How much boost - GN and T-Type Performance Enthusiasts (GNTTYPE) Forums

cherrypie · #1 09-12-2005, 03:59 AM

Hello members, i have an 87 gn that i bought 1 month ago,it has a few mods, big turbo te60, heads,cam 200/200 and a reds 60# chip107. How much boost can i pump in it before the o ring heads let go. I am already about 30#, with no knock the car acts like it begging for more. But i don't know if the turbo can take it. I would like to really turn it up but am not sure what a normal level boost is. I do run good gas in it. The car runs 7.10s@98 but i want 6.80s out of it. Thank you for your help.

Keller · #2 09-12-2005, 02:08 PM

Quote:

Originally Posted by cherrypie

How much boost can i pump in it before the o ring heads let go.

I guess at least 30.

Maybe someone will speak up about how hard you can safely hit an O-ringed top end before you pop something.

But the real question is how solid is your bottom end? Do you have billet caps, studs, or a girdle?

cherrypie · #3 09-12-2005, 07:21 PM

I was always told , that so long you do not knock the motor the sky was the limit. The car sure acts like it wants more boost. I believe the motor has the stock caps.
Thank you for replying

Keller · #4 09-12-2005, 09:25 PM

Well, you may want to rethink that. These cars have a seprate crank throw for each cylinder. So the crank has a natural weakness as a result. And there are some awfully thin areas between throws. Crank flex can happen if the bottom end is not beefed up. And if its not, well...it goes something like http://www.gnttype.org/techarea/pict...ocks/DOTC.html

Be careful.

cherrypie · #5 09-13-2005, 03:24 AM

Yeah i guess i should be safe and leave at 30#

I might add some more timing. Thanks for the reply. I sure love boost

Keller · #6 09-13-2005, 09:12 AM

The stock bottom end isn't terribly strong, either. Not a lot of beef down there. Take a look at the picture guides on this site. If this is something you'll be doing daily, you might want to plan on some work on that bottom end...

cherrypie · #7 09-16-2005, 02:27 AM

Well i installed a bigger cam 218/ 218 so i won't have to run so much boost. It should be easier on the bottom end thus allowing more air to travel through the motor.

kenmosher · #8 09-16-2005, 12:44 PM

If you spin the stock bottom end (especially the nodular iron crank) much beyond 5300 RPM and particularly with the monster boost levels you are running, be prepared to run over the shiny parts.

The mains have tendency to "walk" because the crank flexes if spun really hard. As long as there's no detonation *knock wood* it can live for awhile at those boost levels, but it's advisable to do steel mains or a girdle to avoid being part of the DOTC club (Drive Over the Crank Club).

DOTC membership pictures:

http://www.gnttype.org/techarea/pict...ocks/DOTC.html

cherrypie · #9 09-27-2005, 04:15 PM

DOTC club is a club i would like to avoid. I might have to pull the motor and put a good steel crank with caps in place. It really seems like with a BIG 3500 stall converter you risk the chance of pushing the crank forward and walking the thrust bearings and stock caps. Could this possibly be whats happening with cap walk. I might have to move to a smaller converter, maybe a 2500-2600 stall.

kenmosher · #10 09-27-2005, 07:59 PM

I've seen it in my motors with stock stall converters (2600s).