My Ford 7.5 carburated motor is running rough

[Bilito]

Originally Posted by jmerritt

As someone I think has already suggested there is a two stage power valve available that is not subject to rupture from a backfire through the carb. Also, were you able to find the idle adjustment screws?

John

After I found the BB in the distributer Vac line, replaced the line and got it running almost like new again I suddenly remembered that we totally forgot to connect the wires back to the alternator. I crawled under it friday, connected the two wires and then I had to go and do something before I could start it up. Later I came out and started the motor and one of the belts was squealing, so I shut it off and started it again, more squealing, what the heck, it was running nice and quiet and all I did was make one screw down connection and one plug in connection. I got so mad I shut it off and just walked away.
Yesterday we found ourselves at an RV dealer looking at new RV's as a way, I guess, to get my mind off the issues that keep popping up.
We saw a Jayco Melbourne 27F which was way out of my price range and a Winnebago Aspect 26A which was much less and had that curved roof which I liked much better, even tho the Winnie was less we liked it better, they both had the same floor plan with two slides, but that's just a dream, for now I gotta go back to reality and get this Silver Eagle 32 finished.

[Bilito]

Originally Posted by Bilito

After I found the BB in the distributer Vac line, replaced the line and got it running almost like new again I suddenly remembered that we totally forgot to connect the wires back to the alternator. I crawled under it friday, connected the two wires and then I had to go and do something before I could start it up. Later I came out and started the motor and one of the belts was squealing, so I shut it off and started it again, more squealing, what the heck, it was running nice and quiet and all I did was make one screw down connection and one plug in connection. I got so mad I shut it off and just walked away.
Yesterday we found ourselves at an RV dealer looking at new RV's as a way, I guess, to get my mind off the issues that keep popping up.
We saw a Jayco Melbourne 27F which was way out of my price range and a Winnebago Aspect 26A which was much less and had that curved roof which I liked much better, even tho the Winnie was less we liked it better, they both had the same floor plan with two slides, but that's just a dream, for now I gotta go back to reality and get this Silver Eagle 32 finished.

Turns out it was the alternator belt doing all the squealing, it had just a little play, I gave it a squirt of WD-40 and it stopped immediately, gotta get help to tighten that up. I had no idea that when the alternator made electric it put that big a load on the engine that it could cause the belt to slip and squeal. It is charging, I did look at the gauge to be sure.

[oldbeek]

If alternator was disconnected previously, it will charge heavily and cause belt to slip some. Do not over tighten. If you can turn the alternator using your fingers and twisting the alternator fan, it is too loose. If not you are OK, let it charge some. Lots of vintage vehicle alternators squeaked the belts on first start up. We are spoiled by serpentine belts.

[Bilito]

Originally Posted by oldbeek

If alternator was disconnected previously, it will charge heavily and cause belt to slip some. Do not over tighten. If you can turn the alternator using your fingers and twisting the alternator fan, it is too loose. If not you are OK, let it charge some. Lots of vintage vehicle alternators squeaked the belts on first start up. We are spoiled by serpentine belts.

it was too loose and I got it tightened down a tad more. it is fine now. The carb kit from Holley arrived today. It is now called a high performance TRIC-KIT, Wow it's got about a Kazillion parts, guess I will remove the carb tomorrow and get started. In the instructions it tells how to drill out the plugs for the idle screws, no wonder I could not find them, they plugged them with soft metal

[Dave78Chief]

Carb overhaul - pictures pictures for YOUR reference during re-assembly

Even before you start removing it from the engine so you can remember where things connect to

Dave

[Bilito]

Originally Posted by Dave78Chief

Carb overhaul - pictures pictures for YOUR reference during re-assembly

Even before you start removing it from the engine so you can remember where things connect to

Dave

Taking pictures from every angle, during removal several things popped up.. The body hold down bolts, one was only finger tight, the other three were just a little more then finger tight.

We took primary bowl off so far, looks to be very clean
There was an important note came with the kit that two stage power valves are no longer in production and are being replaced with a new single stage unit.
From what I see on the supplied replacement chart I have a #16 valve and it should be replaced with a 65, the one in the kit is a 45. Actually the one in the kit is stamped 4.5

[whem2fish]

Agree lot of the time this was in the early 1980's you had to add a decimal inbetween the numbers

[jmerritt]

You might be able to get a two stage power valve from Ford by giving them your carburetor number. Not sure but I think going to a single stage which works fine for autos isn't a good thing. Mileage isn't good to start with in a MH but a single stage power valve will probably make it worse.

John

[jmerritt]

I found the Ford abbreviations at this link from a Ford truck site.
Ford Truck Enthusiasts Forums - View Single Post - Vacuum Diagram Acronyms

[Dave78Chief]

The number represents the level of vacuum needed before the power valve opens up (6.5hg or 4.5hg). The power valve enriches the air/fuel mixture under load once a certain vacuum point is reached. When you depress the accelerator pedal, engine vacuum drops. When the vacuum level drops to the trigger point (6.5hg or 4.5hg), the valve opens enriching the mixture. Used to help the carb transition from just using the primary barrels to using both primary and secondary barrels.
http://www.holley.com/data/TechServi...ech%20Info.pdf


Single stage vs 2 stage power valve description: http://books.google.com/books?id=_fT...0valve&f=false


Dave

[Bilito]

Originally Posted by jmerritt

You might be able to get a two stage power valve from Ford by giving them your carburetor number. Not sure but I think going to a single stage which works fine for autos isn't a good thing. Mileage isn't good to start with in a MH but a single stage power valve will probably make it worse.

John

This engine and carb was made in 1989 especially for vehicles with a gross weight rating above 14,000 pounds. when I spoke to the Holley rep on the phone I told him it was for an RV and he assured me the power valve in the kit is what I need.

[Bilito]

Originally Posted by Dave78Chief

The number represents the level of vacuum needed before the power valve opens up (6.5hg or 4.5hg). The power valve enriches the air/fuel mixture under load once a certain vacuum point is reached. When you depress the accelerator pedal, engine vacuum drops. When the vacuum level drops to the trigger point (6.5hg or 4.5hg), the valve opens enriching the mixture. Used to help the carb transition from just using the primary barrels to using both primary and secondary barrels.
http://www.holley.com/data/TechServi...ech%20Info.pdf


Single stage vs 2 stage power valve description: Holley Carburetor Handbook--4150 & 4160: Selection, Tuning & Repair - Mike Urich - Google Books


Dave

Thanks for all this information, where do you get this stuff anyway?

I think it will be fine with this 45 power valve that came in the trickit, from what I got after all that reading about carbs and power valves is that they cannot be blown out and in my case extra fuel when needed will be added later rather then sooner, I will need to mash down more on the gas pedal to lower the vacuum to get more power going up a hill

[whem2fish]

Back fire thru Carberator chances its toast my knowledge cams from old school drag racing

[Dave78Chief]

Yep, you read it all correctly (Google can be your friend). I would prefer to let an mfg like Holley make the claim than myself. Some may disagree with an mfg's claims based on actual experience though.

Holley claims that in 1992 Power Valves were redesigned to prevent the blowout (their words not mine). You will be installing a new one anyway so it is a moot point in your case.

Dave