Re: Transmission? Poor acceleration.
 

Which part?

Re: Transmission? Poor acceleration.
 

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

Re: Transmission? Poor acceleration.
 

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.

Re: Transmission? Poor acceleration.
 

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?

Re: Transmission? Poor acceleration.
 

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

Re: Transmission? Poor acceleration.
 

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.

Re: Transmission? Poor acceleration.
 

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.

Re: Transmission? Poor acceleration.
 

Have you done a compression test

Re: Transmission? Poor acceleration.
 

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.

Re: Transmission? Poor acceleration.
 

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.

Re: Transmission? Poor acceleration.
 

I don't mean to be crude but with your lack of knowledge the best thing for you to do is to find a good trustworthy mechanic and take the truck to them.

Re: Transmission? Poor acceleration.
 

I have come to this website from time to time because the members have always been insightful and helpful. Most of you have more knowledge than I, which is why I come for suggestions even if I already have a good idea of the problem. But just because I don't know every diagnosis due to symptoms doesn't mean I am not capable of doing the work myself and saving $. If I run across something I feel I can't do, then I will go to a shop. If you don't want to help, then don't. And no, I'm not upset...you've just misjudged me. And now, onward we go.

Re: Transmission? Poor acceleration.
 

"doesn't mean I am not capable of doing the work myself and saving $."
OK, it's your truck, do what you wish but it is obvious that you have very limited mechanical knowledge. You are not saving any money by doing it yourself if you don't know what you are doing.
The reason I suggested taking it to a shop was to save you from causing more damage to your truck and costing you more money to fix in the long run.

Re: Transmission? Poor acceleration.
 

Thanks

Re: Transmission? Poor acceleration.
 

So, after warming the engine, I drove it around the loop this afternoon. The transmission was shifting smoothly (around 2800 rpm). When I went up the hill, the engine rpm went from 2600 down to 2300 while the ground speed went from 55 to 51. On flat ground the engine did not want to exceed 3000 rpm at anytime.

Hope to have time to compression test the cylinders tomorrow afternoon.

Re: Transmission? Poor acceleration.
 

It's not the trans, you have an engine problem. I seriously doubt it came from too much oil though. It could be a lot of different things causing it, timing, carburetor, distributor, worn cam, bad wires or plugs, water in gas, and some more I can't think of right away. Check timing and compression first.

Re: Transmission? Poor acceleration.
 

If I can tomorrow after work, I'll check compression and then reset the timing. The distributor, cap, rotor, wires are all new within the year and while it's still possible that one of those might be the culprit I'm a bit doubtful. I have wondered if the carb might be out of adjustment, though. I'll pour some SeaFoam into the gas to see if that helps any.

Re: Transmission? Poor acceleration.
 

Grab you some new fuel filters as well...if you got a q-jet don't forget there's one in the carb to..I've tried seafoam before but never could tell it ever helped anything...just because you had new ign parts a year ago doesn't mean their still good..I've seen new, bad parts before...I'd checkem over good..

Re: Transmission? Poor acceleration.
 

My first instinct would be to double-check the timing. It sounds like it had more power before you re-timed it, so that's what makes me suspect timing.

Re: Transmission? Poor acceleration.
 

I reset the timing due to backfire and it was after noticing a loss of acceleration/power. I'm going to reset it anyway, just to be sure.

Re: Transmission? Poor acceleration.
 

I just changed the in-line fuel filter this afternoon before taking it for a spin. It's not a q-jet (wish it was since I've rebuilt the one in my Camaro and also the one I had in the '70 C10 Stepside I used to own). It's an Edelbrock carb - I have never worked on an Edelbrock.

I agree on the ignition parts. I'll go there after the compression check.

Re: Transmission? Poor acceleration.
 

If its backfiring and then you lost power and then you had to reset the timing there's a chance it may have jumped time on you during one of those 7000 rpm pulls...when you check the timing make sure you get it on true tdc and then see where everything lines up..pull a valve cover and spark plug

Re: Transmission? Poor acceleration.
 

This is what I was thinking at work today. Why was it backfiring in the first place, it may have jumped timing or you have a worn cam. If resetting the timing stopped the backfire it's more likely a timing problem.

Re: Transmission? Poor acceleration.
 

Not sure if it matters, but the engine was only backfiring during deceleration (letting off the gas after passing).

I checked the timing again this afternoon. It was still advanced 12 degrees like I had set it last. I took the truck out and ran it a few miles on the freeway. No backfire issues. It still doesn't have the power/acceleration it used to, but it did cruise along at 65mph and 3000 rpm...still wouldn't want to pass someone on a two-lane road though.

I don't have time to check compression today. Will try to do so tomorrow afternoon.

