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  #16 (permalink)  
Old 01-25-2005, 07:52 PM
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I'm still not convinced is it okay to run unleaded, b/c in 1972 I'm told you couldn't buy unleaded gas and that it wasn't used until 1975 when cars got cats. I don't know why the heads would have hardened valve seats when they didn't need them. I obviously wasn't around, this just what my dad told me. thanks

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  #17 (permalink)  
Old 01-25-2005, 08:21 PM
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75 & later had hardened valve seats to compensate for unleaded gas, you can get them put in your heads too, a valve job probably woudln't hurt either. Call you local machine shop
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Old 01-26-2005, 03:32 AM
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Read the manual more carefully, bet it says:

use low lead regular* or unleaded premium**.

*87 octane burns "hot" and fast, needs "a little" lead for seat protection

**100 octane was still around in 72, burns plenty cool, don't need lead

How many miles are on the motor??? That helps answer what to do.

"cats" are to reduce sulphur and other emissions, not part of the lead question,
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Old 01-26-2005, 04:27 AM
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Cats are part of the lead question as far as cars with cats can never use leaded. It would destroy the cat in no time.

In case there aren't hardened valve seats in your heads (can't tell that) somebody might be able to advise you on what heads you could put on as a replacement from a later engine. Depending on the engine this might be cheaper than having the heads converted? In the meantime using lead replacement additive could be an idea.

Martin
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Old 01-26-2005, 05:09 PM
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it a 72 corvette with 92k miles on the original 350
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Old 01-26-2005, 05:18 PM
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Dang. Howd you get your hands on it? Is it insured? Whats your exact address?

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Old 01-27-2005, 02:49 AM
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spyderdude, 4 jaw,

92k miles, did the previous owners always burn premium or use lead substitute? If not, it "may" be pointless and useless to do it now.

I never have seen or heard a "proven" answer to your question which boils down to:
How many tens of thousands of miles can you use very hot 87 octane in a used leaded gas motor cylinder head before the "three angle" is burned off and the valves don't seal as well as they possibly can?

I would do a compression test now, to know if the heads and motor are "excellent", "ok" or "uh-oh ".

(I hate to "guess" about anything!). My guess is, if it does test "ok", the valve guides will wear out before the (93 octane?) unleaded gas burns off the valve angles.

If they did test excellent, I'd use 104 Octane boost, makes a cool burn and keeps the engine cleaner than lead substitute.

"uh-oh" = time to freshen the heads, adding hardened seats is not expensive, Vette guys are nuts about #'s matching, so I probably wouldn't swap to later heads.
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4 jaw,
I should have added: high lead content gas burning motors, had crummy rings (?) and poor quality (?) iron blocks, idea was the lead reduced wear in the bores

Question for you...explain "4 jaw"? Never saw it before this board
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  #23 (permalink)  
Old 01-27-2005, 02:52 PM
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To lead or not to lead...that is the question!!

You should have no problem running the unleaded gas.


Tazz


Rat Rods Rule!
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Old 01-27-2005, 06:00 PM
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Quote:
92k miles, did the previous owners always burn premium or use lead substitute? If not, it "may" be pointless and useless to do it now.
My uncle has had the car for the past 15 years and hasn't put many miles on it. He did run 93 unleaded and he has no idea about the previous owners. Compression test is probably a good idea. If it was bad, it wouldn't be the cost of the machine work but the cost having the heads taken off, as me and my dad probably aren't up to it. Although if it needs it, it will be done. thanks
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Old 01-27-2005, 06:36 PM
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Quote:
Originally posted by spyderdude
My uncle has had the car for the past 15 years and hasn't put many miles on it. He did run 93 unleaded and he has no idea about the previous owners. Compression test is probably a good idea. If it was bad, it wouldn't be the cost of the machine work but the cost having the heads taken off, as me and my dad probably aren't up to it. Although if it needs it, it will be done. thanks
I'm wondering why you were worried about unleaded gas if it was run on it for the last 15 years? Just continue with Super
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Old 01-27-2005, 06:56 PM
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When I say not many miles I mean less than 4k. He never really drove the car much.

Last edited by spyderdude; 01-27-2005 at 07:02 PM.
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Old 01-28-2005, 03:01 PM
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Thanks for the easy to understand answer red65, when Chuck answers these questions for me I always get the Encyclopedia Britannica version...it was nice to get Coles Notes for once.

As for 4 Jaw...well it's kind of a rip off of my husband's user name...4 Jaw Chuck, so named because being a machinist he likes things that are precision. A 4 jaw chuck on a lathe works better and gives more precision work than a 3 jaw chuck. When I joined I threw the question to the other members "what should my user name be?" Someone came out with 4 Jaw Chick. I liked it, it fits, so there you have it.

You will find that I am by no means the mechanical genius that Chuck is, but I understand the basics and spend most of my time on the board reading rather than posting (except if there's something in the lounge that requires my opinion). I could change my own spark plugs if I had to. I can change my own oil, and have changed many, many tires over the years. I could probably bleed my own brakes if I had to, but wouldn't want to try without supervision. I can tell when there is a problem with the car (except for some reason I can't tell when the tire pressure is low ), and sometimes even diagnose the problem correctly (or mostly correctly). I understand the differences between gasoline engines and diesel engines and unlike a lot of women out there I'm not scared to go and buy parts for my car as long as I don't get some condecending idiot who thinks he's doing me a favour or a kid who knows less about engines than I do but pretends he knows more.

Chickie.
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Old 01-29-2005, 06:30 AM
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spyderdude, 4 jaw,

I agree with "car guy", just burn 92-93 octane, cool enoughfor what's left in the heads life.

4 jaw, got it, didn't put car and machine shop together ,"met" your husband on another thread....wanna good laugh...tell him red65 says "I need a windage tray and a 8 qt pan" on the (your) washing machine...it will crack him up betcha'
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  #29 (permalink)  
Old 01-30-2005, 09:35 AM
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the problem of running unleaded has been pretty much dispelled. I've seen many older motors than yours run on unleaded with NO problems at all, and I'm talking about 50's motors. Hardened valve seats are a good idea, but I'm convinced not necessary in most old motors, it just hasn't turned out to be a problem. I've also read many articles that support what I'm saying. Don't worry, be happy, and run that vette-put it this way, even if it would hurt your valves (extremely unlikely) THEN you get a valve job and have the seats installed. Add aditive if it makes you feel better, but in my opinion it's unnecessary. I've been running a 71 400 sbc with stock heads for 15 yr's, no problem, though the flame throwers finally did a number on the walls.
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Old 02-01-2005, 03:18 PM
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You can find lead additive at farm stores. Some people use it in older tractors for the same reason. I've been told by people who should know, that the only time I would ever need lead additive in my old farmall would be if I was plowing or something and using the engine at top rpm for a long time, in turn building up heat. Heat seems to be the major problem. As far as putting around and doing some occasional bush-hogging, additive not really necessary.
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