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No power up hills

Dedles1

Dedles1

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Oct 20, 2011
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Motherlode, California
I was just recently given a 79 blazer (350 with Q-jet carb, automactic) engines only got about 12K miles on it. Wifes grandpa wanted to get rid of it because it stopped firing up about 3 weeks ago and he doesnt drive it very often. I replaced the coil and distributor module and got the motor running good.
However, when on the drive home it was seriously lacking power. I could barly get it up to 35mph on some hills and it was taking quite a while to get up to speed on flat ground. The engine runs great in neutral, drove fine in town on flat ground, but under a load it just wont rev up or shift right. i could barely even get it up my driveway.... any advice on where to start looking for the problem would be appreciated. I want to get this problem fixed so i can move on to restoring the rest of it and solving all the other problems im going to come across in the process.
 
Oh so many things.
If it runs smooth but just has no power, it could be a carb problem, maybe an EGR, or maybe a stopped up exhaust.
Plus you need to check the timing.

You might need to do a compression check to make sure it is not a problem built in when they rebuilt the engine........
 
How long has it been sitting? Bad gas maybe? Change fuel filter, check timing, check plugs.
 
Its been off the road for several years, But he (grandpa) would start it up several times a week and drive it around infront of the house whenever he felt like it just to keep things moving, adding gas as needed. I replaced the plugs and wires, but had no change. I'll check the fuel filter tonight if I have enough light by the time i get home and ill try to get the timing checked by this weekend... im also wondering if it could have something to do with the transmission vacuum modulator, but I dont know if this would be a normal problem that could be caused by that .. everything listed so far are things I need to do anyway as i dig into this project, so ill get them done and see if there is any change. but in the meantime any other suggestions are more than welcome, i dont want to overlook anything.
 
vacuum modulator = doubtful. That has more to do with a real hard or screwed up shift

problem is under the hood.
 
OK. thats what I needed to hear. I'll concentrate my efforts under the hood and get everything replaced, cleaned, tuned or checked starting with compression and timing then moving on to making sure the carb is dialed in where it needs to be.
 
To dark to do any real work tonight, but I did some poking around and found a few more leaking vac lines. Ill add those to the list too and get them replaced, while I'm picking up some hose I think ill get a new drop light too.
 
sbc not getting driven often = flat camshaft.

do the other stuff. fuel filter and take the distributer cap and rotor off and check the mechanical advance weight system. bang on the convertor and see if it rattles internally. but be prepared to take a valve cover off and check the valve lift, or lack of valve lift.
 
The Power Piston in the carb might be stuck--check the distrubutor vacuum advance if it has one too,see if its diaphram is ruptured,a timing light will show if the mechanical advance and vacum advance works...I've seen pick up coils go bad and cause power loss,yet still run the engine...all the other things listed in previous posts here can do it too...

I hope its not your cam,one easy way to tell if it is besides pulling a rocker cover off and watching how far the rockers travel,is to just remove the air filter and rev it up to 4 grand or so,at top speed you'll hear the tell tale "gargle" and slight backfiring thru the carb --most often an exhaust lobe goes flat,the exhaust valve wont open enough to let the burnt fuel out,so the next time the intake open the pressure that built up in that cylinder escapes thru the intake...if the lobe is real flat a flame might come out of the carb,so stand clear,or prepare to lose your eyebrows!..
 
big pappa b said:
Um, what does not being drove often have to do with a flat camshaft
Click to expand...

well, when the engine sits for long periods, all the oil drips off the camshaft. then you start the engine with basically no oil on the cam lobes. combine that with crappy oil and "voila" flat cam lobe.
another factor is that the cam lobes are not pressure oiled. they are splash oiled from the rod bearings and what comes out of the lifters. which may take awhile to get a significant amount of oil to the cam.

im sure it doesnt matter what engine it is, but sbc's and definitaly bbc's seem to be the worst about it.
 
big pappa b said:
Um, what does not being drove often have to do with a flat camshaft
Click to expand...


The oil leaves a film on the cam when you shut the engine off. The longer it sits, the thinner that oil film is.
This is why I have always wanted to put a preluber on my vehicles. Every time you crank an engine, it has no oil pressure for a few seconds, and the only thing preventing damage is the leftover film.

A preluber will pump oil through the system before you crank it.

If an engine sits long enough, the oil film dries up. Plus, being at the top of the engine the cam is one of the last parts to get lubed.

So, an engine that sits a long time can wipe a cam lobe from being dry started.
 
I can see that. I thought you were saying a cam will go flat from sitting for a long time...

Need more coffee ;-)
 
Nope, havnt got the timing done yet. Somehow now that Ive got something that I WANT to work on, my evenings keep flying by and I run out of time. but I will get it timed and I will post any changes.. picking up a new drop light tonight to extend my working hours, but im starting to think what i really need is a garage and a clock that has 30 hours on it.
 
Start basic...fuel, spark, air....make sure all 3 are sound then look for other issues.

I would really look at the fuel, does it smell foul, stale, gas seems to go bad pretty quickly lately.
 
Yea dude, its going to have no power if its not timed right. I Like to time mine at about 10* with the vacuum advance un plugged and then run full vacuum to the advance.
 
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