Transmission? Poor acceleration.

[telly]

Originally Posted by jjzepplin

OK. So here's my take on this.
What does your exhaust consist of? You could back fire on deceleration due to a small exhaust leak.
Now- if your engine is not stock- your timing will not be as well. You cannot use a stock spec. Your timing might have been just fine but you had an exhaust leak.
Timing too far retarded will make your engine a slug.
Too far advanced will give it a pinging noise cause by detonation. This is bad.
Backfiring is usually something very wrong with your cam being worn or lifters broken and possibly the very rare broken valve spring. All of which can give you good compression ratings but not diagnose the problem.
Now your compression ratings (which can be done many different ways) do not suggest a high compression racing type engine. But that is beside the point now.
9 times out of 10, the new problem with your vehicle is the old problem you just fixed.
So- I would slowly advance your timing a little at a time and test drive just till you hear the pinging and back it off a bit and you should be real close.
You should get yourself a timing "CURVE" kit and study the instructions big time and then give it a go. You will be surprised at the results.
Keep your ears on that exhaust for a leak!
Good luck and keep us posted!

Thanks for the input. I did find that my exhaust was missing a nut on the passenger side...put one on and tightened it down. Quieted the engine some, but did not notice a difference in performance.

I feel pretty confident with the timing. I'm going to chase the other potential issues first.

I'm wondering about what you said regarding the compression...is it possible that it could be a head gasket problem and the compression should be higher than the 150ish readings I got? I plan to borrow a block tester and check on a head gasket leak.

[mongocanfly]

You need to do a leak down test on each cylinder..that way you'll know..not just a compression test

[truckster]

With readings that even I doubt you have a head gasket problem. It's entirely possible you've got a late 70s to 80s smogger in there and that's all it's got.

[jjzepplin]

Only the backfire may have been caused by the exhaust leak.(hard to explain but not a problem with the motor-more with the exhaust.) (wonder how I knew you had one?) Then you backed off the timing to account for it. Fix your exhaust leak. Then advance timing as necessary.

[toolboxchev]

Originally Posted by truckster

With readings that even I doubt you have a head gasket problem. It's entirely possible you've got a late 70s to 80s smogger in there and that's all it's got.

Have you any consideration to the type of fuel? Did your state recently switch to ethanol based fuels? 10% ethanol means less fuel mileage and possibly performance issues also.

Based on the thread I would also focus on timing and maximum vacuum. And what type of carb do you have? If mentioned earlier, my bad, so tune that puppy if its in your skill set. Just did some back reading and see that you have an Eddy carb, good solid simple choice. I have seen 350 chevies turn more RPM with a broken fuel pump, they just run real rough in the upper range. Not more than 3000 rpms make me think you have something a tad more serious with your motor.

Does it sound like its really struggling at 3000 rpm when in motion? That being said something is not letting that motor do what it does naturally. I have beat the heck out a few of them ( mostly stock stuff ) and they are had to beat down, other than running way past oil change intervals or running out of water I have yet to completely break on.

I am leaning on the side of others that you may be throwing good money after bad chasing down something which will only reveal itself with and engine teardown.

[telly]

I'm having some luck thanks to rsd66C20 and the info on the carb. I've put in larger main jets (#1428 to replace #1427) and different metering rod springs. I have new metering rods on order that will be here Monday. When I opened the carb to change the main jets the bowls were dirty...had a layer of film on the bottom. Cleaned that up, made the changes to the jets, then reset the timing again. Took the truck for a spin and it performed better...not quite like it had before, but better than it has lately. I'm hoping the new metering rods make even more of a difference. I'll post again Monday night or Tuesday with an update.

[telly]

Originally Posted by toolboxchev

Have you any consideration to the type of fuel? Did your state recently switch to ethanol based fuels? 10% ethanol means less fuel mileage and possibly performance issues also.

Based on the thread I would also focus on timing and maximum vacuum. And what type of carb do you have? If mentioned earlier, my bad, so tune that puppy if its in your skill set. Just did some back reading and see that you have an Eddy carb, good solid simple choice. I have seen 350 chevies turn more RPM with a broken fuel pump, they just run real rough in the upper range. Not more than 3000 rpms make me think you have something a tad more serious with your motor.

Does it sound like its really struggling at 3000 rpm when in motion? That being said something is not letting that motor do what it does naturally. I have beat the heck out a few of them ( mostly stock stuff ) and they are had to beat down, other than running way past oil change intervals or running out of water I have yet to completely break on.

I am leaning on the side of others that you may be throwing good money after bad chasing down something which will only reveal itself with and engine teardown.

Thanks for the response and thoughts. Regarding the engine rpm's, I drove the truck today after making some adjustments to the carb and resetting the timing and drove on some surface streets in 2nd gear and the engine was able to pull 4000 rpm easily. In Drive it was able to pull 3400-3500 rpm on the interstate at 65-70 mph. It seems to be struggling most on the high end of engine load.

[mongocanfly]

What happened? Did somebody sneak over and change your metering rods and jets when you wernt looking?..if you didn't have the acceleration problem before with those other jets and rods ....I'm not sure your fixing your problems

[telly]

Originally Posted by mongocanfly

What happened? Did somebody sneak over and change your metering rods and jets when you wernt looking?..if you didn't have the acceleration problem before with those other jets and rods ....I'm not sure your fixing your problems

Haha, I don't think I've got a midnight mechanic helping me out.

What I think might be part of the problem was the dirty bowls in the carb. I'm changing the metering rods and jets after reading an article rsd66C20 supplied about comparing the Eddy 1405 and 1406 carb factory settings. I would have made those changes after reading that even if I wasn't having the current issues. I agree that those were/are not the problem, just noting that the change is making a difference.

