I messed some more with my carb and dizzy....

MYBAD79

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OK, some questions have been answered in two previous threads. I am hunting a carb and timing problem after I installed a new carb and a new intake.

My other two threads regarding this problem ended pretty much in a dead end - I installed smaller jets and swapped carbs, no success... yet....

Let's start about ten days ago: I removed my Edelbrock 1405 600cfm carb and my performer intake and installed a RPM air gap and a 1812 800cfm Edelbrock carburetor.
The engine was running fine before I removed these parts.... no timing issues either....:banghead::banghead:

Engine: 383ci, 9.8:1 CR, Comp 230-236 dur hydr roller cam, Edelbrock RPM heads with 64cc chamber and 170cc runners

I started the engine with the new intake and carb and before I even got to the timing it started misfiring. The fumes were horrible - found the jets are bigger that they're supposed to be.

Instead of waiting for smaller jets I re-installed the smaller 600cfm carb on the new intake (air gap). It ran fine in neutral but not under load....It misfired in 1st or 2nd gear, 2000-2500 rpm, I push the throttle and it stutters, bogs and misfires....

I pulled the plugs and they were black...

Yesterday:

Changed the spark plugs and installed the small jets from the 600cfm carb in the new 800cfm carb, installed 800cfm carb and with the new plugs it seemed to run great.... set the timing at 14 degrees (initial) and rev'd the engine a few times. Fumes were not as bad and it did not misfire in neutral. Set the timing to 12-14 degrees advanced. Noticed that it advanced to more than 36 degrees but it did not ping.... set timing to 12 degrees (end of timing tab) and thought it was all fixed....

Today:

Took it out on the road and again, it still misfires under load... :sick:

Checked the timing again: 14 initial. Vacuum advance seems to be too much, looks like it's pulling close to 40 degrees (estimating, no timing tape).... Now my question: a new intake does not change the vacuum ??? I mean, it's not pulling more vacuum (lower pressure) on the can.... ???.... The advance can is stock so it should pull 24 degrees, plus my 12 initial I should be at 36 total... I never had this issue with the old intake and I've tested the new carb with large jets, old carb with its jets, new carb with smaller jets.... only thing that remains is the intake...

My last "test" today was to simply disconnect the vacuum advance: I plugged the port on the carb and again, it runs fine in neutral but in gear it just bogs and misfires at 2000-2500rpm, afraid to force it higher than that....

I'll get the AR12 (1838) advance can and the MRG928G spring kit just to make sure the distributor is ok.... not too convinced it's the problem because it was running fine before I had the glorious idea to mess with it.... is it possible there's something wrong with the centrifugal weight (mech advanced) ???

$700 for a new intake and carb and the car doesn't run anymore... could have had that for less..... :sick::banghead:
 
Do you have a stethescope?? if so, pull the probe off and use the hose or any hose, really next to your ear, and see if you have any air leaks from around that mani to the heads, maybe the carb base too...
 
Have not thought about vacuum leaks - I used new intake gaskets and RTV on the chinese walls.... the engine idles fine, I guess I can detect vacuum leaks with either carb cleaner or deodorant spray.... both should change the idle if sucked in....
 
If the only thing you changed was the manifold, and now it runs like crap, then....................................
Pull it off.
 
If the only thing you changed was the manifold, and now it runs like crap, then....................................
Pull it off.

I'm glad I have not sold the old manifold yet :)

Seriously: there should not be any issues with the manifold, it's supposed to be one of THE best manifolds for a street Chevy SB.... but there could be a leak.... would that make the engine misfire only under load and in gear when driving ?? In neutral I can let it rev and run as much as I want, it all seems to be just fine... as soon as I try to actually drive it all turns to $hit..... :bomb:
 
It's not the manifold, it's the gaskets.
If you JUST changed the manifold, then reused the carb and dizzy, and it runs like crap, then it's leaking.
Is this the one that raised the dizzy gear? Something just ain't right. Pull it off, and check it dry. Gaskets are cheap.
 
