Best way to lower the ports on an .049 cylinder.

**RknRusty** Mon Dec 19, 2011 8:43 pm

I have two identical Black Widows, both made about the same time in 1994, both purchased new. One runs good, steady and dependable, but not what you'd call screaming, in my opinion not as fast as it should. The other one makes me resist the urge to dive under the table in fear when it hits peak RPM, also smooth and dependable. I've rebuilt both enough times to eliminate it being something I'm doing right on one and wrong on the other.

I was comparing them side by side and there are a couple of differences. The fast one has the exhaust ports facing directly front and rear, while the slow one's ports face perpendicular to the prop blast. I've wondered if that matters, but more important is the difference in the size of the SPI gap. The fast one has a gap under the piston that is gaping. You can see the piston rod clearly at TDC. The slow one barely has a gap, you almost need some imagination to see it. The piston dimensions are identical. These are definitely the cylinders that came new on them and each has a "1" stamped on the small port facing, as opposed to on the barrel.

I think the difference in their speed is due to the difference in SPI gap. I want to shave a tiny bit off the bottom of the cylinder on the slow one to increase the SPI gap. I'm curious as to whether when I make them the same, the ports will line up the same way too. I want to get a piece of super fine sandpaper and lay it on a piece of glass and try to remove enough of the threaded end to adjust the position. I have some 1000 grit paper. if that proves to be too tedious, I can use some 800 until I get close and finish with the 1000.

My questions are; have any of you done this? Is there a better way? And do you think the direction the port faces matters?
I know I'll have to watch the piston height at TDC, but I can add a shim or two to make sure it clears the head.

Mudhen Mon Dec 19, 2011 9:10 pm

**RknRusty** Mon Dec 19, 2011 9:15 pm

Hmmm, yeah, big Duh for me. I may try shaving the seat on the crankcase. I don't know if I should try removing material from the piston skirt. It sounds like trouble without tools I don't have. If I butcher it by messing up the timing, I have a spare black crankcase. Not that the color makes it run better.

Mudhen Mon Dec 19, 2011 9:21 pm

andrew Mon Dec 19, 2011 10:07 pm

Mudhen wrote:If you remove metal from the crankcase base, it will alter timing, (the ports will open sooner.)

Mud --

If you lower the deck height, I think the ports will open later. The top of the bypass ports will be lower which means the piston will also have to be lower before the ports are exposed. The charge cycle will also be shorter due to later opening and early closing. Compression should be higher.

andrew

**RknRusty** Mon Dec 19, 2011 10:11 pm

I do have a drill press. My thinking is since the pistons and cylinders in the two engines are identical as far as I can tell with my chinese dial caliper, maybe the cylinder is sitting too high on the crankcase boss, and the timing is wrong now. And by lowering it, I would be correcting a problem.

A few minutes ago I dug out another old BW that I never use anymore, one I bought at a hobby shop in the early 90s. And it has a large SPI gap too. Here's an idea, maybe before grinding anything. I should transfer the guts of my slow engine into that old crankcase and see if it fits together any differently. I should try that first, I'd forgotten I had that old one. Thanks for your interest guys.

Mudhen Mon Dec 19, 2011 10:15 pm

**RknRusty** Mon Dec 19, 2011 10:16 pm

If I do decide to tamper with the piston, I can wrap it in some protective tape and clamp it in the chuck, then use sandpaper while I spin it. Does that sound like a recipe for disaster?

**RknRusty** Mon Dec 19, 2011 10:17 pm

Mudhen wrote:
andrew wrote:If you lower the deck height, I think the ports will open later. The top of the bypass ports will be lower which means the piston will also have to be lower before the ports are exposed. The charge cycle will also be shorter due to late opening and early closing. Compression should be higher.
andrew
I got that totally bass-ackwards, what a dope I am.
Thanks
Mud

That's okay, I think I win the DUH contest in my first post.

andrew Mon Dec 19, 2011 10:27 pm

Mudhen wrote:
I got that totally bass-ackwards, what a dope I am.
Mud

I can only wish that I made such a simple errors --- my life seems to be a series of screw ups. I make my living with numbers, but over the past few years, I find myself really having to concentrate to avoid transpositions. Kinda frightening at times.

