Weird Noise on Engine Start Attempt Post Engine Refresh

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bwatling

bwatling

Joined
Jul 15, 2023
Threads
9
Messages
38
Location
Mooresville, NC
Tried to read as much as I could here and online and not finding much to explain my dilemma at this point. For Context: 1977 FJ40 2F motor with a Weber 38DGAS carb. I was fixing a rear main oil galley leak with the engine out and got a little carried away with doing more work on it (likely than necessary but a great learning experience so far). Had a crack in a mount area of the intake manifold that needed to be welded and then had the intake/exhaust manifolds resurfaced at the machine shop along with cleaning/machining the head and resurfacing the valves/seats after they took a good look at it. Put back together with new head gasket/new manifold gasket and a bunch of other new parts related to the head. Reinstalled everything (had most parts off the block for cleaning/etc but never took pistons out).

On to current although that description above is brief.

Put everything back together, engine back in car, mated up to trans. All fluids in and checked, spun oil pump to confirm oil up at all the rocker arms. Valves all adjusted to spec. Turned over with coil wire off and looks/sounded fine. (see 1st video link).

Attached coil wire and attempted start. This noise keeps happening with some backfiring and after flooding it also had a huge pop in the exhaust that broke open a seal in the muffler :( (see 2nd video link) Went back over timing multiple times since the backfiring and not starting seemed that it would be the most likely cause. Able to confirm TDC on compression stroke for cylinder 1 with both valves closed and rotor pointing at cylinder 5 and plug number 1 on the distributor cap when attached. Went over the intake manifold/all ports are attached or capped off), don't see any obvious source of intake manifold vacuum leaks. This is really stumping me. Have spent the better part of a couple days thinking through it, checking and double checking. haven't gone down the checking spark/coil/etc just yet but it is on the list. The noise is the craziest thing. Haven't ever heard it on a motor. Vacuum leak sound? Not a mechanical sound and not there when not trying to start it (only turning it over). Any and all help appreciated and of course ask any clarifying questions as I tried to be semi brief. Hope I did these video links right.

Turning over without coil wire attached

attempted start noise
 
Sounds like a belt squeal. Take the belt off and see. Spray some starter juice in the carb and see if it will fire it and run.
 
Didn't honestly think about that, kind of sounded like further back towards firewall but.....Will definitely give it a try. If its a weasel its a damn angry one no doubt.
 
I haven’t. It’s never been running, just some weak efforts at starting with some backfires. This is what let me to double and triple check timing/valve position, etc. The noise is befuddling! After flooding it at one point there was an exhaust pipe backfire which actually ruptured the muffler amazingly enough. Also made me think about timing if a spark could make it there. I never took the block/timing gears apart so timing gears still as they were and were aligned as I did have the HB off and timing cover off. Frustrating for sure.
 
To blow the muffler you had to be pumping fuel into the exhaust then had a spark. Your timing is probably not right. Maybe check your firing order. You say the distributor points at #5 at tdc, I thought it was supposed at point at #4 at tdc on the compression stroke. Maybe someone can chime in to confirm.
 
It did sound like a cannon. I’ll start with the electrical and double check the timing again. I thought for sure I had it out by a full turn on the flywheel setting it at tdc on exhaust but have checked and rechecked that since it seemed like the most obvious. To the point of valve cover off and watching rocker arms moving to confirm what part of the stroke I was on with cyl 1
 
That sounds more like a really high forced air trying to go through a restricted opening. Doesn't really sound like a belt to me. Intake and exhaust manifolds might deal with that much air force...although not sure how it could be constricted. Heat riser plate in wrong?
 
It could be air being forced from thru the throttle plates from inside the engine. I see a mist spraying out of the carb immediately after the noise. I'm just guessing though.
 
wimberosa said:
That sounds more like a really high forced air trying to go through a restricted opening. Doesn't really sound like a belt to me. Intake and exhaust manifolds might deal with that much air force...although not sure how it could be constricted. Heat riser plate in wrong?
Click to expand...
Sounds like high pitch/high forced air to me as well. When I put the exhaust and intake manifold back together it just has a block off plate in place with 2 gaskets. Should be wide open from the head through the exhaust manifold into the pipe but another thing to check. Intake wide open. It chugs a little when starter fluid out in carb (that video with the noise is just a little starter fluid).
 
Your timing is off and based on how you setup is incorrect.

Please verify that when motor is at TDC (line on flywheel) that cylinder 1 rockers are “loose” and while looking, verify cylinder 6 rockers are tight.

Then simultaneously remove the distributor cap and verify the rotor aligns with cylinder 1 on the distributor cap.

The rotor itself would subsequently line up visually with cylinder 4 spark plug on head of engine (not 5 like you wrote).
 
mattressking said:
Your timing is off and based on how you setup is incorrect.

Please verify that when motor is at TDC (line on flywheel) that cylinder 1 rockers are “loose” and while looking, verify cylinder 6 rockers are tight.

Then simultaneously remove the distributor cap and verify the rotor aligns with cylinder 1 on the distributor cap.

The rotor itself would subsequently line up visually with cylinder 4 spark plug on head of engine (not 5 like you wrote).
Click to expand...
And this is exactly it. Called and talked with a mechanic friend for a bit and his advice was it’s 100% your timing, now just have to slow down and figure it out. Went back to tdc cyl 1 and yes rotor pointing towards 5/6ish spark plug on head. Pulled distributor and moved oil pump slot to where it need to be, slowly inserted a few times, dropped in once pointing towards 1/2 cylinder spark plugs and with a little jiggling it finally dropped with rotor pointing right at cyl 4 plug. Cap on, started up. Still have work to do but alas a lot of time and mental energy when I needed to just slow down and get the timing right. Thanks to all. I’ll report back on noise if it’s indeed a vacuum leak or just related to timing/air in carb. Cost me a new muffler but lesson learned. If it quacks like a duck well….
 
Vacuum leak ended up being gaskets on the Weber carb adapter plates which I know is common. Made my own with some Felpro rubber/paper gasket material and leak gone. All set. Now to replace the muffler to remind me of my stupidity!! Thanks again all.
 
The leaking between plates is the screws just a tad too long and bottom out causing the gasket to fail … sanding down the screw a bit corrects this issue and I recommend it be done before the issue arises :meh:

Thicker gaskets works as well
 
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