Still considering buying a 69 429 (TJ). The latest thing I've come across in my research is that running an engine that was meant to run on leaded gas on todays unleaded pump stuff will destroy my valve seats. That seems reasonable to me, but how fast will it really happen?

The other thing I heard along the lines of leaded/unleaded is that with the high compression of a 429 (10.5-1 in this case), today's unleaded fuels will cause detonation (pinging). I know that that problem can often be solved by using the higher octane Premium or Super+ grades of pump gas, but what does it have to do with leaded or unleaded fuel?

Thanks for any help with this, AleX

 

Lead was used to control detonation/pinging by slowing down the burning of the fuel. It also provided a cushion/lubrication for the valve seats.

The theory was running older engines on unleaded would lead to burned valves and sunken seats in short order. If that were true, nothing from that time would still be running today.

Heavily loaded engines will suffer more than light duty engines. Certain engines are worse than others.

If you can find gas with enough octane, you might be able to run the stock 10.5 CR. (sure it isn't 11.3 or something--some TJs were that high iirc)

BUT, are you really going to run a 40 year old engine--is it still oem and running?

 

Haven't even seen it yet. It's far away som I'm doing all the research first. From what the guy has told me though it was running very well when it was pulled. It does have 90,000 on it though (from what he says), and hasn't been run in 10 years (garaged, but still). I know it would be a pretty big gamble, especially after spinning bearings and cracking heads just last month on my previous unchecked engine, but I'm not going to buy it unless the guy let's me tear into it a little.
Still not sure though, so opinions appreciated, AleX

 

Been running my 272 Y Block for ten years every summer for a daily driver. Several thousand miles. Plus the trip form western Colorado to Alaska. Valve seats are still just fine as is everything else. Engine is original never touched. Close to 100k on it. I add lead on octane boost about every third fill up.

 

You add lead you say? How, is there some additive?

 

I talked this issue over with a local machine shop concerning a rebuild of a 68 429. I asked about cutting out and installing hardened valve seats.
The shop owner said that when he cleans the parts he uses an oven to bake the heads to remove the built up gunk/ etc and in the process it hardens the existing valve seats. He says it should be no problem unless one is already damaged or cut too thin from previous valve jobs. I need to do more research, but I think he may be on target with his advice as heat treating is pretty much the standard way of hardening metals. He has been in the business for many years now, so he should know a thing or two.

 

Ya I get lead additive at Nappa