Head rebuild question

[ScottH]

I have a 67 250 motor I want to have the head redone.
What recommendations would you have regarding running unleaded in this motor? Also any ideas on improving performance on the head?

Any suggestions are appreciated.

Thanks.

[shifty]

As long as they use hardened valves and all other modern hardened equipment, you can run unleaded.

The 250 I just sold to another member had the head gone over, ported and polished for $200 and I think he said it was 10.5:1 compression ratio after? I forget. Don't have much other info than that.

[ScottH]

Thanks shifty.

Is it the valves, seats, or guides that need to be changed for unleaded?
Anyone?

[shifty]

Seats, sorry. We were talking about it in truck chat just now and it was suggested that you really don't need to bother with any of it, but the consensus was that if you want to be anal, seats at least and guides if you want.

[1970 CST Short Wide]

I don’t usually chime in on these things but I built cylinder heads for 16 years and think I know a little about this subject. If the head has never been work over before you will want to make sure the guides are in good condition by either reconditioning or replacing them. Use a good quality (NEW) exhaust valve (they come hardened) and NEW Stalite (hard) exhaust seats. This will put your cylinder head in new condition and you will not have any problem with the unleaded fuel. If you do not put the hard exhaust seats in I can almost guarantee you'll be doing it very soon down the road.

Good Luck

[Brad]

1970 CST Short Wide, my 68 Camaro has never had the head worked on. Other than black smoke when I start it up in the morning, (which I attribute to a carb issue), how would I be able to tell that my seats are going bad without pulling the head. Any kind of indications other than pulling to get an idea one way or another? I only drive it about 500 miles a year for the past 10 years.

Sorry for the thread hiest!

[mrein3]

Originally Posted by Brad

1970 CST Short Wide, my 68 Camaro has never had the head worked on. Other than black smoke when I start it up in the morning, (which I attribute to a carb issue), how would I be able to tell that my seats are going bad without pulling the head. Any kind of indications other than pulling to get an idea one way or another? I only drive it about 500 miles a year for the past 10 years.

Sorry for the thread hiest!

I believe your question is relevant to the discussion.

I had a head go bad to what I attributed to be a leaded/unleaded issue.

Shortly after I couldn't get regular gas for it it started barking through the carb on the highway when I went to pass somebody. Eventually it got to where it would buck and complain even when accelerating from a stop sign.

To answer your question directly a compression test gave me VERY low numbers on the two middle cylinders on the even side.

When I pulled that head the two exhaust valves over those holes were visibly sucked farther into the head.

I believe the PO put the engine together with heads that were not worked over for unleaded gas.

If memory serves, everything the General built from 1971 on is good to go with unleaded (the called it low-lead back then) gas.

[ScottH]

Great info, thanks guys.

Can u tell me what I can expect (ball park) in terms of $ to have this work done?

[shifty]

Too Much!

[70rs/ss]

Honestly I'd look at your use, if you drive it every day then put hardened seats in it. The guy with the Camaro and 500 miles every year probably not. The lead in the fuel of old was a lubricant and the old head's seats were soft. Unleaded has no such lubricant and every time the vavle shuts it beats up the seat. On a 250 if I was thinking of switching to hardened seats, I'd just find a core from a 74 up to be sure the head has the seats already. Another thing here is that back in the day the valves are two piece, meaning the head of the valve is joined to the stem, so I always change valves in any head I have done. I have seen them break, although it doesn't happen often, I do not build disposeable motors so I put new valves in. You are truely going to have a lot of $$$ in a 250. I know it sounds typical, but put a 350 in it and you'll spend less and get more, if dead set on a 250, find one used and buy it. These run forever and need little to keep em that way. I'd bet a running 250 would cost $200 or less and the head work could cost around $300.

[fixerman]

I just had a 250 head rebuilt and it cost $310.00. This included new valve guides, hardened seats, seals, valve grind, and re-surfacing since it was a bit warped. Not a bad price for all that work. They even painted it Chevy orange!
See the attached before and after pics.

Fixerman

[1970 CST Short Wide]

The later model heads do not have seats already in them - They have a flame harden surface on the cast seat. Works OK but not as well as a good hard replacement seat

[70rs/ss]

I guess I was going more for savings. $300 for a six head seems like a waste, don't get me wrong, I love me some I6 but $300 will get a set of 350 heads done as well. I paid $50 for my last I6 and it still runs and smokes the one tire!! Most folks pull em in favor of a V8 like I suggested earlier, so if you look they are out there in good running shape for cheap. Either way good luck and you can get away with the 67 head, just know it will last longer with the hardened seats than not. I still run a set of double humps with no hardened seats, to each his own.