Holley 770 Questions

[jhv48]

I see you’re in Florida so corrosion in the distributor is a good possibility.
My Roush 427sr exhibited similar symptoms. I tried the heavier spring, lower idle speed, disconnected the choke and cleaned and adjusted the distributor. Didn’t fix it. Finally got rid of the problem by replacing the entire carb base plate. That did it.
And if you want to get rid of that bog, consider a nice 750cfm with mechanical secondaries. I swapped mine and it woke up the engine. Vacuum secondary carbs are not the best choice for our light cars. Even the Holley website will not recommend a vacuum secondary carb for a light car.

[Mattsvtcobra]

Sorry for the delay and thank you everyone so much for the suggestions! I have a few follow up questions.

1) mechanical springs in the distrib cap. Just open it up and squirt a small shot of wd-40 on them? Any warnings here? Is there a cleaning procedure, or is it all inclusive and wd-40 only?

2) Carb base plate- What do you think the issue was there?

3) A couple of people have suggested going with a new carb and I think that would be a good choice. I'll have to start walking down that road some and see what the options are.

4) The air cleaner is resting or pushing on the back of the distrib cap. No clue why it is set this way but is this an issue? I'm sure I can find a small riser piece to get it up off of the cap.

[cycleguy55]

Originally Posted by Mattsvtcobra

Sorry for the delay and thank you everyone so much for the suggestions! I have a few follow up questions.

1) mechanical springs in the distrib cap. Just open it up and squirt a small shot of wd-40 on them? Any warnings here? Is there a cleaning procedure, or is it all inclusive and wd-40 only?

2) Carb base plate- What do you think the issue was there?

3) A couple of people have suggested going with a new carb and I think that would be a good choice. I'll have to start walking down that road some and see what the options are.

4) The air cleaner is resting or pushing on the back of the distrib cap. No clue why it is set this way but is this an issue? I'm sure I can find a small riser piece to get it up off of the cap.

WD-40 is more of a solvent than a lubricant. If you're only looking to clean it, then great. Otherwise I'd look elsewhere for a better lubricant.

Have you confirmed the throttle cable is not binding in any way, at any point in its travel? As one who has experienced a stuck throttle in a Cobra I'd look there first.

[jhv48]

Not sure why the base plate replacement worked but I can only assume that there was a restriction or leak in one of the bushings or the throttle plates were sticking. I think it cost about $150 to replace the base plate but if I were you, I would Save the money, sell the 770 and get a nice mechanical secondary 750. You won’t believe the difference.

[Mattsvtcobra]

Originally Posted by cycleguy55

Have you confirmed the throttle cable is not binding in any way, at any point in its travel? As one who has experienced a stuck throttle in a Cobra I'd look there first.

I have tested and looked over it a couple of times. Seems okay.

[Texasdoc]

I use a thin coat of white lithium grease on the base plate and arms.

[Mattsvtcobra]

Thanks Jim! I will check with a timing light. Also someone in the ignition section suggested that I may have too strong of springs on the weights in the distrib, so I need to look into that too.


Question. The car drove decently today and had some hang up/RPM climbing on me when pushing in the clutch, but every time that happened I could pull the throttle back up with my foot and the RPMs would instantly drop to idle. Any idea what could be getting hung up? I've traced every thing on the throttle cable and I have 2 springs that seem to snap back well. Is there something I need to look into lubing or replacing?

[Bobcat]

I think you`re backwards on your distributor springs .... too weak will not pull the weights back as quickly and the advance will not return to the base setting quickly . The stronger weights will pull the weights back quicker , but also change your advance curve .
Check the MSD spring curves for where the advance comes in with the various spring combos . If your idle is too high , then it may have the advance already starting to come in .
Personally , I think you need to put a light film of lithium base grease under the weights to free them up and help keep corrosion to a minimum .

[cycleguy55]

I'd be concerned about using ANY kind of lubricant that would attract or hold dirt, carbon particles, etc. Clean the advance weight pivot points and either leave them dry or sparingly apply something like a dry film lube. Powdered graphite could work - if it wasn't conductive. I have a spray lube that has PTFE (Teflon) in it - the carrier evaporates and leaves the PTFE behind. The one I have is by GUNK Liquid Wrench, but WD-40 makes it, as do B'Laster, 3-IN-ONE and probably every other maker of general purpose lubricants.

[MaSnaka]

Matt do you have a cable or linkage connecting the pedal to the carb?? When you say you lift the pedal and the RPM goes down sounds like there is a bind somewhere between the two. Then you say you can tell by start up whether it will run good or have the RPM hang up. Vac advance on the dist? Vac leak possible or bad diaphram?? The air cleaner should not be resting on the dist. I have the oval Cobra air cleaner and it clears my dist by about a 1/4" from the side but is nowhere near sitting on top. I have the FE motor which might make a difference. Does the air cleaner contact the choke horn?? Could cause air flow restriction on acceleration. Trying to think outside the box.

