|01-06-2013 01:19 AM|
Very Involved Problem 400sbc
You are not the first person I have read about having problems like you had. Most of the time it turned out to be a distributor bought from ebay for $50. The distributor was probably a Procomp brand. Glad you have it fixed.
|01-05-2013 08:21 AM|
Just to update,
Pretty much we replaced everything! My brother bought a new ignition system for it ( with a digital controler box, new coil, and new distriburator) and I bought a new 650cfm edlebrock carb. After puting all that on the truck runs awsome! Before putting the stuff on, the problem got worse, and i'm pretty sure it was the distriburator. more specificaly the ignition module in the distriburator. By that point I was tired of screwing around and just wanted it fixed. =)
|12-11-2012 09:48 PM|
Change the plugs and check them for heavy black or burnt light brown look. After a short run.
Do you have the accelerator pump in its full on position where the lever has the greatest movment on the pump. That may help if it only help a little it will probably need larger jets.
If you run out first and second up to redline it runs fine? What if you go straight to third at redline in secnd so rpm does not drop will the engine take wot then. Also dont over do it trying just wanted to ask if you have tried it. Dont want to see you hurt it just to see. If wot is ok at high rpm then needles may need to be tweaked. Larger jet will be needed if wot throttle is not working in any gear unless its granny gear trans where third is the first long gear. Also does wot make any power or is it still lame in first and second.
My own lean rich test is simple does it run better when the air is cold or hot. Runs better in the cold then its too rich in the hot its to lean. If the colder it gets the worse it runs then you know its way to lean. Bigger jets or more fuel pressure are in order. Runs better in cold weather then its jetted to rich and fouling the plugs.
And yes timing is easier to check most of the time. I also would not try the holley a second time.
|12-11-2012 09:09 PM|
The timing is easier to get in the ballpark. In a lot of cases when using a GM HEI distributor, two medium or one medium and one light spring w/the stock weights will be about right. Then it's a matter of finding the initial timing it likes (good idle, good vacuum, carb idling on the idle circuit and not into the transfer slot), followed by limiting the amount of mechanical advance to keep the total timing from being too high. The total timing being too high is always the case because the initial timing is always higher than what the factory setting called for.
The MSD distributor uses bushings to limit the mechanical timing.,With the stock HEI you have to use screws like you saw in the link. When you get to that stage, if you need help someone can give you a hand w/that.
Lastly, during the process of finding the right amount of initial timing, you will need to readjust the idle mixture screws as you change the timing. And you'll possibly need to lower the curb idle speed to keep the mechanical advance from creeping in, or raise the idle speed if it gets too low.
|12-11-2012 08:42 PM|
I want to say it was heavier weights and lighter springs.
as for the link on Hot rodding your HEI Distriburator, I went there, read it, printed it off, and read it a few more times. Its good info I just havn't had time to implement said knowlege. Not to mention its cold as heck outside so my ambition level is low. =)
So should I do the timing before messing with the jets? (EDIT: Just read the last line of the last post, please ignore this question....lol )
|12-11-2012 08:11 PM|
The earlier you can bring in the mechanical advance, the better. The advance should be all in by no later than 3000 rpm in most cases. If you used heavier springs, that's going in the wrong direction unless you were having detonation.
Did you read the link I gave you on timing? ANY good timing info will do, it doesn't need to come from here.
Get the timing sorted out first, THEN the carb.
|12-11-2012 07:55 PM|
I talked to my brother and he said he didn't change the jets. We want to get a 650 but can't afford it right now(already had the 750 on a shelf). We had a 650(?) Holley given to us so he got a rebuild kit and popped that on(before we got the fuel pump issue squared away) seemed to make it worse. Probably because it was a Holley. =) Haven't tried it since getting good and consistant fuel pressure. It started way harder than the eldelbrock so I'm not overly excited about trying it.
