WIGDTW: need carb tuning advice - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Bowtie67 · 05-10-2006, 08:02 PM

If you can keep it running long enough to keep spraying around you may find the vacuum leak. Also try and plug all ports on carb except the fuel inlet you can rehook these up later 1 at a time to try & locate the issue. You may also want to have a friend over and have them start it and look in the carb to make sure it's not flooding. Also assume when buying used that what your told and what is, is usually two different things. I've known guys selling rebuilt carbs to just spray them down with carb cleaner and say there rebuilt.

Karl Hoh · 05-12-2006, 01:11 AM

Quote:

Originally Posted by shelby987

The intake was purchased along with an engine I have in my garage, the engine has never been run in a car, so I doubt heat warpage is an issue here.

The red RTV is made specifically for intake gaskets, but I did not use any of this, I purchased new gaskets for the intake to adaptor, and adaptor to carb and installed them dry.

The carb has been sitting for a month, it was purchased as a rebuilt carb that has been tested on an engine after being rebuilt.

To update this thread, my carb is now leaking, the gasket between the body and the baseplate that bolts to my adaptor is leaking fuel. The truck still revs to 3k and dies (even with no linkage attached for those that would suggest this).

I will try to spray carb cleaner around the head/intake surfaces and see if that helps,
ok I went outside and sprayed around the base of the carb, and the intake/head surfaces and fired it up, it felt like it wanted to idle, lasted about a second, and died....does this mean it sucked up all of the carb cleaner in a second and lost vaccum again? If this is the case, can someone please point me in the right direction to properly seal these up....RTV, super glue, tar, tuna, bat guano, cement?

If anyone can offer a suggestion it would be appreciated.....I am starting to pull my hair out over this....its been WAY to long of an ordeal to install a carb, intake and headers....please help, my truck was my salvation from a crappy job.....this isn't helping!

You need to make all mating surfaces FLAT, install new gaskets, NO RTV.
Some part of your adapter setup is warped. This must be repaired before any other fix/tuning can be done.

Karl Hoh · 05-12-2006, 01:23 AM

Quote:

Originally Posted by shelby987

ok, I have completely dismantled the intake, I got down to the adaptor plate I installed and saw that the 4bbl adaptor the PO installed was oozing rtv (looks like he used rtv that wasn't gasoline friendly). But now I can't find a gasket to put the 4bbl adaptor on the intake (just the square one without the ear and with the 4 holes).

Should I be looking at just making my own gasket out of some gasket material for this section? Also hoping to hear back from someone about the RTV, both sides, is it the typical install, wait 1 hour, torque down? Should I be doing this over the course of 3 hours since I have 3 gaskets stacked on each other? How long should I let everything setup before trying to run the truck?

I had another look at this and want to know does the carb bolt to the spreadbore adapter ? If so, look at the bottom of the carb and place the gasket on it. Are there any vacuum channels peeking out past the gasket? The edges of that gasket are very narrow. That spreadbore gasket looks like it could be replaced with one for a GM Q-Jet.

shelby987 · 05-20-2006, 09:16 PM

ok, an update to all of you following this thread.
I contacted the guy I bought the carb from, he said it sounded like there might be debris in the needle and seat, so he suggested I pull that out and blow it out with compressed air, in the opposite direction from how the fuel runs through it, so I pulled it, hit it with carb cleaner and blew it out with compressed air. I had some people express that they felt somehow the inline filter might be an issue of some sort, so I replaced the line from the fuel pump to the carb with a single line with no filter.

Tonight I finally had a helper, so I was able to have her start the truck while I was under the hood. The truck will fire and idle for 2 or 3 secs. with two pumps of the gas, then it does. I disconnected the throttle linkage and tried to work it manuall while my helper turn the truck over.....very slight pulls on the throttle made the engine rev. like crazy again, any attempt to keep it running with the throttle resulted in a backfire through the carb....it shot fire through the secondaries so I am back to the square one.

To answer previous questions, the gaskets do not overlap to allow for a vaccum leak.
Again, this engine ran perfectly before I installed this carb, the 1bbl allowed it to start and run without any issues.....I thought maybe I crossed some spark plug wires during the fuel line install.....but a double check showed they are all in the correct locations....IDEAS???? Would a vaccum leak really result in fire through the carb????

**JMac11** · 05-20-2006, 09:30 PM

Backfiring through the carb is a timing issue, usually. If it has a power valve in that carb, it might have popped that too, more bad news.

Karl Hoh · 05-21-2006, 11:29 AM

Can you get a different carb to try? Backfiring thru the carb is a lean mixture, or a very out of time ignition. After reviewing all your pics, specially the one showing the rtv on the adapter/carb base and text, it seems that you bought someone elses problem. IMHO. Try a different known working carb.

shelby987 · 05-21-2006, 12:59 PM

The RTV was on the intake, the carb was purchased seperately from a different individual. What is a good baseline to setup the mixture screws? Turn them until the bottom out, then back each out how many turns?

shelby987 · 05-23-2006, 08:56 PM

and the winner is......(insert drum roll)......Karl Hoh.....kinda.
The engine was back firing through the carb because it was too lean, but it was because the fuel pump was apparently too weak to keep the carb filled.....I primed it, but because it has no bowls, filling the fuel well only gave me about 10-15seconds of running at idle.....when i turned up the idle screw to try and keep it running, it would suck down that fuel in seconds.

