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Old 09-07-2008, 12:24 PM
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Camshaft question ?

I need a camshaft recommendation for my SBC 350 that consist of.

Std bottom end
GM 3932-441 Cylinder heads W. 1.94"/1.5" valves ( very mild porting )
Compression is 9.03:1, I am using 0.15" head gasket.
I was thinking of using Edelbrock Performer RPM Intake manifold and Holley 650 DP carburetor.
I need a camshaft for my engine and i would like to archive 350 + horsepower if that is possible.

this engine is going in an 3100 LBS (W.driver) Chevrolet Vega
it has TH-350 with 3000-3500 stall converter and a 4.56:1 rear gears, the car sits on a 29" drag radials. This is going to be used 75/25 % Street/Strip

ALL suggestions appreciated.

Best Regards

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Last edited by monzter; 09-07-2008 at 12:56 PM.
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Old 09-07-2008, 12:59 PM
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I would look into the new CompCams Thumpr line of cams. Call Comp and ask for recommendation. The magazine test was inspiring.
Good thumping lope, strong mid range with very little loss above 5500 rpm. They say a fun to drive cam.
With your deep gears and tall tires, street should be a blast in that small car.

added
August 08 HotRod, page 82

Last edited by ScoTFrenzel; 09-07-2008 at 01:12 PM.
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Old 09-07-2008, 06:29 PM
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If I was you I would go for the isky cam that fbird recommended or go for a comp xtreme enegry cam. The thumpr cams are good cams don't get me wrong but they will not make the same amount of power as the isky or xtreme energy series around the same size. The Thumpr cams do put up good numbers but they are based on some type of circle track cam and I have the big mutha thumpr hydraullic roller cam and it sound good but it runs horrible on the street. Hope you find what your looking for.
Eric
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Old 09-07-2008, 09:16 PM
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Check out that HotRod Magazine article.
The plain Thumpr roller beat the snot out of the xe268h cam, and the 280h,and the xe274h, and the 292h......
Flat tappet Thumpr series are available now.

Actually they are based on endurance racing cam lobes.
A plain Thumpr has 85* overlap.

I'll bet your BIG MUTHA THUMPR (two steps bigger) IS pretty agressive for the street. 243*/257* at .050.

BMT has 99 degrtees of overlap !!!!!
Eric, Did CompCams recommemd that excessive cam to you?

http://www.compcams.com/Cam_Specs/Ca...?csid=218&sb=0


Part Number: Grind Number:
Lifter Type: Hydraulic Roller Lifter Engine Family: Chevrolet 262-400 c.i. 8 cyl. 1955-1998
Description: Hydraulic Roller-(Big Mutha' Thumpr™)
Street/strip needs 9.5:1 CR, 2800+ stall, intake, gears and headers, very rough idle Cam Family: Thumpr™ Hydraulic Roller Camshafts for 1987-1998 305-350 Originally Equipped With Hydraulic Roller Camshaft & Most Crate Engines, Except LT1 and LT4
Specifications Intake Exhaust
RPM-Range: 2500-6200

Lobe-Center Angle: 107 Duration @ .050" Lift: 243/257
Intake Centerline: 102

Valve Timing @ 0.006" 299/ 319*

Last edited by ScoTFrenzel; 09-07-2008 at 09:26 PM.
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Old 09-08-2008, 03:31 PM
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Well not entirely I picked that cam out after I was unhappy with my previouse crane power max hydraullic roller cam wich specs out at 234/242 @ 50 538/559 lift 1.5 ratio. I have the right setup and 3500 stall. The big mutha thumpr cam just has to much overlap for my taste.

I had to cams similar size to the thumpr in previous builds the comp 292h and crane 302h energizer. I just like the rough idle like the comp 292h cam and the power max roller cam did not have that nice sound but be able to be driven on the street. I am going to yank it out next year and replace it with a different cam and get better manners with a nice chopy idle with out all the overlap like the bmt cam.

I did ask comp cams about it and they said it would be good with my setup but I disagree with there advertisement about there thumpr cams. The mutha thumpr would probably work better then the big mutha thumpr but I am afraid to loose out on money again. I am tossing up on either a xr 288 or the mutha thumpr cam. What would you get?
Eric
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Old 09-08-2008, 04:22 PM
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Quote:
Originally Posted by monzter
I need a camshaft recommendation for my SBC 350 that consist of.

