Triumphrat

05Truxter · 05-12-2007

Just read an article in the latest Walneck's Classic Cycle about a simple mod, and wondering if anyone has tried this.

The article discusses porting and polishing the intake manifolds between the carbs and heads. Not the heads and valve guides (that would be a job for someone with a lot of experience or for a professional), but just the intake manifolds. I have rejetted the carbs, but never pulled them off to see what the manifold looks like. Basically the work described matches the I.D. of the carbs and manifolds to make air flow more smoothly through the transition, plus the inside of the manifolds were polished. The engine setup used as an example is a little different than ours, in that the carbs bolt directly to the intake manifold, and ours have rubber boots between the two. Might be something to try, or it might not?

I saw a post that someone over in the UK had the head skimmed for higher compression and had the head ported and polished, but I don't have those kind of financial resources right now (someday...) , plus I don't want to take my bike off the road for that long now that the weather is good. Wait what am I talking about - got caught in a downpour today! Well, at least now I know that the Avon Azaros work well in the rain :-D BTW did you know that mesh jackets are not waterproof? Good, just checking.

Jimbonnie · 05-12-2007

As far as porting is concerned the greatest improvement in flow comes from eliminating sharp or uneven transitions between the various components of the intake tract. Those would be between the carbs and the intake tube, and between the intake tube and the head. There should be no abrupt transitions and a relatively smooth tract from carb to intake valve.

The worse the mis-matching between the different components the better the improvement when those errors are corrected. There's also something to be gained by modifying the size and shape of the ports within the heads, but that's quite a bit more complicated and deviates from what you've asked.

I've found port matching worth while on my Sportster which had pretty a pretty sloppy intake tract, and on my BMW's which had far better tracts and showed evidence of at least some effort on the factory's part to knock down the rough edges and joints. I would guess that the Triumphs intake tract is pretty good, what with modern casting and machining and such. Still, the work is curiously satisfying and likely to provide at least some benefit.

One thing to avoid is increasing the size of the ports on a stock motor; in most cases they're the right size for street use. As far as getting a fine polish, don't bother; it looks pretty but flow is better with a slightly roughened surface (its a boundary layer effect, like a golf ball's dimpling). And make sure you don't get any abrasive chips or cuttings into your motor.

[ This message was edited by: Jimbonnie on 2007-05-12 19:47 ]

sweatmachine · 05-12-2007

Quote:

On 2007-05-12 19:00, 05Truxter wrote:
The article discusses porting and polishing the intake manifolds between the carbs and heads. Not the heads and valve guides (that would be a job for someone with a lot of experience or for a professional), but just the intake manifolds.

you mean like this?

This is mine. +2mm intake valves, +1mm exhaust valves, ported/polished intake and exhaust runners, and ported/polished & port-matched intake manifolds.

Looking down the manifold, you can barely tell they're a separate piece.

My machinist did a great job!!! :-D

vertwrks · 05-12-2007

Matching the carb boot to manifold, manifold to head is always a good idea. You can yank your carbs and feel where you need to remove material. A die grinder or even a dremel will do the trick. Would not think that you would notice the improvement seat of the pants cause it would be so minimal but it is the sum of all the improvements that we seek. I guess it took me about an hour to do both manifolds and boots, just be careful cause it is easier to remove material than to put it back.

Porting the heads is best done with the use of a flow bench to get optimal benefits. You can do the basics and get better than stock results, knife edge the Y and remove lumps etc.

05Truxter · 05-12-2007

That's sweet, Sweat. But no, just looking at making the transitions smoother between the carb, intake boots and manifolds. Trying to keep it simple, cheap, in the garage, and the engine together and in the frame. So did your machinist match the manifold and head - not sure of the terminology - is that what "port matched intake manifolds" means?

05Truxter · 05-12-2007

Ah, here we go:
translate.google.com/translate?hl=en&sl=fr&u=http://jeepgarage.free.fr/thruxton.html&sa=X&oi=translate&resnum=1&ct=result &prev=/search%3Fq%3Djeepgarage.free.fr/thruxton.html%26hl%3Den%26ie%3DUTF-8%26sa%3DG

That's pulled from the wiki page - it is a translated version of a frenchman's manifold polishing.

Would rather ride than polish, so I guess I'll wait until winter...

Also, anyone know what size SAE drill bit will enlarge the hole in the carb slide to 3mm? I can't seem to find any metric drill bits. Never got around to drilling the slide when I rejetted the carbs.

05Truxter · 05-12-2007

That link doesn't direct you to the exact page - go to carb/airbox mods, then to the next carb mod page... not sure why that link didn't work.
Sorry that is a PITA - maybe someone with a better handle on this URL ***** can fix my mistakes. :brk:

sweatmachine · 05-12-2007

Quote:

On 2007-05-12 21:45, 05Truxter wrote:
So did your machinist match the manifold and head - not sure of the terminology - is that what "port matched intake manifolds" means?

Yes he did, you can see the seam where the two parts (head and intake manifold) meet, and yes that's what ''port-matched intake manifolds" means.

vertwrks · 05-13-2007

7/64 is like 2.78mm and as close as you will get with SAE bit but close enough. A 1/8 is 3.17mm which I fear may be too agressive, I chose the 7/64 based on what I have read here and/or elsewhere.

monkeyboy · 05-14-2007

You don't want to polish the intake side. Part of good mixture is the tumbling of the air. If you smooth it out too much, the gas comes out of suspension in the air.

Not a good thing.