Perhaps a moderator will move this thread to the "LSX + Carb Swaps" sub-forum.
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I will do a compression check in the morning as well as try to get a vacuum reading. This carb is brand new however, I have also put a slightly used carb(750) that was too much for another truck about four months ago onto this truck, as well as a 670 Holley that I know worked great on a Ford 351 earlier this year. As far as the timing goes the only thing I’ve been able to do, I advance my timing light 32° because I can only time it while it’s revved up so while doing that at about 3000 RPM my harmonic balancer reads zero. I haven’t been able to check what my idle timing is because I can’t get it to get below 1800 and you constantly have to be pumping the gas. I’ll post compression readings as well as a vacuum reading and hopefully everything will start to fall into place. Thanks again for all the advice.I was thinking the same thing re: the valve lash. Along those lines, I'd be interested in what a compression test
would give us? (ie: lower than expected compression = valve lash too tight = idling issues?
The plugs: They are showing rich / loaded up?
The carb: We have 2 separate concerns going on. First, we have to get the fuel bowl
filled to the correct level, but at the same time we don't want to send more pressure
than the float + needle + seat can maintain positive control over. I know that Quadrajets
don't like more than 5 psi maximum? I have to defer to Hipster on what the edelbrock
carb wants, but I'll bet that his recommendations are on the money. (Carbs like adequate
volume at low pressure, but they can't control high pressure at all given the needle & seat
with only a float to push back against the incoming psi. (!)
You know, pulling together the carb & spark plug reading discussions together, it doesn't
matter if you have a carb with a good float setting and too much PSI being fed to it OR
the right fuel pump pressure being fed to a carb with a too high float setting and/or there's
dirt/grit preventing the needle & seat from closing completely. Either way, if you have fuel
coming out the main venturis while the engine is idling then it will be so rich that the engine
can't idle unless you give it a fair amount of throttle. (To match the excess fuel.)
Q: Is there any way you can temporarily substitute a 'known-good' carb onto the top
of this engine? Doesn't matter what it's dialed in for, just need to be able to verify
that the 454 can idle correctly, get the initial timing set, ensure that it can take a
quick winging without backfiring, etc.
And if you don't have that, then do you have a 'known-good' engine that you can
temporarily run with this new carb on it? I don't care if it's a 302, 351W or 390FE motor,
just need a happy motor that we can verify that it will idle, accept winging the throttle
without backfiring, the float level is correct, etc.
From out here in upstate NY, I think that you are trying to troubleshoot through 2 or
more problems at once. But with a known-good carburetor I'm sure that everything
will quickly fall into line with the rest of your 454.
Good luck, and let us know what you find. Standing by --
I run an Edelbrock, a Carter 7 psi fuel pump, and a cheap Holley 12-803 4-9 psi fuel pressure regulator in my Jaguar. When I had the FPR in my Nikki-carbed RX-7 I ran the 2-4 psi spring, but to run the Edelbrock needs the 5-7 psi spring, adjusted down to around 5 psi.Do you have a fuel pressure regulator? I think they only want 4-5 pounds.
The Edelbrocks are a good carburetor for street driving. It's just a modern Carter AFB. They typically run well right out of the box unless your engine is radical. I'd suspect the fuel delivery over the carburetor.use something other than an edelbrock
I run an Edelbrock, a Carter 7 psi fuel pump, and a cheap Holley 12-803 4-9 psi fuel pressure regulator in my Jaguar. When I had the FPR in my Nikki-carbed RX-7 I ran the 2-4 psi spring, but to run the Edelbrock needs the 5-7 psi spring, adjusted down to around 5 psi.
With the fuel pump running but the engine off, does the fuel pump overpower the needle and seat in the bowl? Check to make sure there isn't fuel dribbling down inside the carb.
The Edelbrocks are a good carburetor for street driving. It's just a modern Carter AFB. They typically run well right out of the box unless your engine is radical. I'd suspect the fuel delivery over the carburetor.
I’m going to put a regulator in this morning. Thanks to several of you for the psi tips.I run an Edelbrock, a Carter 7 psi fuel pump, and a cheap Holley 12-803 4-9 psi fuel pressure regulator in my Jaguar. When I had the FPR in my Nikki-carbed RX-7 I ran the 2-4 psi spring, but to run the Edelbrock needs the 5-7 psi spring, adjusted down to around 5 psi.
With the fuel pump running but the engine off, does the fuel pump overpower the needle and seat in the bowl? Check to make sure there isn't fuel dribbling down inside the carb.
The Edelbrocks are a good carburetor for street driving. It's just a modern Carter AFB. They typically run well right out of the box unless your engine is radical. I'd suspect the fuel delivery over the carburetor.
Based on how black all the plugs were this morning I’d say it’s rich plus the inside of the brand new carb is already black like it’s one of my old used ones.its either very lean or your timing is off, maybe both,.., set the base timing with a timing light.. it doesnt have to be running, it just has to fire the plugs.. once u get it timed, start to slowly enrich your idle circuit on the carb,, once u get it idling fine, then tune the throttle response.. running lean is very risky, I wouldnt drive it anywhere with it lean. you can burn thru a piston in short order..
It should have idled with one of those carbs on it.I will do a compression check in the morning as well as try to get a vacuum reading. This carb is brand new however, I have also put a slightly used carb(750) that was too much for another truck about four months ago onto this truck, as well as a 670 Holley that I know worked great on a Ford 351 earlier this year. As far as the timing goes the only thing I’ve been able to do, I advance my timing light 32° because I can only time it while it’s revved up so while doing that at about 3000 RPM my harmonic balancer reads zero. I haven’t been able to check what my idle timing is because I can’t get it to get below 1800 and you constantly have to be pumping the gas. I’ll post compression readings as well as a vacuum reading and hopefully everything will start to fall into place. Thanks again for all the advice.
Less than 10% between all cylinders, all good.Here are my compression results from this morning also I was able to just feather the throttle enough to keep it rough idling around 600-800 rpm and the highest vacuum reading I got was 8. Thoughts??You must be registered for see images attach