3rd gear bogging

[Zach079xxx]

1985 350 Holley 600 carb weiand intake that I just had built and a turbo 350 also built about 2 months ago. Truck ran like a top then I left a buddies house late about 11 PM it was chilly about 55-60 degrees here in VA. First was fine, second fine, third I noticed a problem. It started to bog down, hardly any power. Stomp on it it shifts to 2nd then back to third bogging. I figured it was the cold but it's still acting up 2 days later. What gives? Why is it doing this? I can manually shift it and 1-2 are great then 3rd its ridiculous. I don't know much but if you can point me in the right direction I can figure it out. There's a show Saturday that I'm going to so I wanna have it fixed. I'm taking it to the guy who did all my work if I can't figure this out. I sunk over 3 grand in it and now I'm getting a little angry

[nsulacountry]

Vacuum secondaries? Sounds like maybe they are not opening and/or choke issues.

CT

[Zach079xxx]

Would that cause problems only in third? Idle is fine and like k said first and second are ok wether you manually shift or automatically let it in drive. How do I check? Didn't see any loose lines but maybe I'm missing one

Originally Posted by nsulacountry

Vacuum secondaries? Sounds like maybe they are not opening and/or choke issues.

CT

[Zach079xxx]

Anyone else?

[geezer#99]

Could be your fuel pump.
Hold it in second and put the pedal to the metal.
If it starts bogging(runs out of fuel), it's the pump.

[nsulacountry]

Originally Posted by geezer#99

Could be your fuel pump.
Hold it in second and put the pedal to the metal.
If it starts bogging(runs out of fuel), it's the pump.

This is very valid, especially if you have a mechanical pump. My 79 ate one ever couple of years. Though most of the time it would run fine then just not start back up. Usually in a parking lot. I got good at changing them in the field.

If mechanical, it could have a pinhole in the diaphragm bypassing. If electric, well you know, they fail too!

CT

[Dead Parrot]

Assume nothing, check everything. Especially the trans fluid level when hot. Loose hoses? If using external to fuel tank pumps, check the suction hoses from the tanks to the metal fuel lines.

Is it humid or misty when the problem happens? Could be carburetor icing. The stock GM air cleaners included a THERMAC system to help with this. "Performance" open cleaners and unheated intake manifolds can have this problem. The fact your problem started with chilly weather supports this.

If you reused your existing HEI distributor, check the button in the center of the cap that routes the spark to the rotor.

[Zach079xxx]

It's got a brand new fuel pump AC Delco lol it better not be bad already.

It acted up the first night when it was chilly but then the next day it was hot out and did it again.

I reused my HEI distributor, I'll check that.

Thanks for the tips I'll try them and see where I get.

[Zach079xxx]

I ran medium octane gasoline as told to do so by my mechanic & switched my fuel filter. He said possibly the problem was my old one was too small. Didn't change much.

My problem is hard to explain. The best way I can describe it is say you have a stick shift, it's in 4th gear at about 25. That luh luh luh luh and the truck jumping is the problem because it's in too high of a gear for that speed is the best way to describe it. Once my 350 turbo hits 3rd it does this. It acts like it has overdrive and is in the wrong gear but there is no other gear!

[Zach079xxx]

Third gear is still sluggish. Once it hits third its hard for it to accelerate. Any other ideas...?

[geezer#99]

What's your initial timing?

[Zach079xxx]

Not sure. I paid a guy to do all my work. Built my engine and transmission. Ran like a top like I previously said. Everything is great! Except for 3rd gear and it just happened one night.. The evening before was fine, turned key to leave and it hit third gear and bam surprise.. Sluggy! My mind is blown/ no explanation for it

Originally Posted by geezer#99

What's your initial timing?

[geezer#99]

Time to get a timing light and learn how to use it!

[Zach079xxx]

Maybe so! Would that affect 3rd gear though? It only acts up some. Depends how you drive it. Hard it is ok but gently on the gas and it acts like this.

Originally Posted by geezer#99

Time to get a timing light and learn how to use it!

[77 Big 10]

You could check the fuel pressure, or float height in carb, it might be sucking the bowls dry by the time you get to 3rd.

[Wgesnerjr]

Could be an intake gasket leak. Bolts could have loosened up. Or it was cold that night so things could have constricted enough to the point that a piece of the intake gasket broke. Under higher revs, it can over come the leak but under load it becomes apparent. Just thinking.

Also check carb bolts and gasket for the same thing.

