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

I posted the same suggestion at Post #83, and was met with "why spend the money?" and other "poo-poo's". That was 37 posts ago. It would IN FACT confirm whether the problem is fuel related or not. Guess the OP isn't interested in the possible solution, since he hasn't commented/responded. Oh, well............... after 121 posts (and a full week), he's right back where he started. GEEEZZZ.....

 

That's what I'm seriously considering doing for a full-throttle stumble that I'm having issues with. I fixed a lot of things that needed fixing, but it's still there. AFR should help narrow it down, I just am not excited to install the bung for the sensor.

 

I just am not excited to install the bung for the sensor.

They make clamp-on bungs that don't require welding the bung in.....the bung is fitted to a wide lap band type exhaust clamp.
Just requires a hole in the pipe, you could then cover it with a solid band clamp if you want to remove it later.
I've also seen guys make a short 2" pipe section made to bolt between the header collector flange and the exhaust pipe. It can also be unbolted and removed if you don't want a permanent install.

 

Either clamp-on or weld-in, I'm not excited to add a potential leak to the best exhaust system I have.

 

Whats is the diffrent s , does your Engine have Gaskets????
Thought So !!!

I had a learning lesson about 15 years ago ,
Working on F -H , Chasing Like Op ,Trying to Read new pump gas plugs , I kept leaning it out ,
Plugs Black , Installed AFR , BAM , with in a minute Gauge was max @ 17 , I knew to richen ,

 

Yep, and I've had a hell of a time getting some of them to stay sealed lately.

 

I try to share some experience/knowledge here,
Dont know every thing some times I learn .
I can not tell why you had difficulties with exhaust leaks without seeing it.
I can tell who ever that I have had / use
Clamp , weld in O2 , AFR ,
As many as 8 o2s & 8 ETG probs on one engine , (leaks not common ) not difficult to fix / spot if so...

I have a little ""anxiety"" every time I mess with ""Gasoline""including filling a tank ,, All it tasks is
""Static Electricity or Spark!!!!
Especially when there's more
""Fumes"" then liquid,
THAT GROUND STRAP ON TANK IS LITTLE % of Insurance

 

Thanks, new battery, new cables and terminals so no corrosion.

 

Thanks, but not so simple due to lack of room and distance the orig throttle lever protrudes.I could do it but not real easy.I may rig the throttle to a wire and hand operate it just to see if it matters.As i stated earlier, an extended throttle shaft would be much easier than the bellcrank assembly.

 

Thanks, yes i think thats my next step.

 

Thanks, so i had a forced break from it prior to posting. Had my 2nd bout with cancer and after som surgery was not allowed to do anything for a month ( i spent the time hoping it would fix itself as well as researching the possible issue) so thats why i posted.Been working on engines for half a century so not new at this. I guess i will relent and turn that carb around and figure a way to temporarily work the throttle .It will either fix the problem or eliminate one more possibility.

 

Thanks, not running an alternator so no diode rectifier. Running a generator and regulator.

 

I haven't looked at a Rochester 2bbl in a long time.

My guess your adapter plate is blocking a vacuum port the carb needs to see manifold vacuum.

 

Is it putting out consistent voltage ?
The electtrizical gizmos have a desired output based on the designed input.
If the input is off, the output is likely to be not as desired.
Anytime a component draws attention to itself by causing an issue the first step is making sure it’s receiving the designed input. A ignition system with wrong voltage can’t possibly work correctly and flawlessly.


Checking your voltage may require rigging up a voltmeter and driving it while monitoring the readings. I find the old sweep dials easier to see fluctuations than digital.

Once you rule out any internal engine issues your down to Fuel air spark timing (after compression). Drivability issues- if you’re having a fuel problem, first check fuel pressure delivery while driving. If you’re having an Air problem check for any obstruction or air flow resistance, restrictions, turbulence. ( this may or may not be the backwards carb). If you’re having a spark issue first check the input voltage consistency to the ignition system and it’s grounding. If you’re having a timing issue first verify the timing marks via piston stop test.
Running down The secondary issues of FAST can cause you ass cramps if you don’t do the verification first, and doing anything before verification of no internal engine issues will definitely not help it run better.

 

If you pull the carb, take a picture of carb base and the adapter in place on intake, post pics . It seemed to me you had the position worked out with reference to vacuum ports. That way you get avoid any more posts about "flipping the carb" and leave linkage as is. Take a look at gasket impression if you think something is out of place.

 

So the OP is in fact interested in any and all possible solutions.Thats why i posted.I have been away from the project for a week and have not had the oppertunity to act on any of the suggestions that have been presented.When i do, i will start with the easiest and least expensive options and work my way into the more complicated and expensive attempts to fix the issue.I apologize if i hurt your feelings by not responding to your particular comment which i'm sure was well intentioned and much appreciated.

 

Thanks, i studied the situation prior to making the decision to reverse the carb so im pretty sure i am not blocking anything. It looks like i will be remounting the carb some time this week so i'll know for sure.

 

^^^ this line raised an eyebrow when I read your original post. Define "cleaned and machined". Was a true valve job done? What about the condition of the original valve springs? valves not fully sealing and worn out springs could cause sealing or floating conditions at higher RPM, especially with a new cam, pistons, etc. I always question when someone doesn't do a portion of an engine that's getting a full bottom end build.
Like a MD, rule parts and systems out one at a time. Divide and conquer.

