Thread: What cam to use?

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Trying to find the balance between the good stuff and the wallet, so hoping to use as much of what already exists as is possible, the possible solution seems to be in the cam, I don't know what it is just that is was a circle track grind.
The rest...
350 4bolt .30 over
forged pistons approx 1/8" dome (approx 205 psi on comp test currently)
reportedly balanced and blue printed forged everything in the bottom end and 7000+rpm capable, I can't verify any of that though
weiland intake, single plain
holley 750 double pump
HEI dist with a coil upgrade
aluminum heads 2.02/1.60, 190cc intake, 64cc chambers
1.6 roller rockers
TH400, (I think a standard stall)
3.73 rear

I know it will take a large cam to make the combo work, but what we have now is basically not streetable, brakes are nearly non existant(it has a vacuum can as well), it won't idle etc. 7psi vacuum at 1300rpm. What are my options? cam? 2800 stall? We have pulled the intake thinking maybe it has a vacuum leak.

Thankyou,
Mike

Think it might be time for a streetable camshaft....Double pumper carbs and single plane intakes are not the best setup for the street, automatics seem to prefer a single plane and vacuum secondaries. Should be able to sell the racey stuff and take a large chunk of $$$ off the new parts. An Edelbrock Performer RPM or Air gap with a 650 Vacuum secondary would probaly be a lot better on the street. Might want to check eBay, always a lot of used intakes on there. For the cam, I always call Comp Cams tech line and speak with one of the techs and go with his recomendation. Don't bother calling Summit or Jegs tech, they are for the most part just people filling a job in the phone bank, the cam company techs are a lot more knowledgeable about what would work the best.

Thankyou I appreciate the reply, I certainly do follow what you're saying. If nothing else I have been motivated to get myself a bit more educated.

My concern is the static compression and what cam it would take to get to a dynamic compression that would actually run on premium. After a crash course tonight...From what I can figure a comp cams 294 would barely get me into a tolerable range, and that doesn't look to be the most streetable cam either. If I have to go with a cam that big I think I probably need the intake stuff to support it.

It would appear that this is like trying to switch horses in the middle of the stream. A good lesson in why not to buy someone elses creation. Now I'm thinking forget the cam and go with a stall converter.

Thanks,
Mike

I hate to tell you this, but your head/piston combination is screwing things up. You need to change one or the other to get things right. My choice would be to sell the heads. You need to find some aluminum heads with 72 or 76cc chambers to get your compression down. Then you could run a smaller cam and a dual plane manifold get get it more street friendly and to get the DCR within pump gas parameters. There is no band-aide fix here.

Originally Posted by mykle

Trying to find the balance between the good stuff and the wallet, so hoping to use as much of what already exists as is possible, the possible solution seems to be in the cam, I don't know what it is just that is was a circle track grind.
The rest...
350 4bolt .30 over
forged pistons approx 1/8" dome (approx 205 psi on comp test currently)
reportedly balanced and blue printed forged everything in the bottom end and 7000+rpm capable, I can't verify any of that though
weiland intake, single plain
holley 750 double pump
HEI dist with a coil upgrade
aluminum heads 2.02/1.60, 190cc intake, 64cc chambers
1.6 roller rockers
TH400, (I think a standard stall)
3.73 rear

I know it will take a large cam to make the combo work, but what we have now is basically not streetable, brakes are nearly non existant(it has a vacuum can as well), it won't idle etc. 7psi vacuum at 1300rpm. What are my options? cam? 2800 stall? We have pulled the intake thinking maybe it has a vacuum leak.

Thankyou,
Mike

To use those heads you will have to have a cam with a min. of about 250 at .050.
Then you will have to run a 4.56 gear and a 4,500 stall.
The other problem is you need a min. of 12.0 to 1 to make it work.

maybe you should try the lunati hydraulic flat cam. the one im running in my 406 is
part number# 638-00010LK (on jegs)
Adv. Duration: 292°/292°
Gross Lift: .480''/.480''
RPM Range: 2000-6000

Its a bracket master II designed for great power throughout the RPM range. very streetable.

I'm using the combo off of Chevy Hi performance, and they got 525 ft/lb torque and 425 HP out of the 406. They used the edelbrock rpm air gap, and vortecs. Im using all the same stuff.
Maybe this will help

Originally Posted by rumrumm

I hate to tell you this, but your head/piston combination is screwing things up. You need to change one or the other to get things right. My choice would be to sell the heads. You need to find some aluminum heads with 72 or 76cc chambers to get your compression down. Then you could run a smaller cam and a dual plane manifold get get it more street friendly and to get the DCR within pump gas parameters. There is no band-aide fix here.

