I just built a 402 B.B. Chevy for my 69 Camaro. It has a 4 spd, and a 12 bolt posi. I built it with forged domed pistions, 294 solid Comp Cam with .595" lift, open chamber heads, and a Edelbrock Performer Rpm dual plane intake, and a 750 Holley double pumper. This combination runs respectable, but I am disappointed in how the camshaft sounds. The block is decked and I am estimating that I am running around 8.5 to 9.0 to 1 compression. It makes excellent power from 2000-6500 rpm. I feed it 42 degrees of full advance and it does not ping at all! I am debating about installing a set of closed chamber heads from a 70 454/390 hp. They are originally the bigger 2.19 intake valve, I am not sure if the intake is 1.72" or 1.88". They are professionally ported, with about 80 hrs worth of port work. I have always heard that open chamber heads flow better, because their chamber design does not shroud the valves. But my compression is so low, that I think I would benefit from the smaller chamber heads, and also the bigger valves. I am looking for the killer sound in either a BIG hydraulic such as the 305 Comp Cam or a BIG Solid to go with this swap. Does anyone have any suggestions?

first off, you said you have open chamber heads on the car now, correct ? well, it's not that easy as just switching heads, like on a small block, you also have to match up the pistons. if you go with closed chamber, you have to run pistons made for closed chamber heads. now i know i'm going to go against what i just said, but i'm running open chamber heads with closed chamber pistons. this you can do, but for what you want to do, i believe you will need new pistons. also, a cam that big may need a little more compression. i was looking at solid cams made by comp cams and it looks like they all use higher compression then what you have. somewhere around 10:0 on up. have you called comp cams up and talk to them about it ? i'm running the 294x-treme cam in my 408 and i was told by many that, the cam is to big, but because i'm running 11.5:1 compression i'll be ok. i also think that the 305 cam is too big for your engine, especially with that low compression. call up comp cams and tell them what your looking for and i'm sure they can help without having to switch heads.
good luck,
bruce

ok, you have open chamber heads right now. I would keep them and put money into port & polish and 3-angle valve job for them. Open chamber heads do flow better and have a better combustion and more complete burn thereby resulting in a greater potential for power. Plus, you have to remember that air velosity is equally inportant to power as air flow. Putting too big of a cam in your motor can actually make it run worse. If you are looking for street performance, stick with a moderate grind that matches the other work done to your engine. Good Luck

<BLOCKQUOTE>quote:</font><HR>Originally posted by bruce69camaro:
first off, you said you have open chamber heads on the car now, correct ? well, it's not that easy as just switching heads, like on a small block, you also have to match up the pistons. if you go with closed chamber, you have to run pistons made for closed chamber heads. now i know i'm going to go against what i just said, but i'm running open chamber heads with closed chamber pistons. this you can do, but for what you want to do, i believe you will need new pistons. also, a cam that big may need a little more compression. i was looking at solid cams made by comp cams and it looks like they all use higher compression then what you have. somewhere around 10:0 on up. have you called comp cams up and talk to them about it ? i'm running the 294x-treme cam in my 408 and i was told by many that, the cam is to big, but because i'm running 11.5:1 compression i'll be ok. i also think that the 305 cam is too big for your engine, especially with that low compression. call up comp cams and tell them what your looking for and i'm sure they can help without having to switch heads.
good luck,
bruce<HR></BLOCKQUOTE>

The piston that I have for the 402 is TRW# 2240NF. It is a closed chamber stock-type piston. Same as L66 (265 hp), L35 (325 hp), & L34 (350/360 hp) Compression ratio: 9.59:1 with 100.9cc heads. My info came from Jegs catalog. My block is decked .010".

On the sound issue, I think I know what you're looking for. That tight, crackling exhaust sound comes from high compression, 11:1 and up. The big cam will give you a lopey idle, but if you wanna here it crackle, you gotta squeeze it tight!

