|01-06-2013 12:19 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 07:21 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 08:09 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 07:42 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 07:11 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 06:55 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 02:56 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 02:23 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 08:35 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 08:29 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 08:10 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 07:11 PM|
|89k1500||Well I finaly got some time and messed with the fuel system. Hooked the electric pump up and now I have a solid 6psi. Now when I drive it it still backfires in third and higher gears, but it has a LOT more power. I havent messed with the carb settings since changing the pump(it was 30 degrees outside) and I still think the timing is off, but so far there is marked improvement!|
|12-08-2012 01:04 PM|
Cam has 226 int./234 exh. @ 0.050" lift and needs no where near 26 degrees initial. Start around 16-18 degrees initial and work up from there.
Generally it is better to get the timing worked out, then go on to carburetion- as long as it's running well enough to set the mechanical (should be all in by about 3K rpm).
|12-08-2012 11:35 AM|
The regulator that I am running now is a mallory 3 port competion regultor(return style) PN 4309. I'm going to hook up the electric pump when I get a chance and see if that cures some of my issues. The more I read on setting timing and what-not the more I think I need to address that as well.
Thanks again for the links and info! If you guys have any other helpful links on this stuff feel free to post em. I have no problem reading and I am new to the carburated world, and my brother works weird hours so it looks like if this truck is gunna get dialed in, its going to take effort on my part too. =)
|12-08-2012 06:52 AM|
Thanks for the links and other information guys! Looks like I have a lot of reading to do. I think i'll buy a limiter plate and the crane advance kit and try and dial in the timing.
"If you slowly accelerate and shift into 3rd gear,coast for awhile the hammer it,does it instantly fall down or is it ok for a few seconds?" I will have to try this and get back to you!
I will more than likely switch back to the electric pump also just to eliminate the fuel pump as the problem.
Fuel filter was one of the first things to get changed. =)
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