I did however drive the truck to work and I acualy paid close attention to what was happening. First and second go good with no issues than as soon as I shift to 3rd and the RPMs drop below 1500 it backfired under heavy throtle. as soon as I top 1500 it gets better and at 2000 it pulled very well but is still "missing". The same goes with the other gears. anything below 1500 and it falls flat if i give it too much gas. If I lightly roll into the gas it is not nearly as bad and the higher the RPMs the more gas it will take.
So should I get and try larger jets?
Also I want to say we did put heavier weights on the distriburator(before the fuel pump issue) and I hav't messed with timing since. Might be till after CHRISTmas that I can get the lock out plates and jets. I'm not too worried about squeezing out as much power as it can give. I'm just trying to make the thing drivable without falling on its face.
thanks again for the help!
|12-10-2012 03:56 PM|
|lg1969||Increasing the jets will not get rid of lean bog. Because not producing enough RPM to make the jets work. He is working mainly on idle circuit until he have enough RPM for the main jets to come into play. The smaller the primary the more responsive the primary jets come in.|
|12-10-2012 03:36 PM|
At this point need to read the plugs and see if its lean or rich.
750 should be ok for most apps. 600 650 may make a few ponies moe down low but the 750 should run ok.
Might just be plugs at this point not sure since the fuel pressure change helped. Cleaning the plug may sort it out.
If you have another edelbrock around that you can swap and try i say try it but most ppl dont have an extra hp carb laying around the garage. It is certainly possible to get a bad carb from the factory. Another user on the forum recently had that happen to him and holley replaced it for fre and it resolved the issue. Unfortunely most manufactures will at least want to run over a testing proceedure and try to get things smoothed out over the phone.
A call to edelbrock might not be a bad idea. They have good techs on hand usally that can go over the install and find any gottchas since they deal with the carb every day might be able to fix it faster than any other testing.
|12-10-2012 03:23 PM|
|lg1969||What you get is lean backfire. Your 1st and 2nd gear may be fine, But it may bog on 3rd gear cause by large primary. Your intention on your 4X4 is to produce torque not RPM. Use a 600 to 650 CFM carburetor. 750 is too much. Also increase the advance weight on the dist. Using a Qjet would be a better way to go.|
|12-09-2012 09:45 PM|
Heavy detonation will show up as spotting on the plugs. Black can be because the engine is missing or running rich. You almost need clean plugs to see how the engine is running. Do you have a spark plug cleaner or a way to clean them quickly. Maybe buy a few new ones and use them one at a time and see how they look.
Be sure to clean the plugs they may be fouled after missing for so long.
Do you have the edelbrock tuning kit or did you just buy jets?
|12-09-2012 09:35 PM|
|89k1500||oops, I was kinda unclear. I ment when we put the motor together we put the ebay distriburator in it. Its not a recent thing I have done while trying to troubleshoot the problem.|
|12-09-2012 09:29 PM|
Depending on the distributor that was on it, that could have made all- or none- of the difference. That's why it's a better idea to make ONE change at a time, so you know what helps and what doesn't.
In any event if it's running better, something caused it and that's a step in the right direction.
|12-09-2012 09:10 PM|
I foregot that I had put a distriburator on it from e-bay. Not sure if that makes it better or worse
SBC BBC Chevy 65K Red Hei Distributor 6501 R | eBay
not sure how good of quality it is. It was in another motor and that one didn't have any problems other than being tired.
What am I looking for on the plugs? I had em out today and they were kinda black. They were new when we put the motor together.
are you thinking I have too much timing and that is why I am setting it a 10deg?
|12-09-2012 08:31 PM|
I like to tune on a cold day but not 30 degrees. LOL
Now i would think its time to look at the plugs and see how its running or hook up some type pf lean rich guage even without wide band a regular o2 sensor really helps tune somtimes. But detonation should show up on the plugs. Also should be able to tune it out by setting the timing at 10 degrees and just test drive to see if it cleans up a little if not its surely carb realted. Unless the distributer is completely out of whack with mech advance worn out that should clean up the knocking a little. Maybe even a little less for short trip to see if its ignition problem. bad coil and bad modual are still likely an issue. Its never certain they are good unless they are new and tested.
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