Unfortunately, after I'm done with the sillyness, I don't have a solution, or at least not a cheap one. New pistons with higher domes, I guess, and that's big money all around. And the others are right, you can't put a closed chamber head on oem type or larger domed open chamber pistons, they'll hit.

My two cents worth,
What would happen if you went with a solid of about 238/246 In/ex duration at .050" set on 108/106 LCA/ICA would that "cackle" enough for you???
I'm afraid that you do need compression to get that "explosive cackle". I built an 11.5 to 1 engine and the exhaust was 2.5" with two 18" glas-paks welded end to end per side and boy did it "cackle". pdq67

<BLOCKQUOTE>quote:</font><HR>Originally posted by JimM:
On the sound issue, I think I know what you're looking for. That tight, crackling exhaust sound comes from high compression, 11:1 and up. The big cam will give you a lopey idle, but if you wanna here it crackle, you gotta squeeze it tight!

Unfortunately, after I'm done with the sillyness, I don't have a solution, or at least not a cheap one. New pistons with higher domes, I guess, and that's big money all around. And the others are right, you can't put a closed chamber head on oem type or larger domed open chamber pistons, they'll hit.<HR></BLOCKQUOTE>

I have closed chamber pistons pn"2240NF TRW. But thanks for the imput anyway.

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Jeremy Mc.

<BLOCKQUOTE>quote:</font><HR>Originally posted by BitsNPieces:
ok, you have open chamber heads right now. I would keep them and put money into port & polish and 3-angle valve job for them. Open chamber heads do flow better and have a better combustion and more complete burn thereby resulting in a greater potential for power. Plus, you have to remember that air velosity is equally inportant to power as air flow. Putting too big of a cam in your motor can actually make it run worse. If you are looking for street performance, stick with a moderate grind that matches the other work done to your engine. Good Luck<HR></BLOCKQUOTE>

I agree putting in a big cam may hurt performance, especially if you have low compression. But the low compression is what I am trying to get rid of by installing closed chamber heads, with my relatively small domed closed chamber pistons. But if you run a big solid cam, loosen up the lash for more low end torque and have that killer sound. It may not run quite as good, but people know you mean business. I just kind of get tired of running the lash everytime I go tear the crap out of it, and the 294 Comp Cam I went with doesn't sound all that nasty. I am considering tightening up the lobe separation in order to get the sound I am looking for.

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Jeremy Mc.

<BLOCKQUOTE>quote:</font><HR>Originally posted by 69Man:
The piston that I have for the 402 is TRW# 2240NF. It is a closed chamber stock-type piston. Same as L66 (265 hp), L35 (325 hp), & L34 (350/360 hp) Compression ratio: 9.59:1 with 100.9cc heads. My info came from Jegs catalog. My block is decked .010". <HR></BLOCKQUOTE>

How does that 294 Extreme Energy work? I have been wanting to go with that cam for a long time now, and I shyed away from it to go to a solid. Does it sound nasty? I have heard these cams are very responsive, and hardly ever run out of power, and they have very good drivability. Comp Cams told me that if I had to run that cam, to run 10 to 10.5 to 1 compression. If you could Bruce, write me back and tell me how you like this cam. Thanks for all your imput.

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Jeremy Mc.

You have the 9.5 compression factory replacement style offered by Speed Pro. The heads you are contemplating should be casting # 3964290, and will give you a truer 9.5 compression than the open chambers you have on there already. I assume you are running 114-118 cc. heads, by the open chamber comment. These will give you closer to a 9:1 or a little lower compression ratio. You should get more power out of the ' 70 heads, and a better feel with the bigger valves. As for Cams, the compression ratio isn't suited for a big thumping cam. Those style cams like compression, and they are ground with alot of overlap to offset the higher compression. The cam in there now is actually bigger than I would recommend. Something along the lines of 280 advertised duration, 230 @ .050, and somewhere around .540-570 lift. Big Blocks like more duration and lift on the exhaust also for some reason, so you can factor that into your plans and pick up some more free H.P.