Ive had a couple trucks with the 4.9 engine. The 95 model I have now, I put headers on it, freed up the exhaust, electric fan. Seems to pull a tad better. Had it for 13yrs now, still putts along like it did when I got it. The 4.9 engine makes no sense in a truck until you tow with it, then it seens to come alive and make perfect sense. haha
Little update on the mower situation.
Still revs way too high and adjusting the throttle down via the throttle lever does nothing to slow it down. It does seem like a air leak or vac leak, whatever its referred too on small engines.
This is what I do know.
Engine still has compression.
Oil level appears normal.
Carb is fine, I took it appart, cleaned it. The plastic piece that holds the choke blade melted off due to the fire but I removed the choke blade, so thats not an issue. Right now Im using two fingers as a manual choke, until I can figure out whats causing the over rev condition, once thats figured out, Ill fix the choke blade.
I checked the intake to carb gasket, there are no cracks or breaks. I replaced the intake to cylinder head gasket.
This is what I noticed and am not sure what the correct setting(s), should be, maybe someone can fill me in.
With the throttle lever in the slowest position, the throttle blade is still 3/16 or so open, to me that seems excessive. There is a throttle stop on the top of the carb, if I close the throttle blade until the hinge makes contact with this stop, the engine dies. With the way this thing revs up hard youd think it would have a massive air leak somewhere, so the fact the engine dies when the throttle blade is closed kinda puzzled me, Id expect it to bog down and then die but it just flat dies. As mentioned, with the throttle lever in the slowest position, the throttle blade is still 3/16" open. From this point to wide open, the engine seemingly runs wide open. If I manually close the throttle blade from the 3/16" position until it hits the throttle stop, I can get the engine to gradually wind down, or decrease the rpms in a linear manner until it dies. But from the 3/16" or lowest throttle lever setting, to full throttle setting/ throttle blade wide open, the rpms seem to be the same, which to me suggests a huge air leak somewhere.
I dont know what the head gasket or internal passages look like, so I have no idea if a blown headgasket would cause this issue, the cylinder psi cold was 50 psi and again, I dont know if thats considered normal or extremely low? If its low, then I might think its the head gasket.
Another thing Im not clear on, is if I let this thing run at the rpms its running (excessive) for say ten twenty seconds, oil shoots out the breather tube. Which tells me pressure is building up in the crankcase or whatever you call it on a small engine, which kinda suggests to me it could possibly be a blown head gasket. Maybe not, as again, I dont know how these things work internally, so perhaps if it has an oil pump, then excessive rpms and oil shooting out the breather might be normal but if the oil circulates via another method, then Id have to lean back to excessive pressure inside the crankcase or blown head gasket.
I may very well be over thinking it all, so any input appreciated. Right now Im just guessing.
Im fairly certain the fuel side or carb is fine, hell, it has a little carb like the atc70 I redid, not alot going on inside there. The float inside the carb is fine, I checked its buoyancy.
Again, any input appreciated, and yes, I had my fire extinguisher on hand. :biggrin:
