hello from Lindstrom MN

[Larry Schroepfer]

I am new the the forum. I have a 1984 shasta motorhome with a 1985 sbc 350 engine. It has a quadrajet carb that I rebuilt. I had a holley carb on it with the same problem. The problem I am having is low vacuum. I did somewhat of a leak test with no results. The highest reading I get is 15#. I did a compression test on all 8 cylinders. (I did it wrong as i found out later by not having the throttle plates open.) The engine tested at 155, 150, 145,140,130,130,130,135. The timing is 45* btdc at idle. That gives me the most vacuum. When I adjust the idle mixture screws nothing changes. There is a slight stumble at idle but otherwise runs ok. The exhaust is strong smelling. I can't think of anything else. Can anyone help me diagnose my engine. I thank you for your help.

 

[Charlie]

 

[Old77]

 

[1987 GMC Jimmy]

Welcome to the forum. 45* BTDC? Was that a typo? Just wanted to make sure.

 

[dvdswan]

Welcome to the site. ^^^ what 1987 GMC Jimmy said. Did you check the timing with the vacuum advance disconnected? IIRC mine is set at 8 or 10* BTDC.

Did you spray starter fluid on the vacuum lines or around the intake, base of carb, etc.?

 

[animal]

 

[1973c10]

Welcome

 

[Larry Schroepfer]

it's not a typo. and yes i had the vacuum advance disconnected. at 10* the engine will not run. i checked the timing chain by turning the crank and watching the distributor for movement. i get about 10* on the balancer. i don't think the distributor is off a tooth but i am not a mechanic. i''m just an old man that bought a can of worms.

 

[Rusty Nail]

 

[Rusty Nail]

Larry I think 45° lies at the root of your troubles.
We'll have to start there.
That is bad and wrong. It's likely the cause of your sour exhaust!

If the engine will not run at 10° than yes, it is off. The only solution is to remove and re-install the distributor correctly.

The good news is! Your motor home engine is no different than damn near every single engine the boys run in here and we'll get it all settled out Larry, don't fret.

 

[77 K20]

Just going to throw this out there- I've never seen it but I've heard it is possible. Maybe your outer ring of the harmonic balancer slipped?

 

[TravisB]

 

[Larry Schroepfer]

hello 77 k20. i did the piston stop and the balancer is correct. rusty nail, what i didn't do is check distributor position when i did the piston stop. i'm going on a short trip tomorrow. i will check it out when i get back. thanks guys for your help.

 

[Larry Schroepfer]

i put in a new pcv valve and it did't seem to make a difference. however after running the engine for 15 or so minutes the engine started running smoother. maybe it is a manifold vacuum leak.