let me tell you my set up before i get into the questions. engine is a p code 400 from 1978. meaning its the high performance 400. ive got a mopar m1 singleplane intake, carter thermoquad (unsure of cfm i think its a 650 tho) freshly rebuilt. when i got the car someone had converted it to points. i converted back to electronic so i could put my orange box ignition on. (this box has been on at least 4 cars since the late 80s). there is a 4 degree advance on the cam. also a 1 inch spacer under the carb. running hooker comps straight into flowmaster super 44s at the moment. trying to get her dialed in to a point untill my shifter comes in and i can drive her. NOW to the problem. A: my little plate that mounts to the timing cover for the timing light is non exhistant... B: by ear the timing seems pretty close to dead on. (i know i know never time by ear but i actually have a knack for it and can usually get it dead on... theory tested with a light after setting up by ear... not on this car tho obviously) but when the secondaries open up the engine either seems to be starving for fuel/ or the timing is off... seems more like choking to me. runs a little better when vaccume advance is removed but still seems to be starving for fuel... now it does have a brand new fuel pump and filter after flushing out the tank and lines. filter is installed properly. excellent throttle response... untill you hit the secondaries... any ideas? carb to big? needs adjusted? if so what? do i need to adjust the air metering rods? or the accellerator pump pin? anyone have an idea on how to read the timing with a light without the scale attached to the timing cover? i knwo alot of questions but i am a little lost here. HELP!
engine seems to need more fuel when secondaries open...HELP!
1 - 20 of 23 Posts
Joined
·
21,402 Posts
First confirm correct ignition ignition timing. If you can just get it to barely 'ping' on hot acceleration, that is about the correct timing. This may be difficult to hear with a loud exhaust.
You can use a dial micrometer with a long stem in the #1 spark plug hole to determine exact TDC. Then make a mark on the timing cover to index TDC. Try 10° BTDC with an advance timing light first and go from there. Watch advance as you rev it with the vacuum advance both hooked up and disconnected. You want to see it swing to ~30°-40° BTDC total advance with the hose on and revved.
Make sure that you have the correct carburetor # on the engine. This should be stamped on the base casting. A Carter from a 360 or LeanBurn application would run lean and one from a 440 would run rich. Determine if you are too rich or too lean. 'Choking' to me means too rich. 'Starving for fuel'means too lean. You give conflicting symptoms. A puff of black exhaust smoke on acceleration may be from a rich condition. Carburetor 'pop-back' on acceleration may be from a lean condition. You have to determine which.
Spark plug tips might tell a story of fuel mixture (black=rich and white=lean) and must be the recommended Champion RJ-12YC for best results. Opening the throttle with the inrush of an air/fuel mixture may simply be 'blowing out the candles' if spark voltage is low or the spark plugs are either wrong or fouled.
Was this a rebuilt carb out of the box or did you rebuild it? The secondary air flap spring tension adjustment and the power metering jet rod adjustment is critical and must be in correct adjustment. Playing with the adjustments might make the situation better or worse, but that will tell you which way you have to go with the mixture to get it correct. When you do any adjustment, remember where you started from (how many turns) so you can put it back the way it was before if necessary.
You can use a dial micrometer with a long stem in the #1 spark plug hole to determine exact TDC. Then make a mark on the timing cover to index TDC. Try 10° BTDC with an advance timing light first and go from there. Watch advance as you rev it with the vacuum advance both hooked up and disconnected. You want to see it swing to ~30°-40° BTDC total advance with the hose on and revved.
Make sure that you have the correct carburetor # on the engine. This should be stamped on the base casting. A Carter from a 360 or LeanBurn application would run lean and one from a 440 would run rich. Determine if you are too rich or too lean. 'Choking' to me means too rich. 'Starving for fuel'means too lean. You give conflicting symptoms. A puff of black exhaust smoke on acceleration may be from a rich condition. Carburetor 'pop-back' on acceleration may be from a lean condition. You have to determine which.
Spark plug tips might tell a story of fuel mixture (black=rich and white=lean) and must be the recommended Champion RJ-12YC for best results. Opening the throttle with the inrush of an air/fuel mixture may simply be 'blowing out the candles' if spark voltage is low or the spark plugs are either wrong or fouled.
