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Old 09-09-2009, 03:34 PM   #1
scootchu
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Default Would I notice a big difference with GT40 heads?

My 302 has 2V heads on it presently and although it runs well I am considering buying another block to rebuild over the winter, provided I can get things sorted out in my head as to what I want.

So while waiting for the guy with the 302 block and complete 302 engine to get back to me, I saw he has a set of DOOE 351W heads for sale.

Also another CL-er has a set of GT40 heads nearby.

Would either of these heads make a noticable difference.
I am not sure of the chamber size on the 2V 302 heads, but I know it's larger than the 4V heads correct.

Both sets are complete.
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Old 09-09-2009, 04:20 PM   #2
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I have the 289 on my engine stand i took out of my mustang.
I had done several things to it. GT 40 heads a new cam, eldel rmp intake, 625 carb and malory ignition. Bored 30 over it all wored well together it Felt like a big improvement.

Now that said the new crop of aftermarket heads are the way to go.
I have afr 185 on my 347 but doing another I would go with the new edelbrock.

The gt 40 is a improvement but not as much as the alu heads out now.
My guess if I took everything except the paxton off my 347 and put it on the 289 it would
be like 2- 289s compared to the way it sits now.
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Old 09-09-2009, 04:26 PM   #3
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The 289/302 heads varied in combustion chamber size, but it was due to the year, not the carb size. The only year for a unique 302 4V head, in fact the only year Ford even MADE a 302 4V was 1968. 289 2V and 4V had identical heads, no difference in part number or construction. The 289 4V and 302 4V had higher compression than the 2V because they used flat-top pistons.

You can get much of the advantage of the GT40 heads by porting your 302 heads. The exhaust was the weakest link in the stock heads, even the 289HP heads flowed no better than 2V without porting. I have mine ported, and the difference was immediate and very noticeable.

The GT40 is the 5.0 version of the 351W head. The combustion chamber is larger, though, to account for the 351 displacement. You'll lose compression ratio if you use them with your 302 pistons.

There is a lot of potential for porting the stock 289/302 head. Crane used to turn service replacement Ford heads into "Fireball" heads by porting them. The exhaust ports were so large they required special headers:


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Old 09-09-2009, 05:14 PM   #4
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here's the skinny.....

the gt40 heads are very close to the early 351w heads, but the gt40 heads are better in stock form.

the 351w heads would be a great buy if they are cheap, because you'll have to pay to get hard exhaust seats installed along with whatever other machine work you have done to them. I'd recommend having .010-.020 milled off either set of heads to help drop the chamber size.

point of reference: my 289 that is zero decked with speed pro lyper flat tops (4 valve reliefs) and milled 351w heads (about 60cc) makes between 8.5-9.0:1. getting pistons that were only 2 valve reliefs would have bumped me between 9.0-9.5:1
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Old 09-09-2009, 05:42 PM   #5
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Holy Moly. My head starts to spin, but I appreciate the feedback. The 351 heads have an asking price of $200. The GT40's have an asking price of $195. My gut feeling was steering me towards the GT40's having read that I could have to sink some dough into the 351's. The 40's seemed as you guys said be better in stock form. I would love to go the AFR route, but man they are expensive. I have a problem parting with large chunks of cash. I like bang for the buck.

I haven't had the heads off of this engine yet and I doubt that they have had any work done to them at all.
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Old 09-09-2009, 06:03 PM   #6
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Quote:
Originally Posted by scootchu View Post
Holy Moly. My head starts to spin, but I appreciate the feedback. The 351 heads have an asking price of $200. The GT40's have an asking price of $195. My gut feeling was steering me towards the GT40's having read that I could have to sink some dough into the 351's. The 40's seemed as you guys said be better in stock form. I would love to go the AFR route, but man they are expensive. I have a problem parting with large chunks of cash. I like bang for the buck.

I haven't had the heads off of this engine yet and I doubt that they have had any work done to them at all.
For a couple hundred you should be able to get your heads port matched to headers or HiPo manifolds. This would give you your most bang for the buck.

Of course, if they need to be rebuilt, with seats, guides, etc., you may as well get the GT40s and have them rebuilt.
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Old 09-09-2009, 07:17 PM   #7
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I'd jump on the GT40's. Add in the cost of a valve job and resurface (200-300 depending on the shop) and you should be into your heads for 4 to 5 bills.

Btw, if they are GT40P heads, your gonna need headers that will fit because the spark plug is at a different angle. Also just for the info, the P's have smaller exhaust valves than the regular 40's.
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Old 09-09-2009, 07:42 PM   #8
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Is the larger chamber size going to knock the comp ratio down?
I know my engine is 68,69,70 era. The 68 2V heads were 63cc and the 69-76 were 58.2cc

The Cast Iron GT 40 are 65cc or so.
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Old 09-09-2009, 07:50 PM   #9
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Oh crap maybe I should just go and buy these.
Click the image to open in full size.
Guy is asking $1200. Says they are new and the springs have been upgraded to Pac racing beehives.
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Old 09-09-2009, 08:18 PM   #10
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I heard that there are two different sets of GT 40 heads you gotta watch out for though, one you can put most regular headers on to and the other you gotta have a specific header to those heads or it won't work. Is this true?

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Old 09-09-2009, 08:18 PM
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1992, 289, 302, 351w, 50, cranr, differences, engine, firball, ford, gt40, heads, sale, swap, tuning

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