So..... after trying to get my engine to fire on number 3 cylinder, and failing. it is engine out time. So If i am rebuilding the top end. and obviously the crank bearings as well. What else should i consider. Are the top end rebuild kits from JK any good? THey seem good value. Advice so far is to stay 1600 and get stainless valves, thanks Paul. what cam? i currently have an engle 110. i have the twin webers and my vintage speed exhaust. i want it to be reliable. forged V cast barrels and pistons. Are they needed? At least i dont have any endfloat so that is good, well not that I can tell with the engine in the van. all advice is very welcome. EDIT, who sells stainless steel valves?
It fires once the revs pick up. I am assuming this happens once the compression builds. number 3 is down on compression. it only gave 105 psi compared to the others at 120. I have checked the valve clearences twice now. Always stone cold. changed all the electrics. Even the dizzy. EDIT, i have also checked for air leaks on the manifold. Weber ICT's
Are the carbs set up correctly? How did you do the compression testing? Plenty of stuff to try, and no need to whip the engine out...
bought a compression tester from machine mart. screw in type. on turn over it gave 120 psi on 3 but just 105 on number 3. This was after about 5 revolutions of the engine. if it was the carb, would it not fail on 3 and 4?
I think your answer is elsewhere. If your compression is over 100 on the worst I think your issue is electrical, plugs of fuel ;D
I hope you are right. but it is beyond me. It is going to have to go to Stef at Mac VW. Carbs are just not my thing.
Sounds like it just needs a good going over, step by step. You've got a lot of new stuff on there. It's very unlikely to be anything related to the core engine. If you've got fuel, compression & sparks, all at the right time, it'll run.
i dont understand why 4 will run and not 3. Also if the idle screw it out too far, what does this mean? ie what should I be looking for in the carbs? jets, blockages? i dont really know carbs that well.
Air leak or fuel blockage. As you've tested for leaks I'd plump for blockage, but I see your point - why just one cylinder. That could be explained by the firing order - 4-3-2-1. If idle circuit partially blocked gets petrol for no.4, then not enough for no.3, then gets a rest while 2 and 1 fire for more petrol to get past blockage for 4 again and repeat.
Cheers Zed, that does make sense. Carb off and compressor out i think. Well worth the time i think. Bring on the learning curve. Thinking back It has just had new fuel lines. i wonder if a bit of the rubber could be in the carb.
You never know. Won't hurt to clean up the carb(s) even if you do end up taking out and stripping the engine, but it would be a pain to do the engine then find it still wouldn't run on no.3. BTW you're right and you are down on the compression, but not enough to stop it firing - loads of buses have worse compression on ALL cylinders and go just fine (until you get to a hill).
Have you tried to synchronise the carbs? On my 2 litre engine with twin Solexes it sounded like it was firing on 3 cylinders. If you pulled off no 3 plug lead it made no difference to the performance when idling, so I concluded that no 3 cylinder was dead. However when I balanced the carbs this effect disappeared. I don't understand why it was no 3 and not both 3 and 4. On the Solex when you balance the carbs you don't touch the idle circuit, it's done on the main butterfly in one or other carb, so Zed's explanation doesn't seem to fit my case.