Is this the one that raised the dizzy gear? Something just ain't right. Pull it off, and check it dry.

No, the dizzy was raised because I use a .125" thick intake gasket AND a thick gasket under the dizzy collar.... I have used that thick gasket with the old manifold too.... but now that you bring this up it does (DOES) make sense.... I checked the intake manifold holes to head bolt hole alignment and determined that I need a thick gasket to make the holes line up. I thought that the decked block made the heads sit lower so a thicker intake gasket was required. Maybe I should have checked the gear engagement too... live and learn... this was a long time ago with the old intake and carb so I agree it needs to be fixed but I do not think it's a contributor to the current problem.

I'll pull the dizzy next weekend when I have the springs and vacuum unit from the "zone"....

Maybe I should just go ahead and get a spare gasket from Summit... :smash:
 
Is this the one that raised the dizzy gear? Something just ain't right. Pull it off, and check it dry.

No, the dizzy was raised because I use a .125" thick intake gasket AND a thick gasket under the dizzy collar.... I have used that thick gasket with the old manifold too.... but now that you bring this up it does (DOES) make sense.... I checked the intake manifold holes to head bolt hole alignment and determined that I need a thick gasket to make the holes line up. I thought that the decked block made the heads sit lower so a thicker intake gasket was required. Maybe I should have checked the gear engagement too... live and learn... this was a long time ago with the old intake and carb so I agree it needs to be fixed but I do not think it's a contributor to the current problem.

I'll pull the dizzy next weekend when I have the springs and vacuum unit from the "zone"....

Maybe I should just go ahead and get a spare gasket from Summit... :smash:

If you wish to verify it first, run an unlite propane torch along the top. Listen for the RPM change. If nothing, plug the PCV /vents off, and put a vacuum gauge on the dipstick tube and check for an internal leak.
Me, I would just go to square one. Something is just not right here.

I'm sure Lars will add to this tomarrow.
 
Something is just not right here.

I'm sure Lars will add to this tomarrow.

I absolutely agree that sumtin (spelled incorrectly on purpose) is not right here..... and I am looking forward to see what Lars thinks about this.... looking at how I installed the gaskets and how I sealed the intake I have a hard time believing it leaks... nevertheless: This really sux... like vacuum...
 
Soak the manifold to head area in WD40, if it's leaking there you will notice. Not so if it's leaking on the underside. I agree with Bird, a gasket probably shifter or there is some other issue, pull the manifold and check the gaskets. You should be able to see if they were clamped down. Heads are not angle milled right?
 
Soak the manifold to head area in WD40, if it's leaking there you will notice. Not so if it's leaking on the underside. I agree with Bird, a gasket probably shifter or there is some other issue, pull the manifold and check the gaskets. You should be able to see if they were clamped down. Heads are not angle milled right?

PerZACTly what happened to me once on a set of iron heads, someone angle milled the things, and of course they leaked on the bottom edge, and of course drove me crazy for a while, had to take the damn intake to a machine shop and told him to knock 20 mills off the top edge of each intake flange, sure enough, that oil on the bottom of the head passages, and stains on the gaskets told the tale I didn't wanna hear.....

and the thing that really smoked my ass about it was just setting the mani on there and doing a feeler gauge drag along the ends on top and bottom revealed NOTHING.....the dirty bastard......

:bomb::clobbered::banned:
 
No, the dizzy was raised because I use a .125" thick intake gasket AND a thick gasket under the dizzy collar.... I have used that thick gasket with the old manifold too.... but now that you bring this up it does (DOES) make sense.... I checked the intake manifold holes to head bolt hole alignment and determined that I need a thick gasket to make the holes line up. I thought that the decked block made the heads sit lower so a thicker intake gasket was required. Maybe I should have checked the gear engagement too... live and learn... this was a long time ago with the old intake and carb so I agree it needs to be fixed but I do not think it's a contributor to the current problem.

