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#1
12-11-2018, 04:51 PM
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Comp Cams 270H Grind in 428
This cam appears to have a similar grind to the RAIV factory cam. How will this work out in a 428 with power brakes?
Will low vacuum be an issue with this cam?
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BONESTOCK GOATS '64 GTO Tripower Hardtop (Wife's Car) '64 GTO Tripower Post Coupe (My Car) '99 Bonneville SE Sedan |
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#2
12-11-2018, 04:58 PM
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Are you at sea level?
It's ground on a 110 but duration at .050 is only 224 so it's not all that big. I've run similar cams in engines of that size and up here at 5,000 feet and they still make 12 inches of vacuum once everything is tuned. Plenty for brakes. Down at sea level I generally sea a solid 3 inch of vacuum increase. |
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#3
12-11-2018, 05:11 PM
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We're at 770 feet above sea level in Winneconne, Wisconsin.
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BONESTOCK GOATS '64 GTO Tripower Hardtop (Wife's Car) '64 GTO Tripower Post Coupe (My Car) '99 Bonneville SE Sedan |
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#4
12-12-2018, 02:38 AM
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What makes you think it's similar to the RAIV? The lift is the only thing that's close. Much shorter seat timing, single pattern, 6 degrees less @ .050" on the intake and about 16 degrees less @ .050" on the exhaust, 3-4 degrees narrower lobe separation, ICL 3 degrees advanced from where the 041 was.
I ran that cam in a stock '71 400 (8.2:1 compression) in my '73 with an M-20 and 3.73s. It idled fine at 700 RPM, made about 15" vacuum, was a little soft below 2500 then pulled strong 'til about 5000 then it was done. In a factory 428 with higher compression it would have much better bottom end but still not make power past 5000 without headers and a good exhaust (my heads were stock with log manifolds and a crappy small exhaust system). Should make better vacuum and have a very strong midrange punch. Might be detonation prone in a 10+ CR engine.
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---------------------------- '72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car! '73 Firebird 350/4-speed Black on Black, mix & match. |
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#5
12-12-2018, 07:06 AM
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I have run the similar Isky grind in a 1978 8 to 1.comp high milage 400 with a auto trans and it was nice ,so in your 428 you should love it!
It's a great highway grind with tremendous snap between 2800 and 4500 rpm!
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#6
12-12-2018, 08:32 AM
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The compression ratio will be a BIG player in how much vacuum the engine will make.
Not really enough cam or a very good choice for a 428 build...IMHO. The 428's have EXCELLENT potential, and will make the power of a 455 without much effort, but you need to cam them for it......Cliff
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#7
12-12-2018, 12:24 PM
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This looks like Comp Magnum Lobe # 5201. If I plug this in to EA Pro, using the specs from the cam card and the Comp catalog it predicts a 10:1 CR 428 will idle at 16.5" hg, a 9:1 CR will idle at 15.8" hg. The 10:1 motor shows a cranking compression of 204 PSI with this cam- which is pretty high for pump gas.
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1964 Catalina 2+2 4sp, 421 Tri-power 1965 GTO, Roadster Shop chassis, 461, Old Faithful cam, KRE heads 305 CFM, Holley EFI, DIS ignition. 1969 GTO 467, Edelbrock 325 CFM, Terminator EFI 1969 Firebird Convertible |
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#8
12-12-2018, 12:55 PM
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Since there are obviously much better cams available, I'm just curious as to why you're posting about this one. Is this a cam you already have, or maybe one you can get super cheap ?
If not, I'd definitely consider something else. Everybody here knows I'm no expert. But, if it were mine I'd consider one of these, rather than the single pattern listed. As Cliff said, CR will make a difference. https://www.summitracing.com/parts/s...RoCJdgQAvD_BwE https://www.summitracing.com/parts/c...IaAusEEALw_wcB https://www.summitracing.com/parts/cro-60243 https://www.summitracing.com/parts/h...w/make/pontiac And, since I like Rhoads lifters, I'd run 'em, with any of these 4 cams. Last edited by ponyakr; 12-12-2018 at 01:11 PM. |
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