Projects Comet Update/Need tuning help

Got the carbs and intake on, and now the fun begins. Here's some pics before I get into my problems. Sorry the camera sucks and the lighting in the warehouse is crappy as well.



That throttle linkage has been fixed already.





This is the best picture I've got with the hood and homemade scoop/cover on. Yes I'm going to paint the displacement on the side of the box.


So I got it all together and got it running, but that's where the good news ends. It revs up in neutral real nice, sounds great, but once I let the clutch out and give it a little gas it just breaks up. The more gas I give it the more it breaks up. I'm thinking the 390's are too lean but don't know where to start with the jets. I'm broke and don't have the money to buy the assorted box of jets so if someone knows where I should start that would be appreciated.

Also, is there a cheap A/F meter out there? I know I need an O2 sensor and a meter to read it but where can I get one cheap? I think it would help infinately in getting this thing dialed in.

 

Make sure the float level is set correctly in all the bowls. What size are the carbs and what jets are you running? Have you set the idle screws?

Holleys are VERY tunable carburetors! Only problem is, they always need it.

You've got a lot of carb on a little engine there... don't expect miracles!

 

Call me........maybe I can help in tuning that thing........

Holleys always need tuning?........hogwash.........get em right and forget em.

Mark
972.712.6558

 

The carbs are 390cfm, it's only 180 more than I had with the single 4bbl. The linkage is progressive so it only runs on the back carb until half throttle. I've got to check on the floats, that was on the list, no idea on the jets.

 

You will need to know all that.

By the way, the car is badass... really like the look.

 

Thanks, it's about done since there's not much left to take off. Just have to get it smoking tires again.

 

Running points in that distributor?

 

How cool would that be with a body color ( Orange/red ) clear scoop instead. Like Plexi Glass but in color

 

Have you tried running it without the vacuum advance? It could be retarding the timing a bunch as soon as you roll into the throttle or if you are running points the lead going to them could be grounding out when the cam plate turns. If it was leaning out bad, it would most likely back fire through the carbs but your plugs could give you a good idea how it's doing.

 

That is lookin' Gooooood !!!!

 

Nice hot rod. To tune it you have to start with basics. Have the dist gon through so you can run an initial timming between 14-18* and a total between 35-40*. Since it's a driver you should have the vaccum advance working , but limitted to 6-8* on the ported side, depending on the squeeze, If it has a lot of squeeze in it you'll need to tighten up the plug gap.022-.030 (a good ignition system will make a world of diff.) Once you have the ign kinda sorted out you can start on the carbs. If I can be of any help e-mail me- Pacer377@aol.com. I'm sure we can work it out.

 

Well first things first. The jets have 611 stamped on them, and that's all. No idea what that means. I checked the floats and got them as right as I could, only the secondaries were a little high. It runs a little better now, but still not drivable. It did backfire through the primary carb today so I guess that confirms the general consensus that it's real lean. Got it to idle real nice around 950-1000rpm with the adjusters all the way out and the four enrichment screws out 1 1/4 turns.

I'll try disconnecting the vaccum advance tomorrow, I was kind of thinking that could be suspect as well. It's connected to a vaccum port at the base of the primary carb, but since it idles through both carbs, I guess there's only half the vaccum signal there was before. The distributor has a Pertronix Ignitor II in it and has never been a problem. As far as the timing goes, I've never touched the advance curve and the initial is advanced as far as it could go before it would break up on the top end. Needless to say I've got a depression era compression ratio and I'm a total noob when it comes to tuning the thing.

 

It sounds to me like you have a big vacuum leak. Most of the time it's between the carb and the manifold or a vacuum nipple open.

 

The 611 means it is a close tolrance jet it's a 61 on the lowerside. You need to set the timming before you mess with any tuning of the carb. The inital needs checked then the total some Ford dists. only alow about 10* total so if your at 12* then add 10 you will only be at 22*(this ain't good). where are the plugs gaped? .030 would be a good start, do the basics before you do the more advanced stuff. You will have as much vaccum at the carb as the engine allows, no matter how many. You want it to be on the ported side so it will advance as the throttle is depressed.

 

I don't think it's a vaccum leak, it'll idle fine, even after I let the clutch out and get it going. I've got all the unused ports capped and new gaskets all around.

This is not a new motor by any means. In fact it's 42 years old, with a hone and rings in '79, and only about ten thousand miles since. The timing is ok and the plugs are good with only 2500 on them. It idles great, just breaks up and backfires under throttle.

I'll check the vaccum advance and start drilling the jets out until I get close to what it needs, then I'll buy the proper jets. I'm poor.

 

Just for shits and giggles throw your points back in there and try it. I can almost promise you it ain't the jets.

