Transmission? Poor acceleration.

[telly]

Changed the PCV valve today. It was sludgy and didn't rattle when shaken. I then ran the truck for about 20 minutes and kept watch on the white/gray smoke coming from the exhaust (trying to burn off any excess oil that my have blown by while over-filled). After the white/gray smoke greatly diminished, I took the truck for a spin "around the block" (actually about a 3 mile loop). I don't seem to be having transmission troubles, at least no noise and/or clunky shifts. And, I still don't have any oil leaks that would indicate a main seal issue.

When I replaced the plugs, I did so one by one...remove plug wire, remove plug, insert plug, replace plug wire. I did not gap the plugs...I used them straight out of the box. It is HEI and when I reset the timing I did so with the vacuum advance unhooked and plugged and advanced to 12. I chose to reset the timing as I was getting some backfire upon deceleration...there is no backfire now after the reset.

The fluid in the tranny appears to be fine...not dark, although I haven't yet dropped the pan to see if there is any metal shavings in there.

*A bit of additional info...the truck will currently not spin its tires from a stop if traveling in a straight line, but it does have enough power to spin them when leaving a stop and turning onto another road.

**Another bit of additional info...I believe the engine to be a 350, but I can't be sure. I bought it from a guy who bought it from a guy...that guy supposedly built engines for racing and threw this one into this truck when the person he built it for didn't pay. The guy I got it from couldn't remember or didn't know what block was in it, and had no idea if it had been bored at all or what year. I haven't crawled back into it to take the numbers off the block. It may be a later 70's block, but I do believe it is a 350...just not certain that it's still a 350. With that information, what would you suggest the plugs be gapped to?

[cadillac_al]

It sounds like you may have dodged a bullet here if you are still moving. Maybe the extra oil in the engine was doing something but I have no idea what. The plugs should be .045".

[telly]

Ok. So gapped the plugs to .045, checked the fluid levels again and tranny was fine but the engine oil was dark. That surprised me since I'd not driven the truck more than 10 miles since changing it last. So I drained and replaced that. Then ran the engine for a while and now I'm hearing a "tingy" clunk when I change between Drive and Reverse and vice versa.

[garyd1961]

That could be a u-joint in your driveshaft.

[telly]

Is that possibly due to the issues I've been dealing with or separate?

[telly]

Let me rephrase.

Could the u-joint be causing the loss of power/acceleration? Could the u-joint beginning to fail be caused from the other issues I've been dealing with?

I don't doubt that the u-joint needs to be replaced, and will do so.

[YoungPup1977]

I am amazed that a TH350 moved with a "FULL JUG" low event....now you are chasing a U joint ? How is reverse engagement ? Slow ? accel OK in reverse ? U-Joints will make noises and cause vibration but not poor accel.... very interesting post...have to hang in here to see this one fixed...

[garyd1961]

Originally Posted by telly

Let me rephrase.

Could the u-joint be causing the loss of power/acceleration? Could the u-joint beginning to fail be caused from the other issues I've been dealing with?

I don't doubt that the u-joint needs to be replaced, and will do so.

I wasn't trying to say it caused your poor acceleration just that it could be a separate issue.

[telly]

Reverse and Drive both engage fine. They don't delay but as I've stated, the truck lacks power and acceleration. But I did start to notice a "clunk" when shifting between the two. I'm getting an aftermarket tach to install later today, so hopefully I will be able to have more information about how the engine is operating.

[Dead Parrot]

It is possible that all of your power testing of engine and transmission could have moved a u-joint from the needs replacing in a couple of years category to needs replacing soon. It is also possible that since you are now listening to your truck closely, you noticed a noise it has been making for years. I had a drive shaft that made the tingy-clunk noise for years before the drive shaft started vibrating due to bad u-joint. Still clunks once in a while during a R-D switch due to a 40 year old drive train on its 3rd set of 100,000 miles.

[telly]

Got the tach hooked up and calibrated for 8 cylinders. Ran the engine to check the rpm and would not push past 6000.

[truckster]

Originally Posted by telly

Got the tach hooked up and calibrated for 8 cylinders. Ran the engine to check the rpm and would not push past 6000.

Are you sure?

Just kidding. The LT1 in my Z28 redlines at 5800. That's not a Ferrari you're driving.

I think you're expecting way too much of your engine. Trucks like torque and they like it down low. Most of your driving should probably not go much over 3500 RPM.

[telly]

I figured I'd be able to get closer to 7000 just sitting in the driveway...idk.

Maybe it's a fuel issue...I'll put a new filter in and then check the pump.

[truckster]

Originally Posted by telly

I figured I'd be able to get closer to 7000 just sitting in the driveway...idk.

Maybe it's a fuel issue...I'll put a new filter in and then check the pump.

If you get close to 7000 RPM it won't be for long. Unless you're looking for an excuse to buy a new motor I would recommend you stop trying.

[garyd1961]

Originally Posted by telly

I figured I'd be able to get closer to 7000 just sitting in the driveway...idk.

Maybe it's a fuel issue...I'll put a new filter in and then check the pump.

Stop doing This^^^^!!!!

[telly]

Originally Posted by garyd1961

Stop doing This^^^^!!!!

Which part?

[mongocanfly]

The 6-7000 rpm part..espicially if its stock...unless you want to see the inside of your engine laying in your driveway

[truckster]

It sounds like you got lucky with the transmission. Let it do its job and shift for you. Stop trying to blow the engine up, unless that's your goal.

You've heard it from several knowledgeable people now. If you keep going, you'll be back here soon asking us about replacing an engine.

[telly]

It's not stock, but I get it. From what I understand, it was built to run on the short track and only put in this truck when the customer never paid for the build.

Any ideas as to why it is lacking acceleration and power? Could it be a fuel issue? Carb? Does the engine just need to "dry out" after it had so much oil in it? Do I just need to drive it and see if the performance improves over time?

[mongocanfly]

It could be one or more of several issues..low compression, , worn cam,, fuel delivery,, timing,,,,,,, sounds like you don't know much about the engine except what somebody told you...even more reason to not turn it 7gs

[truckster]

If it was truly built for short track racing, it was likely built for high RPM and a light vehicle. Trucks are just the opposite: a heavy box that needs torque at low RPM. But it sounds like you don't really know what's in the truck, so it's hard to say. Also, "lacking acceleration and power" is a relative term. These trucks weren't built with racing in mind, and the factory 350 (if that's what you have) might be enough to chirp the tires but that's about it. And after 45+ years it would be a tired motor anyway.

A good starting point would be to get casting numbers off the block and heads and post them on the forum. That way you'd at least have a ballpark idea of what your engine really is.

[telly]

It bothers/worries me that it loses speed right now going up hills that it used to accelerate up.

I'll work on getting the casting numbers.

[mongocanfly]

Have you done a compression test

[truckster]

Originally Posted by telly

It bothers/worries me that it loses speed right now going up hills that it used to accelerate up.

I'll work on getting the casting numbers.

What are the RPMs doing as it loses speed? Are they decreasing in proportion to the decrease in speed? If not, it could be that your trans is slipping.

[telly]

I am hoping to have time to do a compression test this afternoon.

I currently don't know what the RPMs are doing as it loses speed, I've only had the tach installed late yesterday afternoon and only ran the truck in the driveway. I'll post that info as soon as I get the chance.