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lnirenberg
Guest
Am about to buy a pre-71 C3 and am curious as to how other owners deal with the unleaded pump gas problem without resorting to expensive mechanical fixes or tetrahydrol (sp?) lead additives.
atmmac
Well-known member
i have a 1966 impala and so far i have had no issues running unleaded gas. I dont think youll have a problem. Where you located in MA?
Hib Halverson
Technical Writer for Internet & Print Media
lnirenberg said:
Great question.
In short, if your pre-71 C3 has an original engine with heads lacking non-induction hardened valve seats, you may have a problem if 1) you run the car hard and/or 2) the engine already has high mileage.
If the engine is low mileage and/or you don't run it hard, depending on how much annual mileage you put on it, you'll probably be ok with unleaded gas and the soft seats. Yes, the wear rate might be higher than with leaded gas but the point in time at which the seat will be excessively worn will probably be beyond the distance you will drive the car before other engine parts require an engine overhaul.
Conversely, if you do run the car hard, if it's high mileage or you drive a lot every year, then you need to either pull the heads and have hard seats installed or you need to run a gas additive such as Red Line's "Lead Substitute". There is no way around one of those two alternatives that will not have the valve seats failing due to recession.
You mentioned "tetrahydrol (sp?) lead additives." You probably mean tetraethyl lead or "TEL", the "lead" used in gasoline in the old days. You cannot obtain TEL because it is an extremely hazardous, controlled substance. There are some pour-in, antidetonant gas additives that also offer some valve seat/face lubrication, but better choices are additives specifically intended as substitutes for TEL.
For more information on gas additives for that purpose, see an article on gasolines for Corvettes at:
http://www.idavette.net/hib/fuel/index.htm
brusso
Well-known member
I went to High School in Hanover. (South Shore Voc. Tech.)atmmac said:
Tom73
Well-known member
I thought that old high mileage engines would do better with todays gas as they had years of leaded gas going through them and thus working over and helping to improve the valve seats vs. a new engine that has never seen lead.Hib Halverson said:
tom...
Hib Halverson
Technical Writer for Internet & Print Media
Tom73 said:
The lead which coats the valve seats and faces and serves as a lubricant is a "mid-term temporary" coating not a permanent coating, thus, after a switch from leaded to unleaded gasoline, the coating and lubrication slowly goes away until you reach a point where no lead residue remains.
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SG4206
Guest
I learned the hard way. Ruined a set of 462 castings in 4000 hard street miles. Exhaust seats recessed about .060 before I really knew there was a problem. I know you can get away with superunleaded; you have to keep the exhaust temps down ;which means no high rpm shifts and no substained 3000 rpm highway trips.
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guido34
Member
Pardon my ignorance. I was alive when the switch was made from leaded to unleaded gas but was in high school at the time and was not paying attention to much. I’ve recently acquired a ’72 coupe with the original 454 in it with 68k miles on it. Should I be worried about running unleaded gas in it?
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lnirenberg
Guest
No expert, but I do know that in '71 & '72 the full line of engines had much lower compression ratios in anticipation of the scheduled removal of lead later in the decade. It is my understanding that they are better able to run on unleaded than the pre-71. If I wre you I would ask Hib (see above) as he seems to have a pretty good fix on this.
atmmac
Well-known member
No kidding my house is right near there. They sure do have a good football team. They are on top in their division every year.brusso said:
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Bender
Guest
I dont know if this has been mention but they make stuff you can put in your take when you fill up so you dont hurt your lead engine. Not sure what its called but I know they make it.
Tom73
Well-known member
The compression was dropped in '71 as a step towards unleaded fuel. But the induction hardened valve seats did not come along until '73. It is the valve seat that is the issue.lnirenberg said:
tom...
brusso
Well-known member
Do you mean Hanover High? Cuz S.S.V.T on Webster St. didn't have a football team. Well not in 1987 anyway.atmmac said:
atmmac
Well-known member
No they have a football team now. Hanover Highs football team (My school) sucks.
brusso
Well-known member
It only makes sense. The school is or was like all dudes anyway. In my class of 140 there were like only 10 "females".atmmac said:
norvalwilhelm
Well-known member
I run a blown big block from the late 60's and never had a problem with the fuel switch. Originally my compression was 11.25 with nitrous and when I went to a blown motor the heads were gone over and there was NO sign of exhaust valve seat errosion.
I now run a 871 blower, run the motor lean and hot for better mileage and wear and have no problems with the seats. I set the valves in the spring and don't touch them until the fall when I back them off for storage.
Other then towing a trailer you should have no problems.
I now run a 871 blower, run the motor lean and hot for better mileage and wear and have no problems with the seats. I set the valves in the spring and don't touch them until the fall when I back them off for storage.
Other then towing a trailer you should have no problems.
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