Will GN JE Pistons be fine in a TTA with Ported Heads? ---

[alwayscode390]

I read on here that the GN pistons bump our compression up a LITTLE.

Will the ported heads lower the compression back down to an acceptable level? They are Champion heads.

# 131996

.020 overbore , block height 9.510, comp. height 1.850

-Head 48cc (stock buick ... i dont know the champion specs) ,
-supposed to keep it at stock 8.5 comp. ratio (for the gns),
-dome volume -29.5

This seems too easy to just pick them and go , isnt there a lot of measurements that need to be taken? Should I be safe with the .020? My car has 150k miles on it, but has strong stock level compression (when tested recently).

I guess I could just let the engine builder pick the pushrods and pistons for me since those figures seem to vary? What do you think? ---

 

[xsbc63x]

ported heads shouldn't change compression since the porting is done above the valves, decking the heads or block would, but that would raise compression. A thicker head gasket could lower compression. In my TTA I went with the .020 over je pistons for the TTA engine.

 

[alwayscode390]

Are you running the stock head gasket with no problems?

They dont open up the combustion chamber a little when they port? ---

 

[magee]

yes let the engine builder get it,and dont be like me i bought crower billet 6.2 rods je pistons and 3400 crank after like $2500 or more its wrong so i just look at them now i needed a wide journal crank and rods. pistons might be wrong due to pin placement and the engine builder i talk to on the phone told me he got to see them, i may half to sell it all and get all new again rods cost me 1,100 pistons were like $800 let the builder get every thing good luck on your build.

 

[89ICBM]

I read on here that the GN pistons bump our compression up a LITTLE.

Will the ported heads lower the compression back down to an acceptable level? They are Champion heads.


To answer your question, the gn piston dish is smaller than the tta.They will bump your compression ratio up 1 point, that's not a little. The tta is 8 to 1, the gn piston will raise you to 9 to 1 hence, the difference in stock boost. Now, that's not really a bad thing. There is pro's and con's for the difference. The higher ratio offered by the gn dish gives you more bottom end power but also gives a higher probabilty of detonation at 17 or higher boost, actually, even lower than 17 but I didn't want to scare you. You can resolve this issue with higher octane, tuning and the weapon of choice, alchohal injection. It really depends on what you want to do with the car. The heads will move more air thru the motor but has nothing to do with the comp ratio.

 

[alwayscode390]

Great advice guys, I appreciate your time

What is the number for the thicker head gasket? Will the thicker gasket be easier to blow out?

Chances are I will just call JE and have custom pistons built ... the custom ones arent any more than the other ones right? I really dont want to go over 8.5:1 ---

 

[89ICBM]

Great advice guys, I appreciate your time

What is the number for the thicker head gasket? Will the thicker gasket be easier to blow out?

Chances are I will just call JE and have custom pistons built ... the custom ones arent any more than the other ones right? I really dont want to go over 8.5:1 ---

Hi!

Trying to get a thicker head gasket is really a bad idea. The size of the gasket is measured by the bore, and, if you can find one, yes it will be much easier to blow out. Have your machinist measure the dish on your stock pistons.
This is not advice, just sayin. And quess what! This ain't NASCAR! Nobody is gonna pull your motor apart to check. If your interested in new pistons check out Wisco's, less money.

Frank

 

[Pronto]

FYI, JE and Wiseco are owed by the same parent company...

 

[alwayscode390]

I guess the crappy thing about getting custom pistons is I wont be able to order them until the car is in the shop ... and they will take 2-3 weeks to get them back.

Does anyone have a clue on the stock dish measurements so I can pre-order them? ---

 

[Pronto]

JE used to make pistons for the TTA. Bet they have the stock TTA piston specs.

 

[89ICBM]

I guess the crappy thing about getting custom pistons is I wont be able to order them until the car is in the shop ... and they will take 2-3 weeks to get them back.

