350 sb stumbles, timing is 51' retarded

Ok, here is the sitch. Bought a 75 scottsdale c-10 longbed with a 350 sb 2 barrel, RWD. Needed a battery and a fuel pump, but otherwise ran. FF to Pomona roadster show weekend, picked up an edelbrock performer mani for like $20, and a holley 850 from a 454 for like $10. At this point the truck runs fine "after replacing the mech fuel pump "PITA" I uninstall the current setup and install the "new" one after rebuilding the carb with the appropriate holley kit "just called and asked" I purchased new plugs and wires "no. 8 was almost done with, due to heat I think, no silicone left" I install everything, torquing the intake mani bolts according to spec, after cleaning everything thoroughly. The engine won't run right, why? I don't have a clue. I did notice that priviously, the timing mark was clearly visible in the "big" valley or 0' this is with the factory gm HEI ignition, I also noticed that the old plug wires were not run the same way as the new ones, in the "gm correct, from mitchells" way, I did not record this information, much to my dismay later. The old plugs showed signs of lean fuelling "bad pump remember?" but other than that still good, replaced with delco coppers gapped to 60 for HEI. Tried tuning the fuel down for idle, and also adjusted the lash for hydro lifters. The engine stumbles, ok, bad plug or wire right? wrong! checked em all "plug to block method" The timing mark doesn't show up so I advanced the timing to 51, no I didn't studder 51 degrees advance, it is now hopping roundabout the big valley or 0'. I did this using a digital timing inductive pickup light and held the up arrow untill the timing mark showed up. I had it on the no 1 "on the front drivers side" piston The timing order is correct, checked it only ten or so times, wires and plugs are brand new. I know what you are thinking, OH! the guys harmonic balancer rubber has worn to the point that the outside has rotated and his timing mark is displaced, WRONG again, pulled the plug and rotated the engine by hand "PITA" until the compression stopped and the top of the piston was clearly visible in the hole now vacated by the now missing spark plug. I am stumped, the timing mark is right on the money. It ran before, possibly with a different firing order? unknown. now it runs but runs and stumbles, the lash helped the idle a little, but it revs, but won't take a load. I am a little frustrated and very confused. Any help would be greatly appreciated. I figure there will be a peanut gallery following such as "hey! you need some more motor for that carb? he he" This is indeed the HAMB and such trollery is expected from the fine community here. It does impede, although only a little, the progress so I would ask that you keep it to a minimum or post it elsewhere, thanks.

Semper Fi,

Sgt Kevin A. Davies, USMC

pictures on my next post, I promise

 

Here are the pictures I promised more on my NintendoKD photobucket account

 

You are sure the balancer didn't spin??? Too bad you didn't note the orig. firing order---not that you should have suspected something was wrong. I dunno--I yield to the wrenchers.

 

850 seems way big. Perhaps he used a different post for #1 wire.

 

did you check the timing with the vacuum line disconnected and plugged? try setting the timing with a vacuum gage.

 

Vacuum leak

 

long time since i looked at a chevy,but isnt #1 on pass side?seems like it is good luck,jack

 

As in the picture the #1 is located on the drivers side, the hei is slightly different, however in that it is rotated slightly counterclockwise about 12.5 degrees from shown stock and the no 1 seemingly points at the no. 1 piston.

 

I have never done this. How would I do this properly with the engine stumbling so? I plugged the vaccum line from the front of the butterfly plate, left the big line connected to pcv, and the brake booster connected to the nipple on the manifold. there is only one other hol, which I blocked but produces no vaccum from the front bowl on the carb.

 

Forget the timing light for a minute. If you start it up and can't time it by ear to run good,then it's probably not a timing issue. But if it seems you cant turn the distributer far enough to run right,because it bottoms out against something,(firewall,intake,etc.)then you may need to rotate the wires on the cap one position. Or pull the distributer and move it a tooth in the direction you need to go.

If that doesn't cure it,I would pull the carb and make sure you have the right gasket under it.Make sure it covers any area on the carb and intake that could cause a vacuum leak.

If you have access to a known good carb you can borrow,install that and see how it runs.

 

Advancing the timing 51 degress makes me think the Distributor is a few teeth off. try and move all the spark plug wires one space clock wise ( that should retard the timing ) then reset base timing to about 32 degress with no vacume. and yes that is a big carb 650ish sound more likely.

