Engine Bog

[Bennett]

OK, start with a tuneup, put on a fresh fuel filter, plugs, make sure the air cleaners are clean, set the timing the best you can, and buy yourself a can of carb cleaner. Also, make sure you have fresh gas in your car. If you haven't changed your plug wires recently the last 3 or 4 years, put a new set on. They're cheap. And be sure you have at least 2 1/2 psi and no more than 5 psi at the carbs.
If its bogging right off the bat, either you got a vacuum leak, or your carbs are way off. Now, I need to ask you, are you running a progressive linkage? Are the carbs in good shape? Check your float levels on both carbs, be sure to adjust your float levels so you are barely have a trickle out of the level holes.

OK, well, start your car, idle her to about 800 rpm, might be loping or slightly rough if you have some cam timing there, but if she won't idle, let us know. Otherwise, Idle her to 800. Disconnect the vacuum advance right now, and plug it off temporarily.
Break out your can of carb cleaner, and where the intake bolts to the heads, spray along the mating surfaces. Then where the lower intake bolts to the plenum, then where the carbs bolt down to the plenum. If the motor automatically goes crazy and idles up fast, you've found a leak. I usually find them at the carb base, but they can be anywhere. Usually if theres a leak, its a vacuum plug removed and/ or vacuum line not plugged. Anyway, if you find any, fix the leak.
Now, lets start a check list here. We need to check for flooding, for leaness, for timing issues, for carb actuating issues. Now, take off your air cleaners, idle the car, get a mechanics inspection mirror, look into the throat of the carb, you should not see any fuel dribbling from the boosters. If you do, you have a problem with power valves or floats/needle valves. DO NOT PUT YOUR FACE OVER THE CARB AND LOOK INTO THE THROAT>>>>IT IS DANGEROUS!!!!!
If there is no fuel dribbling from the boosters, on your front carb, you want to screw the front corner screws on the metering plate in, bottom them out gently, then back our roughly 1 3/4 turns listen to you motor rpm idle up or down to maintain the 8oo rpm. Now go to rear carb on each corner screw on the metering plave, bottom the screw out and back out 1 3/4's turns. Now then readjust the rpm to 800, then back off the front idle aduster, you should hear a difference like its laboring, but it should not die. Now you want to idle off 1 Carb, not both!!!!! Make sure the front butterflys on the front carb are closed, if not, turn your motor off and adjust your linkage so it does close. Now, start her up, she should idle better. Rev her lightly, all should be fine. If all is well in your carbs, when you jump down on the throttle, they'll be a bog, which you can adjust out with your power valves, accelerator pump cam, etc, etc. Worse case scenario, a progressive linkage will be needed. Also, the timing will probably need to be reset.

Now, if your still bogging bad, start on your front carb, disconnect the throttle linkage, and squeeze off the fuel line, what we want to see if she'll run off 1 carb cleanly. have the rear carb hooked up to the return spring. See if she starts up, see if she'll run off 1 carb and rev up some....

Get back with us and we'll talk ya thru getting her straightened out....

Screaming Metal, I started with a bit of a tune up. Filter, air cleaners wires and all new last fall however I did replace the plugs. Now Fuel pressure...You said "be sure you have at least 2.5 psi and no more than 5 psi at the carbs." I have 6 psi...my pump is a "Holley Red". Bogging is right off the bat in my estimation. I am not running progressive linkage (see attached photos). I feel the carbs are in good shape visually. I adjusted the floats tonight. the front carb / front float was fine, front carb /rear float was also fine, the rear carb / front float was a tiny bit low & the rear carb / rear float was way high. I re-adjusted them all to a tiny trickle. (By the way timing is correct). So I started with your next paragraph of instructions (remember, no laughing). Vacuum advance disconnected and ideling @ 800, I sprayed carb cleaner on all of the gaskets, bolts, fittings and mating surfaces. To my surprise NO LEAKS. Made a mess of things though. Next... no dribbling of fuel from booster. Now comes the fun part (remember no laughing). I attempted to adjust the mettering plate corner screws (by the way they were set at approximately 3/4 to 1 full turn on average as found). I failed...I can not figure out what is the best setting for each screw. I backed the idle screws out so that the butterflies are closed and it will idle way down to 200 or 300 rpms. I don't know if this helps? I'm not sure where to set the corner screws...I suck at carb adjustments....Help! I can't test drive tonight because it's poring out and will melt.

