Test results before mods

[forwheeler]

Originally Posted by JFairman

I left both vacuum lines on the '87 USA distributor and turned it clockwise advancing it as far as the adjustment slot allows without pulling the distributor out and reindexing it one more gear tooth.

I'm scared to remove the vacuum retard line so far because I don't know where the timing would go under boost then. Just too risky.

I need to get some kind of degree wheel or tape that can be attached to the crank pulley and has the degree marks on the edge so it will be visable when pointing a timing light down at it before I experiment with timing safely.

At the moment I have the MSD 8762 set to retard timing 2 degrees for each psi of boost starting at 5psi but I will probably change that a little with more experimenting. I run maximum boost 1 - 1.1 bar or around 15 psi with street gas, usually chevron high test.

The motor has stock 7:1 pistons and cylinders, 964 cams, Garretson long neck half bay intercooler, and B&B headers.
It has fuel enrichment with a modified IA fuel head and Brian Leask adjustable WUR to control it.

I agree with the degree tape. I can't tell for sure where my advance but it is about 1mm to the left of the timing mark on my 79 ROW car. This should be -29 which is specified for this car in the manual.

I too run at 1 bar and use Shell 93.
My car does move out pretty before boost onset (maybe due to sc cams and the -20 advance) but I don't have a car to compare it to. I would like to advance the timing a couple of degrees to see the difference but I am afraid to without boost retard like you have or a SafeGuard with knock sensor.

I would think that the guys with US cars could run the -29 advance as long as your octane was 93 or better before adding an any aftermarket boost retard. But that is just my opinion.

[forwheeler]

Originally Posted by DDDD

My third gear is the factory third. The overall ring and pinion was just changed to the 8/41 from stock. I think you would have 9/38 ring and pinion stock....

I can tell you that my 3rd redlines at 115 or so and that is as short as you would ever want to go. I think 120 mph might be perfect for full acceleration.

Bruce anderson's 911 performance handbook has all the possible gear ratios and mph in the back.

Looking at the book a 26/26 gear at 6800 rpms gives 120 mph with a 9/38 ring and pinion. That would be devestating acceleration and just a touch taller than what I have. A 27/26 would put you at 126 mph and stock I think is about 134 mph at 6800 rpms. The 126 mph gear seems like a very nice compromise because your gear would not seem too short either.

You would want to double check those gears numbers yourself...

Yes, thanks for the info.

[tj930]

Originally Posted by JBL930

Tom, that second run gives you a 60-130mph of 17 seconds!! That's really slow! You can hit about 132-134 mph in 3rd with stock wheels and a stock 4 speed, you need to hit the rev limitter but you'll get there.

Mate, I know you moan about me 'short-shifting' but the car had a rotor which was too small for the Distributor cap (and sparking and shorting out at high RPM), SC Cams (which have nothing left by 6k), fuel pumps which weren't delivering enough fuel, an engine that hit 12.0+AFR by 6k, and a Distributor wasn't Advancing/Retarding by the full amount... Also to find where 0.16Bar Boost Pressure is leaking.

And that drag may have been run slightly up hill (I don't remember) - think I was more concerned with 0-60, 0-100 and standing 1/4. But, with reference to the original postee's 60ft time, that was done in ~2.2 seconds (and not 2.5 minutes! )

[JBL930]

Originally Posted by tj930

Mate, I know you moan about me 'short-shifting' but the car had a rotor which was too small for the Distributor cap (and sparking and shorting out at high RPM), SC Cams (which have nothing left by 6k), fuel pumps which weren't delivering enough fuel, an engine that hit 12.0+AFR by 6k, and a Distributor wasn't Advancing/Retarding by the full amount... Also to find where 0.16Bar Boost Pressure is leaking.

And that drag may have been run slightly up hill (I don't remember) - think I was more concerned with 0-60, 0-100 and standing 1/4. But, with reference to the original postee's 60ft time, that was done in ~2.2 seconds (and not 2.5 minutes! )

Sounds like you have quite a bit to sort out mate, fuel pumps need to be in good nick if you're pushing the power up.
I had issues with my distributor, there's an arm in there that had rusted through and wasn't letting it advance/retard. I had it totally rebuilt with new cap and rotor, if i remember it wasn't a cheap job!

[JBL930]

Originally Posted by wjfk32

60-130mph--Is the real test...
Walt

I'm totally with you on this, with 60-130mph traction doesn't come into it. Test your car now doing 60-130, write down the ambient air temp so you know when you're re-testing on similar day, even make a note of how much fuel you're carrying!
As long as you do the test on a nice level road, in similar conditions, it will give you a very acurate idea of how much performance gain you are getting from your mods