Camshaft decision, need professional help.....

[Nuke1]

Hey guys, I appreciate any and all input.

Ok here it is, I have a 68 gm truck that I turned into the best corner carver that I could so far, need more work yet. Anyways, I want to change my camshaft in the truck, but everyone I know draraces and all they want to do is put the best cam in for drag racing. currently this is how my truck sits...

3:73 rear gears,
30.5" tall tires, soon to be changed to 29"
700r4

Engine is:

358
fully balanced and blueprinted
gear drive
xe274 comp cams
zero decked
40 thou head gasket
world products sportsman 2 heads, 64 cc chamber
1.5 roller rockers
hardended pushrods
edelbrock rpm performer intake, want to put a single on I think thou
2 valve relief pistons, 40 thou over
full msd pro billet ignition

I want this thing to have serious mid grunt, any insight would be helpful, remember this is in a truck with a full boxed and triangualted fram.

Thanks James

[Scott Parkhurst]

Do you want to go roller?

(say yes!)

[Nuke1]

HMMMMM!!!!!! I would seriously consider both ways

[MonzaRacer]

OK AS for me one of the torque-iest cams I have ever installed is my LT4 HOT Roller, if using an older block simply use the retrofit hydraulic lifters. Dont forgetto install a mellonized GM dist gear and use an 86 1/2 up roller cam T/C set , take the stock thrust plat and cut ears off and install behind it, then use a simple cam button. Aluminum or roller, dont use the plastic or nylon ones.
You will also need the matching push rods.
You can keep your 1.5 roller rockers, but dont forget this cam specs out at .525 lift with 1.6 and you can even go to the Comp 1.65 ratio roller rockers and get .541 lift or mix and match for power tuning.
It iwll work great with small converters and makes tons of torque. Mine is in my truck and will pull a tank even with factory 2.73 rear gears.
It eve nworks with stock converter in my TH400, but liked the TCI Saturday Night Special in when in my 71 Monte.

[Scott Parkhurst]

My favorite cam for apps like yours is a Comp 12-772-8 (XR286R). It's an angry solid roller that can still idle below 900 and pulls hard from 2,500-6,500. It won't pull much past 6,500, and doesn't make a ton of vacuum, but if you want mid-range grunt in that truck, you've got the heads and compression to support it.

I'd recommend an RPM Air Gap with it, but if you go single-plane you'll kill a bit of bottom-end torque, which might be a good idea in this truck so you'll have a chance at traction. The single plane (Victor or similar) will add a bit upstairs, where you'll have more bite.

You will never regret choosing this cam. I promise.

[Nuke1]

Thanks guys, Scott, I looked up those specs on the solid roller, that is some serious lift, would that work in my engine, being that it is zero decked? I was told I can not have that much lift, it it does, that is what I am gonna aim for, as soon as she comes out of winter hibernation next spring, she will get torn apart again, Thank YOU!!!!

[Scott Parkhurst]

That's the cam I have in my wagon's 383- which is zero-decked also. The only thing you'll have to check for is if the heads (springs) can lift that far without coil bind. If it can (and they should, since World heads are designed to be hi-perf units), you're all set.

[Nuke1]

Now that is what I like to hear, lump lump lump....... just out of curiousity, how often do you have to recheck the clearances for the roller rockers? Not that it bothers me to adjust them time and time, just curious as I honestly have never run a solid camshaft before, always has been hydraulic.

[Scott Parkhurst]

Back in the old days, you used to have to adjust them quite often- but the modern poly-locks holding modern rockers in place are really good. I grew up with the old style stuff, so I got in the habit of checking mine every other month or so. The thing is, with the new stuff, adjustments don't change, so there's no need to readjust them anymore.

I run different clearances for street and track (looser on the street- like .014 intake and .016 exh, and tighter on track days - like .008 intake and .010 exhaust to maximize lift and duration) so this forces me to get in there and check stuff out. But, I could just keep the street adjustments in place all the time. I'd still recommend checking it before the summer season when you're getting the car out of winter storage, but once you've got it set you should be good all summer.

If you're headed to a track event, or if you hear any new ticking noises, it's no biggie to bust out the feeler gauges and check it again. I made sure my valve covers were easy to remove and replace knowing I'd want to get in there more than a normal guy (so no A/C compressors hanging over the valve cover, no wiring or plumbing in the way of removing them, and plenty of clearance to the brake booster...and reusable gaskets of course! I also run studs to make it easy and keep the gaskets perfectly aligned).

So- checking them once a year is all that's truly required...unless you hear a new noise or something. But that's never happened to me with this engine. My new-school COMP stuff held adjustment just fine. I recently upgraded to shaft-mounted rockers, and I've had no issues with those either. I push my stuff hard and since it's a stick and I plan on adding a nitrous plate, I wanted to make sure I was safe if I ever missed a shift and spun past 7,000. With the shaft stuff, I'm better equipped to handle such errors...should they happen. It's overkill, and I never had any issues with the COMP stud-mounted rockers...but I got a good deal on the shaft setup and couldn't say no since I was in the middle of rebuild and it was an easy time to upgrade.