I'm going to perform a leak down test within the next 4 or 5 days to see if there may be an issue with exhaust valve seals. Feel free to correct me if I'm wrong, but from what I understand the increased oil pressure in the block during the time when I had it overfilled could have damaged those seals.

[mongocanfly]

Overfilling is not gonna cause you to have increased oil pressure..

[telly]

Originally Posted by mongocanfly

Overfilling is not gonna cause you to have increased oil pressure..

The gauge inside the truck showed a significant increase in oil pressure (I could have had as much as 9 quarts in the block). It was my first clue to the mistake that was made that started this whole fiasco. Maybe it was a coincidence. If so, what would/could cause a significant increase in oil pressure?

Edit: Could the increase in oil pressure have come from the pcv valve having been clogged (but since replaced and currently functioning)?

[mongocanfly]

Don't know why your gauge would increase..the oil pump is what creates oil pressure..your first clue should have been the truck should never have moved outta your driveway when you drained the tranny dry..I still can't believe its still working..

[mongocanfly]

doubtful...here's how a pcv valve functions....http://www.agcoauto.com/content/news/p2_articleid/197

[telly]

Yeah, I don't know either. Just know that it, thankfully, is.

I really don't mind putting $ into my vehicles. The way I look at it is, it's still cheaper than having a car payment for 5+ years.

[mongocanfly]

doubtful...here's how a pcv valve functions....http://www.agcoauto.com/content/news/p2_articleid/197

[telly]

Thanks mongocanfly for the pcv article. That is helpful.

Per that article: "A PCV valve can also stick in a closed position. This allows crankcase pressure and blow-by to build pressure and can damage gaskets and seals."

I'm wondering if I might have dodged a bullet on the tranny only to catch another one with a faulty pcv valve (I have no idea how long it might have been bad).

[rsd66C20]

I'm not sure about what changed originally, or all of the changes you've made since,.....but it's conceivable that not enough advance and a lean carb could have caused the backfire during deceleration, and a general lack of power.

Sounds like richening up your mixture has helped out a bit (changing main jet from .98" to .100"). Out of interest, did you buy the tuning kit or just individual jets and metering rods? Sounds like possibly individual, if so, which metering rods? Even with the stock configuration on the 1405 (070 x 047), that will be much richer than the 1406 (075 x 047). Just so you know, the .070" is the diameter of the cruise part of the metering rod, that inserts through the middle of the jet. The .047" is the diameter of the power part of the metering rod. In this case, going to the stock 1405 configuration on the metering rod will richen the mixture even more. Just have to figure out the best combo. On my setup, I actually ended up in between the two with the #22 1457 (073 x 052).

I was interesting in your current timing was set at right now (12 initial)? What is the total timing and at what RPM did you reach it (of course without the vacuum advanced connected)?

One last thing, you may want to double check the Idle mixture settings, detailed on Page 11 of the Edelbrock manual. Good thing to reset with the other carb changes....and easy to do.

Good luck!!!

[telly]

I bought the individual carb parts, not the kit. I've got the 1448 metering rods on order (have the 1459 - stock for the 1406 carb - currently in until the new ones arrive). I'm going to use the setup that puts the carb in reference #8 on the 1405 chart. If that doesn't make me happy then I'll buy the 1457 metering rods and try it set up like yours.

The timing is set at 14 initial. I haven't set the total timing yet...also have a timing tape to add to the harmonic balancer so I can do so. What rpm should I try to set the total timing at?

I did a little with the idle mixture screws - leaned them out until the engine wanted to die then backed them out 1.5 turns from there. I will look at the manual again like you suggest.

Thanks!!

[rsd66C20]

On the timing, you don't really "set" the total timing. It's normally built into the distributor (adding say +20 deg of timing). Some distributors (MSD), you can by different stops to tune how much timing comes into play (+18, +22, etc). The curve kit that was mentioned earlier are different weights and springs that change the rate that the timing comes in....resulting in full timing at different rpms (2500, 2800, 3000, 3200, etc).

So if you slowly rev up your engine, while watching the rpms, the timing will stop advancing. Note what this RPM is. That is your total timing. You may need a helper with your dial timing light. Say your total timing is 34 deg BTDC at 3200rpm...your have 34 total - 14 initial = +20 mechanical (distributor) advance.

That's what I was saying in a previous post, the PO had a Summit HEI that only had +12, but it was the "right" distro for the truck...but it really wasn't.

On the metering rods, I would have suggested #1 (1451) to start, but that's ok. With #8, you are leaning out the power side of the carb, which by default starts when manifold vacuum gets below 5 inHg. Are you using a vacuum gauge when you test drive?

This part is trial and error, to see what the truck wants...fuel wise.

[telly]

Really appreciate all the info. I'm not using a vacuum gauge during the test drives.

[telly]

Thank you to everyone who commented and made suggestions on this thread. With all your help (and about 10 minutes of a neighbor) the truck is now running better than ever. I've given it attention that it hasn't had for a while. A new fuel pump, new fuel filter, new vacuum lines, new pcv valve, new plugs, timing set, exhaust tightened up, carb adjusted and reset (still waiting for the new metering rods), etc. And thanks to all of you I am now more knowledgable about my truck and its engine components.

And here's what it all came down to. Somehow the grommet that holds the throttle cable popped loose from its housing so I wasn't able to get full throttle. It took my neighbor walking over to the driver side of the engine and saying "something doesn't look right over here."

I owe all of you a couple adult beverages. If our paths ever cross, I'll be more than glad to oblige. Thanks again! Telly.