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Old 10-13-2007, 04:50 AM
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Default How does the Ho make 20 extra horse power?

How does the 421 3x2 Ho @ 376 HP make 20 extra horse power Over the 421 3x2 356 HP engine? I'm guessing it might have some thing to do with the factory cast iron exhaust headers or did the none HO 421 cars get them too?

Thnaks

Brian

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Old 10-13-2007, 06:28 AM
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I would think the extra cfm from the tri-power, and better heads and the manifolds did help some. I bought a parts car 10 years ago, a 66 2+2. The 421 was gone but I got most of the good stuff that was salvageable. I did not know the rarity of the manifolds. I sold the scrap to a yard and when I went back and found the 65 parts car I bought he told me that a guy jumped up and down when he found the manifolds still on the car.

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Old 10-13-2007, 07:35 AM
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As Hitman said, the exhaust manifolds and the different heads. There is probably something else that I'm forgetting too. But they both have the same cfm.

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Old 10-13-2007, 08:04 AM
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This brings up a question I have always had. Could you get a 421 tri-power car that was not an HO car? If so, it would have to be the manifolds & 10.75:1 heads. I always assumed that all 421 tri-power cars would also have the manifolds, 093 heads & duals.

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Old 10-13-2007, 09:38 AM
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Quote:
Originally Posted by Deadhead
This brings up a question I have always had. Could you get a 421 tri-power car that was not an HO car? If so, it would have to be the manifolds & 10.75:1 heads. I always assumed that all 421 tri-power cars would also have the manifolds, 093 heads & duals.
yes the 421 tripower was the 356 hp version. Same intake,heads (77) and carbs. As Pitt 64 said the HO has a different camshaft and exhaust manifolds. I belive the early 421HO's had forged rods. Somewhere in early 65 they dropped the forge and went with cast. My engine is cast 4-28-65 and has the cast rods. (dangit)
Patrick

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Old 10-13-2007, 01:22 PM
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cam and exhaust are the big diffs.

patrick, you don't want the early forged rods, they're called rubber rods for a reason.

mike

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Old 10-13-2007, 02:19 PM
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In '65

Tripower (HO) Tripower (non-HO)
Forged rods cast rods
Forged crank cast crank
#77 heads (higher comp) #76 heads
068 cam 067 cam
factory headers standard exhaust manifolds
extra block for oil flow? did not have the extra block

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Old 10-13-2007, 03:03 PM
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Like Mike said, the big difference in the 1965 376hp and the 356hp was the long branch exhaust manifolds used on the HO, and the HO also used the 068 cam, plus the HO had the three small air cleaners. The 356hp did use the same #77 heads as the 376hp HO, but used the smaller 067 cam. The 356hp also used the large single air cleaner which was probably more efficient than the three small ones, but the small ones looked cool, because you could see the multiple carburetion. The 338hp 4bbl. motor is the only 1965 421 that used the #76 heads.

Also to answer Deadheads question, Yes you could get a 421 tri-power that was not an HO,only the 376 hp version was considered an HO. On the 093 heads. The 093 head was used on the 356 and 376 in 1966 models, and the 092 head was used on the 338hp 4bbl. You can find all this in Pete McCarthy's book.


Last edited by Doug Hopkins; 10-13-2007 at 04:50 PM.
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