John

[Mattsvtcobra]

Originally Posted by MaSnaka

Matt do you have a cable or linkage connecting the pedal to the carb?? When you say you lift the pedal and the RPM goes down sounds like there is a bind somewhere between the two. Then you say you can tell by start up whether it will run good or have the RPM hang up. Vac advance on the dist? Vac leak possible or bad diaphram?? The air cleaner should not be resting on the dist. I have the oval Cobra air cleaner and it clears my dist by about a 1/4" from the side but is nowhere near sitting on top. I have the FE motor which might make a difference. Does the air cleaner contact the choke horn?? Could cause air flow restriction on acceleration. Trying to think outside the box.

John

Do you have a cable or linkage connecting the pedal to the carb?? When you say you lift the pedal and the RPM goes down sounds like there is a bind somewhere between the two.
--- It's weird, it seems to happen once the engine has warmed up. So something is changing when heat becomes a factor. That's why I wasn't sure if the carb had something that needed to be checked or lubed. Can a lubricant just be sprayed where I see levers moving and also down the throttle cable?

Then you say you can tell by start up whether it will run good or have the RPM hang up. Vac advance on the dist? Vac leak possible or bad diaphram??
---No vac advance

The air cleaner should not be resting on the dist. I have the oval Cobra air cleaner and it clears my dist by about a 1/4" from the side but is nowhere near sitting on top. I have the FE motor which might make a difference. Does the air cleaner contact the choke horn?? Could cause air flow restriction on acceleration.
---Mine does not clear. Not sure what you mean by the choke horn?


Trying to think outside the box.
--- I really appreciate it!

[MaSnaka]

Hi Matt,
I use the silicone spray and lube the external moving parts on the carb with it on occasion, really not very often.

Air cleaner and choke horn- choke horn is the shroud surrounding the choke plates on the top of the carb. Rises about 1 1/2" above the carb opening. Some air cleaners being low profile to fit under the cobra hood, the inside of the air cleaner top is either making contact with the choke horn or very close to it. This can restrict air flow into the carb as you approach wot when the engine is sucking in the most air.

Do you have a phenolic spacer between the carb and the intake manifold? This insulates the carb from heat which might be causing some deflection in your linkages. I have only heard of them being used to prevent the fuel from boiling in the carb but maybe.

John

[Mattsvtcobra]

First off... I want to say thank you to everyone on this post that gave ideas on what rabbit hole to go down. The car is back in order and I'm just getting around to post this update, but I'm not sure which of these fixed it. I tinkered with each area individually, but it wasn't until I tore everything apart at the same time... that any and all of these fixed it.

1) Just spraying wd-40 in the distributor seemed like it would temporarily work, but it was not until I took the springs out and removed the weights. You could not see the rust build up on the posts that the weights sit on or the rust in the little bushing that is on top of the weight.
- Sanded with super fine sand paper and put a very small amount of silicone spray.

2) I cleaned up the cap and rotor posts as well. Carbon build up on the posts, but not a lot.

3) Adjusted the auto choke and fast idle cam but did take it all apart to make sure that it was clean and freely moving.

4) The throttle shaft on the base plate had a small amount of wiggle to it. It seemed to be holding the throttle linkage up and wouldn't fully go back to starting position. This was a PITA to find, but glad I finally did. May eventually replace this part but for now it is working well. I sprayed some silicone on the main throttle shaft and at the next start up, the idle was very high then came back down. I was 100% sure I had a vac leak happening and would not of expected to look at this shaft potentially binding.

SO happy the RPM's don't climb on me anymore when driving! Back to having a fun and responsive throttle.

[Anthony]

Originally Posted by mattsvtcobra

first off... I want to say thank you to everyone on this post that gave ideas on what rabbit hole to go down. The car is back in order and i'm just getting around to post this update, but i'm not sure which of these fixed it.

------

so happy the rpm's don't climb on me anymore when driving! Back to having a fun and responsive throttle.

excellent !!!!!

[Mattsvtcobra]

After much debate and a ton of research, I ended up scrapping the carb and going with a new one as at a min I needed a baseplate and a carb rebuild kit. Brent Lykins built a QuickFuel HR650 for me and it was instantly better. Off idle bog= gone and it is very snappy now!Wish I would of just done that at day 1.

[MaSnaka]

Excellent!!

[Mattsvtcobra]

Originally Posted by MaSnaka

Excellent!!

Yes! Glad I went that route.

So the car had a few good runs and 1 funky one. So in monkeying around, I found that the distributor was barely loose, and I mean barely. I think it was twisting here and there, but could never figure it out.

1) Reset timing and clamped her down good!
2) Put lighter springs on the weights and checked total timing
3) Messed with the 4 corner idle until I was able to get max vac. She didn't like that very much when I took it for a test drive. So I went home and bumped it up, but it is way too rich so I will mess with the air bleeds. Ran like a bat outta hell!


The car starts up immediately again and runs well Thanks for the suggestions!