• I'd first address the carb. Turn it around and run it. If that doesn't change things, swap it out, hopefully from a current, running vehicle.
• What air filter are you running? Some of the aftermarket 2 barrel air cleaners are very restrictive at high R's. Make a power run w/o an air filter.
• Next, bypass your fuel supply system. Swap in a temp (boat) gas can. Gravity fed or via electric fuel pump to rule out your new gas tank, lines, fuel pump, Wix filter.
• Check to confirm the + battery cable terminal is tight on the battery as well as the lead on the starter. Had the nut come loose on the starter terminal on a SBC once and it would fall on it's face under hard acceleration. Took forever to find the problem (after checking jets, ignition, etc). Had the hood open, started it up with a friend staring at the engine, he leaned in and the engine died when his hand bumped the + cable!!! Problem solved! Recently had it happen to my O/T pickup. Was starting to bog down badly on hard acceleration such as a freeway on ramp. Checked the usual stuff, then found the problem was the 8mm bolt on the + battery terminal was about 1/2 turn loose.
• Look at the engine running at night (pitch black) while parked (idle and high RPM) . You'll easily see any wires arcing, plug wires jumping, etc. I learned this trick along with a hand held plug wire pulse light, from my HS auto shop teacher. He was a pure bred Scotchman-cheap as hell and I was a poor kid so we got along fine.
• Lastly, don't be afraid to call in a favor. A friend's fresh set of eyeballs and blank slate brain can sometimes work wonders. About now, you may not see the forest through the trees. Tackle A-Z together. About now you need some moral support. If he happens to have a running car with a 2 barrel all the better. Myself and a couple of close friends in High School all had SBC's. We would partner and swap parts from one running car to a non running car. We didn't have the money to throw parts at a problem, so a coil, or even a distributor cap with all the wires attached wasn't out of the question.

 

Thanks, yes , i didn't just arbitrarily turn the carb around without regard to how ports and exhaust heat outlets were matching up. I suppose there may be some inherent issue with the carbs reversal that i don't understand so i will be turning it around this week . Great idea about taking some pics to post which may help put that issue to rest.

 

Thanks, The heads were stripped, hot tanked,and milled. The stellite seats were cut the valves were refaced and the springs were tested and found to be fine. All this was done by a highly respected and qualified machine shop so sure why you think i did the bottom end and cheated on the heads.I will be turning the carb around this week so we'll see what that does.Not running any air cleaner at the moment.Otherwise i've already done everything else on your list.Appreciate the input.

 

Probably not your immediate problem but hard to believe after sitting for 40 years the valve springs checked ok. Some of those valves were open the whole time with springs compressed. I got an eng8ne sat for 2-3 years running. In a few weeks cruise at 60 broke spring that had been open. Another few weeks broke another that had sat open.

 

5 pages of advice, and the one that jumps out to me is on the first page. Pertronix module. New parts are, it seems, as likely to be faulty as the 50 year old stuff you took out, speaking of condenser and coils. The issue sure sounds like ignition breaking up, and you've replaced everything at least once, but trying an electronic ignition as opposed to the points and condenser, even you're familiar with them, seems like a logical thing to try. It worked for me in this DeSoto Hemi. I couldn't even get the thing to run (it'd fire but not run), replacing the internals with the Pertronix yielded instant starts and a silky smooth running engine.

 

Leaving springs under tension does not weaken the steel in the spring, it is repeated compression cycles that weakens the steel, not sitting still under compression.

 

Thanks, the car sat for 40 years,not the engine.I think it sat for 2 or 3 years. I trusted the machine shop on the issue of what to reuse and what to replace. Maybe i shouldn't have. But to me the shop had nothing to gain by wanting to reuse the springs and they actually would have made more money by selling me new ones. Same with the valves.I guess we'll see. I can tell you that i have reused original flathead valve springs in motors that are still running with them after many years so i guess you roll the dice and live with the result

 

Thanks, i may be heading in that direction out of desperation but after having 3 sets of points and 3 condensers i have a hard time believing they all were bad.Could happen though i guess.

 

Bob , sorry I’ve not read all , but I’m doing a sbc to 41 tudor currently. What fuel pump are you using , where is it located are you still using the 1/4” fuel line ? Vented fuel cap ?
My electric pump is back by the tank and pushes the fuel , new 5/16 fuel line ,
How about blocked exhaust , animals love to make homes in exhaust. If not blocked by nests , could be old double walled pipe colapsed inside .
Good luck

 

OP, I may have read past it, but can you get it to full throttle under load after it stumbles or is it just breaking up and runs poor after flooring it?

 

OK, here are my guesstions........

I'd get an infrared temp gun and check the temp at each cylinder on the exhaust manifold when the engine is running fine and again when it starts to stumble. That may tell you if its certain cylinders or all cylinders.

Second....the float. I know you said its new and you checked it. A friend of mine spent about two years and a lot of $$ restoring an old airplane. He did test runs up and down the grass strip for several hours over a couple of days. No problems.
His carb was rebuilt by a "certified carburetor repair facility".
Once he took off and the plane made a few turns, the engine began burbling and he went down. Luckily he walked away.......somewhat gingerly, but he made it. The brass float had a hole in it and apparently filled with fuel. So being new doesn't mean it can't be bad. Probably not in your case, but thought I would mention it.

Third.....I don't think I would have reused the valve springs as if they are weak they may not be closing the valves properly. Now you are asking them to deal with more lift and ramp speed than they were originally designed for over 60 years ago. I'd buy new ones just for peace of mind. Coil springs in the suspension systems of cars often need replacement after sitting for decades, so I think its at least worth considering.

Fourth..........I always suggest starting the vehicle in a dark garage and watching for any spark jumping somewhere. and double check the plug wire routing (one more time).

Hope you find the problem soon........

 

Is the distributor hold down clamp providing a good solid ground?

 

Some after market lifters use less preload. Check manufacture and look at their specs.
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