Will a '69 427 run on today's pump gas. Will it require modification or fuel additive?

 

Mine ran on 91 with no issue. My new engine is at 9.7:1 also no issue.

 

Sure it will.

Gas today isn't as bad as people talk about. My 11.56 compression 555" made 871HP at the flywheel on 93 octane. Now with a couple of turbos it made over 1100 RWHP on 91 octane with just some W/S washer fluid injected.

JIM

 

So no additives required?

 

Nope. additives don't add octane for the most part anyway.

If the carb has not been rebuilt to handle the alcohol in today's fuel get that done. Otherwise just drive it.

 

Do your heads have hardened valve seats?
Unleaded fuel will wear the seats.

 

if you aren't sure if the seats are hardened (believe around '71 or '72 all seats were induction hardened), then just run some lead additive. I run that in my tractor ('56) but don't in my '68 since I know the aluminum heads have hardened seats. if you were talking just a run of the mill occasional parade car I wouldn't worry about it, but if you plan to drive a lot and beat on it, add the lead...remember if the seats aren't hardened the exhaust valve welds itself to the seat and pulls away microscopic bits of metal when it opens again. the coating of lead just keeps that from happening as quickly...

 

read this technical paper on the topic, unless you are subjecting the engine to constant high rpm use under heavy load you need no additive.
http://www.unep.org/transport/pcfv/p...finaldraft.pdf

 

My 69' 427/400 .060 TRW piston engine ran fine at a true 10.5 to 1.....when REAL hot out it would overrun with the key off....

Jebby

 

My big block and small blocks all run fine on unleaded pump gas with no additives. The need for hardened valve seats is an often repeated myth. Unless you are towing or racing you don't need hardened valve seats.

 

 

I wouldn't install hardened seats. Good way to mess up a good head if not done correctly or if casting is a little off.

No need for it. If you just want to add something to fuel...won't hurt...but not an issue especially if heads were rebuilt with stainless valves.

JIM

 

additives are like snakeoyl they don't work. waste of time and money.

 

it's not a myth, they've been using hardened valve seats since '71. it is a fact that valves will erode the seats when not hardened or there is no "cushion". read the tech paper posted above, or any of the other documentation. the only thing in contention is how hard you drive/how much you drive, and how long you want it to last.

the tech paper makes good points but neglects the collector car/show car/weekend classic segment of the vehicles out there. it makes assumptions that few cars are still on the road with unhardened valve seats, and the ones that are are full of carbon and ash in the valve train which makes the need for lead less of an issue. (which may well be true in some cases)

Unfortunately, that is not the case for SOME classic vehicles from the '60's that are not oil burners, and have clean valve trains or have been rebuilt yet did not get hardened seats installed...

running without lead additive isn't going to make a bit of difference in how the engine runs, there are plenty of alternatives for octane boosting in today's fuel (and there were in the early 1900's as well, just not as cheap as tetraethyl lead (for an interesting read, google Henry Ford, Charles Kettering
and the "Fuel of the Future"

 

Interesting paper to read. I have seen valve seat recession in older engines. I must admit that I question the motives of the people writing the paper, the group who wrote the paper is of the UN.

 

We will agree to disagree then. 3 of the old Corvettes in my garage, 61, 65, 68, have a combined 200,000 miles of driving on unleaded gasoline without hardened valve seats. No valve issues whatsoever. I run no additives and run pump gas. I know many long time owners who can say the same thing. Many engineers with alot more knowledge than me will agree that if you aren't racing or towing you don't need hardened valve seats.

 

200,000 miles / 3 vette's = avg. 66k miles each. normal valve job on those motors is typically around 100k, so that really doesn't prove anything. and how do you know you don't have valve issues? have you taken them apart and inspected the seats? have you owned them since new? what kind of gas was used the first 10 years? nobody ran leaded in them until the 80's when it disappeared? the effect of lead can last up to 20k miles on a mildly driven engine, so theoretically, you could still have some lead coating in there...

We can disagree, but ask yourself this: why would any car company go to the additional expense--and they have for almost 50 years now--of hardening the valve seats if they didn't need to?

believe me, I don't believe in additives generally, snake-oil cure-all's, MMO added to every thing, etc. but to say that you don't need hardened valve seats and that lead makes no difference in reducing seat erosion is just plain ignorant (and I mean no disrespect).

there are lots of variables that can make not using lead just fine for most people, especially just weekend cruising. but it is clearly documented that lead WILL increase the longevity of the valve train. Like the synthetic oils debate, you need to decide "how good is good enough", or how much increased valve train longevity is really needed on a car that will likely never be driven that much in the first place.

 

I have read the tech paper and consulted with engineers on the topic. The motors that experienced valve recession in the testing were stressed to the limits to induce valve recession. There is ample evidence that long term, normal operation does not cause valve recession. I have driven my 65 since 1971 and the only thing I noticed when they transitioned to unleaded fuels was that my spark plugs lasted much longer. I am still on the original L79/350 horse motor. The motor was rebuilt in 1987 after I spun a bearing. Heads were machined at that time. No valve recession was evident at that time. I did not go with hardened valve seats. Burns no oil so I have no reason to pull it apart. 30 years later it runs great.

Go over to the NCRS Tech Discussion Board. This has been discussed many times. There are engineers over there that I have alot of respect for that have opined on this subject. Anyone that feels better about doing hardened valve seats in an old Corvette that isn't raced or used for towing should do it. But they don't need to.

 

I guess to answer your question, if you have 10.5-1 comp or less go ahead and run it on pump gas.