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 Cams / Heads & Valve Train
 Thumper in a 428
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69lemans
Tribal Scout

USA
24 Posts

Posted - 28 Jul 2016 :  9:46:50 PM  Show Profile  Reply with Quote
has anyone used the comp cams part #51-602-5. The motor is bored 30 over and i am using 6X8 heads with the big valves. It was recommended by the shop that did my machine work but I don't know if it is the right choice. do I need different rocker arms from stock or different push rods etc. Its going in a 69 A body with a TH400 and 373 gears 3000 stall. any info or advice would be appreciated.

loosetappet
Sitting Bull

113 Posts

Posted - 28 Jul 2016 :  11:21:20 PM  Show Profile  Reply with Quote
Where will this car see most of it's life? Street or strip?
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Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 29 Jul 2016 :  01:14:09 AM  Show Profile  Reply with Quote
If you ball park a 100 cc chamber, 6cc valve relief, and piston to deck clearance of .010 you get 8.5 to 1 compression ratio.

Not enough for that cam by description. http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1533&sb=0

http://www.wallaceracing.com/cr_test2.php


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 29 Jul 2016 01:21:43 AM
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69lemans
Tribal Scout

USA
24 Posts

Posted - 29 Jul 2016 :  05:59:34 AM  Show Profile  Reply with Quote
That's what I thought. Any recommendations? It will be street driven with an occasional drag race on public roads:). I would prefer to use the stock rockers and push rods, but want to get the most out of the motor without having to re mortgage the farm. Don't know why he went that direction, I didn't want to finish assembly until I got some opinions.
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tjs44
Cochise

USA
411 Posts

Posted - 29 Jul 2016 :  10:04:40 AM  Show Profile  Reply with Quote
Stock rockers and stock push rods you really held to not much more than a stock type cam.Even the RA IV used bigger pushrods and adjustable valve train.Tom
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69lemans
Tribal Scout

USA
24 Posts

Posted - 29 Jul 2016 :  11:46:55 AM  Show Profile  Reply with Quote
If I was to change rockers and Push rods what recommendations would you have? I am not completely opposed to changing to a different set up I just don't want to go too crazy.
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Tub
Sitting Bull

172 Posts

Posted - 29 Jul 2016 :  1:37:54 PM  Show Profile  Reply with Quote
quote:
Originally posted by 69lemans

If I was to change rockers and Push rods what recommendations would you have? I am not completely opposed to changing to a different set up I just don't want to go too crazy.



I ran the 041 clone cams, with well used stock factory 1.5 rockers, on several low budget 455 bracket engines. I ran some cheap, stock length, 5/16, chromemoly, heat treated pushrods. Never had a problem with pushrods, and only broke 1 rocker.

But, the chrommoly pushrods ain't cheap no more.

About $95 shipped is the best price I could find, for 1-piece CM units.

https://www.amazon.com/Proform-66415C-1-Piece-Pushrod-Set/dp/B001G9BQBG

https://www.summitracing.com/parts/cca-7262-16?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-comp-cams&gclid=Cj0KEQjw_eu8BRDC-YLHusmTmMEBEiQArW6c-AbOHdCLoodKPK9noiA3lQ9NZodYuHRI2DeDfJ_1-HkaAmgA8P8HAQ

https://www.summitracing.com/parts/pro-66415c

The Melling 3-piece pushrods are a little cheaper.

https://www.summitracing.com/parts/mel-500274?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-melling&gclid=Cj0KEQjw_eu8BRDC-YLHusmTmMEBEiQArW6c-N_zJb4lOJm0TKviz0HAdiACMMgIVO-mWBWuBSBjhRkaAiGG8P8HAQ

These Manley 1010 steel units are a little cheaper. They have .080 thick walls, and should be OK for open spring pressures up to around 300 or so.

https://www.summitracing.com/parts/man-25726-16/overview/




Edited by - Tub on 29 Jul 2016 2:33:38 PM
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69lemans
Tribal Scout

USA
24 Posts

Posted - 29 Jul 2016 :  4:47:15 PM  Show Profile  Reply with Quote
How about the magnum 270s or the 280H? They use the same springs as the thumper so that can save me a few bucks and it looks like it will work a little better with my CR. I am trying to learn as much about cam selection as I can but there is a lot more to it than I thought. Also comp is showing 2 different push rod lengths for the 270S, 9.30 and 9.15, how do I know which is correct for the 428 with 6X8 heads?
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Tub
Sitting Bull

172 Posts

Posted - 30 Jul 2016 :  12:16:53 AM  Show Profile  Reply with Quote
The 9.15 length is closer to stock, for stock length valves.

