Understanding head specs 351w
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Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=32864
Printed Date: May-29-2024 at 10:39am
Topic: Understanding head specs 351w
Posted By: ny_nautique
Subject: Understanding head specs 351w
Date Posted: February-17-2014 at 9:06pm
Hey guys... it's been a few months since I've logged on.
I've had a busy winter and am just back to thinking about my boats.
I'm back looking for heads for my 351W and while I know the GT40p are the preferred upgrade, I found a cheap set of already remanufactured stock iron heads.
This got me looking at the specs of the various castings and of course opened up a few more questions for me.
My stock heads are casting http://www.castingnumbers.info/site/detail/18359/D8OE-AB" rel="nofollow - D80E-AB which show as 69cc chambers, 1.78/1.45 valves, stamped steel rockers.
The set I found are C90E-G which aren't referenced on that site. I found in http://classicbroncos.com/forums/showthread.php?t=186689" rel="nofollow - this thread that said they are 1.84/1.54 valves 58 cc, but somewhere else it references 60.4cc.
Anyway, looking at the specs for the GT40p, it shows they have between 58-61cc chamber volume and 1.84/1.46 valves.
So... what's the relationship between compression chamber in the cast iron's vs the GT40p's and... are the C9OE-G heads a noticeable step down for me?
Thanks.
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- Jeff
1999 Ski Nautique
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Replies:
Posted By: Gary S
Date Posted: February-17-2014 at 11:05pm
I had D0OE's on my 302 which I believe are the same,18mm large sparkplugs right? I changed to P's from TriState with larger yet valves.In my application the compression stayed the same but in your case would be higher than your originals.There was a noticeable increase in low to mid range with the P's. As to a step down for you,no IMHO but you might not notice much difference between your originals and those C90E's.
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http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS
95 Nautique Super Sport
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Posted By: halfnelly
Date Posted: February-18-2014 at 10:42am
The D8OE castings are about the worst factory head Ford made. Small valves, huge chambers, small ports, you name it. They're from the late 70's smog era. The C9OE and D0OE ('69-'70 351w)castings have much smaller chambers and bigger valves and were the hot ticket back in the days before aftermarket heads (like the C5-C6 289 heads with 54cc chambers). Production heads like the GT40's and GT40P's . However, the chamber and port design is a lot better in the GT40's and GT40P's and will flow more air as-cast. They're also a lot easier to find since they haven't been out of production nearly as long as the early 351 castings.
The 4 bar GT40P's are about the best factory casting for a Windsor motor. Yes, they use a smaller exhaust valve than a 3 bar GT40 head, but they are more efficient and flow about the same. The smaller chambers and lack of thermactor holes give them an edge over the standard GT40. The unconventional plug angle that plagues car guys is also a non-issue in a marine application. I plan on replacing my standard GT40s with some P's when it comes time for a rebuild in my Sport.
Here's everything you could ever want to know but were afraid to ask about the GT40 series heads:
http://www.fiveohinfo.com/performance/gt40-gt40p.html" rel="nofollow - http://www.fiveohinfo.com/performance/gt40-gt40p.html
Brian
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Posted By: ny_nautique
Date Posted: February-20-2014 at 9:17am
Thank you Brian, that is very helpful. While I would like to get the GT40P heads, for this price it may be worth it for me.
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- Jeff
1999 Ski Nautique
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Posted By: cadunkle
Date Posted: February-20-2014 at 10:51am
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Just my opinion but with how cheap good aftermarket aluminum heads for small blocks have gotten I wouldn't spend the time on porting iron and money on machine work for factory iron heads. You'll be into the factory iron heads for at least half the cost of decent aluminum heads and that's generally my threshold for just buying the better/easier/newer/whatever part.
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Posted By: wholman
Date Posted: March-29-2014 at 7:13pm
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Get some World Product Windsor Sr or Windsor Jr heads. Way better than any factory Windsor head and the same price as GT40's
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Posted By: oldcuda
Date Posted: March-29-2014 at 7:34pm
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For a good replacement head World heads are a step above even best oem IMHO.
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