Std bottom end
GM 3932-441 Cylinder heads W. 1.94"/1.5" valves ( very mild porting )
Compression is 9.03:1, I am using 0.15" head gasket.
I was thinking of using Edelbrock Performer RPM Intake manifold and Holley 650 DP carburetor.
I need a camshaft for my engine and i would like to archive 350 + horsepower if that is possible.

this engine is going in an 3100 LBS (W.driver) Chevrolet Vega
it has TH-350 with 3000-3500 stall converter and a 4.56:1 rear gears, the car sits on a 29" drag radials. This is going to be used 75/25 % Street/Strip

ALL suggestions appreciated.

Best Regards
Well...
1) If you go roller it´s going to cost you some extra. But to reach 350 hp it´s hardly nessecary. I´d say hydraulics.
2) Your setup as far as converter and gears is says "rev me"; especially in 1/4-mile. That says "big" cam but you C/R says no to that
3) 441 heads are excellent but not really high rpm heads

I´d go with 4.10 or 3.73 gears and maybe some 230* @ .050 lift. Get a cam with no less than 110* LSA or you´ll bleed too much compression
Forgive my spellning. English is not my native language
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Old 09-08-2008, 06:08 PM
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You have a lot of gear and stall but not enough compression ratio. So, to fix that, use a cam with narrow lobe separation (like 106). Narrow LSA closes the intake valve sooner to help build cylinder pressure. Plus more overlap helps stock heads fill the cylinder (savaging).

I recommend a cam with 236 degrees on the intake and 242 on the exhaust with 106 LSA. Yes, the idle will be rough but a 3000 to 3500 stall and 4.56 gear will easily get it going off the line.

FYI, overlap doesn't "bleed off compression". The engine isn't even trying to build cylinder pressure during the overlap part of the 4 stroke cycle. The intake closing point is what determines how much cylinder pressure is reduced or "bleed off". And a narrow LSA will close the intake sooner than the same size cam with wider LSA.

Use a dynamic compression calculator and input the engine specs. You will need to know the intake valve closing point (advertised point not at 0.050").

here is a good one.

http://www.projectpontiac.com/ppsite...nt/view/16/30/
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Old 09-09-2008, 03:22 PM
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Hello Guys and thanks for the advices !

I spoke to the guys at Lunati earlier to day.
And they recommented this camshaft - http://lunatipower.com/Product.aspx?id=1984&gid=287 The Voodoo 268.
What do you guys think it would work with my Combo ?

Best regards
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Old 09-09-2008, 05:08 PM
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If you use a cam like I recommended, the intake valve would close at the same point as the lunati cam (with in 1 degree at 0.050"). And more duration would be better with those 4.56 gears and 3000-3500 rpm stall.

Low compression with a lot of gear and stall calls for a narrow LSA and a good amount of duration.
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Old 09-09-2008, 05:22 PM
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http://store.summitracing.com/partde...1&autoview=sku

Are you Talking about this Cam 454C10 ? isn´t this too low lift i am not restricted by any other than valve springs that fit in my pockets (1.250)

Best regards.
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Old 09-09-2008, 05:33 PM
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No. That cam has very low lift and very slow ramps (judging by the large advertised duration).

I just gave general cam specs.

Look at a circle track cams. They tend to run low cr with a lot of gear and frequently use 106 lsa.
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Old 09-09-2008, 05:48 PM
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What lift should i be aiming for ?
I would like to stay under .500" though

Best regards
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Old 09-09-2008, 06:12 PM
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cam ?

pianoman, it may not be your native languish, but that why we provide a spelling check at the bottom of the post. I 'm American and I need and us it.
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Old 09-10-2008, 01:49 AM
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"native languish"

And you used the spell checker for this???????
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Old 09-10-2008, 09:46 AM
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With 236/242 degrees at 0.050", the max lift should be around 0.485" on the intake 0.500" on the exhaust with an advertise duration of around 286/292.

If you find a cam with 230 to 236 degrees on the intake and another 6 to 10 degrees on the exhaust, then that would be good enough. But use a narrow LSA, from 105 to 107.

Advertised duration should be around 50 degrees more than the at 0.050" duration. Any less and the engine will make less power than it should and any more it risks a lobe failure. (IMHO)

Use a ZDDP additive to keep your new cam from going flat.
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