Slant Six Forum :: Old intake = gone, new intake 4bbl Carter 400CFM AFB goes on

Ick!

Is the plate still going to seal on the manifold after that bit of hacking?

Yikes! Scrutinize it for cracks and make sure the inlet valve assembly is clean and doing what it should. Perhaps it stuck open and drowned itself.

One Holley 390 user to another.

Vaseline on little tiny "O" ring between primary metering bock and carb body, this would be the path fuel takes to get to accelerator pump, and is exposed when changing a power valve. Vaseline on both "O" rings sealing metal fuel line between front bowl and secondary fuel bowl. If these O rings don't seat properly you will have fuel dribbling every were.

Vaseline on screws clamping quick change secondary spring hat to prevent ripping vacuum actuated membrane.

Check the gaskets for sure. There are some that look really close but will cause things like you are experiencing.

Author:	spacecommander [ Tue Feb 10, 2015 3:36 pm ]
Post subject:	Old intake = gone, new intake 4bbl Carter 400CFM AFB goes on
Hello all, the W150 truck is progressing. Removed the manifolds today and spent about 2 hours searching for a triangular special washer that had fallen off during removal. Turns out it never was there - a regular thin washer had been substituted. Anyway, the old manifold was a welded aluminum one. Super light! Passages were wet with fuel. Guess it was running a bit rich. The good news is all the exhaust ports are oil free. Haven't finished making a Dutra dual setup, so the regular stock exhaust manifold will go back on, along with a offy manifold and Holley 390 cfm 4bbl. Had been working on a dual 1 bbl offy manifold converted to use a pair of the Langdon Carter/Weber carbs - but trying to get the carbs to open in sync even with a beefed up Langdon linkage is difficult as the spring tension on the Carter/Weber carbs is pretty massive. Plus, I'm not sure how it will work here at 5500+ feet. The Holley has re-jetted with a new power valve (3.5) installed so the power valve isn't on during cruise. Oh, the old manifold junction leaked quite a bit:

Author:	spacecommander [ Tue Feb 10, 2015 8:14 pm ]
Post subject:
Wow, this is a real headache. The last 2 I did were about 25+ years ago and I don't remember anything like this hassle-wise. The Offy manifold required a fair bit of work to get it to play with the 1982 exhaust manifold. The exhaust manifold has a stud for the middle manifold-manifold connection, and upon heating the manifold - the stud did not want to budge. So, the stud had to stay. The reason you want to remove the stud is so that it does not hit the carb adapter plate as it is quite tall. Things that needed to be done to get it to work - the three holes in the offy intake that connect to the exhaust manifold heat box needed to be enlarged considerably as the intake manifold mating surface to the head protruded quite a bit (.1!) past the plane where the exhaust manifold would mate to the head - the stud in the exhaust manifold barely slid in to the hole in the offy manifold and located the mating planes of the runners to the head incorrectly. Then the holes in the exhaust manifold had to be enlarged also as the long bolts that go through the intake outer edge of the heat box to the exhaust heat box were angled incorrectly - the bolts would not slip through even though the intake holes were oversized. Lastly the carb adapter plate had to be hacked a bit in the bottom as it hit the heat riser for the choke, and the stud hit it also. See pictures.

Author:	Pierre [ Tue Feb 10, 2015 10:11 pm ]
Post subject:
Ick! Is the plate still going to seal on the manifold after that bit of hacking?

Author:	spacecommander [ Tue Feb 10, 2015 10:27 pm ]
Post subject:
Quote: Ick! Is the plate still going to seal on the manifold after that bit of hacking? Yup, there's plenty of metal surface left for the gasket to seat on. Head mating surface has been scraped clean with razor blade, then cleaned with acetone. Runners to head gasket goes on dry - no hi-temp gasket cement. Ran a huge flat file over the exhaust runner mating surfaces - they're flat, amazingly. Doubt this can run worse than the old 1bbl that the previous owner "rebuilt" - every screw was rounded off, most were stripped. The 390cfm Holley is used - I rebuilt it with a real Holley rebuild kit. The throttle shafts aren't very worn at all. It will initially be a 2BBL as a quick change spring kit was installed and the super heavy black spring - the vacuum secondaries won't open. Once the primary side gets dialed in - then I'll play around with different springs and monkey with the pump shot so the secondaries open smoothly. It will be interesting to see how the vacuum secondaries work here at 5500+ feet. The little 390CFM 4(or 2)bbl should also work better in another way - the venturi ported vacuum line should provide a stronger signal to the distributor. Unfortunately I forgot to hook the vacuum gauge up to the distributor advance signal port of the old 1bbl before it was removed - my guess is it was providing not much vacuum at all - if any.

Author:	spacecommander [ Wed Feb 11, 2015 4:03 pm ]
Post subject:	Massive Holley 390cfm carb problems.
Dagnabit! All done, carb return spring bracket and throttle cable support bracket fabricated, electric choke wired and hooked up, all fuel lines plumbed and vacuum lines hooked up. Cranked engine - cranked some more then it started and immediately the shout was woah! woah! as fuel shot out of the bowl-bowl transfer pipe in a jet about 2 feet long. Ok, that's not hard to fix - started taking carb off then noticed gas was EVERYWHERE inside carb - and as carb was removed I could see gas pouring out above the throttle plates???? Took carb outside and shook - gas poured out of idle bleed circuits - tilted the carb a bit and more gas poured out of idle bleed circuits on both primary and secondary side. What the heck? All I did was disassemble the two fuel bowls and the primary metering plate to replace the power valve and primary jets - put in new gaskets. Obviously I screwed up and pinched an o-ring somehow on the fuel transfer tube. Both floats are working properly. I'm completely and totally baffled. Should add that this carb was purchased used off ebay and I've never used it before.

