Vauxhall Cavalier Centaur 1979

[funkyG]

Hi,

I've just got my centaur (mark 1 cavalier GLS coupe 2000cc) up and running after 15 years. Could anyone tell me if I can use unleaded fuel with the 2Lt engine.

I purchased the car in 1981 and can't remember if unleaded was used in this year, I certainly don't remember using fuel additives.

I have too schools of thought. One mechanic thinks that the engine ignition system can be retarded by 4 degrees and this should be fine. Another mechanic says that I might need to add a fuel additive to the unleaded petrol to protect the valve seatings.

Any help and advice will be gratefully received.

[Shug]

Engines that can run on unleaded have a star stamped on the block by the engine number.

Ideally you'd want the head converted (hardened valve seats) if it doesnt, but additives can help. I dont think they completely remove the problem of weartho, just lessen the effects.

[funkyG]

Thanks for the help, I will check out the engine number, then I will be able to decide, hardened valve seats conversion, seems like the best way to go, if required.

thanks agin

Engines that can run on unleaded have a star stamped on the block by the engine number.

Ideally you'd want the head converted (hardened valve seats) if it doesnt, but additives can help. I dont think they completely remove the problem of weartho, just lessen the effects.

[cam.in.head]

not so much a check of the engine number because heads can be swapped but more a case of looking at the head. on the side of it by the cover plate will be stamped p2 if it is an unleaded head (or p2e if its from an injected unleaded engine,manta gte or carlton)an original 2 litre carb engine up to approx march 1985 will not have unleaded valve seats. best bet IN MY OPINION is to use an additive (which may or may not work !) or just to use it as it is until you notice any differences in the idle quality.since the head will have to come off then anyway. if you realy wish to make it suitable for unleaded now then you have choices. 1 have the existing head converted with hardened exhaust valve seats. 2 fit a head from a manta gte stamped p2e or 3 (the perfect colution but hard to find is) a head from a 1985-6 carlton mk2 with a carburettor engine. this is correct in terms of compression ratio .a gte head may well be fine but it is a bit higher on ratio so will exibit a tad more pinking if set to standard timing . a correct head MAY also need a slight ignition retard but best to experiment.

[funkyG]

Many thanks for the info,

I will have a look tomorrow and then talk it over with Jeff my local, vauhall trained mechanic, who's now running his own business. He's goin to help me with getting it back on th e road.

Thanks again it was very informative and I'm sure I will be asking more q's as the year go's on

[stradacab]

Don't bother knocking the timing back, that was the "mod" for the Family II engines that were compatible with unleaded

[plumster]

In 1979 it was 4 star, or 2 star for two strokers.

Stick a couple of squirts of Castrol Valvemaster in with each fill up.

When posible you can always see if your local Tesco & see if they have the 99 rated fuel.

[Brown Job]

Kind of depends on how much the engine has been used. Valve seats can naturally wear-harden, and will also have a degree of "lead memory". My 1900 Cav has run for 20K on 98 RON unleaded without much, if any, signs of valve seat recession. You have a Centaur*, my guess is that that it won't be doing much mileage anyway. Me, I'd leave it alone and just see how it goes on Super Unleaded, particularly if it can be given a decoke.

BUT: If it's an original engine and head, it's not designed for unleaded. Also, one of the overlooked problems with modern fuel isn't just the lower octane rating and absence of lead anti-knock, but the overall higher volatility. This can lead to excessive pinking and one or two other fuel-related problems. Any insulation of the carb from sources of heat (manifold, exhaust, etc.,) will help overcome this to some extent.

It's a vexed question all round. I do find that a very slight ignition retardation can help, but not more than a coupel of degrees or it brings about more problems than it solves.

BJ

*PS. That should have been in capitals and lots of exclamation marks . You have A CENTAUR!!!!! Wow! How rare is that??? Congratulations and let's have some pictures, please?

Edited November 11, 2011 by Brown Job

[funkyG]

Thanks for all the info, I will talk this over with Jef, a mate of mine who is a vauxhall trained mechanic and with all of your great info and advice, I'm sure we can come up with a solution. On the question of the pictures, I'm going to get my son to add them as I'm not having much luck.

Thanks again

Kind of depends on how much the engine has been used. Valve seats can naturally wear-harden, and will also have a degree of "lead memory". My 1900 Cav has run for 20K on 98 RON unleaded without much, if any, signs of valve seat recession. You have a Centaur*, my guess is that that it won't be doing much mileage anyway. Me, I'd leave it alone and just see how it goes on Super Unleaded, particularly if it can be given a decoke.

BUT: If it's an original engine and head, it's not designed for unleaded. Also, one of the overlooked problems with modern fuel isn't just the lower octane rating and absence of lead anti-knock, but the overall higher volatility. This can lead to excessive pinking and one or two other fuel-related problems. Any insulation of the carb from sources of heat (manifold, exhaust, etc.,) will help overcome this to some extent.

It's a vexed question all round. I do find that a very slight ignition retardation can help, but not more than a coupel of degrees or it brings about more problems than it solves.

BJ

*PS. That should have been in capitals and lots of exclamation marks . You have A CENTAUR!!!!! Wow! How rare is that??? Congratulations and let's have some pictures, please?