289 running problem

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Oct 20, 2004 | 08:50 PM

lowcountry

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From: Haveloce

289 running problem

I have a 289 in a 79 truck 4wd and the problem I am currently having is low vaccum not even enough to operate my brakes. I also have to run with the choke closed in order to keep it running half way decent. also i can pull the spark plug wires off of # 5 and #8 and there is no change in the way that it runs, have check for spark and still have on those cyl (boy it hurts when it fires) have done a compression check and have about 8 to 1 compress. Pulled the intake and look for craks and did not see any.

Any help would be thankful

Oct 20, 2004 | 09:44 PM

smoke n tires

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From: midwest

what was your comp. psi on those cylinders? if they are good (over 100 psi) then you may have a vacuum leak some place else. check around any vacuum lines and check the throttle shaft on your carb. use brake parts cleaner to spray these areas while idling. does it idle crappy? check your firing order also. let me now what you find....

Oct 21, 2004 | 11:08 AM

lowcountry

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From: Haveloce

both cyl are over 100 psi, going to check the throttle shaft tonight, also what is the proper way to set and adjust the rockers on the 289, The book says to torque them to 27 to 30 but i can tighten them down and the valves are open

Thanks

Scott
Low Country Swampers
MIOBI

Oct 21, 2004 | 05:47 PM

hdgapeach

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From: Franklin, GA

The rocker torque amount should be applied while the coresponding cylinder is at TDC. If the cylinder isn't at TDC, the cam lobe is positioned so that there is pressure on the lifter, as you tighten the nut the valve will be forced open.

http://www.users.bigpond.com/ergoff/vac1.htm

That site will help you with vacuum engine tuning. And I suggest a dry, wet and leak down compression test on all eight cylindersl

Oct 21, 2004 | 06:56 PM

lowcountry

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From: Haveloce

could you explain the wet and leak down compression test?

Oct 21, 2004 | 09:51 PM

hdgapeach

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From: Franklin, GA

Wet test is putting a couple of spoon fulls of oil in a cylinder and performing a compression test on that cylinder. If you get a marked increase in pressure as compared to the dry test, it means you have blow by past the rings. If you have a cylinder that is reading lower pressure compared to the other cylinders during a dry test, a wet test will determine whether you have bad rings or a problem with the valves or valve seats. Same low pressure after a wet test indicates valve problems. A leak down test times each cylinder under pressure to see if it leaks down and if so how long it takes to loose pressure in comparrison to the other cylinders. I had to pull a head before 'cause a tech didn't "remember" to lap the valves to the seats before he assembled the heads. Just one example of where a leak down test helped me.

Oct 26, 2004 | 10:00 PM

lowcountry

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From: Haveloce

did the wet test tonight and found that none of the cyl changed in presure. so I would say that it could be a bad valve, I hope

when doing a compresion test how many times you let the engine hit the comp stroke to get the reading you want

Thanks for all your help

scott