side housing tolerances (flatness)

[stuart wizy]

anyone no what the max runout tolerance is for side housing?
my intermediate has a .005" drop where the path of the rotor comes down the straight side of housing.
can the housings be ground flat on a large surface grinder or have they got to be polished flat checking for flatness with base clock?

[Carl]

that is just about acceptable for wear.You are only very slightly over so it shoyuld be fine.
Regards
Carl

[stuart wizy]

can they be ground up because the end plate has a slight groove around the radius right next to the outer water seal groove .010" deep max

[Carl]

Lapping is the way to do it.
They can be,but afterward it is imperative that the housings are really thouroughly cleaned of all lapping compound afterwards.Also most important not to go too deep as the hard layer of Nitriding is quite thin.
Regards
Carl

[alban1973]

I am at the same stage with my engine so thanks for that carl..   What depth of lapping is recommended not to damage the coating? mine sounds very similar condition.... Also just another point, The rotor housings have lasted well, they are shiny apart from around the exhaust port and the spark plugs which these areas are dull, also one of the rotor housings has the chrome damage on the lower part of the exhaust port, Is this a normal failure, and i suppose make the housing un useable. is it also advisable to replace the housings in pairs??   thanks for any help here..

[Carl]

Chrome damage is not good,do you have pics?
The important thing with the rotor housings is that they are flat,and not warped.
If your engine has over heated then they may be warped.
The lapping basically should be the absolute minimum possible,you can usually lap once if the side housing has never been done before.Make sure that whoever you get to do the work does the absolute minimum though,say no more than 0.004".

Stuart,on that side plate with the 0.010" groove I would say that it would be best to get a decent plate,either new or used to replace the one with damage,was it a broken seal?
The limits that are mentioned alot of the time for wear are often not very much,but it is suprising what can be reused.
Regards
Carl

[stuart wizy]

i dont no what they use to lap flat with
ive used a large polishing buffer to polish dents and scratches out of stainless plates that had to be flat and parallel on both faces to high tolerances before, only problem is ive never worked with nitride before.
lapping to me means rubbing with grinding paste like lapping valves into seats, dont know how you could do that in a large surface area and keep flat.
if nitride will grind well i can skim all my plates up flat in minutes with a good surface finish taking minimum material of to clean full face up

[stuart wizy]

carl the rear rotor housing has a large gauge just before exahust port . on the end plate it has a .010" deep groove on the edge of the outer water ring grrove.
im gonna check them for runout and flatness tommorow at work.
carl have you got a fc rotor housing while your on mate?

[Carl]

I don\'t have a good FC housing for turbo,but may have an FD one.
Regards
Carl

[Carl]

Or do you mean plate?
if so which one?
Regards
carl

[stuart wizy]

can i use 1 fd and 1 fc
could call this a special hybrid engine carl! new sales pitch for u there mate :p

[stuart wizy]

sorry, i mean rotor housing

[Carl]

Rotor housings from an FD maybe.
They are compatible.In fact they are better than FC ones.
Regards
Carl

[Carl]

I would change both for either one or the other.I will look tomorrow.
Some engine builders build their FD engines with FC turbo housings cos they are cheaper new than FD ones.I don\'t do that,but they obviously work even though there are a number of differences.
On the FC housings there is a hole for the coolant to flow to the inlet manifold,there is not on an FD housing,but you can easily make that cos the blank is molded into it still.
The FD housings have better chrome,and also better cooling around the spark plugs.
Regards
Carl

[stuart wizy]

how much  for a couple of fd used housings mate?