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OHC 4 cylinder valve timing help needed

D

dazk14

Contributing Member
"Hi Guys,

Lost top end rpm&

"Hi Guys,

Lost top end rpm's (700 after 240' overheat).

Can a timing belt on an AQ 151A jump a tooth and still show good compression #'s? 180-185-190-200.

Ignition timing and advance is set correctly.

Runs smoothly, just no top end - sucking lots of fuel though. Plugs are clean and insulator is rather white.

ANY help would be GREATLY appreciated, this one has me stumped!

Thanks!
Mike"
 
"Mike, I'd go through the

"Mike, I'd go through the timing belt installation procedure again. See your Volvo Penta OEM manual for this.
Not very likely that the ignition timing would still be correct if the belt jumped at the crankshaft. Possibly even more unlikely if it only jumped at the camshaft drive.
Never say never, though!

Check the condition of the belt tensioner.

."
 
"If it jumps, most likely a co

"If it jumps, most likely a corroded crank shaft sprocket providing the tensioner is working and correctly set."
 
"Thanks for the fast replies!

"Thanks for the fast replies!

Have you seen before, a belt jump a sprocket and still have good compression?

Through the chaos, I set/reset the timing - installed a Pertronix - so no clues there.

Any help is MUCH appreciated!
Mike"
 
"[b]Quote: "Have you seen

"Quote: "Have you seen before, a belt jump a sprocket and still have good compression?"

Mike, by the time a mechanic determined that the belt had jumped and/or slipped, he'd be on to replacing the belt, tensioner and probably on to replacing or cleaning up the belt shivs!
I doubt that any of us would bother with a compression test prior to this first being corrected.
So, no.... I'd have to say not!
It's sort of a moot point when checking the indexing of the belt is something that you really need to be doing. And while at it, why not install a new belt and tensioner?
."
 
"The boat is 2 1/2 hrs away, s

"The boat is 2 1/2 hrs away, so it's difficult to lug all the needed tools,etc.. Once I can confirm it's jumped, I'll make all the needed trips.

If I pull only the coolant tank, can I check that the camshaft is indexed properly to the crank.

ie- Crank gear marks will blindly line up when crank pully timing mark is at TDC cyl 1. Cam timing mark should then line up?

Have I got that right?

Thanks so much for the great help, this forum is the best!

Mike"
 
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