Was this a rebuilt carb out of the box or did you rebuild it? The secondary air flap spring tension adjustment and the power metering jet rod adjustment is critical and must be in correct adjustment. Playing with the adjustments might make the situation better or worse, but that will tell you which way you have to go with the mixture to get it correct. When you do any adjustment, remember where you started from (how many turns) so you can put it back the way it was before if necessary.
ok so i dont own a dial mic. but i do own a long thin flat head screw driver. using the old screw driver technique i can nearly find tdc but was unsure where to make my mark... seeing as i am going to have to wait for a friend on that. second pair of eyes and all. also the timing cover is buried i mean buried under the water pump housing. can i mark the water pump seeing as at tdc the balancer mark lines up with the return end of the pump housing. now i apologize i work 3rd shift so my mind isnt as clear as i would like. to advance timing i rotate the dist. counterclockwise correct? that aside i set the timing as close to tdc on the dist. this made the engine fight compression and not want to start. i was forced to advance the timing a bit from there just to get a start as well as a clean idle. now yes i do get the "pop back" during slow acceleration of the throttle. now just slamming it to wot causes the engine to act like its getting no fuel. this tells me it is running lean. but upon pulling the #1 plug it was black and reeked of gas. i give conflicting symptoms because i am getting them so i apologize for that. also there is the matter of the 4 degree advance at the cam. does this change where i should set the timing? also carb came off of a 440. i rebuilt the carb myself btw. i dont trust out of box rebuilds. granted this 400 came stock with the 440 valvetrain and cam (this makes it the p code engine or the high performance 400). also i got alot more "pop-back"..(not even sure if thats what it really is it seems more like backfiring) with the vaccume advance on than with it off. i personally dont want to put the rc12yc plug in for 2 reasons.. a. it is the same plug that goes on brigs and stratton lol. ( i know i know its the same plug for the 400 its just a little joke) also i did a wealth of research into my e3 plugs (lol also designed originally for lawnmowers) and i dont see it possible to "blow out the candle" when ive heard to never use these plugs on late-model engines due the the candle blowing out the piston lol. that is unless my old orange box thats been my dads and my cars since oh say 1985 could be shot? please feel free to shoot holes into anything ive stated. one needs to learn as much as possible.
Joined
·
21,402 Posts
Ugg. I remember that shift, we called it the vampire shift.
A white paint dot can be applied to the damper and timing case by reaching down in there with the tip of a long, thin screwdriver and a steady hand in order to index TDC. It is tight in there, but with the correct viewing angle you should be able to see it, set it once and forget it.
By 'pop-back' I meant backfiring out of the carburetor. 'Backfire' to me is out the tailpipe.
The distributor rotor turns counter-clockwise ↺, so advancing the distributor would be done by turning the distributor body clockwise ↻.
Black carbon/fuel fouled plugs may mean 'rich' and this may be your problem.
The spark would rather cross the path of least resistance across the carbon instead of the difficult task of leaping off the electrode, through the compressed air to ground (this is blowing out the candles).
A lot of science and engineering goes into choosing the correct spark plug for best burn for your 400 application. I don't know the heat range or compatibility of your e3's to your situation, but I would think of them as being the 'wrong' plug for you. Just because the heat range matches a lawn mower plug (mine uses RJ8) means nothing. It is just a plug size and heat range rating. Wrong plugs will foul and misfire easier. Do you have a cross-reference to the e3 number? Don't always believe what the parts counter tells you.
I have no opinion on the advanced cam timing except to say that it is usually done in conjunction with another cam/valve train modification. It will gain you nothing with a stock cam and may contribute to other problems. If the factory thought that they could make more power and a clean, smoother running engine with another 4° cam timing advance, the cam/crank timing marks would be done that way as stock.
A white paint dot can be applied to the damper and timing case by reaching down in there with the tip of a long, thin screwdriver and a steady hand in order to index TDC. It is tight in there, but with the correct viewing angle you should be able to see it, set it once and forget it.
By 'pop-back' I meant backfiring out of the carburetor. 'Backfire' to me is out the tailpipe.
The distributor rotor turns counter-clockwise ↺, so advancing the distributor would be done by turning the distributor body clockwise ↻.
Black carbon/fuel fouled plugs may mean 'rich' and this may be your problem.
The spark would rather cross the path of least resistance across the carbon instead of the difficult task of leaping off the electrode, through the compressed air to ground (this is blowing out the candles).
