Compression Ratios and HP
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Compression Ratios and HP
Ok I got a 1978 302 from a merc cougar. I ditched the low compression heads for a set of 69 heads. First question is whats the compression ratio and second is what would be the hp diffrence?? Thanks.
BTW motors being build for a 88 ranger swap
BTW motors being build for a 88 ranger swap
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Got the casting numbers off both sets of heads?
It appears the '69 heads could be 53.5, 58.2 or 63.
'78's aren't on the list.
Kelly hotrod - Ford Engines Page 3
A '69 might have been 9.5 at the most. I don't recall if they still ran them up to 10 or 10.5 for 4bbl 302s. By '69, the 351w was the upgrade, with the Boss 302 as the real high performance, and the 351c on the horizen.
So if you went from 8 to 9.5 but kept everything else the same including the quite possibly miserable stock cam, you are talking 10 to 15 hp by my WAG.
This is from a Porsche site, and the guy references a "rule of thumb" about getting a 4% increase in torque from a 1 point increase in compression. Enough graphs to make your eyes hurt, but you'll get the picture:
http://forums.pelicanparts.com/911-e...io-torque.html
It appears the '69 heads could be 53.5, 58.2 or 63.
'78's aren't on the list.
Kelly hotrod - Ford Engines Page 3
A '69 might have been 9.5 at the most. I don't recall if they still ran them up to 10 or 10.5 for 4bbl 302s. By '69, the 351w was the upgrade, with the Boss 302 as the real high performance, and the 351c on the horizen.
So if you went from 8 to 9.5 but kept everything else the same including the quite possibly miserable stock cam, you are talking 10 to 15 hp by my WAG.
This is from a Porsche site, and the guy references a "rule of thumb" about getting a 4% increase in torque from a 1 point increase in compression. Enough graphs to make your eyes hurt, but you'll get the picture:
http://forums.pelicanparts.com/911-e...io-torque.html
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Heres the numbers off the 69 head
D0OE
302 69
B / 9
And the ones off the 78 are a little hard to see... Pretty sure it says D8OE
and its got a 15 on it where the "9" is on the 69 head.
Got all these goodies for free (those are the 69 heads) but dont think the headers will work out on this project...
D0OE
302 69
B / 9
And the ones off the 78 are a little hard to see... Pretty sure it says D8OE
and its got a 15 on it where the "9" is on the 69 head.
Got all these goodies for free (those are the 69 heads) but dont think the headers will work out on this project...
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1970 vs. 1978 heads...
Check this thread out:
https://www.ford-trucks.com/forums/9...d-on-351w.html
and this is better:
https://www.ford-trucks.com/forums/6...80e-heads.html
The DOOE heads are better. Only drawback would be the lack of hardened seats for unleaded gas. You can fix that.
BUT the rocker change is a big deal, so check that.
Check this thread out:
https://www.ford-trucks.com/forums/9...d-on-351w.html
and this is better:
https://www.ford-trucks.com/forums/6...80e-heads.html
The DOOE heads are better. Only drawback would be the lack of hardened seats for unleaded gas. You can fix that.
BUT the rocker change is a big deal, so check that.
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The DOOE heads are good but i don't know if there worth the work , i have a set on my truck , but they all ready had new seats and bigger valves installed , and screw in studs , they came off a 69 351 mach I , my comp ratio with them is about 9.5 , i used 1.72 roller rockers with guide plates and hardend push rods , I like the adjustable valves , they went on a stock 92 302 HO short block....Lew
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old75F-100
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
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Mar 13, 2006 07:44 AM
