Track testing the 5.7 litre 911
#1
10-03-2017, 10:45 AM
Join Date: Sep 2017
Location: North East PA
Age: 35
Posts: 5
Rep Power: 0 
Track testing the 5.7 litre 911
For those interested in the high performance evaluation of a V8 conversion on the 911, this might help.
I had taken my 74 up to Watkins Glen International Raceway last weekend to see if the car could be a formidable track machine. The trip consisted of a 4 hour drive up, 2 hours of full throttle track time, and a 4 hour trip back home all in the 911 without any spares or trailer. Car was packed with camping gear and a few simple hand tools.
The Car: 74 911, wide bodied by me, stock torsion bars, pneumatic rear shocks, relatively tame alignment with more toe in front and rear, 16 inch wheels, R888 tires, OEM brakes, 3.2 915 gearbox, 5.7L 4 bolt main, iron heads, performer intake manifold, mild cam, Edelbrock carb, front mounted Afco radiator, 10 gallon fuel tank up front.
The Track: full length using the boot and bus stop. 95 degree ambient temp.
We all know the 915 can be a tricky box to shift and this was no different given my worn bushings. The tactic throughout the track day was to leave the car in 5th gear and never shift. This worked given the very flat and torquey powerband from the V8, the slowest corner put me at about 2800 rpms and was reaching 5800 down the back straight before the chicane.
Brake fade was never an issue, weight transfer was definitely tricky coming into turn 1 and coming into the carousel. Fuel starvation from the tight corners was always a slight issue as the car was never able to throttle steer out of corners, the only hairy moments seemed to be when entering a corner hard on the brakes causing the back end to jack up extremely high causing more oversteer than one would like. Another slight issue was fuel was getting too hot. Having the fuel tank directly behind the radiator preheats the fuel to a very high temperature and can cause boiling in some lines in the engine compartment causing it not to flow properly in the mechanical pump and carburetor bowls.
Insulating the fuel tank, louvering the trunk, fuel injection, rear coilover conversion, shifter kit, insulating fuel lines, and some minor dialing in will address these issues.
Some ergonomic changes as far as lowering seat height and a larger diameter steering wheel would help with fatigue - battling a car with this amount of performance only armed with manual steering and 0 assisted brakes definitely took a lot out of me.
There is a definite fun factor holding off newer machinery with flat out speed and 3 wheeling the car through corners, but this setup might be more competitive just as an autocross machine.
I had taken my 74 up to Watkins Glen International Raceway last weekend to see if the car could be a formidable track machine. The trip consisted of a 4 hour drive up, 2 hours of full throttle track time, and a 4 hour trip back home all in the 911 without any spares or trailer. Car was packed with camping gear and a few simple hand tools.
The Car: 74 911, wide bodied by me, stock torsion bars, pneumatic rear shocks, relatively tame alignment with more toe in front and rear, 16 inch wheels, R888 tires, OEM brakes, 3.2 915 gearbox, 5.7L 4 bolt main, iron heads, performer intake manifold, mild cam, Edelbrock carb, front mounted Afco radiator, 10 gallon fuel tank up front.
The Track: full length using the boot and bus stop. 95 degree ambient temp.
We all know the 915 can be a tricky box to shift and this was no different given my worn bushings. The tactic throughout the track day was to leave the car in 5th gear and never shift. This worked given the very flat and torquey powerband from the V8, the slowest corner put me at about 2800 rpms and was reaching 5800 down the back straight before the chicane.
Brake fade was never an issue, weight transfer was definitely tricky coming into turn 1 and coming into the carousel. Fuel starvation from the tight corners was always a slight issue as the car was never able to throttle steer out of corners, the only hairy moments seemed to be when entering a corner hard on the brakes causing the back end to jack up extremely high causing more oversteer than one would like. Another slight issue was fuel was getting too hot. Having the fuel tank directly behind the radiator preheats the fuel to a very high temperature and can cause boiling in some lines in the engine compartment causing it not to flow properly in the mechanical pump and carburetor bowls.
Insulating the fuel tank, louvering the trunk, fuel injection, rear coilover conversion, shifter kit, insulating fuel lines, and some minor dialing in will address these issues.
Some ergonomic changes as far as lowering seat height and a larger diameter steering wheel would help with fatigue - battling a car with this amount of performance only armed with manual steering and 0 assisted brakes definitely took a lot out of me.
There is a definite fun factor holding off newer machinery with flat out speed and 3 wheeling the car through corners, but this setup might be more competitive just as an autocross machine.
#2
10-03-2017, 01:17 PM
Join Date: Sep 2017
Location: North East PA
Age: 35
Posts: 5
Rep Power: 0 