 

[Bennett]

There are 2 things that can be causing the bog. One is the power valve in the primary metering block. It might be opening too soon, or too late. The second, is the timing of the opening of the secondaries. I would guess the secondaries would be most likely. If you want to eliminate the power valves probability, disconnect the secondary arm on the diaphram, zip tie the secondaries closed and drive it like you do trying to create the bog. If it is clean, no bog, put it all back together. If it bogs, post back and we will go from there. Back to the secondaries. Holley makes a spring kit to change the secondary opening timing. The springs are color coded and the instructions tell which to use to delay or increase the opening. Yours are opening too soon and the engine rpm is not high enough to handle the large increase in air. Ideally, in my mind atleast, the two vacuum pots would have a balance tube between them. Holley also has the lids to the diaphrams with the ports already in them. All you have to do is run a small vacuum line beween the two. You can get by without this. After re reading your post, the power valves sound like they may need tuning. If you do not have one, get a decent vacuum gauge. Here is a test that might help. With no breathers, a power valve will open later, bog will be later in the rpm range, less or disappear. With breathers it will occur sooner. If this is the case. Put the vacuum gauge on the intake source, idling in gear and get a reading. If the reading is less than 12, your power valve number should be half the reading. If above 12, reduce the number by 2 for your power valve number. The accuracy of your gauge and what the power valve really operates at my not be the same, so some adjustments may be necessary to be optimum. Maybe I didn't leave anything out. You also indicated the ign vacuum adv was questionable. Check to make sure it is hooked up to ported vacuum, no vacuum at idle and increases with throttle opening. If you have to change this, reset you base timing.

Railroad, I didn't get to try very many of your suggestions tonight because as I said in a previous post is is poring and don't want to take the bucket out in it again. I did however take the vacuum reading and it is running right @12. ( see attached photos) My gauge is not a super expensive one but I'm sure it in the ballpark. I'm not sure yet what power valve is installed but will check and get back to you. Oh and I'm not sure I understood the ported vacuum statement. It does sound better and start better now that I've set the timing but I agree the carbs have to be way off because I took it for a ride after setting the timing and nothing else and barley had enough power to get back home.
http://s1149.photobucket.com/albums/o583/buiboy/

 

[Bennett]

As the others mentioned you really need a vacuum gauge to determine power valve size. They are cheap and everyone should have one.

The previous posts are all leading to too much fuel but a bog can be caused by not enough fuel off of the idle circuit. A couple things to check are the squirters /pump cam/ accelerator pump. When you move the throttle the squirters on top should start immediately. The rate it squirts at is controlled by the position of the pump cam. The volume of fuel is control by the pump cam shape. The accelerator pump must supply the fuel so it has to be working properly as well.

One other common mistake is people have the idle adjustment on the throttle plates to high causing fuel to leak in through the idle transfer slot. This can cause the engine to run really rich causing idle and off idle problems as there is way too much fuel coming out of the carb.

All these parts are normal tuning items. Also, it wouldn't hurt to pick up a book on tuning Holley carbs. That can be very helpful in terminology and how things are supposed to be seems how others have worked on your car before you.

Fords by Jay, As with everyone thanks for the help! I checked the squirters and they appear to to push a nice flow and is immediate. I haven't checked the pump cam lever with a feeler gauge for the proper setting yet but will do so soon. I also haven't dove too deep into the throttle plate adjustment but will. I took your advice and purchased a couple of carb tuning books and even a DVD (see attached photos) The DVD is great!
http://s1149.photobucket.com/albums/o583/buiboy/

 

[Bennett]

The timing was set very far advanced and when I corrected it the bog got worse
AHA. Theres a clue here. Check your TDC mark on the balancer with a piston stop. We do this every tuneup and long ago stopped being surprised at how many instances the marks were out because the damper slips on the hub. Reset the TDC mark and set the idle timing at 12deg with the vacuum line to the distributor disconnected and plugged.

