Just going over some things on the '61 and noticed the front carb throats are really coated in black soot. Rear carb looks normal. I don't get into the front four barrels that much but the inside of the carb is sure nasty looking. Car is running superbly - no backfiring, hesitation, bogging or anything like that. When I DO
hit the front carb the car rockets off just like it should.

Any ideas on a cause or is it normal ?

 

running a little rich ,but you Fl. people drive to fast , by the way I'll be in Marathon island in a week for three weeks any one near there have Corvettes C1

 

It may be intake manifold reversion.

If you'd keep the hood shut unless something is wrong, you wouldn't even notice that!

 

Alright I have both Engineering and Computer Science degrees and I have no idea what this means ?!

Is it anything like "rectocranial inversion" ? I've been accused of that before!

 

For those of us who have owned cars with Webers, reversion is a household name. In any event, reversion, carburetor/Injector "stand-off" or the general effect of the backing up of the intake Fuel/Air charge normally associated with longer duration high-performance camshafts and is generally associated with a late intake closing.

 

Guess I'll just keep an eye on it then and clean the carb throat's occasionally...I would thnk both carbs would exhibit this though by the above definition...

 

Reversion, carburetor/Injector "stand-off" is the general effect of the backing up of the intake Fuel/Air charge normally associated with longer duration high-performance camshafts and is generally associated with late intake closing. If you have ever owned Webers, this is a common problem due to the lack of scavenging that takes place with a normal intake manifold. With the 48 IDA or the DCOE each cylinder goes mano a mano with its own separate intake port.

 

I have a degree in shadetree engineering and an 8th grade education so I can be easily fooled.

Common sense tells me with the rear carb open/slightly open most of the time while the engine is running and reversion could be a factor, it would tend to keep it a little cleaner than the front carb which stays mostly closed.

You might check your butterfly closing setting and see if it's where it's supposed to be. I don't remember.

But I could easily be wrong.

 

Frank, It's Ethanol .......no just kidding!

It almost looks like results of some backfire at one time , but.............
I had a similar issue in the past. It may be oil vapor coming out of the oil cap getting sucked in the front of the air cleaner. Any oily residue on the air cleaner? Is your cap vented or non-vented? I switched to non-vented and no more oily residue.

 

Frankie grab a can of Gumout and spray the shyte out of the throats, and the outsides for that matter. That stuffs been around for years and years and for a good reason, it works. I've used it on cars, bikes, and it's great on two stroke outboards

 

Makes sense to me. Just need to keep your right foot firmly pressed against the floor board when driving.

 

Frank,

I don't have that issue (my front carb throats are clean). While reversion occurs anytime you have a "stout" cam with overlap (at lower RPMS), it should not get up into the front carb, unless that carb is somewhat opened. I would look at the front carb throttle plates, and see how "closed" they really are. And check the front carb throttle return spring (it may not be stiff enough). Just guessing here...........

Note that I am running off of the idle circuits of both carbs at idle, but my front carb throttle plates are closed. I get a smoother idle that way, and it flushes new fuel through the front carb.

Edit: After looking at your picture, I see some reversion soot in the rear carb, in the front primary throats. You may want to try resetting the valves for a wider gap (less overlap), or increase your operating rpm range (that OD trans you now have is probably "causing" you to run at lower rpms, but that is not where your cam / engine is designed to run). I typically don't go into OD at anything less than 1800 rpm, but that is with my 350 and a different cam, etc.

John

 

Good point.

A lot of these guys that are doing the OD thing with these "cruising gears" ............................... Ah, never mind!

 

I did change to a vented oil filler car when I went with RPO-242...I don't see any blowby products on the oil filler neck though. I supppose I could run a while with the non-vented cap (I still kept it) to see what happens.

I'll also check the throttle plates in both carbs. My valve lash is at the factory specs but (I just reset them last week) I guess I could widen them some - say .002 on the next adjustment.

I abolutely run lower RPMs with the OD tranny (the whole point of it) cruising is between 1400-1800 RPM typically and below where the cam "comes on" for a Duntov 97. But the car is running so darn good I hate to screw with too much. I'll tinker around with some minor changes and see what happens.

 

Frankie, Seeing your picture of those two Hogs sure makes me wish Chevrolet had carried them over into '62. Had a set on a '57 Nomad 270hp car and loved the way they looked and sounded at wot. Don't recall having your problem, then again it had a 4:11 rear and that kept her spinning pretty good. Good Luck

Earl

 

Looking at the picture again, it's strange that it's the secondaries of the carb are the worst. What does the underside of the air cleaner look like? When I get out to the shop I'll have to open up and take a look at my 2x4 setup for anything similar.

Rich

 

Gotta tell you Earl - I had my air cleaner off last night at the Old Town car cruise down here to check on the choke adjustment and I look up and there is an admiring crowd around me. Something about dual quads...

Rich...underside of air cleaner looks spotless (just pulled it off an hour ago) and air filter is clean all the way around too. I found a clean stretch of road and hit the rev limiter twice this morning and the car is freakin' awesome running (well for a 283ci anyway)...

I'm gonna clean things up with some GumOut and try to keep the RPM's up a little more over the next few weeks and see what happens.

 

I don't think anything defines raw power any better than a dual 4 set up. Three deuces come close, and a fuel injection unit looks almost dainty.

 

nope, just the front one or the one not used as much as the primary
this happened a lot back in the pontiac tri power days on grocery getters equipped that way that never saw wot with mom driving....