9.0:1 compression

[fly89gta]

Ok, here's the deal.

My TTA motor is shot. I was lied to about it when I bought it(that's another story, one I do not wish to get into).

I can't find TTA pistons and the idea of spending over $600 for custom ones really doesn't intrigue me lol.

Now, I have found quite a few nicely built up GN shortblocks. With my TTA heads and the GN pistons it'll put the CR around 9:1. Is that too high? I plan on porting the heads a bit, to help bring it down a bit plus I'm planning on alchy.

I have a TE60 turbo but I might keep the stock turbo, not really sure yet...I'm really only looking for low 12's(orginally want to go faster which is why I got the TE60 but my goals are changing).

Some advice would be nice. Thank guys

 

[zam70]

9:1 will be fine - alot of guys do that on purpose (better low end response) In the end, cylider pressure is cylinder pressure.
Just watch your boost and don't fall into the "I used to run X boost...".

 

[fly89gta]

Hmm, interesting.

Thanks

So basically just watch the boost right?

With alchy I should be fine still running a decent amount of boost.

also, with the high compression would I have to change the way I look at cams? Meaning if I was going with, say a 208-208 cam with 8:1 would it still be fine with 9:1?

 

[zam70]

Since we run a turbo - there shouldn't be much difference IMO

 

[fly89gta]

That's what I thought.

Thanks!

 

[jastrckl]

I wouldn't do it. The people that run the higher compression engines usually are stage motor guys that run 116 octane leaded racegas at the track. You know how we make fun of all those honda guys that turbo their stock motored cars and blow them up? Yup, high compression and a turbo is bad. You'll severely limit the ammount of boost you can run on pump gas. The thing about compression vs boost is that compression results in a much higher peak cylinder pressure, boost fills the cylinder gradually while the intake valve is open. I don't know if with the tta heads and different rocker ratio if you run into a problem with valve to piston clearance either. I doubt it, but you ought to check into it.

 

[fly89gta]

Well I'll be running one of Julio's alchy kits if that matters. Also I'm only shooting for low 12's..I'm not going to be pushing the motor too hard.

 

[zam70]

It's common to bump up compression to increase the low end response of the engine. At 8 or 8.5:1, the low end will be lazy. YES - you have to watch the boost, you won't be able to run as much as you would with the lower compression...and the alcohol will help with detonation (as with any engine).
It's common for some of the TR people to run a single steele headgasket to bump up the compression...

Go over to the other site and look up Steve Wood...he runs higher compression on his with excellent results

 

[Louie L.]

Going to 9.1 comp is the best thing i ever did to my motor. The off idle response was much, much better , so was spool up. Before any one says that this is only a race motor I drove this same motor for about 6 mo of daily duty on pump gas before becoming a weekend only car. I could run about 16 -17 spi , no knock.(TE45,unported GN1s,210 roller.)

Now in race only mode i can run 30 psi on 26 deg timing no knock.Of course, Thats in testing only , cause we dont run more than 24 psi in TSM.

This was the 1st Hartline Perf 9.1 comp street motor. There have been several other built after that with similar results.Conleys has also built several motor s with the higher compression.

 

[fly89gta]

Thanks Louie That's what I wanted to hear

GN shortblock and TTA heads it is