A lot of science and engineering goes into choosing the correct spark plug for best burn for your 400 application. I don't know the heat range or compatibility of your e3's to your situation, but I would think of them as being the 'wrong' plug for you. Just because the heat range matches a lawn mower plug (mine uses RJ8) means nothing. It is just a plug size and heat range rating. Wrong plugs will foul and misfire easier. Do you have a cross-reference to the e3 number? Don't always believe what the parts counter tells you.
I have no opinion on the advanced cam timing except to say that it is usually done in conjunction with another cam/valve train modification. It will gain you nothing with a stock cam and may contribute to other problems. If the factory thought that they could make more power and a clean, smoother running engine with another 4° cam timing advance, the cam/crank timing marks would be done that way as stock.
Joined
·
20,101 Posts
The cam timing isn't going to be doing this to the engine, it is a combination of a couple things, the carb is the main thing. Since you do have a Mopar carb off the 440 vice the 400, I know there are references (like Haynes of all sources, along with factory manuals), that do list the tuning for the carbs, both primary and secondaries are off the mark because other than 40 cubic inches difference, the burn of the even larger piston and compression difference doesn't like the carb setup you have. You can get the proper needles and jets to correct this issue. I'm not as worried about the sparkplugs even though they are slightly off as to how it was explained by ImperialCrown, carb'd engines are a little less sensitive in this area in my book. Agree with the timing marks and setting them up, the harmonic balancer is still marked with a grooved line, make a mark to correlate with it on the case, pretty simple. The M1 intake can be another issue for the street, single plane manifolds are not real good operators on the street and they do prefer ported heads and higher compression to function best, but it can be done, just consider it not optimal in function for daily driving. Distributor advance curve is extremely important and may be another major factor here. If the advance curve is too fast, big blocks aren't happy. The factory gives a heavy and a medium heavy spring, to which I have found the medium heavy and a distributor curve kit spring kit medium spring to work best, which gives the curve a little boost up to about 1400-1500rpm then slows it down until it maxes out around 3200rpm. Too fast a curve can cause the popping through the carb (occasionally), but usually just a stumble and pinging.
Now, back to the unregulated lean/rich appearances, it is running rich most of the time, which you probably adjusted the idle just fine, but off idle running on the primaries is a tick rich, then, secondaries, as noted, are probably opening too quick which sets off a lean condition then rich again, primary needles are probably stepped too tiny at the step, big enough on the top step to help run and cruise fairly decent, so find the numbers for the 400 and the Carter TQ and get the carb dialed in and get the timing adjusted, go from there.
Now, back to the unregulated lean/rich appearances, it is running rich most of the time, which you probably adjusted the idle just fine, but off idle running on the primaries is a tick rich, then, secondaries, as noted, are probably opening too quick which sets off a lean condition then rich again, primary needles are probably stepped too tiny at the step, big enough on the top step to help run and cruise fairly decent, so find the numbers for the 400 and the Carter TQ and get the carb dialed in and get the timing adjusted, go from there.
i would have to agree! i feel like a vampire every time the sun comes up lately lol.ImperialCrown said:
i will have to do the timing dot the next chance i have a friend over to lend an eye an a hand. but how will i know what the advance amount is?
i did originally get some "pop back" through the carb before i had the timing even close. so yes it is a back fire now but i believe that o be due to my setting on the mixture needles which im working on now.
ok i thought it was clockwise for advance... that just tells me again that the cam advance is just a bad idea all together because i am having to run the timing quite retarded to get a decent idle.
ok so i didnt pick my plugs because they work in lawnmowers... that was a huge joke on my part lol. (i read the plug part number wrong lol i thought you typed rC-12yc).
now i did do a cross reference and my e3.52 does cross to the rj12yc. actually it crosses to all rj champion plugs. dont know if thats a problem or not...
i used to be the parts counter and i crossed it myself. (on a side note... i really hate parts guys that get it wrong and give ones like i used to be a bad name.... its been 5 years and i can still out smart most of them.)
actually it crosses to all rj champion plugs. dont know if thats a problem or not..
as for the cam advance your statement is confirming my fear... that i did that advance for no reason lol.