Slant Six Forum https://www.slantsix.org/forum/

Old intake = gone, new intake 4bbl Carter 400CFM AFB goes on https://www.slantsix.org/forum/viewtopic.php?t=57074	Page 1 of 1

Author:	Pierre [ Wed Feb 11, 2015 4:52 pm ]
Post subject:
Yikes! Scrutinize it for cracks and make sure the inlet valve assembly is clean and doing what it should. Perhaps it stuck open and drowned itself.

Author:	spacecommander [ Wed Feb 11, 2015 5:03 pm ]
Post subject:
Quote: Yikes! Scrutinize it for cracks and make sure the inlet valve assembly is clean and doing what it should. Perhaps it stuck open and drowned itself. I'm going to get a fuel pressure tester - wondering if it was sky high as there's gas all over the floor of the manifold, etc.

Author:	Pierre [ Wed Feb 11, 2015 5:26 pm ]
Post subject:
Unless it was high enough to bend or break things, I can't see that happening. We're dealing with a mechanical pump right? Even the big ones don't get past what, 8psi give or take? Fuel will come out anywhere it can if the valve doesn't do what it should.

Author:	spacecommander [ Wed Feb 11, 2015 7:16 pm ]
Post subject:
?!!? pulses up to 4.5-5 PSI. Needle valves appear to be working via mouth blow test. Unless - the fuel is flowing in to the carb internals via other transfer areas before the float rises high enough to shut off the valve? Floats will get re-adjusted down as far as they go, carb will get rebuilt and fuel line hooked up and carb will sit in a bucket to see if there's internal problems.

Author:	wjajr [ Wed Feb 11, 2015 7:55 pm ]
Post subject:
One Holley 390 user to another. Vaseline on little tiny "O" ring between primary metering bock and carb body, this would be the path fuel takes to get to accelerator pump, and is exposed when changing a power valve. Vaseline on both "O" rings sealing metal fuel line between front bowl and secondary fuel bowl. If these O rings don't seat properly you will have fuel dribbling every were. Vaseline on screws clamping quick change secondary spring hat to prevent ripping vacuum actuated membrane.

Author:	spacecommander [ Wed Feb 11, 2015 8:23 pm ]
Post subject:
Quote: One Holley 390 user to another. Vaseline on little tiny "O" ring between primary metering bock and carb body, this would be the path fuel takes to get to accelerator pump, and is exposed when changing a power valve. Vaseline on both "O" rings sealing metal fuel line between front bowl and secondary fuel bowl. If these O rings don't seat properly you will have fuel dribbling every were. Vaseline on screws clamping quick change secondary spring hat to prevent ripping vacuum actuated membrane. I use a tiny bit of mobil 1. Thanks - I'm wondering if the metering block to carb gasket is the correct one. Different holes? But - why is gas getting in to the top of the secondary throttle plates? That's just the one gasket between the fixed metering "thing" and the body - there isn't a secondary metering block. Bah. Something is seriously hosed on the holley. Maybe the previous owner decided to drill a few holes somewhere to let more gas in?

Author:	slantzilla [ Thu Feb 12, 2015 3:08 am ]
Post subject:
Check the gaskets for sure. There are some that look really close but will cause things like you are experiencing.

Author:	spacecommander [ Thu Feb 12, 2015 5:34 pm ]
Post subject:
Quote: Check the gaskets for sure. There are some that look really close but will cause things like you are experiencing. That was it. How's this for a gasket mismatch? The new one is in the lower left. The black one was what was there - notice the exposed corners of the secondary plate allowing the fuel to just drain out. So, the proper gaskets got installed as a full rebuild kit was installed. Fuel pressure was applied - no leaks, floats were checked, proper height, then the Carter AFB 400cfm was installed on the truck after a 10 min rebuild with consisted of replacing the accelerator pump. HUH????? Yep, tested the holly on the bench, and upon lifting the carb and in doing so tilted it about 15 degrees watched fuel run out the main jets. It was then I remembered how lousy the Holley carb was on my old Ramcharger that I owned back in the late 1980s. It had fuel problems at any kind of angle. Dug out the ancient Carter AFB, did the accelerator pump swap as the old one was totally dried out. No gaskets involved - the top gasket seemed OK. Bolted it to the mainfold, cranked it up and it started immediately once the fuel got in and idled just fine. Let it run for 5 min and turned it off - noticed a electrical burning smell and touched the choke housing - waaay hot. Removed line from choke housing to air cleaner and routed it to manifold vacuum. Fired car back up, fiddled with the idle mixture screws for a second, put the air cleaner on and took it for a drive. Has at least 10% more power than the old 1bbl, maybe 15% - smooth acceleration, no hesitation and I can go up hills in 4th that I used to have to shift down. No idea what sort of jets or springs are in there. Here's some pics - the aluminum cheezy bracketry is just temporary:

Page 1 of 1	All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/