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Topic Review (Newest First)
02-17-2011 11:41 PM
FastOrange Thanks, Were is this post you made about big cams and timing? i couldn't find it.
02-17-2011 07:44 PM
F-BIRD'88 Ya try the 850. After making the other changes. It sure won;t slow it down any.
02-17-2011 04:46 PM
FastOrange
Quote:
Originally Posted by F-BIRD'88
Seems you are jumping to conclusions based on the appearance of the specs and some negative internet opinions from some that had a less than favourable first experience mostly from lack of knowledge of the setup and tuning changes required for these cams. Or couldn't be bothered to do it.
The thumpr cams and all other high overlap cams need a few setup things that most are not aware of.

To make the most of the cam in your motor will needs some specific set up changes. You have the right 3500 stall converter.

The small 670cfm carb is costing you more performance than the cam is.
Its too small for max performance
A 750 to 800 cfm carb is better. A Proform 750 HP style carb centerbody is a cool upgrade.

The engine compression ratio is way too low.

You need to raise the real compression ratio up as much as is practical.
Your truck motor probabily has factory dished pistons.
Remove the heads, shave them by .040"-.050" reinstall with thin .015" felpro 1094 shim head gaskets.
The closer you can get it to a real 10.50:1 cr the better.
The distributor advance curve will need to be set up for the cam.
See my post on big cams and timing curves.
Start by locking out the timing and try it. (34-36 deg)
4.10's aren't much gear for this 350, heavy vehicle combo for drag racing.
a 4.56 to 5.13 would be better.
Make the best of what you got by using a very short diameter BFG drag radial to max the effective gear ratio. EG: P225/50-15

To make the thumpr cam work best (at the track) you want to open the exhaust and add collector extensions (approx 18 to 22")
The cam has to work with the exhaust system. The engine has to breathe deep and freely to use the high exhaust header scavaging effect to make power.

All these changes need to be done even with the Lunati BM II cam anyways...so......best try the cam you got.
Thanks F-Bird, i will try this before i do anything else, i honestly dont mind this cam, but i think its just my combination of stuff thats making it not perform.

Question, is a 850DP Holley too big for this. all i have are 650's and a lonely 850.
02-17-2011 09:49 AM
F-BIRD'88 Seems you are jumping to conclusions based on the appearance of the specs and some negative internet opinions from some that had a less than favourable first experience mostly from lack of knowledge of the setup and tuning changes required for these cams. Or couldn't be bothered to do it.
The thumpr cams and all other high overlap cams need a few setup things that most are not aware of.

To make the most of the cam in your motor will needs some specific set up changes. You have the right 3500 stall converter.

The small 670cfm carb is costing you more performance than the cam is.
Its too small for max performance
A 750 to 800 cfm carb is better. A Proform 750 HP style carb centerbody is a cool upgrade.

The engine compression ratio is way too low.

You need to raise the real compression ratio up as much as is practical.
Your truck motor probabily has factory dished pistons.
Remove the heads, shave them by .040"-.050" reinstall with thin .015" felpro 1094 shim head gaskets.
The closer you can get it to a real 10.50:1 cr the better.
The distributor advance curve will need to be set up for the cam.
See my post on big cams and timing curves.
Start by locking out the timing and try it. (34-36 deg)
4.10's aren't much gear for this 350, heavy vehicle combo for drag racing.
a 4.56 to 5.13 would be better.
Make the best of what you got by using a very short diameter BFG drag radial to max the effective gear ratio. EG: P225/50-15

To make the thumpr cam work best (at the track) you want to open the exhaust and add collector extensions (approx 18 to 22")
The cam has to work with the exhaust system. The engine has to breathe deep and freely to use the high exhaust header scavaging effect to make power.

All these changes need to be done even with the Lunati BM II cam anyways...so......best try the cam you got.
02-17-2011 08:48 AM
FastOrange
Quote:
Originally Posted by Scandinavian
Hey ive used lunatis Bracket master series And they are great!

Tis one http://www.lunatipower.com/Product.aspx?id=2411 is probably a god choice fore your engine! Send a e mail to Lunati to confirm Wat CR the Cam Requires! your gearing and stall is Hi enough

okey its the same cam as you mentioned!
Yup, thats the one ive been looking at
02-17-2011 08:47 AM
FastOrange
Quote:
Originally Posted by F-BIRD'88
Whats the problem with the muthr thumpr cam?
specs on it are really wacked, and i feel like i felt alot to be desired.
02-17-2011 05:48 AM
F-BIRD'88 Whats the problem with the muthr thumpr cam?
02-17-2011 02:22 AM
Scandinavian Hey ive used lunatis Bracket master series And they are great!

Tis one http://www.lunatipower.com/Product.aspx?id=2411 is probably a god choice fore your engine! Send a e mail to Lunati to confirm Wat CR the Cam Requires! your gearing and stall is Hi enough

okey its the same cam as you mentioned!
02-17-2011 12:10 AM
FastOrange
Need help choosing a cam. (350 SBC)

hi guys, need your help, i should have done this the first time, but i didnt and ended up going for the Comp Mutha Thumpr, which i now realize is a MISTAKE!

anyways, im looking for a cam that is .480 lift (I did get away with the .489 lift, but its damn close) or under cause of my vortec's and is Flat Tappet.

Engine is in a 1994 C1500, Regular cab, short box, currently a Weekend Warrior type of deal, going to be drag racing it this year.

Specs:

1988 TBI 350, Stock Bottom End, 4-Bolt Main.
1997 Vortec 906 Heads
Comp Valve Springs, Retainers, Locks (Need to upgrade to beehives to run higher lift.)
Comp Pushrods
Edelbrock RPM Performer
1" Open Spacer
Holley 670CFM Street Avenger
MSD StreetFire with upgraded MSD Coil and MSD Module
Taylor 8mm Spiro Pros
NGK TR55 Plugs
Cloyes Double Roller Chain
Flowtech Headers

THM400 Stock
Shift Kit
3500 Convertor

10-bolt Rear
PowerTrax Locker
4.10's

Any Ideas guys?

Im currently looking at a Lunati 292 Bracket Master II.

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