Jaspur_x Tue Dec 20, 2011 12:21 am

An easy solution RknRusty, there is now being sold an spi piston/cylinder set that has a lightened&shortened piston.
Purchase this for on your engine and no parts or fingers have been damaged.

Drill press idea sounds like a sound idea to me also.

Solution "C": dremel cut off wheel used to lower the exhaust port on the cylinder. Then very carefully polish the burrs you made inside the cylinder before testing your piston for the spi.............this cutting may actually be easier to do on a drill press than with a dremel by hand though.

fit90 Tue Dec 20, 2011 7:16 am

Why don't you try swapping the cylinders between the faster and slower engine before modifying any parts. This way you have a better idea of what is possibly causing the difference in performance.

**Cribbs74** Tue Dec 20, 2011 8:50 am

Rusty,

I know this may sound stupid but have you compared crank pin heights? Possibly one was poorly machined from the get go. Also the ball socket end play does have some effect on piston position as in the skirt may not be exposed much as the piston is squashed down during the compression stroke. One last thing to consider is con rod length they may differ between the two.

If you used a reset tool in the past is there a chance the piston is domed? That would prob increase the SPI gap though...... Compression would def change and cause poor running characteristics. Just some thoughts.......

microflitedude Tue Dec 20, 2011 9:11 am

Yeah, try some different pistons and see if you get the same effect.

**RknRusty** Tue Dec 20, 2011 9:34 am

I was expecting those questions. I haven't because I'm lazy and just bolted both of them together with threadlocker, and one of them is a true Demon. But if I want answers I'm going to have to leave the computer and teardown again.

dankar04 Tue Dec 20, 2011 12:53 pm

The best TD's I have all have exhaust front to back. Some guys use cylinder shims to get it to be this way. You may need to remove a head gasket. Running 25% or more nitro you should have extra head gaskets to save plugs.
Dan

Cox International Tue Dec 20, 2011 1:43 pm

Cox made 2 versions of the BW cylinders. One had SPI (faster) and the other did not (slower).

The easiest way to fix the slower one is to substitute our SPI cyl/pis combo. The porting inside those cylinders is the TD one and hence more aggressive than the OEM BW one.

The more tedious route (but perhaps more fun) would be to slightly shorten the piston skirt.

Bernie
www.coxinternational.ca

**RknRusty** Tue Dec 20, 2011 8:26 pm

This one is supposed to have an SPI cylinder. And it does have some, just barely though. I'm going to consider all of the above ideas and experiment tomorrow night. When I finish, I'll have an engine that runs like it should. And I'll repoort back with a performance report, and maybe a before and after video.

I am going to stick with the 1995 model #1 cylinder since, as I mentioned above this engine has only been out of the box for 7 months and I want to keep it original for a while. Even though a modern SPI set would be instant upgrade, I'm going to wait a while. When I do upgrade, I might try a new type Tee Dee cylinder/piston. They don't have SPI, but they still out perform the modern SPI sets, if I understand correctly. Or maybe that's not true with a reedie.

Later tonight I'm going to post a video of the faster BW running in my "How much run time..." thread. First I've gotta get my SAD crash video up.

Jaspur_x Tue Dec 20, 2011 9:21 pm

RknRusty, just to help clarify if I read correctly ( big if, but I did in fact purchase accordingly) the spi cylinder sets did outperform the others on the reedies, but on the teedee it did not;thats why they made up a seperate set for teedee performance.
A teedee set may out perform a weak black widow set on the black widow, but a spi set is tops on the reedie engines.

I hope I got that right, or else I spent money in error, read item descriptions before buying (I try lol!

)

**RknRusty** Tue Dec 20, 2011 10:48 pm

Jaspur_x wrote:RknRusty, just to help clarify if I read correctly ( big if, but I did in fact purchase accordingly) the spi cylinder sets did outperform the others on the reedies, but on the teedee it did not;thats why they made up a seperate set for teedee performance.
A teedee set may out perform a weak black widow set on the black widow, but a spi set is tops on the reedie engines.

