Cylinder head swap challenge - be warned, NOT mopar

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octanejunkie

octanejunkie

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OK so just to be clear, I am working on several projects, Ford, Chevy and Mopar; I like to be well-rounded in my interests and find playing with the "big 3" very enlightening. That being said, I am doing a GT40 head swap on a 67 Mustang.

The GT40 heads I pulled (casting F3ZE-AA) are 60-63cc Cobra heads off a '96 Ford Exploder, they have pedestal 1.6 ratio rockers (almost identical to dodge magnum heads) and two different tip length valves between INT and EXH, with the EXH valves running roto-caps.

I can replace the EXH valves and get the same installed height of 1.790 on both INT and EXH no problem, and use valve spring shims to set the correct installed height, but the rocker setup is vexing me; the stock ford setup is not adjustable. Looks like the Hughes 1555 is awesome but not specific to Ford. So I either run the stock valvetrain on the 5/16" ford pedestals or drill and tap the stud bosses and install roller rockers. But that is now without issue either.

Roller rockers required guide plates or self aligning rockers. Going with guide plate requires machining of the stud bosses to accommodate the plates, another operation which is not super costly but does add up. I found these Proform rockers already set up for my exact application, not sure if they are adjustable...

Questions to the experienced masses:
1. replace EXH valves or run roto caps?
2. run stock ford pedestal rockers?
3. machine for studs and guide plates?
4. run the proform retro rollers and skip machining stud bosses?

I welcome all advice, suggestions and opinions - even a mild bit of Ford bashing!
 
Different valve stem heights between int/exh valves? That seems odd.

How would running "roto (I assume that means rotator caps?) caps" affect the stem length? If the application is high performance I would ditch the rotators cause they weigh a ton and will contribute to valve float.

I'm not normally a Proform advocate but they do say their billet and the price sure is good so I think that's the way I'd go as long as you know the geometry will be correct. I bring geometry up because if their designed for a certain valve stem height and you don't have that the geometry can/will be off. Are the int/exh pedestals also a different height = to the different valve stem heights? If so their shouldn't be a geometry issue. If their the same height I'd swap out the valves for = length valves.
 
fishy68 said:
Different valve stem heights between int/exh valves? That seems odd.
Click to expand...

Sorry for any misunderstanding, the valve tip lengths are different on the two valves, overall length is the same. The keeper grooves are lower on the exhaust valves to accomodate the roto-caps. Valve stem height is not an issue.

I'm not normally a Proform advocate but they do say their billet and the price sure is good so I think that's the way I'd go as long as you know the geometry will be correct. I bring geometry up because if their designed for a certain valve stem height and you don't have that the geometry can/will be off. Are the int/exh pedestals also a different height = to the different valve stem heights? If so their shouldn't be a geometry issue. If their the same height I'd swap out the valves for = length valves.
Click to expand...

I agree regarding Proform, but since they do say billet and the price is right I figure we'll give them a try, this is not a high HP build so hopefully we don't get into trouble. I agree, valvetrain geometry is a big issue and concern in any build, luckily all pedestals are the same height and the only issue with the head config was the different keeper groove heights (tip length) between INT and EXH valves - ordered new EXH valves from Rock Auto yesterday BTW
 
octanejunkie said:
Sorry for any misunderstanding, the valve tip lengths are different on the two valves, overall length is the same. The keeper grooves are lower on the exhaust valves to accomodate the roto-caps. Valve stem height is not an issue.

No problem. I understand now.
Click to expand...

I agree regarding Proform, but since they do say billet and the price is right I figure we'll give them a try, this is not a high HP build so hopefully we don't get into trouble. I agree, valvetrain geometry is a big issue and concern in any build, luckily all pedestals are the same height and the only issue with the head config was the different keeper groove heights (tip length) between INT and EXH valves - ordered new EXH valves from Rock Auto yesterday BTW
Click to expand...

Sounds like you should be fine going that direction.
 
...the trick flow rockers on the 93 mustang we built are adjustable... of course we are using 1.7 on them.
 
I'm not versed on Ford... So I'd like to say lose the rotators and the cam and required spring should dictate the rest. I cant say if that causes issues with your heads. On the rockers, typically the exh side can use more ratio in most heads. Again, I dont know enough to be able to say on your choice...lol.
 
Crane used to make a kit for the SBF to convert to stud mount rockers. Hard to find these days. I think the Hughes kit uses Chevy rockers, so no good there.

THis guy sells a drop in spring kit for stock Ford heads that is pretty popular on the Mustang Forums. It has different height locks to take the stock Ford valves into account.

http://www.hunterstyle.com/thumper/

Trick Flow sells this kit: Its cheaper, but can't run as much lift.

http://www.summitracing.com/parts/TFS-2500100

As for adjustability, I wouldn't sweat it too much. You might have to order a set of pushrods, but that's no big deal, and much cheaper than all that machine work. Unless you're planning on changing cams a lot....

I would not run Proform rockers. Lots of companies make pedestal rockers for small block Ford. Scorpion is a good brand that is relatively inexpensive. Just get a shim kit with the rockers and you should be fine.

The GT-40 heads will be a good upgrade flow-wise for the older 289 casting, but I'd definitely get them CC'd and milled. The stock heads are probably like 54cc chamber, and you'll be sacrificing a ton of compression.

Good Luck

Steve
 
let me help, i have 8 fox body mustangs :)
dont run the "conversion" kits, bottom of 3/8 stud is 5/16 and will fail. i have a set of p heads on an 89 with pedestal mount rollers, thats the easiest way to go. you can shim them at the bottom in the stock "troughs" that the pivots sit in for adjustablity. they are available in 1.6 and 1.72.... that car runs low 12's on the bottle and is a full weight (3400 with me) street car (a/c) with an aod and 4:10's
fyi, the valves are all the same length but the keeper grooves are not in the same plane hence the change in the installed height of the spring, not the rockers though.
 
Stormy69 said:
let me help, i have 8 fox body mustangs :)
dont run the "conversion" kits, bottom of 3/8 stud is 5/16 and will fail. i have a set of p heads on an 89 with pedestal mount rollers, thats the easiest way to go. you can shim them at the bottom in the stock "troughs" that the pivots sit in for adjustablity. they are available in 1.6 and 1.72.... that car runs low 12's on the bottle and is a full weight (3400 with me) street car (a/c) with an aod and 4:10's
fyi, the valves are all the same length but the keeper grooves are not in the same plane hence the change in the installed height of the spring, not the rockers though.
Click to expand...

I actually just ordered new EXH valves from Rock Auto, now all keeper grooves will align and new springs will go in as a full set of 16 rather than 8 and 8.

LXguy mentioned stock heads being smaller chambered than the GT40 heads, this is obviously a big concern, I hope it is not so... We will be CCing both old and new heads before installing anything. Might just even out and polish all the combustion chambers while we are at it - in no rush and would rather get it right the first time

I think to start out we will run the stock ford pedestals in troughs and possibly upgrade to pedestal rollers in the future, but the pedestal shims seem to be backordered everywhere I have looked, got a source handy?

We are doing the head swap before any other mods to see what difference the GT40 heads will have over the current heads, some stock 302 or 289 head, then we will swap cam and play with the trans or rear gears. I think an AOD with a 4R70W gear set and 3.23 rear gears will do just fine
 
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