Wild Mango, Thanks for making me do this correctly. So I checked the TDC with a piston stop and the harmonic balancer hasn't moved. All is good.

 

[Bennett]

Screaming Metal, Railroad & Wild Mango,
You guys have provided a lot of helpful posts and I very much appreciate all the help but now for the big question...How do I proceed?
1. buy new carbs? (2 Holly 290 @ $400 each)
2. rebuild the ones myself? (kits are reasonable $50-100 each)
3. send carbs out for rebuild? ($250-300 each)
4. keep moving forward with our quest to tune? (just time & money)

There is a place in Long Island (I think took over for Barry Grant after the chapter 11 deal) that will rebuild and tune for my application but I'm not sure I can provide them with enough engine spec information to get it done correctly and it's almost the price of new factory Holley carbs.

I'm still not ready to go to a conventional intake and carb(s) yet, if I still have options.

Your opinions are valuable to me thanks,
Mike

 

[railroad]

Boy, if everyone followed instructions as well as you,,,,. Try to set your curb idle screws so both carbs are contributing the same for a good idle. Since it will idle down so low, I would shoot for 700 rpm plus or minus 100 rpm as needed for good idling in gear. Use your vacuum gauge to tune the idle mixture screws. If the idle speed increases more than what you will need, reduce the curb idle speed screws on both carbs, then go back to tuning your mixture jet screws. Highest vacuum reading while adjusting is usually optimum. Your vacuum reading indicates you need something in the 6 range for a pv. Since they come in .5 increments, we need to decide whether you need a 5.5 or a 6.5. Does the engine give you any indication of whether it is rich or lean when it bogs? Sometimes you can pump the pedal a little and the pump shot will richen and improve the running. Any popping back in the carb is generally a lean indicator. The higher the number of the pv, the sooner it enriches the circuit. I hope you find the present pv numbers far from what we need or one or both are bad. While you have the front off the carbs, spray all orifaces, jets and ports with carb cleaner. A good protection routine is to add a shot of Marine Stabil at every fill up. I doubt the secondaries are opening too soon and creating your problem, but just to eliminate them from the possibilities, zip tie them where they will not open. Check your linkage after doing this to make sure nothing is going to get stuck open. If you get to the point the carbs need rebuilding, you are plenty capable of doing it. There is no reason to abondon the tunnel ram.

 

[one finger john]

Perhaps 3.73 rear gears instead of 2.73? How tall are your rear tires? Are you sure you are starting off in first gear? Seriously. Does it pop back when you wing the throttle (as in a lean pop)? Give it more lead. Try 20* BTDC initial. Just screw the idle mixture screws in til it starts to stall (one at a time) and then out to where it idles the quickest. Then reset idle speed. Make sure that both carbs are pulling the same vacuum at idle AND at different throttle openings. That is to insure that both carbs are opening the same ammount, not one more than another. I prefer one to one opening vs progressive opening. Pull all the plugs, arrange them in order relative to engine position (two rows of four). You won't see that nice tan coloring, you have unleaded gas. Either black (too rich) or pale cooked white with black speckles (way too lean). Or slightly darker white, O.k. mixture. Check the power valves. Have you gone on line and made sure that all the jets and restricters are stock? All settings are stock?
Then if that doesn't work, take it to the Long Island guy and have him ball park the carbs. Shouldn't need the car, just the carbs. Do you trust him? He could pressure you into new bases, metering plates, etc. etc. etc. Might as well get new carbs. If he is as hot as you say he is he should be able to consult his notes and get it real close. I had 600 cfm vacuum secondaries on my Weiand tunnel ram and it ran fine.

Best of luck.

P.S. $100.0 for rebuild kits or strip kits?

