C2-Unleaded gasoline

[Mike Swanson]

Should I be concerned about running unleaded gas in my 67 L79 or should I be using a lead additive?

Thanks in advance

Mike Swanson

[Craig S.]

Re: C2-Unleaded gasoline

Mike - personally, I would not use an additive. I run straight 92 octane premium in my 67 L79 with no problems, although the exhaust seats were replaced with hardened seats. However, everything I have heard says unless you are running the car hard as in racing, or, doing lots of high speed long distance driving, don't worry. The erosion comes from the seat temperature being elevated, and typical use of our restored cars is just not that hard. Personally, if I rebuild an engine, I like to install the hardened seats for durability anyway, but, I would not bother to use additives if I knew I was running unleaded and iron seats. I just rebuilt an original set of 858 BB 66 heads I bought from a guy that had them on his 70 Chevelle LS6 (it was a beauty, he found an original set of 231 heads and was selling the vette heads) and they had the original iron seats and guides. They had normal wear, and some pitting in the seat faces after bead cleaning, but no recession. I installed hard seats to make them bulletproof on the exhausts only, but the intakes were fine, they never have an issue as they are cooled by intake charge. Anyway, I think this gets blown out of proportion and it is needless worry.

[Mike Swanson]

Re: C2-Unleaded gasoline

Craig,

Thank you for your quick response. You confirmed what I thought so I feel much better now. The car has 51K mile s and I drive it less that 100 miles per year so I am not too worried.

I would also like to thank all the other expert responses in the past. I have been lurking on the NCRS site for several months now and finally decide to pony up for a two year subscription to join this fantastic resource.

Thanks,

Mike

[Craig S.]

Re: C2-Unleaded gasoline

Mike - welcome to the NCRS. You will find everyone on this board is very willing to help as best they can, and I have learned more than I can ever say from hanging out here for the last 5 years or so. The depth and breadth of knowledge from folks here is second to none, I feel very fortuante this medium exists to convey information, and make friends!...Craig

[Clem Z.]

Re: C2-Unleaded gasoline

there is a bigger chance of problems if the seats are not installed correctly than from unleaded gas on the stock seats.

[Joe L.]

Re: C2-Unleaded gasoline

clem-----

You summed it up perfectly in a single sentence.

[Joe L.]

Re: C2-Unleaded gasoline

Mike-----

The Restorer Magazine, ALONE, is worth the price of NCRS membership. Everything else is a bonus. I don't understand why everyone interested in old Corvettes doesn't join NCRS just to get the Restorer Magazine.

[Craig S.]

Re: C2-Unleaded gasoline

Clem and Joe - thx for the input, at this point I guess I am stuck since it is done. However, my machine shop specializes in building racing engines and installs hard seats all the time in both iron and aluminum heads, so I guess I hope he knows what he is doing. He certainly did a first rate job installing the Darton step sleeve. I hear what you are saying though, if the press fit is not correct, it can come loose and really beat up the valve, head, piston, etc, and if too tight it can crack the head. So far I have been lucky and have never had a failure with a seat coming loose...I guess it is as good or bad as the craftsmanship of the shop. So I will cross my fingers he did it right again...Craig

[Clem Z.]

installing and removing insert seats

i have installed seats in both cast iron and aluminum heads to change the shape of exhaust port throat but i always shrink fit the insert into the head. liquid nitrogen or even "dry ice" does a good job of shrinking the seat. here is a tech tip, if you have to remove seat inserts is to use your TIG welder on the seat insert and when it cools it will shrink the seat and it will almost fall out. this is the best way on aluminum heads so you do not remove any aluminum like happens when you just pull them out.

[Craig S.]

Re: installing and removing insert seats

Thx for the tip Clem....I will ask my shop if they used the dry ice process like they used on the cylinder liner before installation....Craig

[Jim T.]

Re: C2-Unleaded gasoline

Have a original owner 68 L79 and the engine is still just like the factory built it but with over 90K on it. Runs very good and just use 93 no lead that is available at the pump and use no additives.

[David K.]

Re: C2-Unleaded gasoline

I have been adding lead substitute with every tankful since I rebuilt it in 1997. (I drive it less than 500 miles/year, and don't race it).
Am I hurting anything?
When I asked about this in 1997, I learned it was merely cheap insurance against damaging the (original) valve seats.
- David Knowles

[Clem Z.]

Re: C2-Unleaded gasoline

TEL is very poisonous so be carfull how you handle it. back before race gas we go TEL from gulf research and we used rubber gloves when we handled it!!! i believe we used 5 ccs per gallon. just don't use the so called "octane boosters" because they eat the plating off of the inside of the carb float bowls making it easy for corrosion to start.

[John H.]

Re: C2-Unleaded gasoline

The commercial "octane boosters" are also loaded with ethyl alcohol, which does bad things to ordinary old rubber and cork seals and gaskets over time. My 10.5:1 327/300 and 11:1 '69 Z/28 run fine on pump premium, and I don't use any additives in either of them.