whos an older sbc carb motor expert

   #52  

Wretch

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I don't know BilletMan, that is one of those electronic bits that either works of doesn't.

I wondered aloud about it even being the right one installed, earlier, since there are different curve values between SBC engines apparently depending on the vehicle/use.
ECM aka engine control module.

Probably cheaper to replace the whole thing as mentioned.
 
   #56  
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baby didnt really let me get out to the garage and fuck with it yesterday..and i spent this afternoon working on her new playhouse!

was hoping to get out there tonight, but its not looking good there either...will update thread when i get the carb apart! (with pics)
 
   #61  

Wretch

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LS swaps ain't cheap and with all the SB laying around, it becomes difficult to justify the more expensive route unless you're going to use it to win at the drag strip.
 
   #63  

Wretch

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what? ls swaps are retarded cheap these days. under 1500 easy.
Really?
I must have been out of the loop too loong then.

I seem to recall it being around $3500.00 the last time I looked and that was with using used parts.

I have a G body I'd love to put an LS in but, it would need some serious suspension/brake upgrades to make it a reasonable daily driver.
 
   #64  
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shit no...you can find a yanked out 5.3ls motor from any one of millions of 2000-2008 or so chevy trucks out of any junkyard...tons of folks even make a business selling them yanked out complete with ECM.

anywhere from 600-900 bucks for a 5.3 few sheckles more for a 6.0. (iron ones anyway)

add in a 4l60 trans for another few hundred and its not uncommon at all to have a full swap for around a grand. heck ive even seen complete tahoes and yukons and sierras that have been wrecked or salvaged for under 2k with those drivetrains in them.
 
   #65  
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i always keep on the lookout for a decent deal to snag up...this truck will certainly get an ls upgrade (if not just for the 4l60 auto trans to upgrade from the th350 in it now).

but it just wasnt worth yanking out a good running sbc just to upgrade to an LS for a truck that drives under 1000 miles a year or so!
 
   #66  
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not convinced it was the source of the problem, but it definitely benefited from a nice carb cleaning. first shot after removing the cover.

1549601186215.png

good bit of stuff gunked up at the bottom of the bowls, but nothing was clogging the ports...even shooting air into all of them and the horns after removing and cleaning those... and nothing significant came out...just a nice layer of buildup shown here.

who knows...maybe this could be the cause of all my issues, but i kind of expected alot more bullshit than that to clog up the carb enough to drag the motor down to what ive been experiencing lately.

will take another test drive tomorrow.
 
   #68  

pimpslayer

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If you go for a ride expecting it to drag down after it gets hot, have someone standing by when you get back to the garage.

Have them help you keep it running while one of you dribble a little bit of gasoline down the throat of the carb. If it doesn't pick up and run better, you have an electrical problem.
 
   #70  

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Most driveability issues I've run across are multiple issues of a little shit here and there going wrong.

That carburetor is/was nasty inside with varnish.
You might check any rubber lines from the tank to see if the ethanol broke them down enough for them to collapse.
Some short pieces from near the tank connecting to the rigid lines too, if I recall correctly.
Ask for specific new fuel line that'll be resistent to breaking down.
 
   #71  
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id already replaced the rubber in the system (as well as the fuel pump) with modern stuff...the og hard lines are still there though.

really need to find a tank to put under the bed so i can get it out of the cab...never much liked sitting on 10 gallons of gas!
 
   #72  
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Can you see if there's shit in the bottom of the tank? If you have a pick up screen that's picking up shit the whole time it's running, that obviously would make it not want to run after a while. Shut the truck off, some of the shit drops off the screen, back to the bottom of the tank... truck runs again.
 
   #73  

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VC is right, clogged sock on the pickup would be a game killer as far as staying running goes.
 
   #74  
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not a bad suggestion for sure! def cant see the bottom of the tank but can likely pull out the pickup tube.

im not sure its anything more than a straight tube...id be shocked if it has any sort of filter on the end of it.
 
