Inliners International Forums General Discussion Engines 500 CFM Too Much Carb for 292?

I have a '68 292 L6, bored .030 over, w/ stage II Crane cam and 1.84 intake valves. I replaced the old 390 CFM Holley with an Edelbrock 1404. I can't seem to get it to idle smooth at low RPM. It floods and then starves. I've regasketed the manifolds twice, installed some studs and/or stainless capscrews on intake [Offy] and headers [Clifford], reset the timing to TDC, checked gap and dwell swapped out the coil and rewired the plugwires. Fuel pump checks nominal at 4.5 PSI. It still won't run right. I'm doing something wrong, but can't find it. Tomorrow I'm gonna put the Holley w/ new 7.5"Hg power valve back on and see what that does.

Have you tried rejetting the Edelbrock? You can purchase a kit with jets, metering rods springs etc from Jegs or Summit and the carb should work great. I ran a 600 on a mild 292 with a 264 hydraulic cam with no problem; it ran great and passed smog.

At idle that 500 Edelbrock is not anywhere too much for the 292 and should adjust idle mixture and idle speed with no trouble. It may need some metering rod changes for driving but it definitely will idle.

Did you check the floats before installing it? The manual has all the specs and this can be done without needing to replace the upper gasket if you are careful taking it apart.

While you have the top off carefully look for fuel in the weight wells for the secondary air baffle. If you find some this is telling you the secondary booster nozzles are not fully seated on their gaskets caused by the screws bottoming in their threaded holes before snugging the boosters down on the gasket. This will cause flooding down through the secondary throttle plates ANYTIME the engine is running. Put a couple of flat washers under the heads of the screws and the problem is solved.

A month or so ago this exact problem was addressed in detail here on the bulletin board so if you browse you should find it. If I remember right the subject title was "Edelbrock 500".

Mike G

Mike, We tweaked with the float bowl levels today and got some indication we were going in the right direction, but ran out of area to bend in. In my next maintenence session I will try changing out to leaner jets and needles. At least it's not a vacuum leak. A quick bugspray of carb cleaner on the intake/head junctions yeilded no RPM increase. Timing is harder to hit than on a stock-built engine. And I'm thinking that all this trouble started after I changed out the hot plugs [#4405] to one range colder Champs [#4404].

Too cold plugs will sure cause that problem. Doug

68 Orange, just a little advice from one who has tuned bunches of those Edelbrock carbs. Don't go making all sorts of jet and rod changes at the same time you'll end up way out of the ballpark. That 500 is most likely very near to what your 292 requires, at least for basic set up puroposes. I've run them out of the box on 350 Chevys with mild cams and headers and they set up good enough to be able to test drive for miles in order to decide what rods changes needed to be done. Follow the manual and work first with only the metering rods going richer or leaner as you move along. If rod changes in one direction or the other get you close and you can't get any richer or leaner by only changing rods, THEN it is time to start juggling jet sizes.

Champion plugs...... hmm. I never had really good results with them and prefer AC instead for a GM engine.

One last tip that is barely mentioned in the Edelbrock booklet is if you have an eratic idle that seems to defy any simple carb adjustments then change the distributers vacuum advance hose from the ported vacuum position on the carb to the direct vacuum position. Although it doesn't seem logical my 250 required this and I've had to run it this way on a 327 Chevy V thing too.

"ran out of room to bend the float adjustments?????" I never came even close to having that happen on these carbs.

I hope by the time you read this post you got it all sorted out. Carb tuning can sometimes be a headache.

Mike G ( 4355 )