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Old 03-05-2012, 09:36 AM
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trouble after replacing timing set on sm350

hey guys, new hear!

i have a 79 k20 with a stock 350. i havnt had a lick of trouble out of this truck long as i been driving it, i got it from my dad, who bought it from the company were he works in 85! we have never had any big issues with it, its been a great truck. truck has just been amazing. any who..

bout a monthago, i startede it noticing is runing rough once and a while, like it needed a tune up, and heard a knocking/ slapping sound coming from fan / water pump areA. figured was the hub or something making noise. (never dawned on me could be timing chain..would explain a lot!), it quit on me at a stop light, tryed to start it and heard horribl noise and cranked real slow ect..dad said prolly timing gears went. pulled all apart, sure enough. so i replaced them, all back together. drove it one day, i noticed a sticking lifter or over head ticking, and running not so smooth, but other than that it ran good. started great ect. couple days later going down the freeway started bogging out and surging, also hearing this nasty knocky type soound while it would do it. just got worse and worse to the point were it will pretty much just idle (still hearing the o.h noise) but soon as you go dsown the road its a mess. im nto sure what happened but it never did this befor i replaced the timing set. dunno if i did something wrong or not? any ideas...? the valves do need adjusting, but i doubt there anyworse than they were befor...? oh ya. when i rev it in park from, under the hood. i get a bad knock sound from the top of the motor like somethings hitting the vlave covers too.! the timing gears are aligned with dots pointing to eachother. fuel pump is brand new.

thanks guys! bryan

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Old 03-05-2012, 10:35 AM
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First off pull the valve covers and inspect for damage. It could have a broken valve spring, broken rocker arm, bent pushrods, etc. If you don't find nothing in the valve train the next step is a compression test on every cylinder.
However, I would still think one in the same that the writing is on the wall, it's rebuild time.
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Old 03-05-2012, 01:24 PM
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yea, i pull drive side and the very far back rocker was very loose. intake valve? have not had chance to pull other side. just valves seem out of adj. on d/s. prolly were the ticking comng from lol, but dunno bout that bad knocking and hesitation at the same time. can just one valve have an issue to make it run that bad? but like i said, havnt checked other side yet.
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Old 03-05-2012, 02:30 PM
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Quote:
Originally Posted by 79k20
hey guys, new hear!

i have a 79 k20 with a stock 350. i havnt had a lick of trouble out of this truck long as i been driving it, i got it from my dad, who bought it from the company were he works in 85! we have never had any big issues with it, its been a great truck. truck has just been amazing. any who..

bout a monthago, i startede it noticing is runing rough once and a while, like it needed a tune up, and heard a knocking/ slapping sound coming from fan / water pump areA. figured was the hub or something making noise. (never dawned on me could be timing chain..would explain a lot!), it quit on me at a stop light, tryed to start it and heard horribl noise and cranked real slow ect..dad said prolly timing gears went. pulled all apart, sure enough. so i replaced them, all back together. drove it one day, i noticed a sticking lifter or over head ticking, and running not so smooth, but other than that it ran good. started great ect. couple days later going down the freeway started bogging out and surging, also hearing this nasty knocky type soound while it would do it. just got worse and worse to the point were it will pretty much just idle (still hearing the o.h noise) but soon as you go dsown the road its a mess. im nto sure what happened but it never did this befor i replaced the timing set. dunno if i did something wrong or not? any ideas...? the valves do need adjusting, but i doubt there anyworse than they were befor...? oh ya. when i rev it in park from, under the hood. i get a bad knock sound from the top of the motor like somethings hitting the vlave covers too.! the timing gears are aligned with dots pointing to eachother. fuel pump is brand new.

thanks guys! bryan
Chevy small blocks do not align the timing marks pointing at each other, unless you set the distributor to fire number 6. The pip marks on both gears go to the 12 O'clock position upon assembly to fire number 1. However, it's a very good idea to rotate the motor around to see that they do oppose each other with number 6 ready to fire.

