High altitude compensator

[neshyynesh]

Hi guys I’m new to this forum and just recently bought a 87 power ram 50 that I just noticed my compensator is broken and truck don’t stay on. I’m in need of one ASAP. I’ve been looking for one but they all discontinued. I don’t know what to do and can’t find any around my local junkyards. I really want to get this truck going. Maybe someone parting out?

[geezer101]

Hi and welcome to mightyram. A quick question - do you live or drive anywhere in areas over 4,000 ft above sea level? I'd bet the compensator can be deleted and the vac port plugged up. A lot of Mikuni carbs weren't fitted with high alt compensators (the top cover on the carb didn't have the port drilled out) so....theoretically you could remove it without affecting your day to day driving. Better yet, plug it up and refit the compensator so it visually passes inspection seeming you are subject to Cali emissions. This will not affect emissions readings and they will be hard pressed to simulate 4,000 ft altitudes in a workshop!

*edit - just found out Modesto is a nose-bleeding 27m above sea level lol.

[geezer101]

I know this site relates to a completely different vehicle and carburetor but - http://datsun1200.com/modules/mediawiki/index.php?title=Altitude_Compensator

The system works under the same conditions and uses a similar method to operate.

[neshyynesh]

Hi and welcome to mightyram. A quick question - do you live or drive anywhere in areas over 4,000 ft above sea level? I'd bet the compensator can be deleted and the vac port plugged up. A lot of Mikuni carbs weren't fitted with high alt compensators (the top cover on the carb didn't have the port drilled out) so....theoretically you could remove it without affecting your day to day driving. Better yet, plug it up and refit the compensator so it visually passes inspection seeming you are subject to Cali emissions. This will not affect emissions readings and they will be hard pressed to simulate 4,000 ft altitudes in a workshop!

*edit - just found out Modesto is a nose-bleeding 27m above sea level lol.


So so basically I’m screwed until I find one right? Or could I still delete it for now? I’d still like to get the part though

[neshyynesh]

Is it possible to still plug or no?

[geezer101]

If you aren't 100% sold on the idea, try temporarily plugging it up. Hand cut a small piece of cardboard into the shape of the mounting gasket but don't add the vacuum port hole through the middle of it and test it out. If it solves your running problem you can then choose to either permanently seal it up (epoxy, JB weld etc) and delete the HAC completely, or seal it up and re-mount the HAC solenoid to keep it looking like it's functional.

[neshyynesh]

So I plug all three? The one going into the hac and the 2 coming out? Sorry I’m kind of a noob to carburetor vehicles

[geezer101]

So I plug all three?

Hmmm, I've only seen the single vacuum port HAC solenoids. There's a single port between the mounting screws - where do the other 2 connect to? The port I mentioned is the one I'd seal up first but there could easily be a vacuum leak being caused by the other ones and it's affecting internal vacuum metering. If you can post a pic or find a related image it would go a long way to helping you out (you might be either the first or one of very few members that have run into this issue)

[neshyynesh]

Will this pic work?

[geezer101]

Ahh, o.k. Clears up a communication issue. Thought you were referring to the HAC mounted to the carb. Because it's hooked up to the vac control module this may be a bit trickier than I first thought to bypass. You're going to need the whole vac circuit diagram to figure out what systems can be bypassed without interfering with how the engine runs. One of the lines from the bottom of the HAC has to connect to a solenoid on the carb so it gets a vac signal to ramp the throttle at altitude.

[neshyynesh]

Haha so it is gonna be harder than I thought. It’s ok if I can’t figure this out then I just have to be patient and find one. Thanks for all your help. Appreciate it