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post #1 of (permalink) Old 10-27-2002, 09:43 AM Thread Starter
 
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Anyone running a Weber with GM HEI

I am having some difficulty with this weber I am trying out.
I have a newly rebiult 258 bored 30, with a 4.0L Head, and GM HEI. I was running a non feedback carter and didn't have any problems (except not too much power over 3500 rpms). And from everything I've serched the Weber is a good carb with lots of power for the 258 even after 3500rpms.
But, I can't get rid of my detonation. I had the Dist recrved, and have done everything, even back the initial timming way back, and have the vacuum canister (vacuum advance) fully adjusted for minimal vacuum advance (compr hei recurve kit). I have taken the carb off a few times to clean and make sure nothing is wrong. I have a fuel regulator installed and set at 3psi. But this thing ain't got much power, and seems ot be runnign lean, and keeps pinging on the freeway at part throttle.
Any one else have this problem with their Weber? Please, I am running out of patients.

Shawn
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post #2 of (permalink) Old 10-27-2002, 06:02 PM
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Re: Anyone running a Weber with GM HEI

It sounds like a timing problem. Do you have the dist. vacuum hooked up to the manifold? It should be. Did you set the timing with the dist. vacuum line plugged? The timing should be set at 8 btdc. Make sure the vacuum advace is working properly. Is the timing advanced from the GM dist. the same as the one from your jeep dist? Did you do both the weber and the gm hei at the same time? Try the weber with your jeep dist.
post #3 of (permalink) Old 10-27-2002, 08:11 PM Thread Starter
 
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Re: Anyone running a Weber with GM HEI

I set the timming (with the vac adv line plugged) at 1600rpms at 8 btdc. That puts the timming at like 0 btdc at idle or so. I have been running this HEI for months now without a problem (after the Comp recurve kit) with a non feedback Carter. As far as I know with the recurve kit the timming advance curves are very similar, am I wrong? Is there something else I am missing? Or is this modified 258 and a Weber 32/36 not a good combination?
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post #4 of (permalink) Old 10-27-2002, 08:32 PM
 
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Re: Anyone running a Weber with GM HEI

Running a 32/36 Weber on a highly modified 258 would be like you trying to run uphill with your fingers in your nose. You need more volume. Both air and fuel. The 4.0L head will flow alot more volume than the standard 258. You should be looking for at least 350 plus CFM's. The Edelbrock 500 4 barrel runs pretty well on that motor with a decent cam. The Weber 40 IDF or 44 IDF would be the better way to go. They sell for abourt 350.00 from Fast Freddy's.
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post #5 of (permalink) Old 10-27-2002, 08:34 PM
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Re: Anyone running a Weber with GM HEI

You need to hook the distributor up to ported vacuum. On the old computer controlled BBD, the engine used manifold vacuum and the computer, with the help of the knock sensor, retarded the timing as necessary. You donít have that now. The Weber has a port for ported vacuum. Use that. You are timing the engine correctly, but the RPMs are too high. Try about 700 RPMs. But when you hook up to manifold vacuum, you are now too far advanced. Hope this helps.
post #6 of (permalink) Old 10-27-2002, 10:05 PM
 
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Re: Anyone running a Weber with GM HEI

What you need to do is throw away your weber. Then get fuel injection, this is the only good way in my opinion. If you every plan on going to colorado or any other high altitude trails you'll wish you had fuel injection or tune it to the altitude.
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post #7 of (permalink) Old 10-27-2002, 10:29 PM
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Re: Anyone running a Weber with GM HEI

1. Reconfirm the timing.
2. If the timing's good.. the problem could be elsewhere.
3. You say the engine's running lean. What happens if you enrich the mix?
4. Is the engine running hot or cool?
5. How many miles on the engine? Carbon build up in a cylinder?
6. Is there a minor vacuum leak ANYWHERE?
7. What do the Spark Plugs look like?

You see, if it ain't a problem with timing, you've got to look for the other causes of pinging...
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post #8 of (permalink) Old 10-28-2002, 12:45 AM
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Re: Anyone running a Weber with GM HEI

I have a -88 Yj with a stock 258" and running a Weber 32/36. I also have problems with pinging under load, but it seems like it`s getting better over time. So my guess is that there is a carbon buildup that is burning away over time? I had absolutely no pinging with the Carter, but it run like crap. And yes, i have disconnected the EGR-valve. I`m going to re-connect it one of these days to see if that can help getting rid of the pinging.
post #9 of (permalink) Old 10-28-2002, 05:45 AM
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Re: Anyone running a Weber with GM HEI

I installed a weber 32/36 and GM HEI on my Jeep about a year ago. I hooked up the EGR valve, but I don't think it was ever working. I had a lot of trouble with pinging. I put an adjustable vaccuum advance on the distributor and tried adjusting it, but even at the minimal vaccuum advance adjustment, I had to retard the static timing so far back that the engine had no power. I put the original GM vaccuum advance on (I noticed it had a good amount less travel than the adjustable one). Even with this, I have to run premium gas to allow timing the engine for decent power. Your problem is compounded by the fact that your 258 is bored .030 over, because that increases the compression ratio (albeit a small amount), which makes the pinging worse. I would say try using a stock HEI vaccuum advance, or limiting the amount of advance the on the adjustable one. Good luck figuring it out, and I hope this helps some.
post #10 of (permalink) Old 10-28-2002, 06:26 AM
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Re: Anyone running a Weber with GM HEI

When I first got this Jeep it was bone stock. Had to run 92 octane and it was still pinging. I did the Nutter bypass and hooked the distributor up to ported vacuum. I now had more top end power and could use 89 octane with a little pinging. I rebuilt the engine (30 over, small cam) and installed the Weber. More power, better drivability, but still ran on 89 octane. I then installed a HEI distributor out of a 79 Nova. I made no changes to the distributor other than a new cap, rotor, and plug wires. With the timing set at 6 degrees, I could now run 87 octane with no pinging. I then installed the 4.0 head. Big power increase, but I did have to rejet the Weber. Still no pinging, even before I rejetted. I am not using the EGR. The Weber is big enough for me. Remember, GM put 400CFM 2 bbls on big block engines. The Weber 32/36 is a 300 CFM carb. Lower the RPMs, retime, and hook the distributor up to ported vacuum. If you are still pinging, you may have a problem somewhere else. Hope this helps.
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