Manx Club

sorry this may be a really dumb questions but i have to ask it is driving my nuts. What is the deal with welding the 3# cyl. I always hear about people saying that they have a case and it is line bored and opened up for 94mm taped for full flow and 3# cyl has been welded for strength. Sorry if this is just common knowledge to everyone else but I gotta know its buggin me. thanks

On some engine cases the #3 cylinder would crack if bored over and run hard. To reduce this they would weld on a plate of metal to make the area prone to cracking thicker. You can buy new cases that have it predone. At least thats how I understand it in simple terms. The more indepth answer I'll leave to the experts.

I have been running VW engines with 94's since 1978 and have never had the infamous "3rd web" crack. None of my cases have ever had the 3rd web welded. I think there are other factors coming into play besides just the fact that the case has been bored for 94's.

Just to be perfectly clear. Its not the cylinder itself, its the case, where the spigot of the cylinder is inserted. The weld is built up on the rear face of the case behind the flywheel, between two reinforcing webs.

Biggest reason case cracks if from detentation. Weakest spot is in front of #3 cylinder behind flywheel. Have seen stock 1600cc engine crack there.