engine rebuild

[Vampyr]

Hi Guys , have two questions that I am hoping to find answers too. 1st, I have a cylinder head that has been tapped and a helicoil put in . It is much larger than the original tread for the standard spark plug and I an assuming it was done to take a more modern plug. a, It has been suggested to have the helicoil out, hole rewelded and then tapped again, never heard of this. b, has anyone encounted this before, if so does it still work fine and should I do the other head. 2nd what VW parts can I use, if any. precisely I am in need of piston heads and rings, push rods, mine are bent and from the Con rods. Thanks for any suggestions/ wisdom. danny

[AustHaflinger]

Danny - I am not able to help much but there is nothing unusual about the spark plug holes/threads in the Haffie - I have had Iridium plugs in my heads and you don't get any more modern plugs than these.

I would not be keen on welding these heads so I would take your heads to an expert helicoil installer and see what they can do. They may still be able to repair it and fit a correct helicoil and if not may be able to put in a threaded insert with whatever thread is needed on the outside and the correct spark plug thread on the inside.

Garry

[heinkeljb]

Take the head(s) to a good engine rebuild garage / shop - they will probably take out the existing helicoil and machine up a threaded insert as Gary has said, which has the appropriate thread size on the outside and the appropriate spark plug thread on the inside.

You can use VW barrels and pistons / rings, but that will require machining of your crank cases to accept the barrels. Several people have made big bore engines by going this route. You could contact this guy and ask: http://thehaflinger.com/viewtopic.php?f=27&t=428
Original push rods can be bought so those shouldn't be too big an issue.

John

[kerry460]

if I remember correctly , Toyota 12 r pistons can be used .
a bit of machining , depth of skirt an a little off the edge of the crown.

kerry

[Vampyr]

Thanks guys great info, will follow advice. Danny

[AustHaflinger]

I have a VW 86mm big bore kit on my engine with standard crank, cam and conrods. There is quite a but if machining involved and it is easy to make a mistake. The person who original did the mod on my engine machined the inside of heads to fit the top of the VW barrels - when the engine was pulled down after a failure it was found that the heads can handle this as there were small cracks where the push rods holes are - too much metal was taken out. When I had my engine rebuilt with new VW barrels a little while back the heads were not touched (bigger inlet valves) and the top of the barrels were machined to fit the heads - no issues so far.

In the old engine, on number 1 cylinder the piston had been touching the head and the piston ultimately cracked and caused engine failure - No 2 was fine so just an small error by the machinist and the VW pistons need to have their crowns machined down lower and valve indents added.

So while the big bore option give the engine plenty of pulling power it does take a lot of work to do.

Garry