Bogie
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Old 03-05-2012, 02:41 PM
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motor knocking

I have a 1978 van with the same problem, as yours...My remedy is a new motor...I have been buying the parts al a cart, since money is tight right now...I am not driving the RV due to an intermittent knock which I thought at first was a rod, but it went away...THought it was then a lifter that failed, but it comes and goes intermittently. Everything on the top end sounds loose...So, time for a new motor, end of story...I have been looking at a place called Mabbco Enterprises out of Tyler Texas and they seem to be top notch according to BBB. I have been looking on internet at them (reviews) for over 1 year...$735 for a short block and then add freight to that, unless p/u in person....They also have an HP version for $995.00...Guess I have not made my decision, since I just invested in a whole Vortec top end...Summit Racing Vortec heads, procomp airgap intake, head bolts intake bolts valve covers, PMW roller tip rockers(1.52), 1 inch phenolic carb spacer, fel pro intake gaskets, Engine Tech head gaskets (.041), pushrods std length, Lunati 60101LK cam/lifters, 600cfm Quick Fuel carb, Headman header and exhaust kit from from Summit, as well as new flexplate/harmonic balancer w/hardware.
So far, I have invested about $1,300+ in parts....
Still need a new fuel pump, water pump, Oil pump and either short block from Mabbco, or new crate short block....Just depends on the cash flow..
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Old 03-05-2012, 02:44 PM
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Quote:
Originally Posted by oldbogie
Chevy small blocks do not align the timing marks pointing at each other, unless you set the distributor to fire number 6. The pip marks on both gears go to the 12 O'clock position upon assembly to fire number 1. However, it's a very good idea to rotate the motor around to see that they do oppose each other with number 6 ready to fire.

Bogie
My chevy service manual shows that the dots face each other...crank at 12, cam at 6, so they line up...Distributor has to go in instead of #1, go 180 from the cap point and drop it in....I have done many like this...
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Old 03-05-2012, 03:40 PM
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Quote:
Originally Posted by Dannyringo
My chevy service manual shows that the dots face each other...crank at 12, cam at 6, so they line up...Distributor has to go in instead of #1, go 180 from the cap point and drop it in....I have done many like this...
that how i installed the set. put crank gear on, then turned cam so gear would be at 6, turned crank so dot would be at 12.. then removed and put chain on.. it ran ok for a day aside from the lifter / valve tickiong, so im not sure wtf happened. i am unclear of what you mean about the dist..?

bryan
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Old 03-05-2012, 03:56 PM
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Quote:
Originally Posted by 79k20
that how i installed the set. put crank gear on, then turned cam so gear would be at 6, turned crank so dot would be at 12.. then removed and put chain on.. it ran ok for a day aside from the lifter / valve tickiong, so im not sure wtf happened. i am unclear of what you mean about the dist..?

bryan
Distributor first, if you put it together with the dots across from each other crank gear up, cam gear down, then you can time the engine using number 6 to set it up, if you put the distributor at #1 then the timing is 180 degrees out.You'd be surprised how often that happens.

My guess would be that if it ran fine when put together and went to crap the next day that some piece of grunge came loose and circulated with the oil. The filter doesn't see all the oil circulated. Something went down a lifter galley and ended up in a lifter.

Pull the valve cover on the side making the noise if a lifter went down on you even for a moment it could have bent a push rod or let it fall off the rocker.

There can be other things but let's start simple.

Bogie
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Old 03-05-2012, 04:10 PM
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cam and timing

since u've driven the car, pulling the time cover now is a pain. pull the d/s valve cover and turn the engine over till u get compression on #1 and watch'n the 2 valves on that cyl. both rockers will be in the back position, leaving the valves with NO pressure on them or very little.. now u'r in tdc.. ck the dist for pointing to #1 plug wire... what the guys were saying above is when u point the timing points together u put the rotor pointing to #6 posititon. so now ur at tdc ck ur manual for what valve to adj then turn motor over 180 and do the other half.. just take the slack out and another 1/2 turn...
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Old 03-05-2012, 04:12 PM
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Hows the oil pressure. i am wondering if you sucked some of the broken parts into the pump
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Old 03-06-2012, 08:27 AM
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Quote:
Originally Posted by T-bucket23
Hows the oil pressure. i am wondering if you sucked some of the broken parts into the pump
oil is right around 40 psi warmed up.
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Old 03-06-2012, 12:16 PM
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Quote:
Originally Posted by 79k20
oil is right around 40 psi warmed up.
At idle or at cruise RPM (2000)?

Bogie
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Old 03-07-2012, 06:13 AM
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Quote:
Originally Posted by oldbogie
At idle or at cruise RPM (2000)?

Bogie
both idle and cruisin
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Old 03-09-2012, 05:24 AM
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ok, i found a bent pushrod on the valve on right hand side on #7. dont know if its intake or exhuast. i want to pull the rest and look at them, is there any thing i should do befor doing this? and how do i go about re-adjusting them once they are all off cause i assume all the valves will be closed with them all off?
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Old 03-09-2012, 06:56 AM
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Possible bent valve stem. The valves may have kissed the pistons when the timing chain let go. Do a compression test. Possible broken valve spring, broken rocker, broken/pulled rocker stud. Collapsed lifter.
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