i had heard that it does numbers for bottom end power but slightly takes away from top end. sounds awesome right? well i though that never finding a reference as to whether it was a stock cam or aftermarket. so naturally i ASSUMED i thought it might work.... apparently lesson learned.... which sux lol. my dad taught me how to spell that its [I should have my mouth washed out with soap for using such terms] u me. lol one of these days ill remember that.
essentially the e3 plugs cover all those ranges because they are hotter than all of them. hence why in newer cars they blow holes in the pistons.
i believe the cam advance is the source of all my problems. i am going to go in and back it down to factory reseal everything and try it again. at this point nicely enough itll be easy to pinpoint tdc on somewhere i can put a light on it lol.
still want to know how to measure 10 20 30 and 40 degrees of timing tho...
basically i am going to start over at zero and put everything at a baseline starting point and try again. also should i get a heat shield for my fuel pump filter and lines up front? they are right next to that header tube there.
Joined
·
20,101 Posts
Tearing the front of the engine off to change 4 degrees isn't going to fix the problem, the different companies do up to 8 degrees for different cams to make adjustments to different engine applications (truck, car, heavy car, light car, etc.), and Crane states they advance their cams 4 degrees initially. This is not to say there isn't a problem with the camshaft itself, it does happen, bad cut cams are out there. How long have you been running the cam, carb, etc, and when did this running issue start?
its factory cam. and it had a similar issue when i first bought it altho i thought it was just a tune up issue plus they had points on it. this is the first time starting and tuning after putting on the 4deg cam advance, m1 intake, 1 inch spacer, rebuilt thermoquad off of a 440, orange box ignition with electronic pickup dist (that was a fun swap over), and hooker headers with the e3.52 plugs, also 8mm plug wires. its a 78 cordoba with the p code 400 high performance.
i might add the car sat for 8 years prior to my buying it.
or rather its the original cam
i might add the car sat for 8 years prior to my buying it.
or rather its the original cam
Joined
·
20,101 Posts
Since it is a new setup, start with the carb. I had a similar issue with a 340 TQ on a 318, running rich and all kinds of fun, had to get the smaller jets and needles, adjust the secondaries a little bit to get it dialed in properly. The single plane intake isn't helping any given the vacuum signal almost completely drops out the bottom as soon as the carb blades are opened and the engine has to catch up to it, and no amount of cam advance or retard is going to fix that issue so you have to adjust what you have. Right now it is too much fuel tuned to a larger engine.
as for the compression i did put in 0.020 compressed thickness steel shim head gaskets in which increased it some... not sure how much dont know the numbers to do the calculations for that.
should i be able to get the factory needles and jets or do you have a suggestion on which ones i need?
also i know how to adjust the secondary air flap.... but how do you adjust the secondaries themselves?
as for the springs.... well i gutted my 318 dist for the electronic pickup and housing (the housings measure exactly the same) because the previous owner put in a points style dist. in and there was no place for the wires to come out for the pickup. i may have gotten the springs mixed up... good news in i still have all the leftover parts from the other dist.
will i be able to tell which springs are the right ones by looking? or should i just invest in the new ones?
should i be able to get the factory needles and jets or do you have a suggestion on which ones i need?
also i know how to adjust the secondary air flap.... but how do you adjust the secondaries themselves?
as for the springs.... well i gutted my 318 dist for the electronic pickup and housing (the housings measure exactly the same) because the previous owner put in a points style dist. in and there was no place for the wires to come out for the pickup. i may have gotten the springs mixed up... good news in i still have all the leftover parts from the other dist.
will i be able to tell which springs are the right ones by looking? or should i just invest in the new ones?
Joined
·
20,101 Posts
Factory springs are thick, aftermarket are thin wire. From there, the thick ones are, one so heavy the eyelet actually has a slot for the centrifugal advance pin to slide back and forth in it before the spring actually starts stretching and the next heavier one doesn't have the slot in the end of the spring. The aftermarket springs are all color coded and the number or wire turns determines their strength.
For the carb parts, once you find the correct numbers you have and compare to what is actually in there, not positive but I do think you can get Edelbrock/Carter parts that actually swap the same. Kind of why I either prefer the proper carb or Holley myself.
