Knocking sound - Web cams 20/21

[Airwolf]

Currently getting my 1988 Carrera Cab.upgraded - Considering, amongst ohers , SSS constraints ,usage of car ( public roads mostly on weekends ) as well as reliability issues i have opted for so-called " bolt-on" solutions.
(Amongst others , the workshop has just completed the 3.2 - 3.4 conversion with Mahle's)
Being on extended travel i receive regular updates of work carried out and to my surprise was advised that, after installing the Web cams 20/21, there seems to be some problems.
quote
We have some issues with the engine. There is a loud knocking sound coming from both sides. We suspect the valve lift is too high and hitting the pistons.
unquote
I am surprised to get this info since i considered usage of Web cams 20/21 as "bolt-on" ( even ater 3.4 conversion)
Was i wrong with my assumption??
Thanks for input.
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1988 Carrera 3.4 (Mahle), Fabspeed Maxflow, Koni Yellow, Centerforce - Work in progress: Web cams 20/21, Steve Wong chip , RS interior and more...

[Airwolf]

Update - Due to different time zones (Asia versus US) was only able to contact Web Camshafts HQ today and received the below promt and comprehensive reply which i want to share with the Forum:
quote
This is in regard to your 20/21 camshafts you received from us. They should be a drop in profile for this engine however since it has a new profile we need you to set the timing either by Porsche method or by lobe center method. Remember the timing will be different with performance cams. We did send you a timing card to do it either way. The simple way which you are probably use to is by the Porsche method. You set them with the valve lash at .1 mm and then you set the cam timing to 1.9-2.2 mm, or you can degree them in on lobe center method which I can send you those numbers if needed. We advise to check piston to valve since the pistons have been changed to the moly. Minimum clearance is .050 on the intake and .080 on the exhaust. Also since you installed new valve guides we suggest to check retainer to guide seal clearance. You can check that by installing a light spring in the cylinder head and make sure at full lift with your new cam .485 on the intake and .452 on the exhaust, make sure you have an additional .035 clearance at full lift. Make sure the stock installed spring height is maintained as well. Check for coil bind just in case you are having issues with that. We highly recommend to clean the spray bar out because they have a tendency to get clogged.
unquote
Pressumably this will sort out the problem - Once project completed will post some pictures and data. Dyno test prior to installing the Mahle's = 201rwp ( stock engine plus Fabspeed Maxflow on a hot day in Kuala Lumpur)

Cheers
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1988 Carrera 3.4 (Mahle), Fabspeed Maxflow, Koni Yellow, Centerforce, Steve Wong chip, Supertech head studs - Work in progress: Web cams 20/21, RS interior and more...
1985 Turbo - 100% stock except for wheels and aftermarket exhaust system

[john walker's workshop]

i use those cams all the time and never had any issues.

[Airwolf]

From reading numerous articles on various formus i concluded the same - hence my choice to use their product.- I am sure i will not be disappoined once they are intalled and got tremendou service from ttheir technical department (Laurie) - Now all clear and will keep updated once up and running.

[RSupdate]

I read your post with great interest as I have the 20/21 cams in my 3.2 w. Mahle euro 10.3:1 p/c and have never had any issues with them other than sparkling performance improvement over the stock cams. My cam timing is set to 2.0 fwiw...

Obviously, it Sounds like your cams were not set correctly. once that is dialed in you'll love 'em !!!

cheers,

[john walker's workshop]

hopefully the valves survived. do a leakdown test.

[Airwolf]

Going a few steps back and will remove the 20/21' to put back the stock cams.
Thereafter compression/leakdown test....Provided all ok will put some miles on the Mahle's and then install the 20/21's.
RSupdate: Did you do any dyno testing before/after installing the 20/21's? Any data avail?l

[RSupdate]

Originally Posted by Airwolf

RSupdate: Did you do any dyno testing before/after installing the 20/21's? Any data avail?l

This the "atmosphere corrected" printout. The actual rwhp at the time of my dyno runs were 247.....

[Airwolf]

Great stuff!! As soon as all is sorted out my end will get the dyno testing done and post the result.
With petrol quality over here NOT being an issue and CR <10 i am running the engine on single plug..

[aigel]

This doesn't give me a warm fuzzy feeling on the shop that is doing the work. I thought that there is a valve to piston clearance check on every build, especially when introducing a new stack of new pistons, cylinders and cams. If the shop doesn't do a mock up assembly to check with clay, they should at least use the valve adjustment screws to set the valves it above clearance and carefully rotate the engine to check. This only takes 15 minutes after timing the cams.

George

[brads911sc]

+1

Id find a new shop. ASAP.

Originally Posted by aigel

This doesn't give me a warm fuzzy feeling on the shop that is doing the work. I thought that there is a valve to piston clearance check on every build, especially when introducing a new stack of new pistons, cylinders and cams. If the shop doesn't do a mock up assembly to check with clay, they should at least use the valve adjustment screws to set the valves it above clearance and carefully rotate the engine to check. This only takes 15 minutes after timing the cams.

George