I see a spacer plate under the carb, that would require more timing alone but 51 degress sounds crazy for a stock engine.

MrC.

 

OK to start with you must have on helluva small block to support that 850 Holley. IE that is way more carb than your engine will handle.

I am guessing that the big valley 0' thing is some sort of 29 palms lingo. As well as some of your other statements, what I am understanding is that you think your timing is set on 51 degrees BTC and you are not sure what your firing order should be but you think that it is wired correctly.

You firing order should be 18436572. The even number cylinders are on the pass side and the odd number cylinders are on the drivers side. The distributer spins clockwise. It does not care which terminal you use for the #1 plug wire as long as the rotor is pointing at that terminal when you want number 1 to fire.

I am not sure how you are coming up with 51 degrees advance at the outside most your timing marks on a stock SBC will go to 14 degrees. You are checking your timing with the vacuum advance disconnected, if not you should be.

The best way to determin TDC or 0 degrees is to take the rocker cover off and turn the engine clockwise until you see the intake valve close and then roll it until the timing pointer is pointing at 0 degrees. This is making the assumption that you have the correct harmonic balancer and that it has not slipped as has been mentioned. Never the less when the intake valve just closes it is ready to fire. If you remove the distributer cap and turn the distributer until the rotor is pointed at the number one terminal you should be ball park ready to run. Put the cap back on and outside most you will need to do tweak it a little.

Getting back to my original response you are not going to get your SBC to run well with that carb. 850 CFM is too damned much air for you engine.

Remeber this one thing son, when all else fails improvise.

 

The carb pictured is not an 850. What's the list number?

 

I also agree that an 850 is way too big, and probably will never get rid of the off idle stumble. A 600 or 650 vac secondary is much better suited for that engine and will make it run like a top. Aside from that check your timing again but this time just pinch the line from the vacuum advance to the carb. Turn the distributor down to where you have 20 to 25 degrees at idle, if is starts to die turn the idle up a little bit, if it seems like its really gonna die then your proble a tooth off on the distributor.

Setting the distributor in.
rotate the motor until your coming up on TDC for #1 and stick your finger on the spark plug hole while your rotating the motor close to TDC to make sure both valves are closed. Next line up the timing marks on the balancer and pointer. Next pop the cap off the distributor to see where the rotor is pointing, then line up the cap to see what post its pointing at on the cap. Is that the post that you have for #1. if not pull all the spark plug wires and make that post #1 and continue clockwise on the cap through your firing order IE 8 will be next then 4 then 3 so on and so forth. Usually I like to have my #1 on the cap around the drivers side but it doesnt really matter at all where it is as long as you followed the previous steps. After you do this re set your timing and see where your at, if its still a no go I would look at the carb

 

I was going by what he said, looking at the pic that is most likely an 1850 600 CFM vac secondary. A good carb for the SBC.

 

did you drop the distributor back in properly? where is distributor getting vacuum from? what is that canister on passenger side of engine that you seem to have distributor vacuum line taped into? for base time pull vacuum line off distrib and cover tube on vacuum cainister with rubber cap or strong tape. put a small bolt or something in vacuum line to block it off. then try timing. you can get things running real smooth without timing light-then dial in with light. seems like plug gap is too wide. why running hose from near top of carburetor to PCV? need manifold vacuum for PCV like from port tube at rear of carburetor base as seen in first picture. sure about what carburetor you have-list numbers usually stamped on front of base. where is brake booster getting manifold pressure from?

 

I agree the carb is not an 850, probably a universal 600cfm vacuum secondary (1850 is the model). I doubt you could have used a rebuild kit for an 850 on it because so many gaskets would be different, but if you did that could be the problem.

More likely there is a vacuum leak somewhere - have you checked for an unused port on the carb?

Also is the spacer under the carb open or a 4-hole? The performer is a 2-plane manifold and gets a better vacuum signal to the carb when the left and right sides stay isolated, like with a 4-hole or no spacer. I don't think that would be your main problem but it should help it run better.

 

^^^^^^ they make an 850 side hung float vac secondary, with a single metering block, and rear metering plate, you cant tell by looking at it. Check the numbers again in your holley book guys.

