TheSamba.com :: View topic

Fri Jun 22, 2012 6:25 pm

Helping a friend rebuild his motor . We installed : AA Performance rebuild kit , Scat C35 cam with stock lifters , New bearings , Oil cooler , HD full flow oil pump . The short block components are all new with exception of the heads .
The motor was originally built by Mofoco about 15 years ago and when he got it the p.o had said a connecting rod was bad , We found the issue to be the # 3 rod bearing had disintegrated and chewed up the crank . As noted above we gutted the motor and started from scratch . The main journals and thrust looked good upon removing the bearings so he opted not to have machine work done on the case .
We got it fired up today and ran the motor for 20 minutes under no load and it makes a noise similar to a rod knocking in the case . I doubt this is really a rod issue as all rods have been torqued to Bentley specs , The motor isn't binding when turned by hand or making noises and the noise stops at around 800 rpms . I'm thinking this problem may have something to do with the heads , Burnt valve , Lap or etc . . I drained the oil and readjusted the valves but still get this knocking noise . Any suggestions on what this might be ?

Alte

Fri Jun 22, 2012 6:35 pm

oh boy. it could be 100,000 different things. if you didn't blueprint the engine and know the measurements, your screwed.

so far, i have 10 hours into a build, and i am at least 10+ hours away from assembly. you could have a out of spec case, a tweeked rod, or who knows what.

it takes way more than torque to book specs to do an aircooled engine. if you didn't take the time to measure every square inch of that engine, you are doomed

best guess is you didn't get the correct mains for your application. again, just a guess

Fri Jun 22, 2012 7:46 pm

I used a set of calipers and checked the bearing saddles (Case bore) prior to ordering them and rechecked both again prior to installation , Perfect fit . However the new cam bearing thrust had to be cleaned up a bit . I dread pulling the motor this weekend if all other checks fail :roll: .

Alte

Fri Jun 22, 2012 9:09 pm

The Bentley provides most of the spec's - but the Tom Wilson rebuild manual takes it further and it too leaves out some important details.

First, what parts did you reuse from the old build?

Second, did you pump oil into the main galley coming off the pump prior to turning the engine over?

Third, were any noises present when you cranked the engine over without the spark plugs installed when checking the oil pressure?

- Andrew in Austin, TX -

Fri Jun 22, 2012 9:21 pm

Parts reused : Cam gear . Distributor drive pinion and gear , Heads and valve train .

Alte

Fri Jun 22, 2012 9:42 pm

Oh boy!, where did you find calipers that measured down to the 10000th of an inch accurately and consistantly?, how did you fit them in all the bearing bores, cam bores and lifter bores without interference from other parts of the case?, was that new oil pump or the cam gear clearanced?, how did you torque the flywheel?, what compression ratio and deck height are you running?, was the input shaft trimmed for the type 1? (assuming it's really a type 1).

Sat Jun 23, 2012 5:04 am

At this point - whatever is causing the rod noise is spilled milk and an abundance of caution is required. So, don't run it. You will have to pull and strip down the motor to find the problem.

To give you an idea of what machine shop tools are use in a pro-build read through the link I am posting below:

http://www.thesamba.com/vw/archives/manuals/Jim_Martin_Engine_Build/Jim_Martin_Engine_Build.pdf

Note the use of a product called plastiguage to double check bearing fit further down in the build. Also, notice how he measures the bolt stretch on all the connecting rod bolts. Note the extensive use of a dial gauge and micrometers.

I first came across the above build pages approximately three years ago. It got me thinking that I had reassembled VW engines in the past - but never really had built one from scratch.

- Andrew in Austin, TX -

Sat Jun 23, 2012 5:25 am

Busdaddy , Thank you for the suggestions and we had a standard Starret dial caliper . The motor was a type 3 pancake that has been converted over to a upright ( Relocation of dipstick tube ) . Yes There is a possibility we overlooked something due to lack of machining tools .

Alte

Sat Jun 23, 2012 5:34 am

Aryue , Yeah after mulling this around last night I decided to just pull the engine this weekend . I was gonna purchase this case myself and take it to a machine shop to have it evaluated originally , My buddy didn't think it was needed after he purchased it . We have built a few motors and had no problems with the techniques we used BUT it seems our luck has run out .

I will add that link to my tech. resources and really appreciate the article , Looks like it's time to add more tools to the bench .

Alte

Sat Jun 23, 2012 5:39 am

Alte - once the deck height was chosen and then the heads were installed, did you check the rocker geometry?

See below:

http://www.thesamba.com/vw/forum/viewtopic.php?t=167378&highlight=rocker+geometry

Also, I would use single HD valve springs with that camshaft.

- Andrew in Austin, TX -

Sat Jun 23, 2012 7:52 am

Honestly no I didn't check the geometry and all specs were based on the original build , Nothing changed outside of replacement of the Engle 110 with a Scat C35 ( Very close grinds ) . Case was not visually damaged internally or externally , Granted I'm not a machinist or a full time mechanic but have built 6 motors so far and never had a problem . All the motors so far are daily drivers including my 65 bug and have ran without problems for over a year now .
This one has bitten me on the arse , Didn't help matters that it was a rush for a local cruise in next week either . Just had to call my friend and break the news , He took it like a champ but I wouldn't want to be in his shoes when he relays the message to his wife . It's her van !!!!!!

Alte