   #75  

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Hit the distributor with a hair dryer before you run it and see if the problem is there from the get go. You are better off with a good used dizzy than that chink POS
 
   #76  

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I'm feeling a coil / distributor issue that doesn't show up until it gets hot. Possibly a fuel pump that's working just good enough until the diaphragm warms up a bit and loses efficiency, but you say there's plenty of fuel in the clear filter, so I'm doubting that. Edelbrock carburetors are pretty trouble free, so I don't think that's your issue, unless you're getting a vapor-lock situation going, which is also a possibility. Might need an insulating spacer between carb and manifold and (or) and electric fuel pump. It seems vapor lockish or sparkish.
 
   #79  

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I have a G body I'd love to put an LS in but, it would need some serious suspension/brake upgrades to make it a reasonable daily driver.
I traded a project car I lost interest in for a junk GMC pickup with a 5.3 a year or two ago. My intention was a new engine for my '94 C1500 stepside, which has a 305. The guy I got the truck from had a sweet, late 80's Cutlass 442 with a 6.0 swap. He was telling me how easy it was, but he works in a fabrication/hot rod shop, so we probably have different definitions of "easy." I also want to keep the manual trans, which looks like a pain in the ass with an auto trans donor. Anyway, two weeks ago, a guy drove by and saw the GMC sitting in the weeds off my parking lot, and made an offer more than I had in the whole shebang, so that ended that dilemma for the immediate future. The 305's got about 190K on it, but still runs great, doesn't smoke or burn oil or anything. I only drive it 1200 miles or so a summer. Just think it might be more fun with a bit more snap.



 
   #80  
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I'm feeling a coil / distributor issue that doesn't show up until it gets hot. Possibly a fuel pump that's working just good enough until the diaphragm warms up a bit and loses efficiency, but you say there's plenty of fuel in the clear filter, so I'm doubting that. Edelbrock carburetors are pretty trouble free, so I don't think that's your issue, unless you're getting a vapor-lock situation going, which is also a possibility. Might need an insulating spacer between carb and manifold and (or) and electric fuel pump. It seems vapor lockish or sparkish.
yea its got one of those plastic spacer rings on the intake (also an edelbrock performer intake)

ill get it sorted eventually...however an 18mo old kid really limits the time I get to fuck off in the garage!
 
   #81  
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I traded a project car I lost interest in for a junk GMC pickup with a 5.3 a year or two ago. My intention was a new engine for my '94 C1500 stepside, which has a 305. The guy I got the truck from had a sweet, late 80's Cutlass 442 with a 6.0 swap. He was telling me how easy it was, but he works in a fabrication/hot rod shop, so we probably have different definitions of "easy." I also want to keep the manual trans, which looks like a pain in the ass with an auto trans donor. Anyway, two weeks ago, a guy drove by and saw the GMC sitting in the weeds off my parking lot, and made an offer more than I had in the whole shebang, so that ended that dilemma for the immediate future. The 305's got about 190K on it, but still runs great, doesn't smoke or burn oil or anything. I only drive it 1200 miles or so a summer. Just think it might be more fun with a bit more snap.



funny you mention that, had a buddy just last night offer his old 2000 trans am complete with ls1 and auto trans for 1k...looks like a swap is coming regardless!
 
   #82  

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If it's already got a spacer ring it's probably not that. I had a clients' old Pontiac that had a weak mechanical fuel pump. I'd never seen that before as they usually either work or don't work. This one would pump o.k. when cold, then lose it's mojo as the engine heated up. Then it would just barely keep up if you were cruising slowly but give it any gas and the float bowls just didn't have enough in them to get you up a hill! I had a helluva time figuring that one out. At least it's got a brand new HEI ignition in it that made absolutely no difference!
 
   #83  

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Didn't those old mechanical small block Chevy fuel pump develop a problem with the arm or the spring on it? Seems like it was a common issue back in the day.
 
   #84  

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I'm not sure M/C. I just know that when I finally just replaced the one on the Pontiac out of sheer exasperation, the problems went away.
 