Re: Transmission? Poor acceleration.
 

Results of compression test:
1) 148 2) 150 3) 148 4) 150 5) 148 6) 150 7) 148 8) 150


Sucked 8oz of SeaFoam into the intake through the vacuum ports and ran the engine in the driveway until it quit producing smoke. Took the truck for a short drive and still same issues.

These are now the possibilities as I understand it; Plug Wires, Cap, Rotor, Distributor, and/or Fuel pump. Am I missing anything?

Re: Transmission? Poor acceleration.
 

Vacuum leak, carburetor, timing chain and gears, bad cam and lifters.

Re: Transmission? Poor acceleration.
 

Replaced vacuum lines to power brake booster, pcv valve (last week), vacuum advance, and another one I don't know (but it goes from the back of the intake just below where the power brake hose attaches to the back of the carb). Didn't see any others.

The carb is an Edelbrock 1406. I just read the owner's manual (which talks about adjustments as well as troubleshooting https://static.summitracing.com/glob...s/edl-1403.pdf). This manual suggests for lack of engine power to: Check air leaks (done), Choke adjustment, Fuel filter (done), Set too lean, Increase accelerator pump stroke, Fuel pressure too low, and Check secondary latching device and rod for proper movement.

I'd appreciate any insight or thoughts from those of you familiar with this carb. I've had experience rebuilding a couple of Q-Jets but none with Edelbrock carbs. Thanks in advance for any and all help.

Re: Transmission? Poor acceleration.
 

Is the vacuum advance working?

Re: Transmission? Poor acceleration.
 

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!

Re: Transmission? Poor acceleration.
 

Yes, the vacuum increases as the engine speed increases.

Re: Transmission? Poor acceleration.
 

I believe the OP is asking about the Vacuum Advance unit on the distributor. Most have a diaphragm in them with most being made of rubber. Rubber and Ethanol based fuels do not mix, the Alcohol in the fuel eats the rubber causing it to leak and disable the unit from functioning properly.

Re: Transmission? Poor acceleration.
 

I checked this and it's in working order.

Re: Transmission? Poor acceleration.
 

Been following your thread. I have a 327 w/ 1966 C20 + TH350, that the PO installed a Edelbrock 1406. Had similar problems that you do, tunes great at idle and basic cruise, but then lack of power accelerating or hills. Evidently, the 1406 is a very lean carb out of the box. Even tuning the jets and metering rods leaves you too lean when you need it. I found the article below which explains this in great detail. The solution is, that the Edelbrock 1405 and 1406 are essentially the same carb, except for the tuning. I bought the tuning kit for the 1405, and followed Edelbrock's instructions to tune, and my truck runs much better. I had a o2 sensor, which made it much much easier, but is not necessary.

A vacuum gauge will help determine which carb circuit you are tuning. I had to tune the "Cruise" circuit side of the carb, but never really got into the "power" circuit side....which you may be doing.

1406 troubleshooting article:
http://vb.foureyedpride.com/showthre...6-Carb-Read-On

Edelbrock 1406 manual:
http://edelbrock.com/automotive/misc...404_manual.pdf

1405 tuning Kit:
https://www.summitracing.com/parts/edl-1479

Good luck, and don't give up. I hope this helps.

Re: Transmission? Poor acceleration.
 

A couple of other things I missed. I like where the thread is going on checking your timing.

The other issue I had, was the PO had installed a summit HEI distributor that only added 12 degrees to the total timing, and the initial timing was only 8 deg BTDC. That gave me a total timing of only 20 deg BTDC. I ended up having to replace my distributor with a new HEI that added 20 deg (my initial=14/my total=34). My experience is SBC like 34-38 deg BTDC. After checking your initial timing (which is I assume 12 deg BTDC), slowly rev your engine up until the total timing stops advancing. Note the RPM that this is at. Is it between 34-38 deg BTDC? The rpm where the full timing is in at, is probably between 2500-3500 RPM.

On my suggestion of tuning the 1406 like a 1405. My recommendation is to start at the #1 stock setting on the 1405 chart. I ended up leaning mine out to the #22 setting.

Re: Transmission? Poor acceleration.
 

Thanks for all the info. I'm working through it and hope to make some carb adjustments by the end of the week. The thoughts on the distributor has got me thinking. I did have some issues with the distributor and external regulator a while back (earlier thread: http://67-72chevytrucks.com/vboard/s...d.php?t=682619) but it has been over a year.

Re: Transmission? Poor acceleration.
 

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.

Re: Transmission? Poor acceleration.
 

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

Re: Transmission? Poor acceleration.
 

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.

Re: Transmission? Poor acceleration.
 

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.

Re: Transmission? Poor acceleration.
 

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.