i have a 1985 1.8 subaru ea motor i

[subarukris]

i have a 1985 1.8 subaru ea motor i am running on propane it is a turbo motor so low compression and i found if i run both cams one tooth retarded and 45 degrees ignition timeing it runns very well with 20-25 psi boost but i have burned the motor up in about 6000k is it true that leaner af ratio will burn cooler with propane and now i have biult another one and haven a hard time getting it to start cod also how do i deal with the vacume advance wont it blow propane in to the cap and ignight it

 

[Tmoose]

"burned the motor up in about 6000k"

What components failed?

 

[enginesrus]

Even super lean gasoline will burn cooler.

 

[EdStainless]

The avg temp in lean burn may be less, but local temps can be much higher.
Most engines rely on some excess fuel to keep from having hot spots in combustion.
Ask someone who has lost a fuel pump during full throttle operation.
The crowns of the pistons are melted out.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

The issue with lean burn is the delay in combustion. Temperature drops rapidly as the charge is expanded but if the charge lights late there is less expansion. This caused overheating of the engine.

 

[gruntguru]

Yes late arrival but also slower burn rate.
If the engine isn't designed for lean burn, leaning the mixture at full load is usually catastrophic especially if boosted.

je suis charlie

 

[Tmoose]

I don't think I've heard yet what components failed, and how to qualify as 'burned up."
- broken piston (s) ? if so, the piston damage can point to any of several different combustion and mechanical problems.
- burnt eroded valves or seats that no longer seal?
- failed head gasket that quickly led to catastrophic major overheating?

http://ww2.justanswer.com/uploads/Protech8/2011-02-13_203622_timing.gif

https://images.simplepart.com/images/uploads/SimplePart - Subaru/fullsize/a_20160908_1151106492.png

Looks like the crank sprocket has about 24 teeth.
So the cam sprockets have 48 teeth. One cam sprocket tooth is about 7.5° on the cam sprocket, but as far as the crank is concerned the cam sprockets have 720 "degrees".
After just one cup of coffee I'm thinking you changed your cam events 15°. That is a whopping change. Much greater than is usually done to fine tune a cam for a given application.

Retarded / late intake closing would tend to mess up low rpm running in the carburetor days.

Were you monitoring exhaust gas temperatures, and looking at spark plugs after some hard running?

 

[gruntguru]

45 degrees ignition timing? Meaningless.

Most engines idle somewhere between 10 and 20 degrees, full load at 10 - 35 (rpm dependant) part load at 20 - 50 (rpm and load dependant)

je suis charlie