"New" GT-40P heads purchased, what now?

I cannot find anything about polilocks, and have never heard of them. Maybe a part number from jegs/summitt so I can see what you guys are talking about?

And how much can I safely machine off the bottom and still fit up with the intake manifold?

74merc, are you suggesting that this swap will increase my compression to 8.8:1? Is that due to the heads, or the thinner gasket, or both? I did not expect that big of a compression change.

But wouldn't complain ONE BIT if it did

as an edit, can you provide the part number for those rockers also?

 

No need for all that if your running a hydraulic cam
Get the polilocks and go.
Make sure you get them for aluminum rockers even tho you have steal ones. OR make sure they come w/ a allen head set screw in them. Because I ordered a set from Summit and they were the wrong ones.
Here's a good cheap set.
http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=1252&prmenbr=361

 

I still don't get the polilocks. What do they do, and how do they work? What benefit do they provide over my current setup?

 

Ploy Locks are rocker arm retainers that allow you to adjust the valve lash - whereas the factory attachment is fixed.



You'll have to get 3/8" studs to screw into the threaded holes that in the heads now (to screw the Ploy Lock nuts to).

I'm not a mechanic - but I did stay at a Holiday Inn Express last night.



google google google

 

Poly locks are for stud mounted rockers, P heads have bolt down rockers. Once you know you have the correct rocker tip-to-valve stem geometry you never have to adjust them. If you take them apart later, you just reassemble, torque the bolts and your done. I'm running Crane Energizer 1.7:1 rollers, PN 44746-16.

 

What's next?

"Current cam is hydraulic flat tappet, 218/228 .050 duration, .471/.471 lift, kinda mild, I know."

The problem is that what's next is up to you and you have a lot of time to think about it. And the above quote is pointing to a snowball getting ready to roll down the hill. Push it!!!!
Compression can be whatever you want, just requires pistons, gasket selection, and shaving if you really want it, you can do the block too you know. Cam? Back to compression and what you really want. Of course too much change and you need a new carb and intake.
Or you can just do the head job and the headers and be done. 3-6 months to think about it and not go for mo' power? You're a stronger willed man than me if you make it. You're going to have some decent flow. Use it or not? I feel like one of the crowd watching a guy on a building ledge. JUMP! JUMP!
Have fun going through the possibilities the next couple months Scott. The Vegas bookmakers are giving odds there will be more to this story.

 

Your compression will go down a bit, 2cc larger chambers. I was saying while it was down I'd try to put a set of flat top pistons in there. Rings are cheap, pistons aren't too bad. Compression is what you need.

And I'm not just talking either, my daily driver just broke a timing belt. If I have to pull the head, I'm reringing the block unless the bores are egg shaped.

 

Thanks for the encouragement. I, too, believe I will end up pushing it more, but I think I want to run this motor as is, only changing the heads and headers, until it starts to wear out. It runs too good right now to overhaul. But, I want parts now that will work when I stroke and bore it later. I may not use the parts to their optimal performance levels now, but after rebuilding in a couple years...

Those polilocks sound like a good idea, and only $30??? I think I might do those now, and then put the roller rockers on a little later. We will see as the project continues.

Does anyone know if they make a oval-holed exhaust manifold/header gasket,and what part number? I keep getting square holed. Even on various websites showing these heads, you can see a black square around the exhaust ports, showing that they were using square gaskets. Mine has the black square around it also.

I need the gasket now to start gasket-matching.

Did the GT40 cars have round gaskets, and if so, what years were they, so I can ask the parts guy?

 

You want to match whatever headers you get.

 

They make the oval gaskets.
They are just harder to find locally, at least in my experience.
Stockers will be oval, but they might not be the best header gaskets.
Then again, they might work great.
Use locking header bolts...
Dave

 

I don't think your gaining enough performance to justify all the work to fit the GT 40P heads to a stock 74 motor.
First the 74 block has dished pistons unless they have been changed to flat tops.
The block deck height is higher.
May need different push rod length.
The gt heads have larger chambers that will lower compression ratio.
The spark plugs are at an angle and interfere with header flanges.
The valve train is different.

 

If I can get a part number on the oval gasket, I can find them. Anyone have a #?

Also, what is the technical difference between exhaust manifold gaskets and header gaskets, besides the extra $12?

 

Like I said before, you don't need oval ports, you need to match the exhaust port to your headers. Oval port exhaust with rectangle headers will HURT performance.

 

If i use oval port headers and heads, then a square port gasket, how much will this screw things up?

PS--check out the other thread for progress on porting and polishing the exhaust ports. http://mmb.maverick.to/showthread.php?t=17832&page=2