Thread: Finally Building the 350 this week... what do you think about the setup?

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I had my 350 bored 40 over, and am building it this week finally. I just acquired the last of my parts from Summitt. What do you guys think of this setup:

1. Speed Pro Flat Top Pistons
2. Comp Cams - .525/.525 lift, 253/253 duration @ .50 inch
3. Edelbrock RPM Air Gap intake
4. GM Performance Fast Burn Heads (62cc comb. chamber, 210cc int. runner
5. Comp Cam Magnum Roller Rockers (3/8" 1.52 stud mount)
6. Holly 650 double pumper
7. Standard Crank... Still just a 350.. or 356

I had my radiator rebuilt, but was informed that I probably needed a bigger or aluminum performance radiator... I'm looking to go with an electric fan setup. What other specs do you guys need to figure if it's gonna run right on pump gas? My buddy was just telling me to retard the timing, but I hope it'll run good without having to do that. Still looking to put a 2800 or 3000 stall on my TH350, and it's going into my 67 Camaro. Let me know!

id be running a 3000-or 3500 stall with that cam.

Originally Posted by 67CamaroProject

I had my 350 bored 40 over, and am building it this week finally. I just acquired the last of my parts from Summitt. What do you guys think of this setup:

1. Speed Pro Flat Top Pistons
2. Comp Cams - .525/.525 lift, 253/253 duration @ .50 inch
3. Edelbrock RPM Air Gap intake
4. GM Performance Fast Burn Heads (62cc comb. chamber, 210cc int. runner
5. Comp Cam Magnum Roller Rockers (3/8" 1.52 stud mount)
6. Holly 650 double pumper
7. Standard Crank... Still just a 350.. or 356

I had my radiator rebuilt, but was informed that I probably needed a bigger or aluminum performance radiator... I'm looking to go with an electric fan setup. What other specs do you guys need to figure if it's gonna run right on pump gas? My buddy was just telling me to retard the timing, but I hope it'll run good without having to do that. Still looking to put a 2800 or 3000 stall on my TH350, and it's going into my 67 Camaro. Let me know!

1.Not enough compression for the cam.With a cam this size you will need 12.5 to 1 comp. ratio.I would take 15 degrees off the cam at .050.The cylinder heads are to large.I would look for heads that have a port volume of 180 cc.I would cut the gear back to 4.10 and run a 3,000 stall and run about what I listed above.

Yup, way too big of runners, and way too much cam. Also, you've said nothing about ignition components or a distributor.... Personal preference, but I much prefer a vacuum secondary with an automatic transmission for street use. With a secondary spring kit and some jetting it is easy to match the timing of the secondaries opening with the stall of the converter and the cam coming in on the sweet spot. Double pumpers IMO work best with standard transmissions and/or on the drag strip where maximum performance is the issue and not driveability..... And a reminder, higher converter stall speeds in traffic increase tranny temperature, make sure you also install a good transmission fluid cooler....

I think the compression ratio on that motor might be too high with flat top pistons and 62cc heads. If you could give us information on the piston to cylinder deck clearance as well as the valve relief volume and head gasket thickness/bore, we can give you a real compression ratio number.

Originally Posted by 76GMC1500

I think the compression ratio on that motor might be too high with flat top pistons and 62cc heads. If you could give us information on the piston to cylinder deck clearance as well as the valve relief volume and head gasket thickness/bore, we can give you a real compression ratio number.

What?He never states what his comp. ratio is.Either way he does not have enough for the cam he listed.

That's the 305 Magnum. Comp Cams says: Pro Street/Bracket, limited street driving, 3,500+ stall, racy idle, 10.5:1 CR. If you run less than 3,500 stall, you've got problems. Also, your compression ration is likely too high for pump gas.

I wouldn't judge these heads strictly on the intake port volume. This is the head that GMPP puts on the ZZ-4 block to produce the "Fast Burn 385" motor, and that the dealers like Sallee Chevrolet use on their "ZZ-383." In both of those engines, they get about 9.7:1 compression with a flat-top piston. (I'm not saying that these are the same flat top piston in 67's engine.) All I'm saying is that with the right piston and cam, these heads work really well on a SBC.

With all that said, it's still too much cam and too much compression for the street. Eric's recommendation for about 15 degrees less duration on both sides is in the ballpark, and makes the cam very similar to Chevy's LT4 "Hot Cam." Get the compression down to about 10:1 and use about 2400 stall. Seriously, you will not like that cam on the street. I like the heads, though.

Originally Posted by Henry Rifle

That's the 305 Magnum. Comp Cams says: Pro Street/Bracket, limited street driving, 3,500+ stall, racy idle, 10.5:1 CR. If you run less than 3,500 stall, you've got problems. Also, your compression ration is likely too high for pump gas.

I wouldn't judge these heads strictly on the intake port volume. This is the head that GMPP puts on the ZZ-4 block to produce the "Fast Burn 385" motor, and that the dealers like Sallee Chevrolet use on their "ZZ-383." In both of those engines, they get about 9.7:1 compression with a flat-top piston. (I'm not saying that these are the same flat top piston in 67's engine.) All I'm saying is that with the right piston and cam, these heads work really well on a SBC.

