Rochester Guru?

[baja gs]

I didnt see if you have you checked for vacuum leaks. If not, spray brake cleaner around the carb gaskets, if rpms surge, you have a leak.

[jonnyc]

It is a bit leaky around the carb shaft, but nothing that I can find that wasn't there before.

[Lance]

I had a problem with my 109 that took me months to figure out, but the short version is there was a hole in the intake manifold where the two manifolds connect,up inside the intake manifold but on the exhaust side. The exhaust had eaten away the aluminum, you can't reach it to test it for leaks. I removed the intake manifold, plugged the intake hole were the carb. goes then slowly poured water in the manifold & sure enough water started leaking out of that black hole were the exhaust goes. Can't see it & there is no way to leak test it because of it's location. I don't know how common this is on Rovers, I haven't been around them very long but it took me about 6 months to find this. I fixed it for now by making a plate to go between to two manifolds.

[willincalgary]

I had a problem with my 109 that took me months to figure out, but the short version is there was a hole in the intake manifold where the two manifolds connect,up inside the intake manifold but on the exhaust side. The exhaust had eaten away the aluminum, you can't reach it to test it for leaks. I removed the intake manifold, plugged the intake hole were the carb. goes then slowly poured water in the manifold & sure enough water started leaking out of that black hole were the exhaust goes. Can't see it & there is no way to leak test it because of it's location. I don't know how common this is on Rovers, I haven't been around them very long but it took me about 6 months to find this. I fixed it for now by making a plate to go between to two manifolds.

My truck has always had some indications of a vacuum leak. It lopes on idle when choked and has a persistent miss despite having stellar compression, new cables, good timing, new properly gapped plugs and an electronic distributor. I have tried everything imaginable to find a vacuum leak as whenever people get under the hood they immediately suspect one. Never had any luck. I will have to check on this.

[Lance]

Willincalgary: My simptoms started out of the blue & I had a misfire on two cylinders. I to tried everything I could think of to make it run. Check your manifold, It's pretty easy to remove.

[jonnyc]

Well, this is getting frustrating.
I checked everything I did to the carb, put a bigger jet back in, ran 2 doses of upper cyl./head cleaner/lube, hunted for any possible vacuum leak.....and it's still running worse than before I rebuilt the carb.
Timing and ignition system are good, fuel system from tank to carb inlet are good and clean.
Idle is still too high, surges a bit, and is too rough and "poppy".
I really appreciate the input so far, but I feel I need more. It's too cold to start with the manifolds, some I'm looking for some quicker ideas.

[Lance]

Did you ever find anything? Fixed?

[jonnyc]

No, not yet. Weather's supposed to be nice tomorrow, so I will go through all I can to solve the problem. I'm leaning towards some kind of major vac leak, or a few small ones. If not the hoses, it surely must be someplace between the head/manifold joints and the carb air-horn. A semi-intelligent guy like me should be able to find the problem(s).

[Lance]

Thats what I thought with my problem...I no dummy. My bet is on the intake manifold leaking at the bottom where the exhaust goes through. It's in a location that can't be tested and we would never find.

[jonnyc]

Which is why today I ordered a set of manifold gaskets......just in case.

[Lance]

Good luck.... hope you find it. I'm new to these Rovers but I have learned alot in a few months.

[jonnyc]

OK, checked every source for a vac leak and I think I have lots of little ones adding up to a big one. Engine rev'd when sprayed at:
-head-manifold joints (mainly at the exhaust ports?)
-engine side of the int/exh manifold joint
-front of block betw manifold and carb
-front of carb base
-ends of throttle rod

Manifold gasket set is on the way, so I will take the manifolds off and do everything I can do to tighten up all the seam. I will also look for any problems in the int/exh manifold joint.

I hope all this solves my issues.

[jonnyc]

Lance,
You're saying your leak was INSIDE the intake manifold and invisible from the outside, not at the joint between the two manifolds?

[Lance]

Thats correct. Not sure how common this is. I took my manifolds off the engine, seperated the two, poured water slowly in the void "under" the intake where exhaust heats the intake & water came out the inside of the manifold. Then I plugged the hole where the carb bolts on and slowly poured water in the intake ports and water came out the exhaust void. (not sure what the correct terminology is for that void/cave on the intake). My Rover always ran great, one day I got in it to go for a drive and it ran terrible. It didn't happen while I was driving but sitting over night???

[jonnyc]

***UPDATE***
Weather and schedule cooperated today and I got a chance to start it up and see if I fixed anything.

1. Large number of small vac leaks seem to be gone, probably due to new gaskets and a bit of judicious sealing and tightening.
2. Vac gauge is showing too low, bouncing in time with the idle between 6 and 10.
3. Idle is a little better, still sort of rolling and surging, backfiring seems almost gone.
4. Mixture screw can go all the way in without stalling or going very rough.
5. Idle screw has to be almost all the way in to prevent stalling.

I found no cracks, leaks or apparent damage in either of the manifolds when they were off.
Next???