Logo
FULL SITE MENU

454xl backfire through exhaust

Heads will be done this week. He has them cleaned and will pressure test. The shop was closed because of a busted water pipe during our cold snap then the Holidays. And now of course I'm busy. Will update when shop calls and lets me know what if any issue.
 
Got the heads back. # 3 exhaust valve was stuck open . other side was ok.
I'm thinking that was part of problem and exhaust manifolds cracked due to the explosion.
I have new head gaskets and bolts on the way and will order new manifolds.
Of course we are taking the RV out for a 2 week jaunt so boat is on schedule when we get back.
 
Heads are re-installed. Easy job. New exhaust manifolds (Crusader) installed. Everything is back on the engine. I could not find Crusader exhaust elbows, so went with Barr. They will be here Thursday.
Anything I should do before turning the key?? Should I do a compression test before installing the plugs?? Leak down test again??
 
I think you are ok on the heads...I'd say consider changing the oil if you had any significant antifreeze drip into the block...other than that, add the antifreeze and bleed it out...after going thru the hot and cold cycle to do that, probably be good to retorque the exhaust parts and checking the hose clamps wouldn't hurt either...I'd be inclined to get a few hours on it and make sure the coolant level stabilizes...when it does, you should be good.
 
Thanks mako, the coolant level will be closely monitored. I changed the oil/filter and plugs and wires. Just waiting for the elbows.
 
Got elbows on and turned the engine over for first time in a long time. Everything sounds and looks good. Oil pressure gauge is showing pressure. I will install plugs and try it again and hopefully it will start.
 
sounds like progress...
smile.png
 
DONE!!!!! Well, kinda. Every thing is re-installed and the engine fired up. No leaks or wierd sounds. Got it up to tempature and shut it down, cool down and started again. cool down, re-tourque manifold and elbows. Topped off coolant and is maintaing good level. I disconnected the MSTS connector and put a timing light on it just to check. The timing marks are WAY off. If I turn the distributor to try and get the marks even close, the engine dies. This is the first time I ever put a timing light on the engine. Never really had a need to. I haven't done sea trials yet. Just put it in gear at my dock. No issues, just the timing marks.
 
when checking the timing, you disconnected the THREE wire timing connector, correct?
you did the 'disconnect' after the engine was running?
Finally, did you check the max advance of the ignition timing, with the connector re-installed? The data I have says 37 deg, max, at 4000 RPM...personally, I'd do this one and not worry about the initial timing as long as the engine restarts when warm..
 
No. I disconnected the one wire (pink) MSTS connector. No. I disconnected the connector with engine off. No. I did not check max advance.
Was going to do sea trials today, but low tide and windy. Maybe tomorrow
 
I guess I didn't ask the question clearly...on your timing connector - the side you remove should only have one wire (my diagrams dont specify that color) in a 'loop' . does that plug into a connector (with three wires) that goes back to the MSTS box?
 
Yes Mark, that is the wire I disconnected for intial timing. I let the engine warm up and shut it down and waited about 5 minutes and started it back up. It fired right up and ran good. Still waiting for good weather condigtions for a boat ride
 
understand on WX...at least it isn't cold up here this week.
The data I have for MSTS describe the check timing procedure different than you did.
Did you check the timing on the other engine?
 
No, I did not check timing on other engine. BUT, I ran the boat yesterday. Got on plane and ran at 2800 RPM for 5 miles and everything is running perfect. All the gauges are right where they are supposed to be. Got back to my dock and shut down and checked oil and coolant. I used IR gun and took temps on elbows, exhaust manifolds, shafts. Both engines were real close on temps and all fluids were fine. Sooooo, FIXED!!!!!
Now the question, What was it?? My theory is that when it exploded, the blast cracked both exhaust manifolds as my pressure test in water tank proved. I had one sticky exhaust valve and I'm sure the head gaskets suffered some damage.
Lessons learned? First is use the right tools for diagnostic testing. My compression test and leak down test were done with cheap equipment and my air compressor used for the leak down test had a leak in the hose that was buried, and I did'nt really know how to interpret the numbers.
Going to get her cleaned up and take the bride out for a boat ride and lunch at the beach.
Thanks MakoMark, you are invaluable in your straight thinking and knowledge.
 
Sounds like you can look forward to enjoying the rest of the spring time afloat this season.
agreed that using cheap equipment isn't always the best path...little quality issues as you noted, can let you off the best path very easy - congrats for sticking with it.
As far as exactly what happened, hard to say with certainty...could have gone like you suggest or some variation - big thing is that its behind you know.
thanks for the kudos.
:)
 
Back
Top