My 351 Heads Thread

[Brown_Muscle]

Allright we'll as some of you know I recently aquired some GT-40 Heads from a 97 explorer with about 75K miles on them. I decided to stop jumping around from thread to thread and make a dedicated one.

I know theres plenty of info and threads on the subjects relating to 302's but I had some questions not answered about 351's.



1) will my factory pushrods work with these heads?

2) All the accessories for the police 351 for 1982, will they bolt right onto the front of the heads without modification??

3) Will my stock valve covers fit?

4) Can anyone point me to a place with all the torque specs for the Heads, rockers, and anything else i might need

Thanks in advanced guys its GREATLY appreciated! I'll post pix and updates too!

[RunUoveR]

your stock push rods are the rigth length and will work

the stock springs on GT40s tho are ment to be used with roller lifters. just something to keep in mind depending on the lifters you have and if you plan on getting alot of lift on the cam

stock valve covers fit assuming everything under them is stock, rockers and such

the external castings of GT40 heads are just about identical to anyother 302/351w head. accesories, bolt patterns, valve covers, all that will bolt up the same and i believe the head tq specs are the same as any other iron W head and i think the rocker tq is 25 ftlbs and the head bolts are 60

[Brown_Muscle]

I plan on using the stock cam for a decent amount of time, I should be allright with that correct? I wont be loosing power or effeciency from the different springs correct? I guess What im asking is weather it will hurt anything to have the stock springs on it?

4) will my compression ratio change with these heads (just out of curiosity)

[RunUoveR]

depends on what your stock combustion chamber size is in compairson to the GT40's


ya, you'll be fine with the springs. but when it comes time for a new cam just plan on buying springs to go with it while your at it. i knew someone who put a pretty high lift flat tappet cam under stock GT40 springs and ended up flattening out a few lobes and lifters. stock cam should be fine tho

[Brown_Muscle]

gotcha, thanks!!

[gadget73]

1) Maybe. You'd have to check once they're installed. Not all factory 302 pushrods work on gt40 heads so there is no way to say for sure.

2) Should work fine.

3) Yes. Same valve cover.

4) I'd suggest picking up some sort of manual for reference. It will give you the torque pattern and values. Most any will have this, even if you have some manual for another Ford product laying around that covers a 351.

[Brown_Muscle]

ok, if the pushrods do not work what rods would i have to order to make them work?

[gadget73]

You'll need to install the heads and get or make an adjustable pushrod to figure that out. Basically you need the ones that fit. No idea what that size is, but its what fits.

[Brown_Muscle]

ah i c. Well if they dont fit I'll definitly need to find out what does somehow...

[Tiggie]

Your current heads should have 69cc combustion chambers. The GT-40 has a 64cc I think, which would bump your compression a bit. Nothing to require premium fuel or anything.

[Brown_Muscle]

sweet, cause 8.3:1 is a sad number for a N/A engine... lol, at least IMO... haha.

Sorry for the newby questions, This is the first time taking heads off an engine, and first time doing anything really major, but how will i know if pushrods are the incorrect length? And how would i determine what length i needed? Just grab rrandom pushrods from different 5.0 engines and put them in there? It would be a real disappointment to take everything apart and go to put it together only to find i have no way to know how to make the pushrods work...

I've been trying to look it up on the general internet, and havnt been able to find much...but the one source i found said i could just bolt it right up and it would be fine....

[gadget73]

There is a lifter preload figure. The plunger is supposed to depress a certain amount when you torque down the rocker arm. The best way to do it is with a dial indicator, but you can set it to zero lash and count the number of turns of the rocker bolt from zero lash to torque to determine the preload. Its supposed to be between 1/2 and like 1 1/4 turns past zero lash. If its outside that, you need longer or shorter, depending. If your stockers don't fit, what you do is stick the adjustable one in there and mess with the length until the preload is where it belongs. Measure the adjustable at it's final length with a caliper, then order pushrods of that length.

[Brown_Muscle]

ooh ok i see! thanks! Well I'll cross my fingers and hope it goes together. Should I try to just do the 1/2 turn at first so i dont overtighten and have the valves hanging open? or go a little beyond that? This is assuming i cant find the figures and a dial indicator. thanks again Thain!

[gadget73]

you want to reach torque. You can't over-tighten the valves unless the pushrod is wrong. Its not like a Chevy, you just make the bolts tight. The adjustment is made either with shims under the rocker for a too long pushrod, or a longer pushrod if its too short.

[Brown_Muscle]

ohh i gotcha... I'm wondering weather i need to take the heads to a shop and have them do a valve job...but that makes me nervous, plus it'd cost 150+ and i cant spend that kind of money on this project, the water leaking past the valves from the intake and exhaust ports has me worried and im unsure weather the Permatex valve grinding compound will do the job to make everything fit together tight...

an article like this one from yahoo answers: http://autos.yahoo.com/maintain/repa...ques054_1.html
has me shaking in my boots at all the expensive and extensive work that needs to be done.

I guess all i can hope to do is lap the valves..and use that fluid test to see if they leak... and go from there.

The main problem here is money... and if i cant get these at least worthy of going on the car I'll have to sell them, hopefully for at least 100 more than i got them for because they'll be cleaned up and primered