18rg problem

[kent]

Hope someone can help !!!

I have a ra28 from 1977, it had the 18r as standard, i converted it to a late model 18rg(head nr 88270, and solex carbs)
It has lunenition optronic ignition (came with eletronic ignition but parts where missing)

The problem is that it runs unstable when i drive at constant speed but not when acclerating and when it hits 5000rpm it sounds weird, (like when you pull a cats tail)

I used the sump and pickup from the 18r and the oilpresure is great, it dosend get hot and it dosend mix oil and water.

I have tried with new sparkplugs, leads, rotor, distributer and fuel filter.

Am i using the wrong oil ?, i was recommended a classic oil 20w-50.

Or do i need to rebuilt the carbs/engine ?

[airfireman1]

Sounds much like a carb problem, air,vacuum leak. The reason it runs fine on acceleration is that it is probably putting plenty of fuel in on that mode but on cruise it is running a little lean.

[orangea22]

Did you diagnose the problem buddy?

By pulling a cats tail do you mean it has a fan belt whistle sound? like squeeling? My 18rg has a similar problem. (its not the fan belt; i haven't spent time on my problem).