How can I tell if my valve seats are hardened? I need to know so that I know which fuel to use. The guy at the auto parts store didn't want to sell me anything w/o know if the engine had been rebuilt or not. It doesn't run REAL great on the 87 that's in there right now. Any ideas?

 

It doesn't matter. Hardened seats have absolutely nothing to do with what fuel you use. All they do is make your valves and valve seats last longer in the absence of leaded gas, and you can't buy leaded gas, anyway.

Run the lowest grade of gas that doesn't make your engine knock. If it knocks on 87 octane, switch to 91 and see what happens.

If you really want to know, you need to pull the heads. The only heads that came from the factory with hardened seats were those produced in the last few years of production (74 and up, I think). They would be D2TE-AA heads, but not all D2TE-AA heads have hardened seats (early ones did not).

 

So was the guy totally on crack then? What he told me was a total crock? If that's the case then I'll probobly just use 92.

 

What did he tell you? Your initial post indicated that you needed to know what fuel to use. But you also said that the guy at the "auto parts store" didn't want to sell you anything without knowing whether your engine was rebuilt. Do you buy gas at the auto parts store? What were you trying to buy that he didn't want to sell to you?

 

yeah sorry I forget that the people that are reading this don't know the story already. No I went into the store and I asked him what additive he recomended for a 428. He asked if the engine had been rebuilt, and I don't know if it has been, I'm almost positive it has been, but he says it matters because if it hasn't been then you need a high octane fuel. If it has been rebuilt, then you can run lower octane. He didn't want to sell me lead substitute or octane booster w/o knowing either way. What do you think?

 

I think he's an idiot. Just knowing whether it's been rebuilt doesn't tell you anything. I give him credit for not selling you something, though. Too many places will sell you stuff regardless of whether you need it.

Basically, just run the lowest octane gas you can without the engine knocking or dieseling. If it still knocks or diesels on the highest octane you can buy, you've got some work to do. My first step would be to switch to a lower temp stat, and 2nd would be to back off the timing a couple of degrees. If you're still knocking or dieseling after making those changes, consider an octane boosting additive. The only one I would recommend is Lead Supreme-130 from Kelco Oil, because it's the only real TEL additive out there. If you don't need it, though, you're wasting your money. And don't worry about whether your valve seats have been hardened -- if they haven't, just have it done the next time you need a valve job.

 

Thanks again man, case closed!