I concur. If your $$$ is the rpobelm get some reconditioned used stuff. Even if you go to a decent iron head...you can get a decent set of reconditioned heads 76cc for about $300-$500...then a used dual plane intake off ebay like someone suggested, and the correct hydraulic flat tappet cam, and a 600-650 cfm carb..then your ready to have some fun on the street. Just doing a cam change or a Torque converter change isnt gonna fix everything. You need new head for sure to bring compression down, a smaller cam and a smaller carb and well as intake.

I appreciate the replys. Unfortunately replacing the untire top end and cam just isn't going to be a viable solution. The parts on hand seem well matched just a bit too much to be cormfortable on the street. Looks like a big stall and then a trip to the track to get a time slip and sell the thing, I'm sure someone wants a car that's too fast to drive. LOL makes more sense to me than spending a bunch of money to try to slow the thing down and having a garage full of more expensive parts.

I am curious about some of the replys...Erik, I follow on the cam needing 250 at .050, that's exactly what I came up with (the 292 cam), but I got there based on my compression rather than on the heads. I'm an old school guy, haven't played with this stuff in years, but we used to always look for the old camel hump heads that had 2.02/1.60, 64 cc chambers and i think 180 cc intake, they would work magic on a stock bottom end. I was really thinking these heads fit that exact mold, just 10cc extra in the intake runners. Does the extra 10cc make that much difference or were we just not as bright as we thought we were back then?? What criteria is stall converter speed based on? I'm seeing the 250 @ .050 cam showing it crosses the 350 tq mark at 2800 or 2900 and then back below it at just over 6000, so thought that looked like good numbers to go from. I'm assuming the cam in place is in this basic range as detonation is not a problem. What magic number of tq or hp should I be looking for? I mean if a 4500 stall is what this thing needs then that's what it gets, I just like to understand why it is I'm doing what I'm doing.

Thankyou,
Mike

Originally Posted by mykle

I appreciate the replys. Unfortunately replacing the untire top end and cam just isn't going to be a viable solution. The parts on hand seem well matched just a bit too much to be cormfortable on the street. Looks like a big stall and then a trip to the track to get a time slip and sell the thing, I'm sure someone wants a car that's too fast to drive. LOL makes more sense to me than spending a bunch of money to try to slow the thing down and having a garage full of more expensive parts.

I am curious about some of the replys...Erik, I follow on the cam needing 250 at .050, that's exactly what I came up with (the 292 cam), but I got there based on my compression rather than on the heads. I'm an old school guy, haven't played with this stuff in years, but we used to always look for the old camel hump heads that had 2.02/1.60, 64 cc chambers and i think 180 cc intake, they would work magic on a stock bottom end. I was really thinking these heads fit that exact mold, just 10cc extra in the intake runners. Does the extra 10cc make that much difference or were we just not as bright as we thought we were back then?? What criteria is stall converter speed based on? I'm seeing the 250 @ .050 cam showing it crosses the 350 tq mark at 2800 or 2900 and then back below it at just over 6000, so thought that looked like good numbers to go from. I'm assuming the cam in place is in this basic range as detonation is not a problem. What magic number of tq or hp should I be looking for? I mean if a 4500 stall is what this thing needs then that's what it gets, I just like to understand why it is I'm doing what I'm doing.

Thankyou,
Mike

The 292 Comp. cam is 244 at .050.
The double hump heads do not have a 180 cc port volume more like 160 cc.
250 is the min. at .050 to make those heads work.
Stall speed is effected by engine torque.
For a 292 cam you need a 3000 to 3,500 stall.

Are you sure about the dome on the pistons? Things just don't add up here. 0.125 domes would put you at 10.72:1 with 64 cc heads and I just don't see that combination making 205 lbs cranking pressure with a long cam. Is it just me? I also don't see gettin' by with 205 on pump gas unless everything is right on the money. You can't go with a shorter cam, it would make even more cranking pressure. And you can't advance the cam, that would give you more low end, but would give more cranking pressure and the cam would lay down on the top where the motor is built to operate.

If you want a street motor, I think your best bet is like you said, change out the converter, make a banzai run and sell the car on the merits of the time slip. Then build yourself a nice 9:1 383 for tooling.

I think Erik was being very generous saying the hump heads were about 160. My memory is that they were a little less than that.

A rule of thumb for a good street motor is 1/2 cubic inches for intake runner volume. That would mean 177.5 for your motor, but then as you've stated, yours is not a street motor.

I really appreciate all the info, the camel heads correction helps me understand things alot better.

I am sure about the dome and after reading your post I ran out and rechecked a few cylinders all about 202, 203 ish.

Thanks again.
Mike