closer to a 2% power gain. It is a gain, but doesn’t match up to the expectations a lot of people expect. It requires more cam to utilize the aftermarket heads extra flow capabilities to see bigger gains in performance. Unless the cam is to big or poorly picked out, often times even fuel efficiency can increase with the higher compression engine that has a bigger cam over the low compression engine with the smaller cam. My most efficient street cars have generally been shift at 5500 or more. If I want to putt around, I just stay out of the throttle.

[spawn_x]

Originally Posted by 7D4 TA

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

where do you live??

[spawn_x]

Originally Posted by JLMounce

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.

great info. Definitely NO plans in doing any bottom end work anytime soon.