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bolt on heads for 392?
I have been researching heads for my 392.
The seem to be a lot out there. The only problem is having to flycut the pistons for most of them for valve clearance. Taking apart the engine for new heads would totally negate the reasons for purchasing the FMS 392 as an economical powerplant. Has anyone found a good head that bolts onto an existing motor? Do you like the new heads? Did you do a before and after dyno? I talked to an engine builder who heard that Trick Flow 'High ports' will bolt on, but Trick Flow does not produce these anymore. Still looking. |
Dana;
Check with the guys at AFR. They make a great head,it is CNC cut from the start and one of the best on the market and the price is comparable with the other head manufacters. The info I have seen says these heads are bolt on and you should have no problems with most cams. I would guess anything around .550 lift or less would work just fine. Go to their web site and ask thru the tech line and they could give you specifics. When I build my 393 (hopefully soon) that is the combo I will use. It should be good for 500-525 hp. David |
I know of a guy who will port the 392 GT40X heads and has recently promised my friend a 75HP gain on his 392 FMS crate motor for $500, no milling. I can attest to that as I have the same heads on a 351W and for $350 he promised me 50HP. I gained 42rwhp on the chassis dyno after his bowl and port job with a 64-55cc flat mill. I may have gained another 10HP but limited his time on my heads. The 392 stroker has more potential. They say GT40X heads do not respond well to porting by those unfamiliar with their turbo swirl design. He does shelves of them and he knows just where to touch them. No doubt there are better heads out there and AFR's are by far superior to the GT40's but dollar for dollar they can be worked for a cost effective gain. I did the install myself . All I added to the cost were gaskets and new head bolts. E-mail me if you would like more info.
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My mechanic checked with AFR and they said I might have to flycut the pistons. One article I read said I wouldn't , another said i would.
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One of the features of the TFS is, you shouldn't need any additional piston/valve clearance with the major caveat, "Depending on the cam you're using".
Assuming you got the FMS short block, which is why you're shopping for heads, and unless the FMS 393 has a roller cam in it, you may want to shop for a retrofit cam as well. Clay at least one piston on either side of the block with checking springs. You should have a minimun of .100 clearance on intakes, and .150 on exhausts. |
AFR 185's are almost certain to require flycutting. MM&FF put on the same motor you have and got 75HP. Heads were milled and required flycut pistons. You could try the AFR 165's. They are good too but do not flow as much as the 185 but more than the gt40. I have them on a supercharged 306 in a Mustang Cobra. I would personally try the port job on the GT40's. Cheap and effective
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If the pistons you're now using clear the valves, and you're using the same camshaft, and the existing heads have the same valve diameter as the new ones, you should be OK. However, if your existing heads are using 1.94 intake valves for instance and you put on the AFR's with the 2.02's or the 2.08's you will probably need to flycut the pistons to allow for the larger valve O.D. and not the cam lift. But use a little bit of clay on the top of the piston, put the cylinder head on and turn the crankshaft 720 degrees by hand and see if you have any clearance. If you feel any resistance stop immediately. Use the clearances that Jack21 gave you and you should be OK.
h dog |
No fly cut with Jeff at Modern Cylinder Head
810-468-7914. He does the Ford Racing warranty work. He will make your GT40X's sing. |
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