   #85  
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fuel pump is also brand new (swapped it when i did the cam since it had to come off anyway).

it certainly appears to provide plenty of punch visible via the filter. i cant imagine those things were meant for more than single digit psi either way.

im hoping for my next test drive im able to hop out and have someone keep it running while i can take a look under the hood and shoot some gas or carb cleaner down into it. its response to that should eliminate at least half the possibilities.
 
   #86  

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Ignition problem, module in the distributor...heat sensitive...
 
   #88  
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finally got out to try to start it, damn thing starts right up and shoots to nearly redline even without my foot on the gas.

thats super fun...clearly i did something wrong in reassembly!
 
   #89  

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finally got out to try to start it, damn thing starts right up and shoots to nearly redline even without my foot on the gas.

thats super fun...clearly i did something wrong in reassembly!
You're going to have to do better than that. Did you take something apart and put something back together? Is it fixed now, or not? If it's revving up high on it's own right after startup, that sounds like a fuel problem. Choke? Faaaaaack. . . I thought it was dying, not it's revving...
 
   #90  
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id rebuilt the carb a few nights ago (well, i say rebuilt...more like took it apart and cleaned it all out...pics above).

the truck is obnoxiously loud so i try to refrain from running it late at night and with a sick kiddo ive not had any time at all to go fuck with it since I put the carb back on.

today i was out there doing some woodworking items and decided to see if it would fire up...and it did. but i had to immediately shut it off due to it not actually idling but instead running up near 4k rpm with my foot not on the throttle.

did a few cursory looks, no vaccum lines are loose or disconnected, choke is working as it should (engages/disengages the flapper as normal)...throttle cable looks to be fine, its certainly not stuck open and has normal free range of movement and return spring works as it should also.

im not terribly sure what i could have done to cause something like this, its not like these old carters are terribly complex! if it was just a slightly high idle id start messing with the low/high speed adjusters...but the fact that it shoots up to 4k leads me to believe something more significant is off.
 
   #91  

BigGar

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Sounds like the butterfly must be partially open. Maybe it's up on a choke cam or the fast idle is set way too high?
 
   #92  
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yea, its def getting air from somewhere...just dont see anything obvious at the moment.

i cant even fathom the fast idle adjustment would let it rev as high as it does.
 
   #93  

Wretch

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The linkage is closed and it's revving to 4K?

You have the gaskets properly in place under it?

Accelerator pump is working, squirting fuel?

Secondaries aren't still open when engine is off?

The last two is where I'd start looking.
 
   #94  

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More than a few times after I've cleaned a set of carbs, I've had to crank the idle speed screw out a few turns because it now has clean jets and passages. Over the years, the things start to run a bit off, and the guy just keeps cranking the idle screw in to keep it idling, and then it gets to the point where it doesn't run.
 
   #95  

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More than a few times after I've cleaned a set of carbs, I've had to crank the idle speed screw out a few turns because it now has clean jets and passages. Over the years, the things start to run a bit off, and the guy just keeps cranking the idle screw in to keep it idling, and then it gets to the point where it doesn't run.
Oh yeah. Always fun having a big Jap 4 cylinder go to the redline after just a tap on the starter button. :eek:

Wakes up everybody in the Service Department...
.
 
   #99  
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well sho nuff it was the idle adjustment screw!

disconnected the throttle cable, backed the adjuster all the way out and cranked it up...idled great! Id have never thought that would have as much play in it to crank an idle up that high!

reattached throttle and let it heat up for at least 20min and took a short drive, all seems well! will try a longer drive later this evening.
 
   #100  

Master-Cylinder

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well sho nuff it was the idle adjustment screw!

disconnected the throttle cable, backed the adjuster all the way out and cranked it up...idled great! Id have never thought that would have as much play in it to crank an idle up that high!

reattached throttle and let it heat up for at least 20min and took a short drive, all seems well! will try a longer drive later this evening.

If you had to crank the idle speed screw way out, and it also runs better, sounds like you did the job right. But, a longer test drive will tell the tale.
 
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