TA short block vs GN short block

[mwolfe1969]

Here's the questions. I have a TA short block in my car now, with ESP heads. The engine has always seemed to have a lot of blow by out the breathers. I found that someone had put a ground down bolt in the hose between the PVC and dog house. Could this cause alot of blow by. Second Are the cranks and rods and pistons the same? which is better? Third I know the heads are different for the 2. But my heads are for a GN. Also what would the difference in compresson be? Any help would be great. Thinking about redoing one of them but what parts are better to use. Also I have a cat crank is it worth doing with the 2 center caps and how much work is involved in installing the parts. Thanks, Mmike

 

[Reggie West]

I would post this in the Stage 2 section. Lots of guys using that block are in there.

 

[corymc]

think he means trans-am block

 

[Reggie West]

Oh.

 

[bison]

Here's the questions. I have a TA short block in my car now, with ESP heads. The engine has always seemed to have a lot of blow by out the breathers. I found that someone had put a ground down bolt in the hose between the PVC and dog house. Could this cause alot of blow by. Second Are the cranks and rods and pistons the same? which is better? Third I know the heads are different for the 2. But my heads are for a GN. Also what would the difference in compresson be? Any help would be great. Thinking about redoing one of them but what parts are better to use. Also I have a cat crank is it worth doing with the 2 center caps and how much work is involved in installing the parts. Thanks, Mmike

The pistons are different and that is about it. Not sure about combustion chamber cc's. I think they may be different also witht he GN heads less cc's. Im almost positve the GN heads on a block with TTA pistons will give you a compression ratio in the high 8's. TTA is 8.3:1 stock anda GN is about 8.0:1 stock. It will cost about $2500 to have a block machined and steel caps installed. It may be a couple hundred extra for the CAT crank since they are not drop in. The stock rods should not be used if you are running a CAT crank and steel caps. Kind of defeats the benefit of the whole build with caps and crank already replaced. Id replace rods and do steel caps before i put in a CAT crank if i was strapped on the $ i could spend.

 

[A2000RICH]

The pistons are different and that is about it. Not sure about combustion chamber cc's. I think they may be different also witht he GN heads less cc's. Im almost positve the GN heads on a block with TTA pistons will give you a compression ratio in the high 8's. TTA is 8.3:1 stock anda GN is about 8.0:1 stock. It will cost about $2500 to have a block machined and steel caps installed. It may be a couple hundred extra for the CAT crank since they are not drop in. The stock rods should not be used if you are running a CAT crank and steel caps. Kind of defeats the benefit of the whole build with caps and crank already replaced. Id replace rods and do steel caps before i put in a CAT crank if i was strapped on the $ i could spend.

i can't say for sure----------- but i was under the impression that the pistons in the ta were dished slightly more that the tr pistons to make up for the slightly smaller combustion chambers of the ta head-------the result was a similar compression-------also the crank was slightly different ie it was cross drilled at the main journals-------otherwise the same-----------if no one knows for sure i have several new ones in the crates (ta and gn) and i can make some measurements if you really need to know..................RC

 

[TT/Ameasap]

Here's the questions. I have a TA short block in my car now, with ESP heads. The engine has always seemed to have a lot of blow by out the breathers. I found that someone had put a ground down bolt in the hose between the PVC and dog house. Could this cause alot of blow by. Second Are the cranks and rods and pistons the same? which is better? Third I know the heads are different for the 2. But my heads are for a GN. Also what would the difference in compresson be? Any help would be great. Thinking about redoing one of them but what parts are better to use. Also I have a cat crank is it worth doing with the 2 center caps and how much work is involved in installing the parts. Thanks, Mmike

1.Yes,Need a check valve or PCV valve going to the intake from the dog house.Take the ground bolt out.

2.Cranks are crossed drilled for oiling purposes on the ta motor. The rods are the same as GN and pistons are deeper dished.(crank is better) IMO.

3. TTA motor is 8.0 compression. That is why the boost is 16 vs 13 on a GN. I dont know what compression would be exactly. It would be higher tho.

HTH
Bo

 

[turbodave231]

The bolt in the PCV line won't cause blowby. That is a function of piston ring seal. If there is no PCV flow, crankcase pressure will build up giving you the impression that blowby is excessive. Put a PCV valve and a checkvalve in the line and remove the blockage. Then make a decision if blowby is excessive.

The TA block is still a 109 block, right? The heads will be different, but all the good internal parts will fit.

 

[mwolfe1969]

thanks

I'm going to take the bolt out, but I wanted to do a compression check and see if the rings were worn. But not sure what compression would be. Also any + or - with the ta pistons and ESP heads. Thanks, Mike

 

[bison]

3. TTA motor is 8.0 compression. That is why the boost is 16 vs 13 on a GN. I dont know what compression would be exactly. It would be higher tho.

HTH
Bo

Have you actually verified this? I measured one out before and it was just about 8.3:1. An 86-87 LC2 is just about 8.0:1. I dont remember the head cc's on the TTA though. They run more boost because they have less timing at WOT/max boost, more fuel flow potential (better pump and higher psi regulator) and the chip burning abilities had improved since the 86-87 years.

 

[bison]

I'm going to take the bolt out, but I wanted to do a compression check and see if the rings were worn. But not sure what compression would be. Also any + or - with the ta pistons and ESP heads. Thanks, Mike

A leakdown test is a better indicator. I wouldnt worry about it too much since they seem to seal up under pressure and make the power even if there is a lot of blow by though fuel mileage will be less.

 

[NCTURBOS]

Back in the day we used to run the TTA piston with GN heads in our GN's to lower the compression. More boost allowed for a given octane was the result. Richard is correct, they are dished more than the stock GN pistons.


K.

 

[Jicaju]

Have you actually verified this? I measured one out before and it was just about 8.3:1. An 86-87 LC2 is just about 8.0:1. I dont remember the head cc's on the TTA though. They run more boost because they have less timing at WOT/max boost, more fuel flow potential (better pump and higher psi regulator) and the chip burning abilities had improved since the 86-87 years.

My stock heads measured 41cc's. Stock compression ratio on TTA is 8.0:1.

Michael

 

[bison]

My stock heads measured 41cc's. Stock compression ratio on TTA is 8.0:1.

Michael

Maybe the one i checked had thinner head gaskets. I think they were .040 head gaskets.