 

[railroad]

Here is something to read, while it is raining, pending Mike's OK here is the site
http://www.bob2000.com/carb.htm

 

[Screaming Metal]

I'm not gonna get into the mix here, too many people telling you what to do is bad, I'll be on the sidelines listening. Its best to do as you are doing....one thing at a time, systematically, when you find it, it'll be sweet! The inside of those carb throats are Dirty! Now, when you set the timing, vacuum advance blocked off, correct?. After setting the timing, when you hooked up the vacuum line, it should have idled on up. Correct?

Yes, I agree there is no reason to take off the tunnel, theres alot of them running on the street, so, we'll just get yours tuned to do the same. As a last ditch effort, trade your 2X4 top for a 1-4 and a doublepumper, and it'll be fine.
There is one thing that puzzles me though....it idles really well down low, eh? Hum....well, most of the time, it carbs are all out of kilter, they usually won't idle, they'll do it, buts its usually a ugly thing!

Pull your plugs as you were told, you want a dark sand color. Ideally, a light sand color would be good, but as much intake as your running a dark sand will do fine for now. If your a sooty black, its way too rich, if its wet black, its flooding. If its glossy wet black, you have oil on your plugs. If its a dark brown, its kinda rich....you get the picture. Normally I like to 'Read the Plugs', if your in town, theres no chance of that.

On your idle mixture screws, run the screws in lightly, bottoming them out gently, then back out 1/2 turn on all front metering plates, front and rear carbs, start her up, seeing if it smooths out enough to give it some throttle, if not, see if 3/4's out does any better. Keep backing the screws out, don't go past about 2 1/2 turns....
If it starts to run better, your lean. If your motor trys to die, run your screws in till it'll run. Do it little by little, and take your time.

Your getting a good flow of fuel, the floats are correct, nice stream of fuel when you kick the throttle, the timing is OK, if you got a good hot spark, with decent compression, it ought to run pretty decent. Find out from the previous owner if he installed the cam 'straightup', if he remembers. If the timing were way advanced and if you tried to rev it and it didn't backfire....we might have to look at a few other things also....

Get back with us, we're gonna have to talk you thru this slowly....

 

[railroad]

After setting the timing, when you hooked up the vacuum line, it should have idled on up. Correct?
Ported vacuum should not increase the timing and increase the idle. I know there are 2 diff opinions on this, but I think we should keep the vacuum adv out of this until we get the carbs sorted out. Am I wrong on this?

 

[Wild Mango]

I suppose being an Auto Electrician I would say this, but ignition is one area where things can easily appear to be working OK when they are not. We have a Bin Test for suspect leads and plugs where you throw them in the bin and if they climb out by themselves they are OK. Ditto for the Distributor cap where cracks and tracks steal voltage and are hard to see. Timing is only correct if the marks are correct, the centrifugal advance only works if the weights move freely and the springs are healthy, the vacuum advance only works if the sensor or breaker plate moves freely. All this stuff is easy to check and relatively cheap to fix. Once this is done you have a healthy ignition system to support your work on the fuel system. JM2CW

 

[one finger john]

90% of your carb problems are in the ignition.

 

[Bennett]

Hi Guys,
I had an opportunity to play a little more tonight. I went back and attempted to adjust the metering screws. (Air cleaners off, vacuum plugged, in drive @ approximately 700-800 rpms, vacuum gauge attached. I don't seam to be able to make any changes by adjusting the screws. No responce on front carb and very little on the rear. Vacuum tonight is 11 on both carbs. Timing set @ 12* btdc. I took it for a little ride with the following results...Bog comes on right away but I did thy the pump the throttle a couple time and it will come into it and add power. When I returned and shut down the engine tried to diesel and run on.

I pulled the squirters and they are a 25s. I pulled the bowl and metering block of the front carb to check PV and jets. The jets are 49 and the power vales are...who the hell knows...doesn't look like anything in the books or DVD. (See attached photos)

http://i1149.photobucket.com/albums/o583/buiboy/DSCN0659_zps274444e6.jpg

Doesn't look like a valve to me. Looks like a plug.

I forgot to zip tie the secondaries shut so don't have anything to report there. Any thoughts?