 

You might wanna check for vacuum leaks anyway. I've had them, but with a propane carb, and it'll stall under load. I used starter fluid to check for leaks, and when you find one the engine will rev a little above idle.

 

Using the tunnel ram requires a large shot from the pump and squirters to fill the volume of the intake, it gets worse with two carbs because there is that much more air to come in and not enough fuel so you get a lean pop or backfire under load. The 390's should work but down the road a pair of 450's to 500's would benifit you on the top end also. My 351W that is built with the same heads as you and about the same compression uses two 575 cfm Carter AFB's with out progessive linkage and comes out hard and pulls the top end just fine.

Jon

 

Before I went drilling the jets(witch is a bad idea) I would mess whith the shooters and the secondery opening. If I'm not mistaken you'll have .025 shooters, way to small.

 

I agree with Ladderbar on drilling jets out not a great idea, you will have to go bigger but if you go to far you will be screwed if you drill your only sets. Look around for some 600 vacuum sec, guys have them just laying around that are in need of rebuild, take the jets out of them they are 66 and grab the squirters, you can drill them out and start at .032 on both and see if you get better responce. The bigger jets will come in once you get it moving off the squirters. I agree with everybody who has posted ideas and to make sure you check your basics also just to make sure.

Jon

 

I think you can go to Holley.com and download the installation manual for a Holley carb including tuning and troubleshooting.

 

Well... It's getting frustrating. Nothing seems to be making any difference, and if it does, it's negative.

Checked the timing. Advanced it, not any better. Retarded it, not any better.

Checked the plugs, they confirmed that I have lots of blow-by, knew that. As far as rich/lean, can't tell.

Disconnected the vaccum advance and plugged the carb port, no change.

Started drilling the squirter on the primary carb, since I haven't even been able to open the secondary yet. They are 31's not 25's as stated earlier. Got up to .0465 with slight improvement, but only in 2nd gear. It still will not rev up to 2k in 1st. Just breaks up to the point that it tries to stall. Feathering, flat-footing, and everything in between. This seemed like a huge change with little effect so I gave up and decided I needed more advice.

Tried adjusting the screw on the arm that pushes on the Accel. pump, both in and out, made it worse.

Tried changing the accel. pump cam from screw 1 to screw 2, no change.

Tried various combinations of all of the above, nothing good happened.

I'm at wits end, anyone have any idea?

Oh, I'll try to get some video to give a better idea of what's going on. I suck with the computer but I'll do what I can.

 

The main jets effect alot of things including idle and transistion. The thing with drilling them is you'll change the opening and exiting chamfer and put drill marks through the jet witch can reduce fluid flow and make it leaner. I have had to put very large shooter in combo's like this some as hig as.040 and very light secndery springs. Before you lose your way don't go to crazy.

 

One more idea I had is are your secondarys opening too soon? This could be even worse when running both diaphragms tied together with a balance hose. Even with progressive linkage and running on only one carb at low speed all four secondarys would be open as well. This would not be as evident when free reving (engine unloaded). Try pinning them closed with zip ties and driving it once.

 

As said previously you need a big accel pump shot. I would run 35 or 40 shooter nozzles and some BIG jets in the secondarys. There is no "adjustment" screw that'll make em work on a tunnel ram. You have to jet and pump size em up, trial and error. I don't think you will have much luck running them progressive either.

 

Have you tried another ignition yet?
I've had two bad experiences with the Pertronix electronic conversion.

What intake gaskets are you running? Are you using the cork end seals or RTV?

 

Ok, I'll try something new. Shot this half an hour ago. The glasspacks kind of overpower the speaker on the camera, and driving one handed is hard, but you kind of get the idea. Everytime the camera jolts forward is the car trying to bog/die. This is with the .0465 squirter. In gear it's a constantly popping and missing. The exhaust should be smooth even with the crappy camera, all the popping and crackling is the car.

If you listen to it kind of loud it's easier to tell what it's doing.

 

I don't think you can run a progressive linkage with that manifold.Seems to me you would be runnin half the motor lean till the front carb opens.Make it so they open at the same time and give it a try.

 

If you bring the rpm's up slowly instead of revving quickly is it still smooth? (out of gear) If so are the boosters dripping when it does it? Have you put a vacuum gauge on it yet? Also is it possible you may have a valve not sealing?

 

trouble shooting online is a bitch...but check vac...and then see what power valves you have in there..most likely they are blown.........tie yer vac lines into one line and hook to ported side.........

We have run into the same problems that you describe and solved it with a few easy changes...also...make it run on the FRONT carb first, but you need them all to run together, not just one ...like I said earlier..call me
972.712.6558

Mark