Small Block & Big Block Chevy Specific - bigger cams suck

I recently put a bigger cam that was custom grounded by Comp cams. I was using a crane hydraulic roller 488/502 lift and 224/230 @ .050 112 center lobe. This was in a 3600 lb 4th Gen with a 355 vortec 170 cc heads, 12:1 compression, 850 proform carb, 3500 stall, 700R4 with 4:56 gears 28 inch tire. Comp recommended a 562/571 lift 248/258 @ .050 witha 112 center lobe. The went from running 7.80's @ 86 MPH with a 1.65 60 ft time to a 8.20 @ 86 MPH with a 1.85 60 ft time. I have 4 inches of vacuum in gear and 8 at an idle. Should I advance the cam 4 degrees, get a bigger stall, or put the old cam in. I have no bottom end at all.

Well,

Before you rip it all apart, can you advance the cam without too much trouble, I know its not easy, but at least the intake and lifters stay in.

Also what intake are you using? If a dual plane, that sounds like alot of dur. .

I was told to advance the cam 4 degrees. The previous cam was ground in advanced 4 degrees. I am using the dual plane manifold and was told to stay with it due to the weight of the vehicle.

You get the springs and everything you need to go with the cam? Did you change your shift points, the new cam will need to turn more rpm to work its best. A bigger stall would help probably advancing the cam also just be careful of valve clearance. You are also getting to the point where the small runners of the vortec heads may hurt you, unless they have been heavily ported.

They are heavily ported. The car picks up mid track, but is a dog a low RPM. I have a 150 shot, but I want to tune the car all motor first. I'm building another motor in the mean time, but I want to have fun this year.

something is definitely not right. even with that big of a cam torque still shouldn't be that far off at 3,500 rpms and top end should have picked up 2-4 mph.

Personally, I would get rid of the intake. The dual plane is not giving you much torque over a single plane. Plus the dual plane is suffocating the remainder of the engine - i.e., the cam and heads are big breathers but the air has to work it's way through the passages of the intake. Let it flow...

What car and is the cam from Comp a Hyd. Roller too?

I agree, that much cam needs a single plane (I run a Victor Jr on my combo and have good luck) and I'd consider a 3800 or more 10" stall convertor. Is the new cam a solid or hydraulic? I'm sure you could run this cam to 6500-6800 rpm shift points without a problem, provided the rest of your combo is up to it.

Good luck!

Derek

You can't really add that much duration and expect to not have to change the torque converter and raise the shift points to match the cam, it's really as simple as that IMO. With as big a change as you've made there are 3, possibly 4 things total that would need to be changed to optimize the raised power band that you'll now have

1. Torque Converter
2. Shift points
3. Rear end gears
4. Compression ratio, I don't know if you need a change here or not, it but it sounds like you have plenty of compression. One thing is for sure, you've lost dynamic compression ratio over the old cam, and so have lost torque for sure. An engine is a combination, and does not necessarily add up to the sum total of it's parts. If the 3500 stall was ideal on your old cam, then a 4000 stall might be ( just an example ) ideal with the new one. If you were shifting at 6000 rpm before ( just an example ) then 6500 rpm might be required with the new one. And since rpm band dictates gear ratio, if you were running 4.56's before, 5.13's "might" be required for the new one. These are some possible area's to look at. Do you have dyno graphs of before and after cam install to compare the new powerband with ?

The new cam is a hydraulic roller. It was custom grounded with the combination I have. I was told stick with the dual plane because the vortec heads make the most power with it. The old cam was ground 4 degrees advanced and had all bottom end. I figure if I advance the cam 4 degrees I should pick up at least 4 MPH because the car doesn't get going till mid track, and get my vacuum back because I only have 3-4 inches in drive. I don't really want to pull the motor out now, its too much work advancing it is much easier. I building a new motor for next year anyway.

The new cam is a hydraulic roller. It was custom grounded with the combination I have. I was told stick with the dual plane because the vortec heads make the most power with it. The old cam was ground 4 degrees advanced and had all bottom end. I figure if I advance the cam 4 degrees I should pick up at least 4 MPH because the car doesn't get going till mid track, and get my vacuum back because I only have 3-4 inches in drive. I don't really want to pull the motor out now, its too much work advancing it is much easier. I building a new motor for next year anyway.

did you contact the cam company that recommended this cam and see what suggestions they have? Also, I would have tightened up the LSA to at least 110. That would give you back a little more low end. Thats a pretty big hyd cam though. I had a solid cam with the same duration in a 327 and it had tons of low end. How high does your converter flash to? What can you foot brake it too? Your gears are fine. sounds like you need to fine tune it. Have you played with the ignition timing curve or anything? Have you done a compression test? One thing you can do is advance or retard the cam untill you get the highest cranking compression. If you do that then the cam is installed in the position that wil give the most power. Good luck.

From the numbers on the cam and looking at your combination I'd start by advancing it 4 degrees, then I swap to a single plane intake. In my opinion that dual plane is hurting you with that cam. That cam will pull to around 6500 RPM, that's a bit high for a dual plane intake. Then I'd swap the converter for about a 4000 RPM converter, if you're running a lock-up converter it won't be too bad to drive on the street. If not, I'd stick with the 3500 and spray it out of the hole to make up for it, that is traction permitting. That cam will make peak torque fairly high probably around 4000-4500 RPM, which is also why I'd suggest getting rid of the dual plane intake. What size headers are you running? Do you have any flow numbers for the heads? What is your timing set at, Vortech heads usually work better with a little less timing. How much nitrous are you going to run on it? Once you get everything tuned and dialed in it looks like it will make some nice power. Just remember that the cam is heart of your engine, a chnge as big as the one you made will require some time to dial it in. Don't give up on it!
Jeff Georges

They are heavily ported. The car picks up mid track, but is a dog a low RPM. I have a 150 shot, but I want to tune the car all motor first. I'm building another motor in the mean time, but I want to have fun this year. what grear are u runing an what size tire are u runing...
at leassse a 410 or a 430 :drive: at lease 28 by 11.5 or 12.5 on a 10'
ins wide rim by 15 in.. :confused: :) more :punch: :drive: :thumb: :wavey: now u can make that bottom;
end work... can u dig it warrior........... :engarde: