THETANK

I am looking at doing an engine swap and am trying to decide between a couple of different combinations. I am looking at a ZZ4 or a vortec headed L31 with modified heads and a different cam. I know the ZZ4 cam and the LT4 Cam are often recommended. However, I heard a sound clip of Comp Cams Thumpr cam and loved the way it sounded. I did some research on it and the consensus seemed to be that there were better cams out there and in fact these cams were not all that good performance wise compared with the Hot Cam. My question is Why does a ZZ4 that is upgraded with just a Hot Cam have aprox 378 HP and 409 ft/ lb of tq, yet a zz4 with the following thumpr cam package (Jegs 249-08-600-8K) is supposed to be rated at 399 hp and 410 ft/lb of tq. I don't understand what makes the zz4 cam or the Hot cam a better cam based on these numbers.

If someone could explain what I am missing I'd appreciate it.

afremont

You can't just look at the peak numbers. That "thumpr" cam probably just peaks at a higher RPM. You need to see the whole curve IMO. That's what I'd be interested in anyway.

Driveability is another thing that probably differs between them. Your butt dyno won't be able to tell the difference between those peak HP numbers, but a few inches of vacuum difference at idle will be noticeable.

THETANK

This is the graph of the cam

Guest

I'd drink a bottle of salt along with that chart.
More power from 2500 up? Not buying it.
I think the cam they're using is 227/241 with 107LSA. You didnt mention what you plan for induction but if its TBI its not going to like it.

THETANK

I am planning on switching from TBI to CARB

Atilla the Fun

The last dyno sheet I saw for a virgin ZZ4 with only the HOT cam kit showed 394 hp and 417 ft-lbs. I can believe the Thumper giving that horsepower, but beating the ZZ4 cam at 2500 rpm? We need an independent dyno shop to test this, one that can give exact numbers rather than just COMP's relatively vague graph.

afremont

I agree with you and madmax. I'm skeptical of ANY cam that promises across the board gains like that. And this is all using a stock TPI induction system?

Atilla the Fun

No, all of these tests are carbureted.

*86EYEROK*

tell you what, im running the ZZ4 with the muthathumper cam and fast burn heads with the holley 750 DP and its a beast.. and yes they test that zz4 with a carb

Atilla the Fun

Id be willing to bet a c-note that '86 Eyerok would love the car even more with a built 200-4R in place of that TH350.

THETANK

Does your car have any vacuum issues with the muthathumpr cam ( power brakes etc..). Did you have to install a vacuum reserve?

*86EYEROK*

no, there is no vacuum issues, all my vacuume lines are running of the carb, power brake booster is running of the back of the carb and the vac gauge in the car, the modulator for the tranny, and the vacuume advance are running off the side of the carb.

*86EYEROK*

thats funny that you say that, cause i just had that tranny rebuild 50 miles ago, and before i did that i thought about switching to another trans like the 200-R4 for the streetability instead if the th350. but i heard the 200-R4 trannys cost more to build