63 Power Loss on Acceleration - Continued

[Joel T.]

Hi all;

For those of you who have contributed to this issue, I figured that I would start a new thread, with current updates.

For starters, I swapped out the coil; putting in that Goat Hill unit I have had sitting around.. ran strong but still had the power loss. Interestingly enough, this time around I kept my foot into the pedal when she started to go... wound up with a surging as opposed to a straight dying off... Smells like a fuel issue, me thinks.

Anyway, I ordered up a set of those CS89 points which Duke recommended and they will be in tomorrow morning, so I will swap them out then and give her another run. I suspect I will find the same thing but what the heck, at this point we need to eliminate stuff.

I started looking for another carb... to do a swap with and think I have located one... Should I swap that out and still have the issue then the fuel pump will be next on my list.

Will keep you all posted and thanks again for all the help!!!!

Joel

[Tom H.]

Re: 63 Power Loss on Acceleration - Continued

My vote is for fuel delivery. You are getting warmer, I suspect !! Best of luck.

[Duke W.]

Re: 63 Power Loss on Acceleration - Continued

I can't remember if you checked the fuel filter, but assuming you have the correct GF90 setup... or whatever for that manner, remove the filter, empty it, and blow through it. There should be next to no resistance - like blowing through a same length piece of 3/8" fuel hose.

This happened to me once. The 340 would rev to about 4500, then just quit as if the key had been turned off. The filter was clogged, and a few seconds of WOT would empty the fuel bowls. In normal driving other than WOT/high revs it ran fine.

With the filter off you can also check the fuel pipes for blockage. If you disconnect the hose from the fuel pump inlet, fuel should siphon freely from the tank.

Duke

[Joel T.]

Re: 63 Power Loss on Acceleration - Continued

Duke,

You may be right with your thoughts on the fuel filter... I will check that before I do the carb swap...

Up until about a month ago I had one of those Paragon supplied GF90's and did not have a problem.... Then I saw the accurate ones which Corvette Specialties is now peddling (along with correct looking GF 416's) so I picked one up and installed it. Looks great but as John DeGregory said who knows what is inside it!!

I'll let you know what I find.

Regards,

Joel

[Timothy B.]

Re: 63 Power Loss on Acceleration - Continued

Joel,
I bet it's points, but if not why don't you check fuel pump pressure before going through all the work to change it out. If you have a vacuum /pressure guage it's a pretty quick check. Also keep in mind there is a screen in the AFB inlet fitting but I am sure you checked this.

[Stuart F.]

Re: 63 Power Loss on Acceleration - Continued

Tim;

A screen in an AFB inlet fitting? I don't recall ever seeing such an animal. What year or model has such an item?

Stu Fox

[Timothy B.]

Re: 63 Power Loss on Acceleration - Continued

Stuart,
There is a screen in the brass fitting the screws into the AFB where the fuel line attaches. It's cup shaped and fits neatly into this fitting. If I get a chance tomorrow I will take a picture for you.

[Joel T.]

Re: 63 Power Loss on Acceleration - Continued

Guys;

I think those of you who voted for a fuel issue are probably the winners in this one, but the jury is still out.

I spent today swapping out points for those with increasing spring tension... even tried the CS89's. Figured out (with Duke's help) that I do have some distributor issues... checked dwell (no vacuum) from idle after setting new points at 30 degrees. Had a full 5 degree fall off to like 25 degrees as I got to the 3500-4000 RPM range. As I stopped increasing RPM and held them steady, dwell crept back to about 28 degrees. This can't be a good thing. Looks like we have too much up-down play in the distributor shaft.... like at least 1/8"

Wife and I took the car out tonite for a quick spin just to see how she would run. Noticed some minor surging off idle but more importantly started to have surging/stumbling during normal acceleration, not even hard acceleration. It would come and go..

Next stop, this weekend, maybe Friday, will be to disassemble the fuel filter, test it and look for that strainer which Tim talked about, will also do that fuel line pressure test. I also spoke to the local carb rebuilder who is telling me it is a fuel problem as well...