Also, while filling the fuel well the fifth or sixth time I spilled some raw fuel down the carb and found what was likely the primary vaccum leak at the base of the middle intake runner.....tightened that up, replaced the fuel pump with a new one....and she fired right up!
p.s. open headers on an I6 sounds SURPRISINGLY awesome! Still have some issues to work out, but I will post those in a follow up thread.
Thanks to everyone who tried to help!

Karl Hoh · 05-23-2006, 10:51 PM

When you know it worked fine before something was changed, the battle is to figure out what is wrong. I'm happy that you have it running.

05-10-2006, 08:02 PM	#26
Bowtie67 Registered User Join Date: Jan 2004 Location: NH Posts: 2,266	Re: WIGDTW: need carb tuning advice If you can keep it running long enough to keep spraying around you may find the vacuum leak. Also try and plug all ports on carb except the fuel inlet you can rehook these up later 1 at a time to try & locate the issue. You may also want to have a friend over and have them start it and look in the carb to make sure it's not flooding. Also assume when buying used that what your told and what is, is usually two different things. I've known guys selling rebuilt carbs to just spray them down with carb cleaner and say there rebuilt. __________________ 1967 C10 - SWBSS Pro Street 427sbc, 700R4 & 4.10 Gears 1948 Chevy FleetMaster Coupe, LS1, (almost done) 1950 Chevy StyleLine Coupe 250/6 3x2 Dueces 2009 Toyota Tundra 1996 Harley RoadKing "I maybe getting old, but I can still burn rubber with the best of them" Last edited by Bowtie67; 05-10-2006 at 08:03 PM.

05-20-2006, 09:16 PM	#29
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	Re: WIGDTW: need carb tuning advice ok, an update to all of you following this thread. I contacted the guy I bought the carb from, he said it sounded like there might be debris in the needle and seat, so he suggested I pull that out and blow it out with compressed air, in the opposite direction from how the fuel runs through it, so I pulled it, hit it with carb cleaner and blew it out with compressed air. I had some people express that they felt somehow the inline filter might be an issue of some sort, so I replaced the line from the fuel pump to the carb with a single line with no filter. Tonight I finally had a helper, so I was able to have her start the truck while I was under the hood. The truck will fire and idle for 2 or 3 secs. with two pumps of the gas, then it does. I disconnected the throttle linkage and tried to work it manuall while my helper turn the truck over.....very slight pulls on the throttle made the engine rev. like crazy again, any attempt to keep it running with the throttle resulted in a backfire through the carb....it shot fire through the secondaries so I am back to the square one. To answer previous questions, the gaskets do not overlap to allow for a vaccum leak. Again, this engine ran perfectly before I installed this carb, the 1bbl allowed it to start and run without any issues.....I thought maybe I crossed some spark plug wires during the fuel line install.....but a double check showed they are all in the correct locations....IDEAS???? Would a vaccum leak really result in fire through the carb???? __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

05-20-2006, 09:30 PM	#30
JMac11 Registered User Join Date: May 2005 Location: Tallahassee Fl Posts: 773	Re: WIGDTW: need carb tuning advice Backfiring through the carb is a timing issue, usually. If it has a power valve in that carb, it might have popped that too, more bad news.

05-21-2006, 11:29 AM	#31
Karl Hoh A little east of nowhere Join Date: Feb 2006 Location: LaBroquerie,Manitoba Canada Posts: 168	Re: WIGDTW: need carb tuning advice Can you get a different carb to try? Backfiring thru the carb is a lean mixture, or a very out of time ignition. After reviewing all your pics, specially the one showing the rtv on the adapter/carb base and text, it seems that you bought someone elses problem. IMHO. Try a different known working carb. __________________ 68 C10 250 4spd 69 C20 327 4spd 69 910 250 3spd 80 K10 350 4spd 76 C60 366 5spd school bus "THERE'S NOTHING YOU CAN BREAK THAT SOMEONE CAN'T BE PAID TO REPAIR"

05-21-2006, 12:59 PM	#32
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	Re: WIGDTW: need carb tuning advice The RTV was on the intake, the carb was purchased seperately from a different individual. What is a good baseline to setup the mixture screws? Turn them until the bottom out, then back each out how many turns? __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

05-23-2006, 08:56 PM	#33
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	Re: WIGDTW: need carb tuning advice and the winner is......(insert drum roll)......Karl Hoh.....kinda. The engine was back firing through the carb because it was too lean, but it was because the fuel pump was apparently too weak to keep the carb filled.....I primed it, but because it has no bowls, filling the fuel well only gave me about 10-15seconds of running at idle.....when i turned up the idle screw to try and keep it running, it would suck down that fuel in seconds. Also, while filling the fuel well the fifth or sixth time I spilled some raw fuel down the carb and found what was likely the primary vaccum leak at the base of the middle intake runner.....tightened that up, replaced the fuel pump with a new one....and she fired right up! p.s. open headers on an I6 sounds SURPRISINGLY awesome! Still have some issues to work out, but I will post those in a follow up thread. Thanks to everyone who tried to help! __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

05-23-2006, 10:51 PM	#34
Karl Hoh A little east of nowhere Join Date: Feb 2006 Location: LaBroquerie,Manitoba Canada Posts: 168	Re: WIGDTW: need carb tuning advice When you know it worked fine before something was changed, the battle is to figure out what is wrong. I'm happy that you have it running. __________________ 68 C10 250 4spd 69 C20 327 4spd 69 910 250 3spd 80 K10 350 4spd 76 C60 366 5spd school bus "THERE'S NOTHING YOU CAN BREAK THAT SOMEONE CAN'T BE PAID TO REPAIR"



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