[knot750]

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What things above the cylinders (on this model) can cause major vaccum lost? The cam timing is correct, the compression and leakdown numbers are good. Sync gages read nearly nothing (for all cylinders)when hooked up to ports. The idle sticks high before returning to normal just as if the sync is off. The engine starts ok and revs ok above 2000 rpm. Any suggestions/comments/questions??

Thank you for all input!

 

[plainmech]

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first hought is vacuum leak. can be tested by carefully spraying carb cleaner around intakes and vacuum lines and listen for fall in rpm. careful with paint ect. can also be done with small propane torch not lit. result will be if you have a leak it will pull in foreign substance and reduce rpm. personally i prefer the torch, you'll need to fit a length of hose to fit into engine area as bottle is too big to get in all areas.:action::waving: good luck

 

[rcmatt007]

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I would think unlite propane would increase the rpm as now you have a too lean mixture getting more fuel.... just a thought

 

[plainmech]

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my thought as well when i was introduced to this procedure but in fact it drops:?

 

[ding dong]

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plainmech wrote:

my thought as well when i was introduced to this procedure but in fact it drops:?

Hi plainmech: Everytime I do that with propane it rises. Everything in Texas is bass akwards don't you know that by now.

 

[ELKMAN121]

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Knot



I had the same thing going on with my 1500 and it turns that I was messing with the throttle cable adjustment to take up some of the slack and I took up too much. I to thought I had a vac leak because I was replacing my air filter at the time when it started. I never though that there had to be that much play in the throttle BUT I check my manual and I was wrong> Check it out.........

 

[DaveO430]

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rcmatt007 wrote:

I would think unlite propane would increase the rpm as now you have a too lean mixture getting more fuel.... just a thought

True, that used to be a method used for adjusting carburetors on cars way back in the stone age and even on early fuel injection. If it's lean the idle will increase, rich and it will drop.

 

[Hatchetman]

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There are "O" rings on your carbs where they join to the heads vai the rounded pipes but Im thinking that your plenim might have a seal gone?!:baffled:

 

[plainmech]

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DaveO430 wrote:

rcmatt007 wrote:

I would think unlite propane would increase the rpm as now you have a too lean mixture getting more fuel.... just a thought

True, that used to be a method used for adjusting carburetors on cars way back in the stone age and even on early fuel injection. If it's lean the idle will increase, rich and it will drop.

hey i'm not that old but the guy i see in the mirror is :cheeky1::cheeky1::cheeky1:

 

[knot750]

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Thank everyone for their input.

 

[plainmech]

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please return and post what you find so it could help someone else good luck