I hope I got that right, or else I spent money in error, read item descriptions before buying (I try )

I thought that might be a possibility. I'll make sure I have it straight before spending money. I was told at RCG that the old #4 cylinder would run great on a BW, but that's a moot point now. I have 2 brand new SPI sets. One is on an engine with a Killer Bee backplate that's not in use and the other is on my Medallion awaiting a plane to fly. So I have those to tinker with. They both have loose fitting pistons, I was surprised they had no bite at all at TDC. I wonder if they are all that way. I know the speed guys sometimes liked loose fits.

Jaspur_x Wed Dec 21, 2011 3:16 am

The old #4 was the high standard of high performance back in the day, loved to run those with teedee glowheads on my black widow. Can I confirm that combination ran better than Bernies new spi set on a reedie, nope.
I only have a banged up used #4 set that I just recently got on a used teedee and immediately replaced with bernies new teedee set,and a couple old worn out #4 etc. sets awaiting new tech in cylinder coatings.

A lot of speed guys liked the loose slippery fitting sets, some like myself liked that pinch at tdc;but like you said, moot point.

Bernie had tests to see which combo had higher yields, I`m buying those results as good enough for me, a lot better offerings than a couple years ago, and much better than none at all.

If you really want to see, open up your bank account, original #4 sets,still in the old cox packages;cardboard blister pack style, as well as the 80`s style plastic cox bags types can be found on ebay. I bid on a couple and watched a bunch more, fetching $50+ each these days Shocked

.......................yeah,exactly!!!

I`m very very happy bernie, matt , and a couple other scources are around and bringing new products and or new options our way and hope that continues into my childrens generation so my kids can continue to enjoy a lifetime of cox as I have Beer Cheers

I cannot express my appreciation enough!!

Cox International Wed Dec 21, 2011 11:29 am

IMHO the old 1970's (80's?) #4 TD cylinders were the best for performance but, as was correctly pointed out, are so expensive to obtain that they become a moot point.

The newer #4 (Tee Dee) cylinders that Estes made in the 90's are almost as good, however. Ok, perhaps 1,000 RPM short of the old ones.

The new Surestart cylinders are nothing but these #4 with a slit exhaust and the port opening raised slightly, negating SPI. The porting inside is identical.

That is the reason we used the Surestart cylinders to make the "Tee Dee" ones. They are non-SPI but SPI seems to make little difference on a TD engine. They do not perform as well as the SPI slit-exhaust version but for those out there that want the "authanetic" look or just don't believe this, we have the "Tee Dee version" at a higher price Smile

Today I will be measuring some old TD cylinders and, if the exhaust port measurements permit, will be making real TD #4 cylinders (machining Surestart ones). That is open port, SPI, TD porting. They would then become our most powerful cylinder.

Bernie
www.coxinternational.ca

fit90 Wed Dec 21, 2011 12:29 pm

If that all happens would it be possible to lighten the piston (as you do with the SPI combo) yet leave the piston height unchanged? I woild think that this one change alone could produce a noticable RPM gain .

Cox International Wed Dec 21, 2011 12:40 pm

The piston could be lightened but we would be creeping up towards the $20 retail mark by then.

I did some measurements on my stash of #1 cylinders and they will be perfect for the mod. Should then have real Tee Dee cylinders available in January. They will be identical (inside and out) to the # 4 ones that Cox made. The only differences will be a port opening 0.4mm bigger and silver colour showing there the metal was machined.

At the same time will also have Venom/Killer Bee drive-plates available.

Bernie
www.coxinternational.ca

**RknRusty** Wed Dec 21, 2011 12:55 pm

So am I understanding correctly; if I had to replace the original cylinder on my TD .049(pre-estes)) I would get a little better performance from your SPI slit exhaust set instead of the one called the Tee Dee set?
Suits me, I'm not worried about looks and it keeps it simple.

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Best way to lower the ports on an .049 cylinder.

Best way to lower the ports on an .049 cylinder.

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