Technical SBC guys, help me get my 283 runnung right before i put a match in the gas tank

Was the heads or block cut & how much if so?
Asking might need thicker intake gaskets , sealing between runners ,
Those Rv cams pull alot of Vac, (20)
I find they like 14-16 btdc , timing.
I run hyd 1/4 to 1/2 turn adjustment
It also sounds lean ,rich it up,
Hard to read plugs , they always look rich on new blend of gas formula

 

Just for the hell of it, try replacing the coil. I once had to diagnose a 56 Ford, that would go in reverse, but stall and not run in drive. No one could figure it out. Coil was bad. I guess there is more load going forward, than in reverse.

 

Thanks, the heads were milled very slightly just to remove any inperfections. I've had the timing all over the place w/o any real effect.I adjusted the valves to 3/4 turn but think i'll loosen them up 1/4 and see. I do hear some popping through the exhaust but currently i only have the header pipes on and no mufflers so it's noisy.When you say rich it up are you suggesting bigger main jets or the idle mixture? i've been adjusting the mixture using a tack and vacuume gauge and have adjusted the numerous times as i mess with the timing etc. Yea, the plugs really arent telling me much.Appreciate the input.

 

Funny you should say that,it does seem that this issue is much more prevalent going forward than in reverse.I have changed the coil to a new accel unit which tests within spec. .I am tempted to change it anyway because i have had coils that tested good but were bad but i'm trying to avoid just throwing parts at it without any real focus.Plus, i tested each plug with one of those testers that light up when the plug fires . It is getting good spark (at least when the car is stationary). . Thanks for the input

 

When I set my valve adjustment I do it not running ,
I back nut off so I can feel the slack in push rod , tighten slowly turning push rod & up & down to
"0"'lash , then the 1/4 to 1/2 adjustment , when sneaking up on "0" lash make sure not to push plunger on lifter ,
Richen up mixture ,
& more likely a main Jet change , Remember most fuel of pump has ethanol So more jet needed.
All so you installed a Bigger cam , I assume is around .460 , .480 lift on a 114 -118 center line?
( CL is my so much Vac)
Go ahead set initial timing at 13 or 14,

 

Just a couple things how close is distributor cap to fire wall. Could it be hitting fire wall under load. Had a 55 that would do that and miss under load. Also could pistons be just touching spark plug tips maybe wrong plugs or piston clearance a little close.
I had a a 283 bored 60 over that would bend electrode on several cylinder under load. Ended up putting two spark plug gaskets on each plug. Problem solved good luck

 

Thanks , cap it very close to firewall. If that is causein the issue, i should be able to replicate it by putting some rearward pressure on the dist while i rev the motor ( while the car is stationary ) i'll experiment with that . I've turned the motor over by hand alot and not felt anything that would indicate the pistons hitting the plugs. Plugs are ac delco and correct for that motor. Pistons are just stock type flat top .40 over. I guess it wouldn't hurt to double up the washers though.

 

I use the same method for adjusting the valves. Lifters were dry when i did the adjustment ( other than a couple of drops of oil in the seat to keep it from galling). I don't think the lift is that much but can't remember off the top of my head, i'd have to check the card. how many sizes should i go up on the jets? i'm running 55's now. Thanks

 

you had mentioned the car set for a while, could it maybe be some old nasty fuel? I know that can make them run pretty bad.

 

This sat for 40 years. Did you clean out all the manifold runners? They may be full of mouse mess or wasp nests.

.bjb

 

I don't KNOW what is the issue; but the very first thing I would try after all you have done would be to orient the carburetor normally on the manifold, rather than reversed.

The above is a SWAG!

Not knowing which Rochester probably makes it more of a WAG than a SWAG.

Some of the Rochesters have ports covered by the mounting gasket that then open to the throttle area. It is possible, even though you are using the "correct" mounting gasket, that internal passages are causing you issues.

And the switch doesn't cost anything except some time.

EDIT: quote "Thanks, put in a brand new brass float when i rebuilt the carb and checked it for leaks." end quote

I hope you kept the original!!! The new brass floats mostly come from that country beginning with a "C", that is quite far away. What is used for solder is NOT compatible with ethanal diluted fuel. About 3 months is the norm before the seam begins to leak.

Jon

 

I read a 2 barrel Rochester,
I would Jet it like a 69 327 w 2b carb
Or like 350 2b carb , 68-70 chevy, Pontiac , Buick . Olds .
I would think your 283 is 250-275 hp ,
I never played with a sbc under 300 cubs less it was 7,500 plus Rpms
A decent air fuel ratio gauge would make your life easier for turning on the fuel, it can be removed afterwards

 

In my experience a problem like this has been either low voltage to the coil or a faulty coil. The fact you've covered these...and pretty much all of the obvious culprits leads me to focus on the carb not liking being backwards for some reason. I once had a hot rod Norton with an EI flat slide carb. One day I managed to flip the slide around without realizing it. The bike would do as you describe, start, run fine, then try to move and blaaaaa. Your problem reminded me of that, so I thought I'd mention it. Good luck!