Does anyone have a clue on the stock dish measurements so I can pre-order them? ---

Hi,

It appears that your gonna build a motor, so, the machine shop you use will ask you what brand of pistons you want, they will make the choice in size. Why you ask? Because they know what is done to the block and you don't until they tell you. Let them order the pistons of your choice, well, unless your a trained machinist and own a machine shop or possibly have one in your garage. Also, be careful on your choice of machine shops. Make sure they have done work on these motors before.

 

[89ICBM]

FYI, JE and Wiseco are owed by the same parent company...

Hi Pronto,

What's your point? It's really not clear to me other than you supported my point.
It appears you are saying that JE and Wiseco are made equally by the same company except Wiseco's are't as expensive. I think this is called an engineering no brainer. Just an FYI!

 

[xsbc63x]

JE used to make pistons for the TTA. Bet they have the stock TTA piston specs.

je did make pistons for the TTA as of last year, but i guess a lot can happen in a year!!

 

[Pronto]

Hi Pronto,

It appears you are saying that JE and Wiseco are made equally by the same company except Wiseco's are't as expensive.

OP mentioned JE and you mentioned Wiseco so ya, that is pretty much my point. Although they are separate companies, on the parent website they say they share technology. JE used to make the TTA pistons so there's a good chance they still have the specs. Don't know if Wiseco has them or can get them from JE.

 

[BandAid]

or you could always do what i do to every GN i have owned... J/K

 

[89ICBM]

Hi guys,

Again, I'm just sayin! I'm in no way trying to insult anyone.
I keep reading this thing about TTA pistons, fellow members, there is no such thing anymore! The original TTA piston was a hypereutectic cast piston with a steel skirt, very heavy and designed for the original stock bore. If a person is having any block work at all, the original would not work. The hypereutectic piston was used to get very tight clearance in the bore. This is why the machine shop doing the work needs to order the piston for the exact vin 7 rebuild spec. Some may argue that you can go to over sized rings, not a good idea.
A persons choice of brand of piston isn't relivant, pick the flavor you want. What is important is the dish on the top of the piston. If anyone doesn't know what the dish is just post to this thread and I'll explain.

 

[alwayscode390]

I just got an email back from JE and they gave me the GN part number first.

Then I asked if he could find a part number for their old TTA castings ... and he said he had been there since 1995 and never heard of them.

IF SOMEONE HAS STOCK PISTONS LAYING AROUND, can you please get the dimensions for us on the dish volume ... custom pistons are only $50 more


THANKS ---

 

[bison]

I just got an email back from JE and they gave me the GN part number first.

Then I asked if he could find a part number for their old TTA castings ... and he said he had been there since 1995 and never heard of them.

IF SOMEONE HAS STOCK PISTONS LAYING AROUND, can you please get the dimensions for us on the dish volume ... custom pistons are only $50 more


THANKS ---

Post the bore, measured deck height, stroke, rod center to center, compression height, gasket compressed thickness, and combustion chamber displacement and what compression ratio you want and I'll tell you what dish you need. This is simple math.

 

[bison]

Hi guys,

Again, I'm just sayin! I'm in no way trying to insult anyone.
I keep reading this thing about TTA pistons, fellow members, there is no such thing anymore! The original TTA piston was a hypereutectic cast piston with a steel skirt, very heavy and designed for the original stock bore. If a person is having any block work at all, the original would not work. The hypereutectic piston was used to get very tight clearance in the bore. This is why the machine shop doing the work needs to order the piston for the exact vin 7 rebuild spec. Some may argue that you can go to over sized rings, not a good idea.
A persons choice of brand of piston isn't relivant, pick the flavor you want. What is important is the dish on the top of the piston. If anyone doesn't know what the dish is just post to this thread and I'll explain.

they were not hyperuetectic. Just very strong eutectic.

 

[89ICBM]

they were not hyperuetectic. Just very strong eutectic.


OK! But, does that make a difference in the conversation here? I think not!