Port wall finish different for turbo'd engine?

[bill jones]

-I curious if anybody is doing anything specific to the port and/or chamber walls and piston tops for blown engines, like making the surfaces smoother, highly polished or rougher than normally aspirated engines, or maybe found that certain coatings make a significant positive difference?

[Fkned]

Your gonna find alot of different opinions here from what I've seen.Every import head porter uses a different grit to finish their intake ports.I use 40 grit and like to make it rough just like I would with a carbed motor.Some like a 60-80 surface and one person I know of uses more then a 320 surface then scotch brites it also it get it even smother.I tend to think it's just like most other things if the cross sections and shapes are right then the surface texture doesn't make a whole lot of power unless there are fuel suppension problems that no type of surface will help much.

[bill jones]

-On the EFI engines do you do the full length of the intake manifolds that 40 grit or just from the EFI nozzles to the valves?
-what do you do about the chambers?
-What about the sharp edges at the top of the valve reliefs? what do you do there?
-Why don't you use a smoother finish? had some sort of problems that coarser finish gets rid of?
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-When you are talking about a carbureted engine do you do the entire surfaces of the intake manifold and the heads and the carburetor spacers this 40 grit? or do you just do certain areas of the port etc?

[cboggs]

I use 80 grit sand rolls on most everything.

For chambers, exhaust ports sometimes I'll go back with
an 80 flapper and toch up the finish, .. for looks only.

I think anything smoother then this is not good, .. we want some
boundry layer, .. even in a dry port.

Curtis

[Fkned]

I use 40 thruout the intake tract,but not because I feel it helps the fuel suppension for fuel inj motors,I just don't see why it would make much difference going any smoother.I do the intake ports for that reason because most of the import heads I do are turboed w/large fuel needs and I feel that the inj fires long enough before the valve opens that the fuel could stick to the walls w/smooth surfaces and I'd like to prevent that from occurring.
On chambers I use 120 grit to try and reflect/retain as much heat as possible,and exhaust ports are 120 also for the same reason.
I worked at a shop that did work for some Busch and Pro Stock and 40 int and 100 exh was good enough for them and the Busch stuff won at Taladeaga with the same grits I use.I don't build blocks up so I can't help you w/info there but I would put a small radius on the edge of the valve relief in the piston.

[cboggs]

To be safe, .. I would do the opposite of whatever Ed says.

Kidding, .. Hi Ed, haven't talked in a while, .. hope you're well.

Curtis

[Robert Kane]

Ed, who did you used to work for? was it in the Philly area? Where in Philly is your shop located?
Robert

[Fkned]

I worked for Mike Androwick at Mike's Racing Heads in West Chester.My shop is in Collingdale,south of Philly near the automall and airport.

[Grocerius Maximus]

Taking a 3M finger disc to all the sharp edges on the pistons helps delay the onset of detonation quite a bit, say a 1/64th radius, along with evening up the chambers and getting them centered on the bores. Many of the castings have very bad shrinkage and are offset a bunch on the end cylinders.

At high injector duty cycles you'll have several CC's of fuel sitting there on a closed valve. Even more with methanol. Most of the commonly available high capacity injectors are pretty much garden hoses- narrow, dense spray patterns.

[Fkned]

A buddy of mine Rich Matrie from Ram Racing worked at Grumpy's for a little while when he was doing the trucks.I asked him if smoother surfaces made any more power for them.He told me they tried many different levels of grits and while it showed more flow on the bench w/higher grits it didn't make any more power,no less but no more.

[sc2dave]

"there but I would put a small radius on the edge of the valve relief in the piston."exactly what is a radius? a small cut? any pics?

[bill jones]

-from what I've seen most pistons have just rounded off the sharp edges of the notches with a nice pronounced CNC machine or just hand deburred with a sanding roll.

[ChrisU]

So there's no opinions about velocity in a dry manfold intake runner, in terms of wall finish???

I'm surprised about that.

There's no such thing as fuel suspension in a dry manifold, so why are we talking about boundary layers???? Someone fill me in here.

[bill jones]

-Well I have a different deal here.
-I'm doing a turbocharged 408Windsor Ford street driver with an Edelbrock EFI intake and the guy doesn't want to use any intercooler.
-But our idea is to use an auxiliary system of 8 small nozzles (Kinslers) that shoot methanol across the plenum and into the top of port openings during boost conditions.
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-The plan here is to add around 200PPH of methanol at wide open throttle (25PPH per cylinder) and during boost from the auxiliary fuel system.
-So this manifold will be definetly be wet during boost.
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-One thing I don't like about it is that 4 ports curve like a "C" and 4 ports curve like an"S".
-So I visualize two distinctly different wet fuel paths that I have to contend with.
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-Speaking of wet flow testing like you guys using the Mondello bench, can that bench do tricks like actually test against blower pressure?
-Or does anybody have any good ideas about how to test wet flow against boost pressure?

[sc2dave]

any tips on how to improve the flow of a dry-flow intake? e.g. polishing,dimpling?