327 piston suggestions.

I have a base model 327 with the small 2bbl set-up. I wanted a retro looking motor so the 2bbl stays on top. I ended up getting a "free" set of power-pak heads for my base 327. I had a set of 305 (1.84) valves installed with 3 angle bevel. Of course I had a set of hardened seat put in. I plan on replacing the original open chamber small valve heads with these prepped power-paks. This cruiser is running a powerglide with 2.73 open gears. I want to run pump gas, so, what I'm looking for is suggestions for pistons.


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There's a guide HERE that shows the end casting differences of SBC heads.

Note that "Power Pac" heads were primarily for the 283 engine.

The high performance head most recognized on the 327's were the "camel hump" or "fulie" heads.

Either of these heads have small chambers, so for street use you will prob. be looking at using dished or D-cup pistons to keep the CR reasonable.

Do you know the combustion chamber and valve sizes of these heads?

you are needing around a 12cc dish piston to make around 8.75:1 cr with a 327 using 64cc heads.

I would use a cast piston.

This compression ratio will work well with a mild cam (200 to 205 degree at 0.050"), stock converter, and a 2.73 gear.

I would go with coated hyper pistons- not that much more cost than cast, but better wear and durability. I wouldn't go higher than 9:1 on compression. And no more cam than about the 260 range (adv dur).

My chambers are 58cc, intake is now 1.84 and exhaust is still 1.50. The runner length is 137 (I think). I'm comfortable buying premium fuel so I think I could go as high as 9.25 CR (gas is cheaper on base). Do you dissagree? I need gsaket suggestions to go with piston suggestions.

With a 'glide and 2.73 gears, this motor will be under considerable load at low rpm's most of the time. If you raise the static compression ratio, you'll have to use more cam to keep the motor out of detonation. More cam is going the wrong way for what you want to do. You need a very short cam that will make good low rpm torque and a very short cam calls for a very short static compression ratio.

I'd be thinking 8.5:1 to 9.0:1 and a cam with somewhere in the range of 205-210 degrees @ 0.050" tappet lift. This would give you an operating range of somewhere around 1200 to 4800 rpm's and as was stated earlier, you could use your stock converter and also make good manifold vacuum to operate accessories like power brakes. I'd set the squish at 0.035" to 0.045".

With a +0.030" 327 using 58cc heads, you'll need a piston with a 20cc dish to make 8.9:1 SCR.

Thanks for the education. This is all voodoo to me. I started looking for dished pistons but didn't find much. Most applications have domed or flat but little or no dished. Any suggestions?

Those "free" heads are getting more expensive by the minute.

Yeah, I think what I would do for a pump gas cruiser is to use these pistons....
http://kb-silvolite.com/performance...details&P_id=43
with a set of 64cc L31 Vortec heads. This would make 9.0:1 static compression ratio. Problem is, you'd have to use an aftermarket Vortec 4-bbl intake with these heads, such as a Edelbrock Perfomer RPM Vortec and ditch your 2-bbl in favor of a 600cfm 4-bbl. By using this cam, you'd have a dandy little tug motor with high torque, just what you need for your application....Use 1 3/4" primaries, long-tube, equal-length headers with an "X" pipe right behind the collectors, then run 2 1/4 to 2 1/2 inch pipes to the rear with mufflers of your choice.
http://www.compcams.com/Cam_Specs/C...px?csid=71&sb=0
RPM HP TQ
1500 110 387
2000 157 411
2500 192 404
3000 237 415
3500 274 411
4000 302 397
4500 315 365
5000 283 297
The motor is all done by 4500. You don't need any more rpm's than that anyway. At that rpm with a 2.73 gear and 28" tire, the car is going 137mph.
The alternative: leave it alone.

Don`t waste your time on power pac heads. They have a 137cc runners and really aren`t aimed at performance use. a set of 416 casting 305 heads would be far better. I would also get rid of the glide and replace it with a TH350, the glide has a high first gear thats not good for accelration especially with real high 2.73 gears. The TH350 would give you far better acceleration as well as mileage since the engine wouldn`t have to labour so hard to move the vehicle.

I'm sticking with the nostalgia look on this motor. It's in a numbers matching '67 Camaro Sport Coupe with 65,xxx original miles. The glide is staying, as are the power pacs without the accessory holes and the two barrel carb. I'm keeping the original ram horns, too. Even though it's just a base model cruiser, I'd like it to run a bit better. No one will know the heads have been swapped (with the valve covers on). The carb has been flowed by a local circle track builder.

The 20cc dished pistons sound right. I really do appreciate the input.

Suit yourself. damned or not.

"I'm sticking with the nostalgia look on this motor. It's in a numbers matching '67 Camaro Sport Coupe with 65,xxx original miles."
.
In the interest of accuracy/nostalgia, if I'm not mistaken, the power pack heads were not used on 327's after 1964.
JA

johnya,

You're right, but who would know without opening the valve covers? I will be keeping original heads, too.

They'd know because of the pyramid cast into the end of the heads.

Camaros didn't come with ram's horns, just logs. They did come with 4-bbl carbs, though, but they were Quadrajets. If you're bound and determined to use a 2-bbl, the 235hp 327's found in the late '60s big cars used a bigger-bore Rochester 2-bbl than what you have. It won't make the power that the Q-jet will, but it'll give you some more airflow and still fake out most folks in the looks department. Might be some of the early 2-bbl 350's used a similar carb, but I don't know for sure.