I think the RA4 engines had longer valves, and used closer to the 9.3 length. So, if you use longer valves, in order to run bigger springs, you may need longer pushrods. Of course, rocker arms, deck height, gasket thickness, and head shaving can all affect valve train geometry, and therefore pushrod length needed.

I don't think the cam should make any difference in the pushrod length needed. I used several different cams, over the years, but always used the stock length pushrods.

"...How about the magnum 270s or the 280H?..."

The 280H is a single pattern cam. Most agree that a dual pattern, with between 6 & 10 degrees more exhaust duration, runs a little better in a Pontiac engine. And, that 270S is a solid lifter cam which is also a single pattern. There are better cams for your 428.

I'd recommend somewhere between 220 & 230 degrees intake duration @ .050 lift, with an LSA of 112-114. With this in mind, the Crower 60242 & 60916 come to mind. Then the Crower 60243 is a step up.

http://www.cnc-motorsports.com/crower-60242-hydraulic-flat-tappet-camshaft.html

https://www.summitracing.com/parts/cro-60916?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-crower&gclid=Cj0KEQjw_eu8BRDC-YLHusmTmMEBEiQArW6c-BMTgdcT0Io-uZlLbF2s6MmVuh9GHmkk46F7RfZEmhIaAk1H8P8HAQ

https://www.summitracing.com/parts/cro-60243?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-crower&gclid=Cj0KEQjw_eu8BRDC-YLHusmTmMEBEiQArW6c-OyuDrXj-vNhEg3YLIXr_WMf8x_V8CAPnG629lKOoBgaAoCf8P8HAQ

I also like the looks of the Howard's 410051-14 cam.

https://www.summitracing.com/parts/hrs-410051-14/overview/make/pontiac

A Summit 2802 with Rhoads lifters might work.

https://www.summitracing.com/parts/sum-2802?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-summit-racing&gclid=Cj0KEQjw_eu8BRDC-YLHusmTmMEBEiQArW6c-G2zr2CKqjw3qzZPFrKoktN7povGtJfEizJoxQHvspAaAnnU8P8HAQ

https://www.summitracing.com/parts/rhl-9518

BUT, if you have only 8.5 or less compression, either a Summit 2801 or a Lunati Voodoo might be a better choice.

http://www.wallaceracing.com/cr_test2.php

The 2801 is sort of a higher lift version of a Pontiac 068 grind, which was used in the low compression 455HO engines.

https://www.summitracing.com/parts/sum-2801

The Voodoo builds more cylinder pressure, which helps low compression engines. So, for 8.5 or less comp I'd probably go with this small Voodoo, for plenty of low end torque for everyday driving.

http://www.lunatipower.com/Product.aspx?id=1775

https://www.summitracing.com/parts/lun-10510702?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-lunati&gclid=Cj0KEQjw_eu8BRDC-YLHusmTmMEBEiQArW6c-GI-fghIk5YGVj7JYfrn6MXmxmOft_m0IVQwMJ-ql0MaAnN88P8HAQ

My guess is that any of these cams I've listed will be better than the Thumpr.




Edited by - Tub on 30 Jul 2016 09:28:00 AM
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69lemans
Tribal Scout

USA
24 Posts

Posted - 30 Jul 2016 :  06:12:00 AM  Show Profile  Reply with Quote
Great information, thank you. I will look those up.
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69lemans
Tribal Scout

USA
24 Posts

Posted - 04 Aug 2016 :  8:56:51 PM  Show Profile  Reply with Quote
So I have picked the Lunati Voodoo 262/268. Any idea of what stall converter would be best for my set up?
I appreciate the input.
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Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 05 Aug 2016 :  01:58:30 AM  Show Profile  Reply with Quote
General rule of thumb is 500 rpm's over the low number of the rpm range. so with the cam above, a stock converter could be used. Double check your rear gear ratio.

I would Call or E-mail Mr Cliff with all currant engine and drive train specks for cam and converter recommendations. Mention your a PSP member.

http://www.cliffshighperformance.com/

cliffshp@embarqmail.com



Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 05 Aug 2016 02:08:30 AM
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Phil
The Great White Buffalo

USA
7214 Posts

Posted - 05 Aug 2016 :  1:55:57 PM  Show Profile  Reply with Quote
Those cam manufacturers "power ranges" aren't of much value IMHO. There are just too many variables with the main one being the cid of the engine. I laugh when I see an rpm range listed for 301-455's. Aside from them being a marketing gimic, who knows what size engine they even tested it on, if they tested it on a Pontiac in the first place.

Do your due diligence and try to find actual real world examples here and on other sites as that would be more reliable.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.

Edited by - Phil on 05 Aug 2016 1:57:53 PM
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