So, I pulled a set of GT40 heads off of a 1996 Explorer for my 351W build to go in my 1995 F150. What all do I need to do have the machinist due to the heads?

Here is what I think I need. Please let me know if I am wrong or missed something:

1) Bore the bolt holes out to 1/2"
2) Resurface all mating surfaces
3) New valve guides
4) New freeze plugs. Some recommend brass?
5) A good cleaning
6) Grind valves and seats,
7) Get out the 2 intake bolts that snapped off...one in each head.

What I don't know:
1) Should I just replace all the valves now, or reuse the old valves?
2) Do I need new springs? (I plan to go to 1.7 rockers)
3) Do I need to mill the head surface down to increase the compression ratio, as I believe the GT40's will give me a lower compression ratio than the E7 heads?
4) Any recomennded 1.7 rockers? Or just go with a set of stamped rockers? (This is a mild build to replace a 302.)

Thanks

 

Subscribed, what machine shop in VA are you working with?

 

None yet. Any recommendations?

 

Magnaflux is cheap most places & will find cracks in seats saving $$$ & time.

Measure your bolt holes first. I had one head 1/2, one 7/16 off the same Explorer.

Would not have exhaust or intake faces resurfaced, clean-up pass on the chamber side is fine.

Valves should be OK, but check for run-out or pitting.

Standard valve grind is fine for 90% of rebuilds, 3-angle is gravy, but costs more.

New guides are great, but it depends on just how much wear there is.

Roller tip/roller trunnion rockers will decrease wear on guides over sled type rockers & decrease oil temps.

I like brass freeze plugs. Steel is OK & will probably last as long as you have it.

Most aftermarket/greater-lift-than-stock cam's manufacturers will strongly recommend a better than stock spring package.

Stock SBF springs are known to float when approaching 5K RPM & a more aggressive profile than stock will do it in a heartbeat if there is any dip in oil pressure.

I have Crane "Cobra" rockers & longer than stock push rods to get somewhere near the correct lifter pre-load. Lots of folk have used Scorpion bolt-down rockers.

Some people say they have gotten away with stock length, but if you machine head, you're changing push rod length.

Invest in a push rod length checker ($15 & up) and some "checking" springs (under $10) to set correct spring height with the shims that come with the springs.

My next set I do, I'll definitely have the pedestals machined for adjustable rockers rather than bolt-down. But that's just me.

The cheaper cost of the adjustables will off-set the cost of machining & there is a much wider selection than bolt-downs.

E7 heads have a chamber volume of 62-65 cc, F3ZE (Cobra/Lightning/96 Exp) heads are 60-63 cc.

Measuring is the only way to be sure.

All the above is strictly my interpretation. Your results may vary. Others will differ greatly. Good luck.

 

Thanks for the list. That is very helpful.

I tried to look up adjustable rockers. I really don't know anything about them. The few I found seemed much more expensive. What am I missing?

 

Adjustable rockers (If I understand previous comment) are stud mount, and not applicable to the pedestal mount heads to picked up. I think Scndsin covered it all, but what I would like to add in the way of deciding what to replace or reuse, it Alexesparts.com. All I'm saying is that they offer affordable, quality replacement parts especially for the SBW cheaper than Summit. I got everything listed in the above post from them when I did my GT40 heads and have had zero issues since.

 

OK, there are 2 basic types of rocker arms, bolt down & stud mount (adjustable). The GT40s & all stock small block fords for a couple decades back are bolt down or "pedestal."

These were sold by Crane for Ford & called "Cobra" because they came on 93 Mustang Cobras, stock.

https://www.summitracing.com/parts/crn-44746-16

When you rebuild and install a head other than exactly what you had (and sometimes with a stock head too), you increase/decrease distances & things like push rods aren't long enough & you measure then buy a custom length push rod like I did.

Even with adjustable rockers, you still have to buy custom length push rods most times.

This is like the least expensive set (summit) of full rollers for a SBF & except they are stud mount, rather than pedestal & 1.6 ratio, identical in construction to the Cobra rockers I paid about $240 for.

https://www.summitracing.com/parts/c...44-8/overview/

Like I said, on my next set of GT40s, I'll pay a hundred bucks or less to have the pedestals machined down & tapped for bigger studs & buy a better set of rockers with adjustability.

Wish I could find a good rocker tutorial for you right now.

I'm certain I could take the Cobras off my 5.8 & swap them over to my 5.0 GT that's never had a valve cover off & they'll fit with no issues.

It's all a matter of preference, budget & mechanical skill/comfort.

Sorry if I've confused the issue for you.

 

Could he use these? They are adjustable pedestal rockers.

https://www.jegs.com/i/PRW/228/0335101/10002/-1

 

That's a new one on me, but sure I guess so.

 

Thanks for all the education. It is really helpful. Looks like I have 3 options. When I find a machinist, I'll go over the pro's/con's of each one.

I also found a post in another forum while researching this topic where someone made "homemade" adjustable pedestal rockers using a 3/8" washer and an additional nut to lock the 2 nuts together. See post #8 here:

351w nightmare! | Maverick/Comet Forums

I apologize if my questions sometimes seems basic. I am not a mechanic and a lot of this is new territory for me. I learn as I go.

 

Not a problem. We all learn when we can. Hobbies get expensive when you mod stuff with only partial knowledge.

Good luck to you.

 

More questions:

Should I replace the springs or use stock springs with the following setup:

Stock 351W cam and 1.7 rockers?

And what is the max lift for the above setup? (I read .552 elsewhere, but wanted to confirm.)

 

There is a formula for max lift, but I can't give it to you. But I'd bet you'd be perfectly safe. Measure with clay.

A complete new spring kit (springs, retainers, keepers, seals) is the best insurance to see you get all the performance from a cam change, that you don't float a valve, or drop one in a cylinder.

Yes you can use the stock springs.