Proper fuel for 71 high compression

Dunno about being a 'real authority', but lessee... you have a 'high compression' engine. How did it drive on the fuel thet the p.o had in it? If it ran OK, what was it? Until I had a chance to open the engine up & see whats really in there, I'd stick with what works. If you don't do your own work, I'd recommend contating a big hot-rod shop in your area that may have an engine displacement gauge and let them "pump a few of your cylinders' to find exactly how high is "high" compression. If its over 10:1 and this motor has iron heads, you are sorta stuck with either a radical reduction in ignition advance or some level of race or av-gas, both of which are illegal on the street as well as being expensive & complcated to get. The real fix is to have a knowlegable engine shop rebuild the 30+ yr-old engine for todays fuel so it can e enjoyed. What area of the country are you in?

The car has the original 351C 11:1 compression engine. The PO used the Sunoco 94 octane with 104+ octane boost. The timing has been set back to 2 or 4 DBTDC. It runs OK, but like I said, I want to know that I'm not doing any damage with this coctail. I'm in Ontario, Canada and both racing fuel and avgas are readily available but also not legal for street use. Since my car has only 14000 miles, I want to keep it as original as possible. Also, the cost of a rebuild may be a bit much. How would that improve it's running ability on regular pump fuel? Would I not need to reduce the compression and thus the power? What did these things run on in the 70s when Ford was selling them? Thanks for the help.

In the late '60s & early '70s, Sunoco sold 102-octane'Super' at their pumps. Most guys with 11:1 engines have pulled the cylinder heads & replaced the steel-shim head gaskets with modern fabric-composite gaskets that are thicker & drop the C.R. to a more mamageable 10.2- 10.5:1. Remember, while your engine may be very low mileage, the castings have had water in them for 32+ years, and most ownerse STILL don't change anti-freeze every year. As the antifreeze additives are used up, corrosion begins- usually on the steel gaskets and steel freeze plugs.
Adding to this, an aftermarket cam, hydraulic or solid- your preference- with a little more duration & lift will further reduce the internal pressure in the cylinders. This usually results in a more driveable engine with more horsepower, that runs fine on 92 octane with no additives. Being forced to use additives in an engine to keep it running is to me like being on drugs....

Thanks for the explanation Jack. I am new to Panteras. Most of my mechanical experience is with old French cars and there is a fair whack of difference between the two. I'll be sure to change the coolant regularly until I can face the cost/effort of a rebuild. I haven't run the car without the 104+, so I don't know if it is addicted or not. I have recently met an experienced mechanic who is an expert in the 351C engine, and has previous Pantera experience, so I'll get his input as well. Thanks again for the help.

Far from an expert, and Jack will correct me if I'm wrong, but the key to what fuel you should be using is if you hear the engine pinging. The real risk to running a high compression engine with insufficient fuel is to get pre-detonation, which will eventually burn through the pistons. If you don't hear pinging, then you are probably ok.

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Charlie McCall
1985 DeTomaso Pantera GT5-S #9375
"Raising Pantera Awareness across Europe"
http://briefcase.yahoo.com/gt5s_1985