 

Thanks for the reply,
I agree that turning the carb around would at least put that question to rest one way or another.Not sure how familier you are with early ford type throttle linkage but it would take quite a bit to remove it and replace it with something that would work with the carb properly mounted.Especially with the engine in place. I may at some point have to go that route but it will be a fair amount of work thats whu i havn't done it up to this point.As far as any ports that may be open or closed as a result of turning the carb around there is nothing. i was very carful about checking that when i was contemplating turning the carb around to begin with. The original float was plastic on this carb. They call it something else but to me it's plastic and it was saturated with gas. If the current brass one leaks at some point i'll deal with it but for now it floats fine. Again, always happy to hear any ideas.

 

I may have to turn it around but it will be alot of work with the engine in place and then having to rig something else up that will work is another issue . I'd really like to be more confident that that is what is causing the problem before i do it.Someone did mention that maybe the fuel in the bowl is being forced away from the main jets under acceleration . That would be the only thing i can think of that would be effected by the carbe being mounted this way. Thanks for the reply!

 

Thanks, everything was thoroughly cleaned in preperation for building the motor

Thanks, so before the engine was put in the car i replaced the gas tank with a new one, also new fuel line and fuel pump so no chance for contamination

 

Make sense on starving for fuel , carb backwards ,,,
When running a Holley backwards Jet extension required
Simple Bell Linkage can solve the gas pedal arm if like 32 Ford Leaver ball / arm on passenger side off fire wall ,
Here is a quick scribble of a drawing see if it makes sense to you for linkage
Requires/ make usable

 

I struggled with a Rochester 2 bbl, hesitation on tip in, I went through it, a buddy went through it again, couldn't find an issue, couldn't resolve it. Grabbed a crusty one off the shelf, bolted on, and no problems. Sometimes, they just don't behave. Do you have another to try?

 

If you put the rear on jackstands and ran the car in gear so you could load it would you be able to better troubleshoot it? Might need an assistant to sit in the car and apply brake while you apply choke, observe spark from a partially pulled coil wire, etc.
My Merc flathead with a 2G backward runs great and accelerates fine...even up some very steep inclines.

 

^^^
Might not affect a Flathead with carb backwards
Does not require /need that much fuel

 

Have you checked for vacuum leaks?

 

Thanks for the drawing! I understand the concept and what it would take to make it, not a problem. The issue is there just isn't enough room. I could move the coil which is mounted between the dist. and the carb but still the distance is very short and then there is the issue of how to mount the pivots for the cross shaft. It would cause alot of clutter on the top of the motor. I think a better idea might be to get an extended throttle shaft , like if you were building a multi carb setup.Just mount a pivot arm and ball on the end that extends , which would be on the passenger side ,and still use the existing throttle linkage . Thinking about it, i may just order the parts and get that question out of the way ( the question of carb orientation). I hadn't thought about it that way until you mentioned the bellcrank idea. Thanks !

 

I could try that. I'm not sure if that would put enough load on the engine. It would just be turning the back wheels and not trying to move the weight of the car from a dead stop. Might be worth a try though. Thanks!

 

I did ! 9,472 times

 

You apply a load with the brake being applied either the emergency brake or with the brake pedal while running it.

 

Just to get this straight, early sbc intakes had one version of heat cross over that was 2 holes in line with throttle bores, other version had a trench across front of base flange . What do you have? 2 hole deal easy to block off , trench one is tricky when flipping carb , if not careful, exhaust would get into intake, made an adapter plate of some kind, correct? Why needed if you don't trench cross over. Exhaust heat is useful for street car by the way. The carb base should have a triangle shaped recess that joins T-plates to large vacuum nipple that would be for PCV or brake booster at rear of carb. Just want to be clear as I think about this problem.

 

Something else, RV cam should have more than 16hg. vacuum, and this gem should like more than 8 degrees of base timing, with say 14 degrees, the idle should increase and a "crack" of the throttle should show an improvement in response, does this happen?

 

I don't have another one. Almost ready to spent the $250.00 bucks to get another auto parts rebuilt one. Maybe i'll ask around to a couple of local guys to see if i can scare one up.

Thanks for responding, The intake is the 2 hole type no trench. Had to make an adaptor plate because when turned around the carb base slightly hangs over the rear edge of the intake mounting flange and i wanted to ensure a good seal. You are correct about the configuration of the carb base. The large vacuume hose goes to a vent fitting on the rear of the block,no pcv.
I initially set the timing at factory spec ( 4 degrees) and kept re setting it up to about 18 or 20. Throttle response varied and improved to a point but the problem of it dieing out and missing under acceleration never improved with timing change.

 

Just to be clear,throttle response is good when not under a load .I also thought i should have a bit mor vacuume and it should be steady, which it isn't.

 

Thanks, but this is a 3 speed.Trying to accelerate with the clutch out and the brake on will stall the engine.