For the carb parts, once you find the correct numbers you have and compare to what is actually in there, not positive but I do think you can get Edelbrock/Carter parts that actually swap the same. Kind of why I either prefer the proper carb or Holley myself.
after doing some research ive found (unless you know something i do not...) the you cant buy jets and metering rods for these carbs anymore.... at all.... would you recomend a 600 cfm eddy? or do you know where to get jets for my carter? i suppose if not the third option is robbing a salvage car of its jets and rods. all needles and seats are the same on all carters so i assume by "needles" you meant the metering rods.
also where can i get the spring kits?
also where can i get the spring kits?
i agree 100% valiant67... but im still afraid that the carb may have to be relaced due to lack of aftermarket jets and metering rods.... specifically the secondary jets. i have a friend to help me with the tdc marks today... but once tdc is found how will i know what the degrees advanced or retarded is? seeing as i dont have marks for either.
Joined
·
37,280 Posts
Once you find make your TDC marks, you can get a timing tape (it's basically the same for any Mopar V8) which applies to the damper and has marks for degrees of advanced or retarded timing marked. Or you can get a timing light with a dial in advance/retard and you only need the TDC marks.
As for the carb, since the Thermoquad is a vacuum secondary design they don't tend to have the over rich problems a mechanical secondary design does because the vacuum controls how much it opens up. It could be lean, but it sure doesn't seem like that would be the case.
As for the carb, since the Thermoquad is a vacuum secondary design they don't tend to have the over rich problems a mechanical secondary design does because the vacuum controls how much it opens up. It could be lean, but it sure doesn't seem like that would be the case.
Joined
·
20,101 Posts
Going down to a 600cfm carb is just going to choke the engine and not make you happy at all, that is too small for a big block with your build.
Anybody on here have a 400 B block stock 4bbl carb parts? I know they are out there, more 400s were built than 440s, so we should be able to find something.
The distributor spring kits can be gotten at O'Reiley's and most any speed parts accessories in a parts store. Doesn't matter if it is a GM set, the springs are the same, the counterbalance weights are not, but you want the springs. Costs a couple bucks.
Anybody on here have a 400 B block stock 4bbl carb parts? I know they are out there, more 400s were built than 440s, so we should be able to find something.
The distributor spring kits can be gotten at O'Reiley's and most any speed parts accessories in a parts store. Doesn't matter if it is a GM set, the springs are the same, the counterbalance weights are not, but you want the springs. Costs a couple bucks.
Joined
·
37,280 Posts
There were tons of 400 cars with the 4bbl Thermoquad setup. Most of them were Lean Burn standard output 400s in the late 70's C bodies and Cordobas. But the Lean Burn carb won't have a vacuum advance port for you. Does the 440 carb you are using have the vacuum advance port? If so you can keep the baseplate and use the guts from a 400 carb. But I don't think the carb is the real issue here.
yea its got the vaccume advance port. its a non emmision tq off of a 440. my father actually has rebuilt this carb 3 times in his life and i and the one to rebuild it the 4th lol.valiant67 said:
id have to find a 400 with a tq first which shouldnt be too hard... just sux to have to rebuild another one lol wether im using my baseplate or not. but like i said before im going to wait untill i get the timing and the mechanical and vaccume advances correct first.
the only part of the secondaries that is vaccume is the flap in the airhorn.
the actual venturies (i think thats what the butterflys are called) for the secondaries upen at a cetrain point in the mechanical throttle and im wondering (for future reference if there is a way to adjust the timing of when those open and how.
ill be picking up the springs and the timing tape friday morning when i get paid.
after timing the motor i will let you all know if the carb is still giving me trouble.
also should i put a heavy spring and a medium heavy spring on there or a light and a heavy? and what size is the allen for adjusting the vaccume advance?
Joined
·
20,101 Posts
Go back to my previous post which describes the springs in the distributor, easier that way. The venturi is the tube shape through the carb and the butterflies are located inside the base of the venturi. The secondaries open by way of a connecting linkage rod on the passenger side of the carb, between the slot and the linkage, the secondaries could be altered, but it doesn't matter too much unless you want to reduce the ratio of opening to the primary given the vacuum signal secondary butterflies which reduce the amount of air pulled through them until it is needed.
The secondaries can open but until the vacuum opens the butterflies, nothing should be happening in the secondary area. If the springs are set to low on their tension, you will go into a lean condition. Set the secondary lockout so that they cannot open and floor it. If the front is set right, you will not have the lean out condition. Then you will know if it is front or back of the carb.dana44 said:
1 - 20 of 23 Posts
Join the discussion
Join now to ask and comment!