Rochester Carb swap

[ScottT]

I was able to determine that my zenith knock-off carb is the issue with odd running addressed in a previous post.
I am looking at converting to a Rochester, ease of parts, their cost (parts) and positive reviews I have read and heard; instead of rebuilding.
Anyone one out there have first hand experience with the swap and running?

Thanks
Scott

[graniterover]

I read your issues. Those were the exact issues I had with my Rochester. I swapped to a weber and have been running beautifully since.

On the same truck with all things the same, I had:

solex, rochester, motorcraft, weber. Weber is so far beyond all the others. The motorcraft actually wasn't bad, it just leaked.

If you do go the route of the rochester, I'd really make sure that you take the time to set it up properly with the right jets. Mine may have sucked because I did not do that, I just bolted it on.

If I had time, and I don't, I'd love to try fuel injection. I'm sort of surprised someone doesn't have a kit available. Seems there is for every other engine out there.

Good luck.

Mark

[ScottT]

Mark,
I too have gone through various carbs over the years and rovers.
I went from a Weber to a zenith on the 88 I had years ago. That was a noticeable change I thought. The current 109 has had 2 zeniths (or knock-offs) over the last 8-10 years.

I've read over TeriAnns page on Rochester carbs and found a place that sells them rebuilt for $160. I am checking on the Jetting

I emailed someone with a series truck on ebay in Nicaragua that was running a Toyota Corolla carb that was bolted on a plate that was welded to the manifold. I like the idea of that but I'm not sure I could commit to it.

As for fuel injection, I have zero clue as to where or how to do that. I may be tempting if it meant more time behind the wheel.

Thanks
Scott

ps- what motorcraft model was it ?





I read your issues. Those were the exact issues I had with my Rochester. I swapped to a weber and have been running beautifully since.

On the same truck with all things the same, I had:

solex, rochester, motorcraft, weber. Weber is so far beyond all the others. The motorcraft actually wasn't bad, it just leaked.

If you do go the route of the rochester, I'd really make sure that you take the time to set it up properly with the right jets. Mine may have sucked because I did not do that, I just bolted it on.

If I had time, and I don't, I'd love to try fuel injection. I'm sort of surprised someone doesn't have a kit available. Seems there is for every other engine out there.

Good luck.

Mark

[SeriesShorty]

Hey Scott, where'd you find the rebuilt Rochesters for $160? I'm working on a deal for a used one off a forum, but if it falls through I'd appreciate a back up connection for one.

Thanks!
J

[mechman]

I've found that 2.25's seem to run best with the Zenith carbs (even the knock-offs). I've gotten pretty good at rebuilding the buggers. Did you try taking it apart and cleaning it out? If you pop the top, yank out the accelerator pump (the vertically oriented bright aluminum piston) and check it for scoring. Polish the sucker with a piece of crocus cloth until it shines, then gently polish the bore it rides in. Check the ball valve at the bottom of the bore - make sure it's a bit loose under the retaining clip and rattles when you shake the carb body. Clean this really well, and make sure carb cleaner passes through the valve.

I've found that a scored accelerator pump piston hangs up, and that if the check valve ball is even a little dirty or stuck, your truck just will not run correctly.

I've built these Zeniths back up from multiple junk units into reliable working carbs. Make sure they are clean inside, and the accelerator pump is polished and working correctly, and they are quite reliable and easy to tune.

Mech

[lew_sa]

I'm running a Rochester now. I had a big problem with the engine hesitating under acceleration. I tried increasing jet size, closing the gap for the accelerator pump, mixture adjustments, constantly messed with engine timing, you name it... I finally realized that the carb wasn't getting warm enough b/c the PO installed headers. When I installed a new stock exhaust manifold the hesitation disappeared. I was able to go from a 54 jet down to a 48 jet. That being said, anyone want an unused header?

R/,
Lew

[ScottT]

J,
Found them at www.carbjunkys.biz. They can jet however you want.





Hey Scott, where'd you find the rebuilt Rochesters for $160? I'm working on a deal for a used one off a forum, but if it falls through I'd appreciate a back up connection for one.

Thanks!
J

[ScottT]

Mech,
Thanks for the detailed post I will try that.
I didn't know what crocus cloth was but google again saves the day.

Did you need a rebuild kit or to do what you mentioned or just the fine grit and tools?

Thanks again
Scott



I've found that 2.25's seem to run best with the Zenith carbs (even the knock-offs). I've gotten pretty good at rebuilding the buggers. Did you try taking it apart and cleaning it out? If you pop the top, yank out the accelerator pump (the vertically oriented bright aluminum piston) and check it for scoring. Polish the sucker with a piece of crocus cloth until it shines, then gently polish the bore it rides in. Check the ball valve at the bottom of the bore - make sure it's a bit loose under the retaining clip and rattles when you shake the carb body. Clean this really well, and make sure carb cleaner passes through the valve.

I've found that a scored accelerator pump piston hangs up, and that if the check valve ball is even a little dirty or stuck, your truck just will not run correctly.

I've built these Zeniths back up from multiple junk units into reliable working carbs. Make sure they are clean inside, and the accelerator pump is polished and working correctly, and they are quite reliable and easy to tune.

Mech

[mechman]

Scott,

I've always had a rebuild kit on hand when I redid them, but in all honesty I often only needed a new gasket for the top. If your carb is dirty and worn, throwing in a kit while you're at it is usually a pretty good idea.

If you do get a kit, check the new mixture screw very carefully against the old one - the kits are made for the Solex-Zenith carbs, and the thread is much coarser than those on the earlier Zenith units. If you have an early carb body, polish and reuse the old screw. Amazingly, almost all of the rest of the parts are interchangeable between the early and late carbs (except, as I recall, anything threaded), including the tops.

When cleaning the ball valve in the bore of the accelerator pump, be careful not to pop out the retaining spring clip. They're a real bear to get back in place, and correctly. Typically I would soak it (sometimes overnight), then gently use a small chemical brush and lots of carb cleaner to get it clean. Make sure you put the wand on the can of carb cleaner, and clean out the passages in the carb as well.

I know crocus cloth can be tough to find, but don't skimp. Emery cloth is too coarse for the fine polish you want on the pump piston. You don't want to open the tolerances, just remove as many of the scratches as you can. The cloth I use feels almost silky against my fingers, it's that fine.

Mech