Anyway, the good news is that we are ruling stuff out and finding things to focus on and fix!

Regards to all,

Joel

[Stuart F.]

Re: 63 Power Loss on Acceleration - Continued

Tim;

I don't doubt you at all and would like to see the picture if you can take one. It's just that, well I know I'm slipping, but It's funny I've never noticed one. I just rebuilt my original 3461s and I was very careful as so much of the kit parts and gaskets today are sub par, to say nothing of the generic instructions and specs. I had to go back to my 3x5 card file from the 60's to confirm the adjustment specs and, sure enough, they differ. I paid premium for a Holley mfg kit thinking I would get better stuff, but heck, I might just as well bought from Joe's Discount Chinese Auto Parts.

Stu Fox

[Stuart F.]

Re: 63 Power Loss on Acceleration - Continued

Can't remember how many times I've been down that road throwing all kinds of parts at a car and eventually ended up being the plugs.

Stu Fox

[Stuart F.]

Re: 63 Power Loss on Acceleration - Continued

Just as an adder; the worst one was a 59 Biscayne w/335 hp that we had built at the best shop in S.E. Wisconsin. It would pull like a banshee up to 4500 then shut down. Each thing we tried and each part we threw at it made it just a little better, then we noticed it was bending push rods and, yup! You guessed it; the cam was in a tooth off. Drove us nearly crazy. Who'd a thunk it - the best shop in the area, sponsor of Paul Russo's midget racer.

Stu Fox

[Timothy B.]

Re: 63 Power Loss on Acceleration - Continued

Stuart,
Picture of screen at AFB inlet fitting. Fits nicely into the inlet fitting as you can see but I still suspect the problem with Joel's car is electrical.

[Stuart F.]

Re: 63 Power Loss on Acceleration - Continued

Tim;

Thanks for taking the pictures. Very interesting! I can't say I can recall ever seeing one of those. Guess I've lived a very protected life. I've baby sat my original AFB since it was new and I can't recall there ever being an inlet screen, not even like it was something you pitched out as a possible problem or performance enhancement (like we did in the old days). I've rebuilt and modified about 21 AFB's back in the early 60's, according to my 3x5 card file, and not on one of them did I mention removing, changing or even cleaning an inlet screen. Could it be that that was a later model change in perhaps the late 60's or beyond? I used to bore Venturis, modify clusters, tried all kinds of metering rods, jets, and needle/seats, etc. with them, but never an inlet screen. WOW! I lost a lot of knowledge and experience by going to work for Uncle Sam in 62! The car world passed me by.

Stu Fox

[Jack H.]

Re: 63 Power Loss on Acceleration - Continued

My take is you can change MANY parts, one at a time, only to find that didn't 'get it'.... Have you considered putting science to work?

By this I mean put the car on a chassis dyno, monitor the spark wave forms on a scope and have the exhaust sniffed while you take 'er up to speed to see what's going on. Those guys around town here in Denver with these facilities get $100-150 for this kind of diagnostic run and that can save you a LOT of personal time and parts swapping!

Plus, it just might be that there's nothing wrong with ignition/spark or fuel delivery and you're fighting something internal like bad valve springs, a flat cam, Etc. I know that's something you don't want to hear, but it can happen....

[Stuart F.]

Re: 63 Power Loss on Acceleration - Continued

Jack;

You are probably right; that the scientific approach is best. However, these cars and guys are from an era where the Shade Tree or Backyard mechanic in you tackled a problem with your ride straight on using your good ol American common sense and mechanical knack until you solved it. It's the challenge of it all that makes it worth while, to diagnose a problem according to the basics you learned from friends, magazines and old mother experience and keep after it until you either you figured it out or a miracle happens and it cures itself. Then you gloat with great satisfaction and sleep well at night. Besides, what do these fancy (expensive) diagnostic shops know about a Carburetor or a distributor? Most of the kids that work there never saw either.