 

that looks like a vacuum secondary 600 cfm.sounds like the timing is to low.also my chevelle did this it turned out to be the accelerator pump squritter jet was stopped up

 

Id lower the plug gap. .060 was for emissions stuff back in the 70s and unless you know your coil is really strong its super hard for it to jump that big gap. Id lower them back to about .045...

 

^^^X's 2^^^^^ 60 thou is gonna work your coil to the bone.
Also-make sure you remembered to put that little gasket under your dizzy or you've got another place to loose vacuum.

 

If you are showing 51 degrees at idle, you must have the vacuum advance hooked up directly to the intake (non ported). Look for the vacuum leak, set the timing with the vacuum line off the distributor and plugged, and work out from there.

 

I have plenty of movement in my distributor, it is not bottomed out against anything I will check under the carb to make sure that there is no leak. Is it possible that the intake manifold isn't all of the way on ? I hope not, I put it on without the valve covers so I could be sure it lined up right. I will have to try a known good carb option when I can get my hands on one.

 

I think you probably did ok putting the intake on.It's pretty foolproof.You might take a look at the gaskets to make sure they didn't slip down when you put the intake on.Should be pretty obvious if they did.

Also,Chevy used different locations for their timing pointers over the years. One spot was at about 12:00 looking at the front of the motor,the other was at about 2:00. Each position takes a different damper and if you use the wrong one,a timing light will not be much help in getting it timed.
This may be why your timing looks 50 degrees off.

Edit:I see you already checked for that way back in post#1.

 

This particular carb has vaccum secondaries, it will run on just two barrels just fine untill I get the other speed parts. The distributor has plenty of free play, has a gasket, and is not so tight that it can be turned. all vacuum is plugged. I realize that a spacer will require more timing.

 

I am guessing that the big valley 0' thing is some sort of 29 palms lingo. As well as some of your other statements, what I am understanding is that you think your timing is set on 51 degrees BTC and you are not sure what your firing order should be but you think that it is wired correctly.

You firing order should be 18436572. The even number cylinders are on the pass side and the odd number cylinders are on the drivers side. The distributer spins clockwise. It does not care which terminal you use for the #1 plug wire as long as the rotor is pointing at that terminal when you want number 1 to fire.

I am not sure how you are coming up with 51 degrees advance at the outside most your timing marks on a stock SBC will go to 14 degrees. You are checking your timing with the vacuum advance disconnected, if not you should be.

The best way to determin TDC or 0 degrees is to take the rocker cover off and turn the engine clockwise until you see the intake valve close and then roll it until the timing pointer is pointing at 0 degrees. This is making the assumption that you have the correct harmonic balancer and that it has not slipped as has been mentioned. Never the less when the intake valve just closes it is ready to fire. If you remove the distributer cap and turn the distributer until the rotor is pointed at the number one terminal you should be ball park ready to run. Put the cap back on and outside most you will need to do tweak it a little.

Getting back to my original response you are not going to get your SBC to run well with that carb. 850 CFM is too damned much air for you engine.

Remeber this one thing son, when all else fails improvise.

0' big valley represents the timing marker on the engine little valley, little valley, little valley, BIG valley, little valley. motor is wired correctly, with the aforementioned firing order. I checked for tdc when the #1 piston was on it's way up and I know this because my finger was on the plug hole feeling the pressure of the air. once at the top, I checked for my timing mark, BINGO right in the BIG valley, or 0'. Thanks for the advice.

 

got it floating around somewhere, I'll get it for you

 

That carb should work fine if jetted and tuned properly,I think some quadrajets are 850 cfm.

But,I had a cammed up 305 that was guttless with a couple quadrajets I tried. I put the 850 Holly vac. sec. back on and it went back to screaming.

 

Everyone here seems to want me to fix my timing, there is one very big problem with that, I cannot see my timing mark, I have no Idea whwere it is so I cannot set it "properly" I will try tuning it by ear using a vacuum guage. I did notice some soot on the number one plug, which indicates too much fuel, I will tone down the idle fueling a bit. thanks

 

I can only tell ya what I think I know, the holley guy on the phone, "Mike"' I think his name was, told me it is an 850cfm offa a 454BB I have the list no. but it's floating around on a piece of paper somewhere.