What happens at the mating point?

[euro911sc]

I've been reading a lot on port diameters, throttle plate sizes, and throttle body diameters, carb diameters, etc... I've read a lot about boring these out to specific diameters for a variety of engine volumes setups...

If I am correct, there are several parts that all mount up together to make up the 'pipe' from filter to combustion chamber. Some of what I have read indicates that each part would have different diameters. If they are bored out then there is no taper into the next part's different diameter and that leaves a step.

Shouldn't the mating surfaces of the parts be matched to remove the steps and smooth out the transition?

Best regards,

Michael

P.S. Pics looking down the pipes would be great so I could understand how they all go together

[neilca]

Steps in the inlet can be your friend or enemy depending on which way they face. If going down the throat the step creates a smaller throat, that is bad. It will cause turbulance and of course choke off the flow. If going down the throat the the step creates a larger throat that can help by reducing the amount of reversion. (definition: reversion- when the intake valve closes the flow is reversed in the inlet).

Hope that helps,
neilca

[len911]

I'm including a couple of pictures (first 2) of what my 3.2l engine looked when I got it. The actual gaskets and spacers were not matched to the ports. I figured that you probably want a nice clean shot from the carbs into the cylinders. A little work with a Dremel tool made it nice and smooth (last 2 pics). Might be overkill, but why not do it right... Lou

[euro911sc]

Yeah that's what I thought should be done. Though that part about reversion, I'm not sure I understand how a step prevents/helps with it unless it simply breaks up the wave?

Thanks for the pics Lou.

Best regards,

Michael