[My427stang]

Have you driven it with the current cam? Also, when you say more mid range grunt, does the current cam peak too high, or too low?

Camshaft / performance expectations are different with everyone, just clarifying

[funcars]

I would talk to several different cam manufacturers and get somebody who actually cares to help you. The guys who grind them can get you the best compromise for what you want (there is always compromise). You will also need the actual compression ratio, the weight of your truck, converter type and stall speed and what octane fuel you use. A custom cam costs just a tiny bit more than a generic one and can be tailored for exactly what you want. You should also re-check valve to piston clearance with a new cam if it is larger lift and/or more duration/ different lobe separation than what you were using before.

[Nuke1]

Back in the old days, you used to have to adjust them quite often- but the modern poly-locks holding modern rockers in place are really good. I grew up with the old style stuff, so I got in the habit of checking mine every other month or so. The thing is, with the new stuff, adjustments don't change, so there's no need to readjust them anymore.

I run different clearances for street and track (looser on the street- like .014 intake and .016 exh, and tighter on track days - like .008 intake and .010 exhaust to maximize lift and duration) so this forces me to get in there and check stuff out. But, I could just keep the street adjustments in place all the time. I'd still recommend checking it before the summer season when you're getting the car out of winter storage, but once you've got it set you should be good all summer.

If you're headed to a track event, or if you hear any new ticking noises, it's no biggie to bust out the feeler gauges and check it again. I made sure my valve covers were easy to remove and replace knowing I'd want to get in there more than a normal guy (so no A/C compressors hanging over the valve cover, no wiring or plumbing in the way of removing them, and plenty of clearance to the brake booster...and reusable gaskets of course! I also run studs to make it easy and keep the gaskets perfectly aligned).

So- checking them once a year is all that's truly required...unless you hear a new noise or something. But that's never happened to me with this engine. My new-school COMP stuff held adjustment just fine. I recently upgraded to shaft-mounted rockers, and I've had no issues with those either. I push my stuff hard and since it's a stick and I plan on adding a nitrous plate, I wanted to make sure I was safe if I ever missed a shift and spun past 7,000. With the shaft stuff, I'm better equipped to handle such errors...should they happen. It's overkill, and I never had any issues with the COMP stud-mounted rockers...but I got a good deal on the shaft setup and couldn't say no since I was in the middle of rebuild and it was an easy time to upgrade.

I could not agree more, the vehicles I always build I try to make everything as easy to access as possible. I have never had a problem adjusting things, does not bother me, just gives me a reason to tinker alittle more.


Have you driven it with the current cam? Also, when you say more mid range grunt, does the current cam peak too high, or too low?

Camshaft / performance expectations are different with everyone, just clarifying

I have about 2ooo miles on her now, it has good midrange, dies off flat on its face at about 5800 rpm, it just does not seem to perform as well as it should, maybe I am expecting too much from a 350, but I know that there is more there, and i need to unleash it somehow.


I would talk to several different cam manufacturers and get somebody who actually cares to help you. The guys who grind them can get you the best compromise for what you want (there is always compromise). You will also need the actual compression ratio, the weight of your truck, converter type and stall speed and what octane fuel you use. A custom cam costs just a tiny bit more than a generic one and can be tailored for exactly what you want. You should also re-check valve to piston clearance with a new cam if it is larger lift and/or more duration/ different lobe separation than what you were using before.

A friend of mine that builds drag bikes suggested this to me, he suggested the same thing to me, I think when I bring it out from winter storage next year, i will get him to tear the engine down and figure the max lift.... and maybe go from there,

thanks for the advice guys, definetly gives me some food for thought to think of.

[My427stang]

I agree you could use a more cam, but with it will come a converter swap and a loss of low end.

I would also expect a valve spring swap with it, and really, only a gain to about 6000-6100 unless you go with a solid flat tappet or solid roller. Hyd lifters of any sort are hard to control over 6000 rpm.

[Mudweizer]

My favorite cam for apps like yours is a Comp 12-772-8 (XR286R). It's an angry solid roller that can still idle below 900 and pulls hard from 2,500-6,500. It won't pull much past 6,500, and doesn't make a ton of vacuum, but if you want mid-range grunt in that truck, you've got the heads and compression to support it.

I'd recommend an RPM Air Gap with it, but if you go single-plane you'll kill a bit of bottom-end torque, which might be a good idea in this truck so you'll have a chance at traction. The single plane (Victor or similar) will add a bit upstairs, where you'll have more bite.

You will never regret choosing this cam. I promise.

How much vacuum does this cam make at idle? I currently have a Comp 12-900-9, it barely makes 5" in park lol.

[Scott Parkhurst]

How much vacuum does this cam make at idle? I currently have a Comp 12-900-9, it barely makes 5" in park lol.

Around 7...LOL!

But I run it with power brakes and don't have issues. Go figure.

[Mudweizer]

Around 7...LOL!

But I run it with power brakes and don't have issues. Go figure.

Thanks for the info! I have hydro boost on mine, no way I could run a vacuum booster.