250 with HEI Questions

[G8rN@te61]

I had been posting questions in a different model thread I found so I thought I would bring it back to this Model year forum even though my engine is 250 out of a '71 camaro put into my '61 step side. Good ole google has provided me with more questions than answers....

I installed an offy intake, 12bolt dual headers to porter mufflers, an Edelbrock 1404 500cfm carb, and an assault racing 50kvolt HEI and wires. Compression for all cylinders was ~120 -125 which is pretty good since factory is 130. 3speed saginaw.

Truck runs great! Starts right up. Way smoother, no stalling, and no pinging whatsoever. Sounds great! However, I noticed that its now spitting some black soot out and thus probably running rich. Smokes a little too.

I turned the mixture screws 1/4 turn clockwise (leaner) on the carb, I also bumped the timing up to 10 and gapped my NGK UR4 plugs to .6 which is in the middle of the recommendations of .45 to as high as .8(Langdon).

#3 plug is really black which I understand is common on IL6's so should I go with a different plug or gap? Other plugs seem to look good. Brownish and clean. I might need to tighten the manifold bolts i've read.

Is there a better plug to use since I am modded? Go hotter?

Should I increase the timing to 18 which Langdon recommends?

I tried the relay trick for the HEI but I have since read that is a waste since the amperage draw is so low at 2amps and I only see a .5 volt max difference across the relay. Intermittently it won't turn off either. Its a cheap relay from Oreillys so I could buy a Bosch one and try that. I am probably going to go back to just hooking it up to the solenoid output since my electrical system doesn't have that resistor wire connection like 67's plus do.

Thoughts and suggestions?

Thanks,
Nate

[The Rocknrod]

If you want I can move this thread to the Engine section - http://67-72chevytrucks.com/vboard/f...splay.php?f=24

[G8rN@te61]

sure didn't even think of that

[vince1]

Just take this as opinion because I am not knowledgable on the parts you are using.

I think you've got carb problems. Aside from that engine not needing such a large carb it needs to be jetted properly. As far as I know turning in the mixture screws only affects the idling.

https://www.youtube.com/watch?v=wR_AfQjyT-A

I agree you don't need a relay to run the HEI. As far as timing I have usually done it by ear and feel that I get it right after a few tries. By all means experiment a bit with your timing light.

[D13]

Chevy 6's run lean on the outside, insides are always a little wet, but it sounds like you do need to lean the whole thing out.
Increase timing 1-2 degrees and see what you think, but it won't overcome a rich mixture.

[G8rN@te61]

Maybe the offy intake and bigger carb compounds that. I might start over on the lean screws on carb. Supposedly they come 1.5 turns out as stock. I might check it and go from there.

Plugs are stock oe according to NGK website. Wondering if someone has experience with something else.

[Dead Parrot]

The idle mix screws ONLY adjust idle mix. They have little to do with the mix once the throttle plates start to open.

Did you check the float levels on the carb? Eddy carbs often need the float levels set out of the box. If you open the carb to check the floats, note what jets are installed. Then consult the manual on what jet/needle combos will lean the mix. While you have to open the carb to swap jets, the needles are easy to swap via the power piston cover plates.

A lot of Eddy carbs come from the factory set rich on the assumption they are going on 'race cars'.

Another 2nd on the ditch the HEI relay thought. One less thing to fail.

[G8rN@te61]

I naturally assumed I wouldn't have to dismantle the carb once purchased lol. I am still wondering about plug and timing specs...

[vince1]

I wouldn't worry about the plugs. UR4 is correct according to the NGK chart and should be gapped at .035". With HEI you should be good at .045". At that you have more than enough zing to light off the fuel air mixture.

Like has been stated your biggest obstacle to having it run correctly is getting the carburetor set up correctly. On the upside, think of all that you will learn through the process.

When is the turbo charger going on it?

[G8rN@te61]

no turbo lol.

I thought the .045 was for hei with monojet and no other mods? BAsed on what i have gleened form multiple sites i put it at .06(some say even .08) since its more modded with intake, headers and carb. I also read as high as 18 degrees timing according to Tom langdon. I'm at 10 degrees initial now. I might bump it to 12 and see how it goes. I might but a hotter plug for cylinder #3 to see what it does too.

I do think its not burning all of its fuel like it should. I don't think its getting flooded by the carb though either. Im trying to find an ase mechanic near me that can do a gas analyzer to see where i am at but all of these people on facebook marketplace advertise they can work on it but wont respond to me either... I think many guys nowadays just plug in a laptop and dont know what to do unless it tells them to.