 

[2old2fast]

Those are indeed PV plugs , get rid of them & try 5.5 [althogh because these cars are so light you can probably get away w/6.5] The inside of the carbs is filthy , need to be tanked & new gskts. . check your pri. jets [390-8007 should be #51] if they aren't , you'll have to get jets. After you get thru all that , then you can start .to tune. Shooters could stand to be a little bigger, but wait 'till you sort out the other things.

dave
almost forgot, if not already installed , do yourself a favor & get a set of PV blowout preventers. You'll thank me later!!

 

[Screaming Metal]

I concur 2O2F, it looks mighty crappy in there. Someone put those plugs in there trying to bypass the power valve circuitry.I'd try 6.5's after getting those carbs boiled out. Its been a long time since I seen a carb that filthy, plus the idle mix. seemed marginal.
I hope that the inside of the card is that dirty, and theres not paint in there.
What kind of ign . does it have ? MSD? You can run a small dist. HEI, the reg. big dist. hei won't fit with a TR. I believe once he gets it all to good solid baseline, then things will turn around.
Mango and OFJ are right, ign. is hell to diagnose piecemeal, alot of carb problems are ign. related. Just from the looks of things, its been run, but hasn't been taken care of. OR someone switched carbs. I don't trust carbs with paint on them....its a quirk of mine.

 

[railroad]

Great find on opening the carbs. You can clean the carbs with spray cleaner, but I think you will better served by a 5 gallon bucket of carb cleaner. It rinses with water and you will need compressed air to clear all the passages. Also be warned it will remove any gold hue from the outside of the carb. If you have an out building, use it to store the cleaner while soaking the carbs, Mama will not like the smell getting in her house and it will. I concur with the last posters, everything you have uncovered can create the bog, poor running, and dieseling after shutdown. Things are looking up. I will bet most of that corrosion is from ethanol, do not forget the Marine Stabil.

 

[Wild Mango]

One more thing on the ignition. Pop the cap and rotor off and have a real good look for loose or broken wires, get in there with a small screwdriver and tease things around a bit. The HEI's have a bad habit of breaking the little wires that go to the module, and when you hop on it the breaker plate moves, the wires pull apart, big flat spot, you button off, the vacuum pulls the plate back and the wires reconnect. The earth wire to the breaker plate does this too, and the broken end trolls around on the plate making contact when the fancy strikes it. Another highly amusing trick is the little carbon button that conducts the HV to the center of the rotor goes on the fritz or succeeds in being lost during some earlier teardown. This is fun because the engine will idle and generally behave but when you give it a footfull the resistance across the plugs goes up and all the spark energy happens in the cap. All pffffft, no vavavoom. Drive you nuts, makes you think why on earth you put yourself through this, yes, we know

 

[Bennett]

Carburetors:
I'll order a couple of carburetor rebuild kits. (Anything to make sure it contains that some don't?, Brand?, Best place to get?) I have a brand new gallon can of Berrymans carburetor cleaner to soak parts in. I will also order two 6.5 power valves to replace the plugs. Should I wait on the new main jets and shooters until learn more later or just go ahead and get now?
Ignition:
Any suggestions on a brand or maker for the small HEI distributor. It is very tight for space around the back side of the tunnel ram. Oh, and before I forget (Screaming) the engine is a Chevy 350

 

[2old2fast]

Summit, 37-1542 fast kit-$24.95 is what I use. Check your main jets & replace as necessary !
dave

 

[Screaming Metal]

I pulled the squirters and they are a 25s. I pulled the bowl and metering block of the front carb to check PV and jets. The jets are 49 and the power vales are...who the hell knows...doesn't look like anything in the books or DVD. (See attached photos)

Well, I'd say someones been inside there jacking around. STD. Jets are 51's....it has 49's, has powervalve plugs, stock are 6.5's. Plus a bad case of dirty carbcraps....
Evidently the car ran decent at one time like that, probably not good. 390's are pretty mild carbs.

I say after cleaning and gaskets, put your old jets in a small box and keep them in your toolbox. Put the 51's back in it with the 6.5 PV's....if she's way rich after the carbs are done correctly, you can always go to the 49's agian!