basic manifold matching

[tonydevon]

Hi, I just received my MB inlet manifold for my smallblock 66mm mugello

upon offering it up and looking at it properly I can see that as expected there are lips and steps in places around where the manifold meets the barrel.

my basic and logical understanding is that obviously this needs to be smoothed out, so I plan to get rid of the step/obstruction from manifold to barrel, making the step smoother and spreading it out over a small distance rather than simply a 45 degree angle, but what about the opposite type of step, I have a step down from manifold to barrel, while this wont cause any obstruction is it likely to create an "eddy" of some sort and ruin air flow, should I therefore work the inlet manifold in a similar fashion

I have read about not polishing inlet manifolds and ports so plan to just leave them as is after some gentle dremel and needle file work.

with the exhaust I assume its the same principle.

sorry if these are very basic questions, but I have no experience of "tuning/tidying" 2 stroke motors

I have no plans to look at the actual ports and cylinder. Im not that rich or stupid, would just be an expensive paperweight if I did that LOL, I do plan to try and find a rollnig road tuner in the south west to take it to once up and running, but obviously cant do that until its run in.

[jason frost]

Some pictures here

http://www.facebook.com/media/set/?set= ... 888&type=3

[scooterslag]

Hi, I just received my MB inlet manifold for my smallblock 66mm mugello

upon offering it up and looking at it properly I can see that as expected there are lips and steps in places around where the manifold meets the barrel.

my basic and logical understanding is that obviously this needs to be smoothed out, so I plan to get rid of the step/obstruction from manifold to barrel, making the step smoother and spreading it out over a small distance rather than simply a 45 degree angle, but what about the opposite type of step, I have a step down from manifold to barrel, while this wont cause any obstruction is it likely to create an "eddy" of some sort and ruin air flow, should I therefore work the inlet manifold in a similar fashion

I have read about not polishing inlet manifolds and ports so plan to just leave them as is after some gentle dremel and needle file work.

with the exhaust I assume its the same principle.

sorry if these are very basic questions, but I have no experience of "tuning/tidying" 2 stroke motors

I have no plans to look at the actual ports and cylinder. Im not that rich or stupid, would just be an expensive paperweight if I did that LOL, I do plan to try and find a rollnig road tuner in the south west to take it to once up and running, but obviously cant do that until its run in.

I think Simon at B-Race Tuning has a dyno Tony, might be worth getting in touch with him once you're ready. Paul

[tonydevon]

excellent, many thanks, them pictures have answered a lot of questions that I had, especially also about removing the rough bits in the manifold and what type of surface finish to leave behind.

thanks Paul, tried a little while ago but no response and was told that he no longer trading???

been recomended of someone that was up wiltshire way? but failing that I suppose the one in Wales isnt that far out of the way, van hire and fuel stacks up, but I cant afford to blow this thing up through a stupid jetting lack of knowledge LOL

[Darrell Taylor]

as your post says id keep it to basic manifold matching,try to keep it as small as possible (ever wondered why piston port motors like big carbs, its to compensate for the oversized inlet)
most important job is checking the mating surfaces are level and use a good sealant as an air leak here will toast your motor

[tonydevon]

ok thanks, so is it advised that i use a sealant/gasket compound as well as the supplied gasket?

I normally use a loctite product on my bike engines and diffs etc

if so then where? just on the intake?

I dont want to mess with base gasket thickness as this surely moves ports etc

[Darrell Taylor]

if you build without sealant then a leak down test would be advisable,but when doing the leakdown test any gasket surfaces found to leak are treated to a smear of sealant ,so might as well seal in first place on all gaskets on both sides,just a light smear is fine,id pay particular attention to the base and inlet applying a bit more at the outer edges
the base gasket/s will move ports but theres no knowing your crankcase base gasket surface is high or low to start with so a std gasket has a good chance of being wrong

[B-Race Tuning]

Hi Tony, I am currently re-vamping our dyno set-up, that we hoped would see us up and running again mid Jan. (xmas eve = broken ribs, so may be tail-end Jan). Simon.

[tonydevon]

ok cool thanks for letting me know I will pass on that info to the club member that wrongly informed me you had closed LOL

I need to build the motor first then run it in anyway.but certainly be interested in dyno time, not worried about big pub talk numbers, more that the mixture is safe and that it will be ok for rally season next year

next stupid question

I have been busy removing bearings and old crank etc, so started looking at how the new parts will go on.

I noticed that there will be big steps at the base of the barrel to the crankcase, there isnt in my opinion (that usually isnt worth much) enough meat in the case to get rid of the step completey, I assume that this is what I read about with welding and building backup etc.

would it help to just put a 45 degree slope on the edges to take away the 90 degree "step"

I planned to use the base gasket as a template, I have checked and it matches the barrel perfectly.

or could my basic and limited knowledge etc actually cause more damage than harm?

thanks for your time and patience,