Engine in trouble.2 x blown/melted vac hoses.

[Wingit100]

Hello all, your experiance is needed. Following an engine rebuild i have strapped on my original solex twin carb set up, they are 32-34 PDSIT 3's. The engine fires up now but both carbs are popping away like good uns. When I look into the carbs (which I have given a good clean out) I can see a spark flashing low down when the carbs are popping. They are both sucking away quite strongly also? Not sure if the loud sucking is good? The other day the silicone vac house/t piece which links the two manifolds and the brake servo vacume blew off then melted a little and ruptured. I could then see the sparking or flashing coming thru the pipe rupture down by manifold. I assumed wrongly that this rupture may have been my problem and duly ordered a new one. Put the nice new one on today and the same issues prevailed. There is an awful lot of heat building up in the breather tube which links the two manifolds. Again this heat melted the new t piece and ruptured it again. I gather from reading that the popping could be caused by an air leak of some description causing carbs to run too lean or could it be fuel starvation? Having viewed the fuel filter while ticking over the fuel seems to be squeezing thru at a very slow rate. I can sort of understand the possibility of air getting in and fuel starvation but what is causing such heat to build in the breather tube?
Any help advice would be greatly apreciated.
The van has defeated me and I am now packing to go away with the kiddies in a miserable little tent.
Happy days eh.
I shall keep smiling.
Thankyou all in anticipation.

[BOXY]

Have you re-set the tappets recently? If not it sounds like a valve seat issue. Check the compression and make sure the valves are closing when they should.

[Wingit100]

Cheers Boxy. Had the engine rebuilt by a pro so I would hope he would have set tappets right but you never know. I will ask him. Could that cause the heat and rupturing of the vac hoses?

[ghost123uk]

Just popped in to say that whilst these engines normally have hydraulic tappets, some of them have been retro fitted with solid ones. With the std hydraulic tappets one sets a "pre-load" which involves turning the adjuster in a further turn or so after the tappet has touched the valve stem. If your has solid tappets and your man didn't know, that would cause the valves to not close properly and could result in what you are getting.

Ignition timing a mile out could also cause it.

[Wingit100]

Thanks ghost. I purchased all the parts for the rebuild which was done away from the vehicle so the builder didn't test it. It was a hydraulic cam and followers to match although it was a mild performance cam. not sure if that makes a difference? Am i right in thinking that those breather pipes just should not be getting hot? I just don't know what to try next.

[Wingit100]

Also ref the ignition timing I have loosened this up and tried adjusting but it seems ok with it in its old position as previous owner had marked it. The engine fires up straight away and will actually rev but pops/blows away and sounds generally extremely rough until it blows the pipe and sparks away there.

[BOXY]

The popping / flames coming out of the vac pipe sounds like at least one of the inlet valves is open when the spark plug it firing. Either a valve or seat is buggered or a cylinder is firing out of sequence. (and that means at least two are) Check the leads are connected to the right plugs, maybe two have been switched over?

[Wingit100]

Well Boxy I would like to say that that is not possible but knowing my skill set it is sadly quite possible. I will check and double check,,,,,, when i return from my camping trip that should have been our first post Resto trip!! thanks for all your help, I really hope it's that simple.