gt40 p heads with flat top pistons?

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tiptop

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#1

• Sep 27, 2008

• #1

hey, just wondering if you can use the gt40 p cylinder heads with flat top pistons? or do the pistons have to be notched, also using a trickflow stage 1 cam, thanks.

 

85_SS_302_Coupe

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#2

• Sep 27, 2008

• #2

I can say with 99% certainty that you'll have to notch the pistons. Are we talking about an '86 short block?

 

90 lx convert

Stanger

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#3

• Sep 27, 2008

• #3

Don't guess.......check your clearances. Most of those parts will be expensive if they meet each other. Been there. Mike

 

85_SS_302_Coupe

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#4

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Honestly i wouldn't even take a chance and do a piston to valve test on a piston that doesn't have ANY valve reliefs...just turning the motor over by hand could potentially bend a valve. Valve reliefs are there for a very good reason....not only are you going with a head that wasn't designed for a piston without reliefs, but you're going with a cam that is bigger than the one used with the heads that were designed for no reliefs.

Some, and i mean SOME cams will with in an '86 engine with the stock E6 heads because the valves themselves are really short and don't come very close to the pistons to begin with...but then again they flow so horribly that adding more cam doesn't really get you anywhere so it's a waste anyways.

At least if you notch them you'll have true flat top pistons and get better compression, just make sure you don't get too crazy with how deep you go or you'll sacrifice piston strength down the road.

 

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2000GTdriver

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#5

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• #5

Measure once, cut twice...oops

 

NIKwoaC

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#6

• Sep 27, 2008

• #6

I've seen this debated a million times. Is there really a tool to notch pistons easily, or would it be better to pull the engine and just rebuild it with notched pistons? I've done some searching and have yet to find a good tool that can notch pistons while they are in the engine.

 

85_SS_302_Coupe

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#7

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NikwoaC said:

I've seen this debated a million times. Is there really a tool to notch pistons easily, or would it be better to pull the engine and just rebuild it with notched pistons? I've done some searching and have yet to find a good tool that can notch pistons while they are in the engine.

Click to expand...

IMO, it's always better to buy new pistons. Isky makes a notching tool that does a great job, but it's a bit of a PITA to use. It's basically like 2 valves (intake and exhaust) that have a grinding/cutting style head instead of a typical valve head. You have to remove your valves from the head and put the bit in its place and use a drill to grind out material, and you have to do it for all 16 valves. You can imagine how time consuming this will be with 16 valves and you have to bolt the head down every time and you can only do 2 valves at a time, not to mention removing and reinstalling the valves and springs. The other thing to take into consideration is that production heads don't have any "extra" metal for this purpose, whereas most aftermarket pistons do, meaning you're weakening the piston by cutting the reliefs.

It's not such a big deal to cut down .03 or so for valve relief in a piston that already have reliefs, but on a total flat top piston you're potentially grinding out 1/8 inch or more of material. I would do it on stock pistons that have reliefs, but probably not on flat tops, and i definitely would only do it on an all motor setup, no way would i trust it on nitrous or forced induction.

 

T

tiptop

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#8

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• #8

thanks alot for the responses. I have a 85 gtblock, but i have had the engine rebuilt a few years ago and the builder just put in flattop pistons in with no valve relifs, so i guess thats ou of the question then. How about using a set of pistons made for trickflow heads? but instead of using the trickflow heads, just use the gt 40 p heads, thanks.

 

85_SS_302_Coupe

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#9

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tiptop said:

thanks alot for the responses. I have a 85 gtblock, but i have had the engine rebuilt a few years ago and the builder just put in flattop pistons in with no valve relifs, so i guess thats ou of the question then. How about using a set of pistons made for trickflow heads? but instead of using the trickflow heads, just use the gt 40 p heads, thanks.

Click to expand...

Most heads that are cut for Twisted Wedge heads have duel valve reliefs, so you shouldn't have any problem there. You could even get a set of '85-93 pistons (excluding '86 of course) and use those since they have valve reliefs. You'll be limited to around X303 cam specs but that's plenty enough if not too much for GT40s so you're good there too.

 

thumper460

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#10

• Sep 28, 2008

• #10

I agree... you dont know enough!! mic it and see!! the question would be why use the flat top 86 piston ( No valve reliefs) on a re build?? HHHhhhmmmmmm....

But.. the cam will not kiss the pistons ( save the 86 no valve relief pistons) when you pull the heads for a change... see what is there.. no notches?? Clay it!! 2 Notches should be fine with the P's and the TFS1 !! ( but always IF there is consern... clay it!!)

Just me...............................

Thumper

 

T

tiptop

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#11

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thanks agian, if i am going to spend 400 or 500 on a set of pistons, then i may as well buy a stroker kit for 799 at ford strokers, I wonder what the pistons in that kit are? how would a 347 stroker perform with a set of gt40 p heads, and a trickflow stage 1 cam .

 

T

tiptop

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#12

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I dont know, wasen't my call I recived my engine back that way, with no valve relifs, I guess the builder is an iddiot, But it is already bored .30 over

 

thumper460

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#13

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• #13

The P's will allow a lot of power on the 347 with the TFS cam, however, they would be much better suited for the 5.0!! You can pick up a set of forged pistons for 450.00, and then add ARP rod bolts/ ring set/ bearings.. possibly a balance ( I would).. I agree that it would be a "better deal" for Woodys 347!! But then there is the head and cam issue... ( never ends, huh??) on the 347!! LOL

ME?? Build what you want... the P's are a good head, and with port work will support over 450 HP. Just keep it where you want.. and dont get into the 5000.00 budget build...lol

Just me.............................

Thumper

 

85_SS_302_Coupe

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#14

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My buddy had a mild 347, i think it came in around 10:1 compression, and he had GT40P heads with an X303 and a Typhoon intake and make 300hp even at the wheels, but i don't recall the torque. The heads were definitely the limiting factor, but the car ran strong as hell.

 

T

tiptop

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#15

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• #15

thanks agian, what about a 331 stroker then? may be a little better ah. Im really looking for lots and lots of bottom end torque, would love to be cruising in 2nd gear with my mustang at 2500 rpm,s or so and smash the gas and be able to smoke both wheels from a roll. also dont really want any thing that going to make power in the top end cause its just a street car, and there is no where to use the top end power around here.

 

T

tiptop

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#16

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• #16

oh one more thing, im gonna try and email woody to see what kind of pistons come with his stroker kits, I highly doubt that the pistons have valve relifs in them for that price, but will see.