Decking the block would move the heads together (slightly). If anything, thinner gaskets would be required.
 
Not so if it's leaking on the underside.

I agree with Bird, a gasket probably shifter or there is some other issue, pull the manifold and check the gaskets.

Heads are not angle milled right?

I'll pull the intake, nothing else is going to fix it anyways.... new gaskets on order tomorrow.....

Decking the block would move the heads together (slightly). If anything, thinner gaskets would be required.

I just chose whatever lined up the intake manifold boltholes best... you're correct, I must have had a brainfart about the decking and moving the heads down.....
 
Dry set the manifold and gaskets, and check the China walls with a feeler gauge. The manifold bolts have washers, and the clearence holes should be larger than 3/8".
 
To be honest, I doubt it's a problem with the intake but I'll pull it anyways just to make sure... uncertainty is not my best buddy...

With all due respect : It's not that I just yesterday started working on engines: What really confuses me is that the engine runs fine in neutral, I can rev it to 3 or 4 K rpm and it runs just fine.... only in gear it stutters and misfires....

I guess what I'm trying to say is that I can't figure this out and I thought I was not too bad when it comes to a combustion engine.... :blush:
 
To be honest, I doubt it's a problem with the intake but I'll pull it anyways just to make sure... uncertainty is not my best buddy...

With all due respect : It's not that I just yesterday started working on engines: What really confuses me is that the engine runs fine in neutral, I can rev it to 3 or 4 K rpm and it runs just fine.... only in gear it stutters and misfires....

I guess what I'm trying to say is that I can't figure this out and I thought I was not too bad when it comes to a combustion engine.... :blush:

Join the club man, that damn Dodge 318 van was kicking my ass but good too, which is why I was cussing some p/o for having the rong injectors in there when we got it, among all sorts of other crap, must have had 1/2 dzn electronic parts for that thing, all the rong ones, in the bins behind the driver....he tried all the rong shit.....crazy...same exact symptoms, ran like shit when hot, fine when cold, but as you know in this weather, THAT don't last long....maybe to top of my hill, putting in my first smaller set of injectors it ran ever so much better, but still no go, going back to that small set it came with was totally messed up, and so 24 lbs set works fine....for 3 sets of injectors in that thing to cover the mess up someone caused....

:eek::surrender:
 
You can try this, it a little less PITA than removing the intake etc, but not by much.
Cover the intake plenum with a plate and base gasket bolted down, plug all vacuum ports on the intake, and duct tape the dipstick to the tube, cover both the valve cover holes with masking tape, use a air/sparkplug adapter in each cylinder, one at a time with less than 10psi while slowly rotating the crank. If you have an internal manifold leak, then it will lift one of the pieces of masking tape.

If you don't have the plate and adapter handy, then this might be more of a pain than it is worth.

Engines will run pretty good with no load (idle).
 
I was busy today: it's about 95F here in FL and it felt like 110F when I pulled the intake today.
The intake gasket was torn is several places, however that most likely happened when I lifted the intake.I used RTV sealant when I installed the intake so no wonder the gasket ripped into pieces...
New intake gaskets (thin and thick) are on the way, should be here tomorrow...

Also changed the jets and rods in the 800cfm carb: stock jets are .113 and .101, secondaries smaller than primaries ??/talked with Edelbrock tech guru and he confirmed that's the stock jet size....
Since it was running way too rich I used smaller jets for the primaries: 107 instead of .113.
The stock rods are .068x.047, I installed 063x037 which is #23 on the chart in the owner's manual and is 2 stages lean in cruise mode and 1 stage lean in power mode. I'll soon find out what that means....LOL
 
Only spot I ever use RTV on intakes is on the water passages, and RTV on the bolts so to stop weeping from the water/oil passages....

:crutches:
 
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