engine problems

[1980Gbody]

this past weekend i swapped a 350 in to my car and now im having problmes wiht it the timing is set pretty much perfect it has all new spark plug wires, plugs, cap, rotor, and i went to take it for a drive and when i put it in gear the motor idles realy ruff then when i take it for a ride and stomp on it it bogs and backfires out the carb i was wondering whatr could be the problem

 

[1980Gbody]

when the cars in park or nuetral it seems to run fine even when u get it up to high rpms everythign seems fine no carb backfire nothing then u put it in gear and it idles ruff and runs like crap the whole car sits there shakin but in a bad way

 

[Uncletruck]

It sounds like it is severely leaning out under load. As mentioned a bad vacuum leak is a common culprit for this. Check and make sure the intake manifold bolts are torqued properly and all carb vacuum sources are being used or are blocked off.

Properly (and safely) chock your wheels and set the parking brake so you can idle the car in drive. With it there loosen the distributor and slowly move it in either direction and see if this will improve the idle smoothness as sometimes you can't rely on timing marks and it could be way off either way, probably too far advanced as its backfiring through the intake.

About the only other things are the carb metering is too lean, there is a valve sticking, or the timing on the cam chain is off a tooth. Also, if you are using EGR, make sure the EGR valve isn't stuck open.

-Mark-

 

[illregal82]

my freinds had the same problem with this car

everyone kept saying the timings off , vacum leak , bad carb , who knows what else. it was the heads they had to do a valve lash adjustments all i know is that damn car moves now . i stopmed on it a couple days ago going 50 on a highway and it chirped the tire i have never had a car that could do that and my tire has well over 70% tread . now im no expert mechanic but nobody mentioned the heads so i thought i mention my own exsperince.

 

[85 Cutlass Brougham]

Check for an exhaust leak at the manifold or a cracked manifold as this can also cause a lean backfire. I had this problem when my air injection check valves were faulty on my car. I blocked them off and the problem went away.

 

[Uncletruck]

It is possible that the lifters are not properly preloaded, but this will usually result in ticking noise from the engine that gives it away. Unless the engine is using a solid lifter setup, there should be zero valve lash with a standard hydraulic cam/lifter setup at all times.

-Mark-

 

[srercrcr]

Where did the engine come from?

 

[1980Gbody]

its a gm crate motor out of a k5 blazer

when do i kno the valves are adjusted right

 

[85t5mcss]

You have to pull the valve covers. If its running, then do 1 side at a time and loosen the rocker arm nut. When u hear it "clatter" (and u will), start tightening slowly until the noise stops. Then another 1/2 turn. It will get messy as oil will spray off of the rocker arms. An old valve cover with the top cut off and oil deflectors help this problem. Invest in them.

When an engine is on a stand there is a different method, but we won't get into that right now since the intake being off the engine helps out dramatically.

This is assuming u have the hydraulic lifters and not solids. I'm also not sure if a roller emgine is the same, but I believe it is.

Unless the engine is using a solid lifter setup, there should be zero valve lash with a standard hydraulic cam/lifter setup at all times.

Doesn't solid run near zero lash and hyd run zero lash minus preload?

 

[Uncletruck]

With solid lifters you set a "cold" engine valve clearance with feeler gauges. With hydraulic it is zero valve lash with the addition of the preload, which is what presses down on the lifter plunger slightly, allowing the hydraulic lifter to function. That's the additional half turn you mention.

Here is the procedure for adjusting the valves with the engine turned off:

With number 1 cylinder at top dead center and timing mark lined up, (check distributor rotor or watch valve motion to be sure it is #1 at TDC) adjust the valves on the following cylinders:

Exhaust: 1,3,4,8
Intake: 1,2,5,7

Back out adjusting nut until lash is felt at the push rod, then turn adjusting nut until all lash is removed. This can be determined by checking push rod side play while turning the adjusting nut. When play has been removed, turn adjusting nut in 1/2 to 3/4 an additional turn.

Crank the engine one full revolution until the timing mark lines up again. This will be the #6 cylinder firing position. Now adjust the following valves:

Exhaust: 2,5,6,7
Intake: 3,4,6,8

-Mark-