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Discussion Starter #1
Appologize for asking a question about a beaten to death topic..

A friend has an 86 GT. Original plan was to buy an upper/lower/T body & heads from an 89 H.O. and put it on the 86.

I read somewhere.. [maybey here?] that the 86 heads have the same ports & flow the same and are no different than the newer versions save for the combustion chamber being heart shaped on 86s.

So another friend at work told me the other day that while swapping the upper & lower intakes & T body was worth it, I should leave the 86 heads on it, as the 86s had more compression than the newer 87 & up H.O.s and installing the newer E7s onto the 86 will lower compression a tad...?

Is this true? Intakes and T Bodies aside, where does the power gain come from installing E7 castings onto an 86 GT... if the ports & flow are the same from the 86 to the E7 heads.. ?

Would the compression ratio go down if I install the E 7s on my buddies 86? Intakes aside.. Whats the HP gain worth both versions being unported/untouched by just swapping to the E7s..?

Thanks!!! :)
 

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Ok, the 86 heads just plain suck. For racing anyway. They are a high swirl head made for emissions. The E6's actually have a larger combustion chamber than the E7's. But the pistons on the 86's are bone flat where as the 87-up have a 4 eye brows in them. If you put E7 heads on a 86 engine you actuall raise compression from 9:1 to about 9:3 Not huge but some. The intake runners are also smaller on the 86 VS the 87 on up, so is the TB. Thats why the 86 were rated a 200hp and the 87 's were 225 . It just added up. I did this swap on my brothers car and we put on 1.7's on it with no problems. You just need to keep a stock cam when you do it. Hope this helps.
 

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The reason compression is higher in the 86 5.0's is because of the pistons, not the heads. The 86 pistons are completely flat, whereas the 87+ pistons have valve reliefs. Compression won't go down, BUT, be sure to check valve clearances.

The E6TE heads are even more restrictive than the E7TE's. The best thing you can do is melt them down into a boat anchor. Not kidding.

The 86 TB's are 58mm vs 60mm on the 87 and newer stangs. The upper intakes on 86's are a little more restrictive as well.

What will the power gain be? I'm guessing at least 25 HP. That assumption is based on the HP difference betweem 86's and 87 up stangs. Prolly even a little more due to bumped compression. You'll have ~ 9.2:1 with the 86 pistons.

Note: since you have them off, why not freshen up the E7's? Get them rebuilt for relatively cheap. Port them yourselves. You could go to a local parts store and ask for 1969-70 351 intake and exhaust valves. They are 1.84"/1.54" vs stock 1.72"/1.45" and they are inexpensive. I dunno if that will work with 86 pistons, though. Go the extra mile and upgrade the springs, too. Prepares you for future cam upgrades.
 

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Discussion Starter #4
Wow, thanks for such fast replies!

Told me everything I needed to know! Looks like we'll grab the 89 heads along with the intake... He's staying with the stock cam.. so clearance shouldnt be a problem...

Thanks alot! This board rocks.. Didn't even take 15 minutes to find out what I needed to know :)
 
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