RS Motorsport :: Classic Speed Restored

i am currently working out (again) what fuel to use in my 'new' 2L pinto motor. The last owner used Avgas and commented that it used to ping (maybe he meant knock?) on 98 octane fuel. The stats I was given with the motor indicate a CR of about 10.5:1. It uses a Kent GT4 cam with webers.

Are there any rules of thumb to determine which fuel I should use based on the above? I guess the options are 98 pump, E85 or one of the 102RON race fuels (exy and the max RON allowed under the regs). I really dont want to have to use expensive race fuel if I can avoid it but I am concerned the motor may not be happy on anything less.

Leaded Avgas is not an option under the regs although I have not investigated the unleaded avgas yet. I recall from a prior discussion that Danny M used 110/130 avgas but do not know if he has since dabbled with unleaded avgas.

E85 might be an option but I am told it does nasty things to carbies?? i assume the jets in the carbies would also need to be changed due to the higher consumption of E85 versus petrol?

I am thinking of pulling the head off to check the compression ratio. Is there anyway of checking if the head bolts are stretch ones or not? Do they appear different? Is a Pinto even likely to use those? (engines are NOT my area!)

Cheers Warren. I have just dug out the spec sheet and the stated compression is 10.8:1 and the dizzy timing is 12 degrees BTDC @ 1000rpm.

The knocking on 98 octane issue was evident when the last owner had the motor dyno'd and I have no doubt that all the settings were optimised at that time. He does think that the 10.8 CR is not right and low. Best for me to take the head off and take a look me thinks.

How do I recognise "torque to yield" bolts? They are believed to be ARP bolts but to be quite honest I would not know the difference between them to look at.

What is the max CR you might suggest such a motor will handle? If it turns out to be higher than on the spec sheet then my only option might be expensive race fuel or unleaded avgas (still sat here researching that stuff).

IF I went for E85 what would need to be changed?? Carby jetting (not really an issue to do), fuel lines (what type?), tank is new and alloy so should be ok? Flush with PULP after each use?

Glenn which head are you using and are the pistons flush with the top of the block and flat tops or do they have lumps on them

If it's got flat top pistons and a 2lt head you will not need anymore than 98 and if it was pinging it's either a poor setup or theres an issue somewhere

cheers. will pull head, check piston tops and height and CR.

Do you know anything about the unleaded avgas? Ever tried it or are you still on 110/130?

never looked at it as I'm using Mobil

I'm running 11.5:1 on BP98 with no problems.
Flat tops 0.010" above the deck with a heavily machined head, over 0.125" by now.

Clayton

Thanks again. The motor has not been run in the car yet. It really sounds like 98 should be fine so I should perhaps dyno it on 98 to check the timing curve then take it from there.

Most targa events have refuellers that carry 98 and E85 (I am led to believe) so hopefully my crew would not need to carry much. I get what you are saying re quantities though. I will talk to my carby bloke to get his opinion as I am sure he has gone down the E85 path before.

Thanks Clayton. That's 3 knowledgable people offering the same opinion re 98 which makes me quite comfortable.