Kevin and Rob, you are only confirming what I have known for a while now that a 6-speed manual makes all the difference. I am just waiting on enough money to buy a wreaked 4th gen that has everything I need for the swap into my 87 GTA because the outright cost people are charging just for the T-56 is out of this world. Very impressive times tho with the long runner setup. You are definately one of the exceptions as most long runner setups can't run with the big dogs around here.

 

yeah if part of your swap price includes tranny and you can get a t-56 with it (just not out of a 93 fbod) then it becomes much more worth it to step up to the LT1 and getting the T-56 with it. Despite what the LS1ers want to say, its the T-56 that was made by the hands of god

 

Rob, 60' is where it's at, as you know...ET's are usually made or lost here, traction might become a problem and down play gains from gears...And gears keep you from falling out of the powerband on the 1-2 shift,(auto) and let you cross the traps in the band, or 500-700 rpm past, which is desirable!...My fav gears are the 355's, but unfortunately don't come in my size..so I'll roun up a little especially with an auto..
(a little off topic)
What boost / chipwere you runnin to go 12.1 with stock set up?Curios b/c I help my bud work on his '86 GN, I like to gather info that might help him...he's still dealin with Detenation @ 17psi up...

Kev, you're right my book says a little more = 9.8:1, '90-'92 SD cars..9.3:1 ;87-'89...(I know actual will vary a little.)
Yeah, as HP goes up it's harder and more expensive to get that 100HP, like for you, rather than me or other near stockers..
Dyno sheet looks funny with the "Negative"graphing, an untrained eye might think the HP is flat and torque falls off...but I used to graph production and product tests as a tech in the Engineering dept of a local factory... Nice!
I'd like to find a chassis Dyno near here, but they're scarce...I'll try to catch one this year at an event tho..

 

I was running 18psi on 93 octane with a Xylene mix. So roughly 99-100 octane. That was with a Thrasher 92 chip. Tune for 0.0 retard and you'll be golden. But it was traction that did it. I was running mid 12's at 110-111 with the Firestone's. It wasn't until I put the Nittos on that my short times dropped to the 1.6's. The stock exhaust was straining as were the stock injectors. I was getting duty cycles in the 120% range on Direct Scan. The stock D5 converter was doing a great job with the stock turbo. Almost wish I never would have started modding the car.... Here's the dyno from back then. Higher numbers are with the converter locked.
http://users.adelphia.net/~tta1387/1-13-02dyno.gif

 

I don't ever remember the comp ratio being that high in the TPI. I think 3rd gen says only 9.3:1 for all 350's. I could be wrong but I think I would have remembered such a big jump in compression back then.

Of course that was awhile ago and my memory isn't what it used to be

LT1's had 10.4:1.

 

Rob, I think you are correct, the compression stayed the same at 9.3:1 for all years of the L98.

 

I'm not remembering, I HAVE the service manual open right here, right now...1990 = 9.3:1, 1991 = 9.8:1, 1992 = 9.8:1
Switched the same time as the new body hit..and the "Oil Pressure" dropped for the '91-'92's from 55psi to 18psi@2000...
245HP@4400/345lbft@3200!...(NET)
Actually the '87-'89's are listed @ 9.5:1 in the service manual!..my bad. Only My 'lil ROC is rated @ 9.3:1..

 

Yes, those times are after dynoing those numbers in my sig. But I had a T5 at the time. I havent been able to get the same numbers since putting in the T56, for various reasons. But my biggest problem is the 60' time. 1.9 is horrible for that much torque. My best is a 1.88, but my dad got a 1.81 with the new runners, but didnt get in the 12's with it. I should be running a lot quicker but I just cant launch consistantly.

I can guarantee with 100% authority the 1990-92 TPI 350's have 9.75:1 compression. They got different pistons in 90 that gave them a bump in compression up from 9.3:1 the previous years. The 305's stayed the same at 9.3:1.

 

I can guarantee with 100% authority the 1990-92 TPI 350's have 9.75:1 compression. They got different pistons in 90 that gave them a bump in compression up from 9.3:1 the previous years.

Not according to thirdgen.org:

TPI Engine Tech Specs

Or transamgta.com:

More TPI Engine Specs

Or according to the gtasourcepage.com website:

Even more TPI Engine Specs

The TPI L98 350 did not change compression ratio during any year of its run in the f-bodies according to the above tech pages.

 

Chilton, part#8260 (total car care manual)
And GM's Service Manual...

Beware of some Web Sites "Poll Data"...
Make sure they site their sources..

 

Well Go get'em Cleatuse............
Just thought ya needed so releif from da shutin/Arguein.
ok and continue on in 5..........4.............3............2........... 1

 

Make sure they site their sources..

Good point, but unless I'm mistaken, thirdgen.org is about as definitive as it gets on the net for the specs on our cars. The guys that run that site know their stuff. Check it out.

 

I used to be a regular there years ago, they're just , year specific, "3rd Gen", they are still human and on this one they're mistaken..
As said the 305's did maintain the 9.3:1, they probably assumed the 350 did also...
Think about it: 4.00"bore + Flat tops w/4cc reliefs + 64cc chambers +.028"Head gasket...I'll check my deck height and give you my specs, but it changed in '91 according to "2" manuals I have...
**I would hope companies in the "Information" buisness researched their subjects before spending all that money printing books...
I guess it comes down to, "who would you believe?"...

 

Problem is, Helm's is wrong also.

My TTA shop manual has compression at 8.5:1 and 8:1 in the same book. That's a GM book!

The real compression is 8:1 just like the Grand National's but had different pistons because of the front wheel drive heads.

Also, why no bump in HP with almost .5 more compression? And when the LT1 came out in 93 for the F-Body's, one of the big "improvements" was the over full point in compression from the previous year(92).

 

Because your LC2 in the TTa had to use different heads to fit between the strut towers, it changed compression slightly. The book was quoting a standard LC2 and yours. You recieved better heads and a bump in compression, I know, most GN guys druel over your heads. The manual therefore is correct on both accounts..
A .5 increase in compression alone, won't increase output that much, and I believe my IROC cam was different than the '91-'92 Z's, acounting for the same output with .5 less compression.
(mine = 202*/206*, .403"/.415" 115*LSA)

The point about the LT1 is like I said, for the :
1 point increase in compression
MR style intake
reverse cooling
Tall port, vortech chambered heads
more cam
**For all that, it still only managed a 30hp(advertised)increase and aprox 4 tenths increase in performance..**
WOW!