[Zach079xxx]

I did notice something.. On my intake around a bolt in particular every couple days it has oil sitting on the intake and I have to clean it out with a rag to soak it up. They're arp intake bolts. Could that be it?

[Wgesnerjr]

More than likely the oil is a leak. you could try pulling it out and using teflon tape or sealer of some sort.

But, if that bolt backed out, some other may have also resulting in a vaccuum leak.

[Zach079xxx]

I'll find out this week. Going back to my mechanic

[Zach079xxx]

So I still haven't gotten this fixed yet. Just to make sure we're on the same page, turbo 350 lockup with 2500 stall converter, less than 1000 miles on complete rebuild. 1st gear great 2nd gear great 3rd gear great when it wants to be! Sometimes it'll shift into third and I have great power other times it'll bog down and be very sluggish and can barely make it up hills or even accelerate. As previously said, it was fine for a week or two after my engine build then bam! Started bogging itself. People have told me fuel, timing, carb issues, fuel filter, everything!

My question is how is it fuel/ fuel filter when it runs AMAZING until 3rd?
How is it timing when it runs great until third?
How is it the carb when it runs great until third?

I bypassed the fuel filter with a piece of brass, didn't change a thing. It shifts into third with a nice shift then a second after its in third, it slips into this unknown slug mode. It is driving me crazy. My schedule won't work with my mechanic with night school going on and other things. It blows my mind because its only sometimes too. The other day I drive thru town and on the highway and it ran great. Today, its done it all day.

Is there a band you can adjust?

WHAT GIVES?

Does all my linkage look correct? I'm new to this stuff, I paid a well repped guy to build this. Maybe something came out of adjustment.

[rich weyand]

Linkage looks fine.

I keep thinking timing. When it gets cold, and metal shrinks, the distributor clamp can loosen enough to let the distributor get pulled retarded. Then performance depends on vacuum, but I wouldn't expect it to change back and forth. Still, GET A DAMN TIMING LIGHT and check the timing. 12-14* BTDC, at least.

Weak spark, maybe. Did you put a new coil in it when you did all this work? New cap and rotor? New wires? I can recommend the Accel 8122 cap and rotor, Accel140013 coil, and Taylor 74206 solid wires. (No need for resistor wires when you use resistor plugs!) Pricey, but you only get what you pay for, and sometimes less.

[Zach079xxx]

What's the process of checking timing? I got a buddy in town tomorrow that's going to help me. It's got a coil less than a year old along with plugs and wires cap ect. Less than 1000 miles on them.

Originally Posted by rich weyand

Linkage looks fine.

I keep thinking timing. When it gets cold, and metal shrinks, the distributor clamp can loosen enough to let the distributor get pulled retarded. Then performance depends on vacuum, but I wouldn't expect it to change back and forth. Still, GET A DAMN TIMING LIGHT and check the timing. 12-14* BTDC, at least.

Weak spark, maybe. Did you put a new coil in it when you did all this work? New cap and rotor? New wires? I can recommend the Accel 8122 cap and rotor, Accel140013 coil, and Taylor 74206 solid wires. (No need for resistor wires when you use resistor plugs!) Pricey, but you only get what you pay for, and sometimes less.

[geezer#99]

https://www.youtube.com/watch?v=UYGU7mTwsZc

[SkinnyG]

Going out on a limb - try a run with the gas cap off. Perhaps (long shot), that the tank isn't venting enough to keep up with the fuel needed, creating a partial vacuum. A cheap test anyway, on your way to buy a timing light (grin).

[rich weyand]

Originally Posted by SkinnyG

Going out on a limb - try a run with the gas cap off. Perhaps (long shot), that the tank isn't venting enough to keep up with the fuel needed, creating a partial vacuum. A cheap test anyway, on your way to buy a timing light (grin).

That's a good one, too. Say somebody put a sealed cap on a truck that needed a vented cap....

Except it's a 1985, so it should have sealed gas caps and tank vent lines to a vapor canister. Now if the vapor canister was removed and the vent lines capped, maybe even back at the senders, then it will need vented gas caps. When would this be the biggest problem. Why, when it gets cold, and the gas shrinks and creates a vacuum in the tank....

When it gives you trouble, stop and open the gas cap. If you get a whistle of in-drawn air when you remove the cap, that's probably the problem. Put the cap back on and get back in and see if it now runs fine. If so, just run a 1/16" drill through the center of the gas caps.