['68OrangeSunshine]

I have a similar rig to yours. '68 C/10 Stepside. 292 L6 (bored .030-over), Badger cast pistons, 260H Crane cam. I went oversize on intake valves [1.84'', stock is 1.6''], stellite valve seats. Offy 4 Bbl intake, EDL-1404, Clifford headers, dual exhaust w/ N-pipe crossover, turbo mufflers. Trans is SM 465 4-speed, 1-piece prop shaft, 12 Bolt 3.73 rear w/ Eaton posi. 235/85/R16LT tires.
The Edelbrock carb is a simple design, a reboot of the original Carter AFB [Aluminum Four Barrel]. Obtain the Carb Owners Manual from Edelbrock [free] and a parts kit EDL 1477. You will have to look on the charts and replace Metering Rods and/or Jets to match the performance configuration you desire. With vacuum secondaries, it will only pull in as much fuel/air mixture as necessary. You can't be overcarburated. Maybe 500 CFM is too much for a 250, but nobody makes a 400 CFM Edelbrock Performer.
Edelbrock tech is friendly and will talk to you on the phone or by email.
Sounds like it's too rich right now. Replacing those components is not hard, and can be done with the carb still on the manifold. You have to pull the ''air horn'' top to get to the jets, but the metering rods and springs can be accessed by the little hatches on top of the airhorn. You may also have to swap out the different colored metering springs in the Edelbrock system.
I had an HEI distributor from Assault Racing. It failed right out of the box, but was out of warranty by the time I got around to that end of the project. I kept the billet aluminum body and rebuilt with every electrical component US-made [when possible]. Original Chinese module was a dud. Runs OK now. I run NGK plugs gapped .045. Can't remember the part number.
I use 12* initial timing.
I have to pass Arizona emissions annually. My mechanic buddy and I have a set of ''Emissions - Jets and Metering Rods'' we put in the carb for the test, [leaned waaay down] and once it's thru the test and passed, switch back out to performance mode.
Good luck and keep Inlining.

[G8rN@te61]

Nice setup! This is helpful. What rod and jet setting are you at according to Edelbrock chart? I think I just need to rod "down" to #4 maybe....

['68OrangeSunshine]

Originally Posted by G8rN@te61

Nice setup! This is helpful. What rod and jet setting are you at according to Edelbrock chart? I think I just need to rod "down" to #4 maybe....

I'll get back to you, I have to look it up.

['68OrangeSunshine]

Originally Posted by G8rN@te61

Nice setup! This is helpful. What rod and jet setting are you at according to Edelbrock chart? I think I just need to rod "down" to #4 maybe....

Sorry I didn't get back to you sooner. I could not find my Edelbrock Carb Owners Manual with all the dope in it.
So I called my mechanic buddy, and he looked in his book.
When I jet down my EDL-1404 for emissions, the set up is:
Chart position [11]
Jets -- .083
Rods -- 65 x 52
Once the State inspectors are satisfied, we retune to:
Chart position [6]
Jets -- .086
Rods -- 67 x 55
I run it that way all year, until September, when I go thru the whole process again.
If I registered the truck with a Vintage Year-Of-Manufacture [YOM] Plate from 1968 ARIZ, I could bypass annual emissions, but I'd have to change insurance companies, and since the Stepside is the daily driver for now I want full coverage.

[Dead Parrot]

Another thing to consider: https://www.summitracing.com/parts/edl-1486
A calibration kit for your 1404 that contains an assortment of jets, rods and springs.

Take a look a image #4 and #5 on the website, it is a calibration chart and matching parts list.

Stock GM HEI gap settled on .045 after starting with .060.

I would dial in timing first(sounds like you are close), carb second, and then worry about plug heat range. If #3 is still black after everything is done, might go a step hotter on it only.

[G8rN@te61]

yep just ordered that kit. going to put timing to 12 and see how she goes until it arrives.

[G8rN@te61]

awesome thanks!!!!

[G8rN@te61]

Question on the throttle arm. I have the stock 1961 throttle pedal and arm. The 2 piece throttle arm that attaches to it needs to be flipped so I can use the longer side. Once I remove the bolt, it won't come loose. Do I need to just tap it with a long screwdriver and hammer?

I changed out the rods in the carb to a step down leaner and it seems to run great now. I am just having problems getting the throttle to open up now and I feel its because its no pulling the cable enough.

['68OrangeSunshine]

I have a '68. It also had a pedal arm that was connected to a rod in the engine bay, that moved a bellcrank that pushed the short rod that connected to the throttle. It was a major Rube Goldberg. It never got WOT, It could jam, ice up in extreme weather, and lose small parts required for proper articulation.
I swapped out the in-cab pedal for a MY '72 pedal/armature assembly and used a Jen-E throttle cable direct to the carb throttle.
No more jams. Full WOT. Hair trigger response. [That took a while to get in the habit of completely lifting my boot off the gas pedal at stops.]