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Unread 08-10-2015, 10:54 PM   #1
STJP
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Engine break-in with new Weber

Friends,

I started my engine rehab (1985 4.2) with plans to clean up all and install a new Weber 38. The Weber will be the only performance upgrade. Now caught in the "might as well since I've come this far" Jeep money pit, I have decided to have the engine rebuilt and have found a good shop to do it.

My question to those with more experience is: So when I have the engine back from the shop and reinstalled in the Jeep I will install the Weber, is the time spent running, stopping, restarting, warm ups of the engine to tune the Weber going to be a problem for proper break-in for cam, rings, etc? I have never properly tuned a Weber before. I know...I am anal!

Thanks for your advice,

JS

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Unread 08-10-2015, 11:13 PM   #2
Chrisinchwk
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My thought would be to use the old carb you removed if its dialed in. Problem with starting from scratch with a new one is too lean and you run the risk of burning up valves, to rich and you wash the oil off the cylinders. I just went through similar. Full rebuild top to bottom (think mybe they didnt replace one washer on a nut . Rebuilt my carb at the same time but i had baseline numbers to go off of to get it pretty close. After running in the new cam (assuming you will replace it) dont brek it in too easy.
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Unread 08-11-2015, 12:24 AM   #3
BagusJeep
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I would just go with it. If you buy the proper kit from Redline they will have been jetted correctly.

The trick on assembly is to follow the instructions. Amazingly some people do not and it runs poorly as it is not set up correctly.
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1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
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Unread 08-11-2015, 03:35 AM   #4
Matt1981CJ7
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That's a tough one.

I know from experience that a redline Weber 38 is virtually plug and play on a 258. But you never know what problems may arise on a new install.

If you have an old carb that's tuned and known to work on this engine, I'd be inclined to use that for the break-in, then swap to the Weber.

Matt
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Unread 08-11-2015, 05:28 AM   #5
Mike Romain
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Some Webers are plug and play, some are plug and pray. I would not use an unknown carb of any flavour for a first run up, could be trouble.
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Unread 08-11-2015, 05:33 AM   #6
Matt1981CJ7
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Quote:
Originally Posted by Mike Romain View Post
Some Webers are plug and play, some clones are plug and pray.
I fixed it for you, Mike.

Matt
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Unread 08-11-2015, 05:53 AM   #7
Mike Romain
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Quote:
Originally Posted by Matt1981CJ7 View Post

I fixed it for you, Mike.

Matt
What, you think every new Weber coming out of the box will just work? None could be defective?
That is way too much trust for my liking. I wouldn't use a new untested carb of any flavour on a first run up, the consequences could get extremely expensive fast.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 08-11-2015, 06:10 AM   #8
Matt1981CJ7
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Quote:
Originally Posted by Mike Romain View Post
What, you think every new Weber coming out of the box will just work? None could be defective?
Well, I base my comments on installing 2 different Webers on my 258, and countless others that I've helped guys install. What do you base your comments on, Mike? What you've read?

Quote:
Originally Posted by Mike Romain View Post
That is way too much trust for my liking. I wouldn't use a new untested carb of any flavour on a first run up, the consequences could get extremely expensive fast.
You do realize that some guys have no choice, don't you? Particularly guys who swap engines with different displacements and don't have multiple carbs laying around.

I'd opt to run a new Weber on a fresh 258 rebuild over a used or rebuilt Carter any day of the week, and twice on Sundays.

Matt
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Unread 08-11-2015, 06:20 AM   #9
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I've painted myself into this corner. When I started this you (Matt) recommended I take it one step/component at a time. Didn't listen too well did I?

I had a Solex 34 DGEC on it that was running at time of removal. Tended to rich, but was running. With the Weber 38 I plan to have all applicable smog components related to EGR, vapor canister, and OEM air cleaner. Possibly you fellows could advise (when I get there) how to set up 38 initially with abbreviated vacuum lines to those specifically required for carburator proper function.

With that said..........at present the intake is completely stripped. I could install the 34 for break-in with rinky-dink air cleaner etc, but am not confident I will have all back to same point prior to disassembly. The 38 with careful setup may be as good as the 34...who knows? One key would be for me to make sure the distributor gets put back in correctly.

Thanks for you comments Chris, Matt, and Mike
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Unread 08-11-2015, 06:31 AM   #10
Matt1981CJ7
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STJP,

I wouldn't bother with the Solex clone, personally. They are just too trouble prone.

If I were you, I'd confirm the jetting, mixture screws, and idle speed screw on the 38 are to factory specs, then throw that thing on. It will be fine.

As for a basic vacuum layout, that's an easy one. We can cover that when you get there.

Matt
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Unread 08-11-2015, 06:41 AM   #11
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I appreciate y'all debating these issues on my behalf.

I respect your experience Mike, but it does occurs to me.....what do those with say a a newly rebuilt 304 and have a new intake and carb do? I am here out of inexperience and ignorance, but it occurs to me now that Matt has a point, many don't have a choice.

The builder told me he generously lubricates the cam etc etc with break-in lubricant and I will make sure I use a top break-in oil for first start to help insure no engine damage.

Thank you all......got to go make money...........

JS
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Unread 08-11-2015, 06:44 AM   #12
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Thanks Matt!
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Unread 08-11-2015, 06:54 AM   #13
swatson454
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The challenge with Webers is nearly always the idle settings. Since this is a start-up on a new engine, you're going to zip right past all of that stuff and go up to ~2,500 rpm so I wouldn't worry about the idle jets, mixture screws or idle speed settings.

I'd just have a timing light already hooked up and make sure you're getting ~40* during the break in. Just twist the distributor if you're not. Once you're done with the break in, you can drop the rpm back down and start fiddling with the carb settings and initial timing.


Shawn
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Unread 08-11-2015, 07:02 AM   #14
Matt1981CJ7
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Good point about the idle settings, Shawn. They don't mean much at 2500 RPMs.
That said, it takes about 30 seconds to confirm those screw settings. Just sayin'.

The primary jetting of the 38 is probably the most critical thing for the OP, IMO.
Chances are good the Redline factory jetting will work just fine, but I'd probably check them anyway, since is so easy on a Weber.

Matt
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Unread 08-11-2015, 07:29 AM   #15
pedal2themetai
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Something no one said.. was the break in procedure on a fresh motor.. you well blow past any idle system.
2500 RPM's for the first 20 minuets Varying to 3000 rpm's burst.
timing around 28* at 2000rpm's. look for leaks or problems.
Good luck
tim 48 years experience
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