With all that said, it's still too much cam and too much compression for the street. Eric's recommendation for about 15 degrees less duration on both sides is in the ballpark, and makes the cam very similar to Chevy's LT4 "Hot Cam." Get the compression down to about 10:1 and use about 2400 stall. Seriously, you will not like that cam on the street. I like the heads, though.

When I made the post about the heads I did not go into great detail about them.
They have a large port volume but they are not very efficient.
A good street head would be the AFR 180 cc street head.The AFR head is 30 cc's smaller and will out flow the other heads from .100 lift to .600 lift.In fact in the mid-lift area .300 lift the Chevy head flows 173 the AFR flows 195 cfm.
On the exhaust side the Chevy head flows 120 cfm at .300 lift.
The AFR flows 156 cfm at .300 lift on the exhaust side.
The whole idea is to have a smaller cross section and great flowing port.
Before anyone say's the Gm head is less money which is true.From what I can tell there is around $100 difference in cost.
Which head would you rather have?

He actually hasn't done a bad job of matching the cam to the compression ratio. I figured the ratio at 10.7 with a zero deck and 0.041 gasket. The problem that I see with it for a street motor is the compression ratio. If he backs off on the cam, the motor turns into a turd because the dynamic compression ratio will be in the crapper.

He can, of course, keep on with what he has, but like others said so far, you ain't gonna like it much. It will be fun for about 10 minutes. After that, you'll be kickin' yourself.

I don't like electric fans, but do as you like, it's your money.

..hmm... so can I keep everything else I have and just swap out the cam? I hope that's what you guys are telling me. What cam would be the best with the rest of the setup staying the same?

Originally Posted by techinspector1

He actually hasn't done a bad job of matching the cam to the compression ratio. I figured the ratio at 10.7 with a zero deck and 0.041 gasket. The problem that I see with it for a street motor is the compression ratio. If he backs off on the cam, the motor turns into a turd because the dynamic compression ratio will be in the crapper.

He can, of course, keep on with what he has, but like others said so far, you ain't gonna like it much. It will be fun for about 10 minutes. After that, you'll be kickin' yourself.

I don't like electric fans, but do as you like, it's your money.

One way we could try to "bleed off" some of your comp. ratio is to have the cam ground on a narrow lobe seperation.
We don't know your exact comp. ratio.
Will this be enough to keep the engine out of detonation?
It is really hard to tell.Every engine acts a little different.
We don't know if the block has been decked,have the heads been flat milled ,angle milled?
I would look at some on the smaller Crane hyd. cams for drag racing.
In stock form your heads have an exhaust to intake ratio of approx. 68 %.
To help with the detonation and help with the exhaust side of the heads I would look at a Crane part # 110591 cam.Specs. are in. lift.480,Ex. lift .494,
Dur. at .050 In. side 228,Dur. Ex. 234,lobe seperation 106.
Will this work?
I don't 100% but you will be much closer.
Anyone else have any thoughts about this?

It's not which head I'd rather have. It's whether or not '67 should throw away the heads he has and buy something else. That train may have left the station. The simplest change to make most of the parts work seems to be in the cam, which you have pointed out.

Originally Posted by Henry Rifle

It's not which head I'd rather have. It's whether or not '67 should throw away the heads he has and buy something else. That train may have left the station. The simplest change to make most of the parts work seems to be in the cam, which you have pointed out.

Jack,that was not directed at you.I was just trying to give some facts about the heads for everyone to compare.I hope you did not take it the wrong way.

Originally Posted by 67CamaroProject

..hmm... so can I keep everything else I have and just swap out the cam? I hope that's what you guys are telling me. What cam would be the best with the rest of the setup staying the same?

No you can't. With 10.7 static c.r., if you shorten up on the cam, you'll raise the dynamic c.r. to the moon, making so much cylinder pressure that the motor will not operate on pump gas. You are pretty much optimized with your combination right now. I just don't think you're gonna like it for very long.

The only way to do the whole thing differently is to start over with either different combustion chamber volume or different piston crown volume to lower the static c.r. to where it will be pump gas compatible (around 9.0:1) with a short cam. The shorter cam will make power down lower and you won't have to run a high stall converter.

Bottom Line: Maybe you have spec'd the motor the way you want it. If that's the case, bolt it together and enjoy.

Originally Posted by techinspector1

No you can't. With 10.7 static c.r., if you shorten up on the cam, you'll raise the dynamic c.r. to the moon, making so much cylinder pressure that the motor will not operate on pump gas. You are pretty much optimized with your combination right now. I just don't think you're gonna like it for very long.

The only way to do the whole thing differently is to start over with either different combustion chamber volume or different piston crown volume to lower the static c.r. to where it will be pump gas compatible (around 9.0:1) with a short cam. The shorter cam will make power down lower and you won't have to run a high stall converter.

Bottom Line: Maybe you have spec'd the motor the way you want it. If that's the case, bolt it together and enjoy.

Tech,are using part Speed Pro #H345cp in your formula when you are figuring the comp. ratio?