manifold crossover filled for 38's

[aqua]

I know people fill the crossover for the 44's but do people also notice easier tuning and better performance by filling the cross over tube on the oem 38's?

 

[sjetrider]

Cant see it being a bad thing. Should get better signal to ea. carb this way same as a duall 44 mnfld.

 

[Mark44]

Yes!

Mark44

 

[sjaddicted]

whats the best method to fill the passage?

 

[aqua]

whats the best method to fill the passage?

jb weld....i will be doing it tonight. will i need to run richer or leaner jets with the increase in signal. i can get away with leaner jets right?

 

[douglee25]

Devcon.

 

[Mark44]

Devcon.

x2

Mark44

 

[surferdude345]

my local hardware place had devon metal expoxy, thats what i used

 

[Sanford]

FWIW,

Devcon has a max operating temp limit of 250 degrees. Ironically, J.B Weld has a 500 degree limit.

Keep in mind these are upper limits, the threshold actually begins well before the peak and dramatically rolls-off (or fail) once limit is reached. The longer the part is exposed to a high temp, the quicker the service limit is reached.

I actually found some exotic very high temp putty/epoxy but for most situations, good 'ol JB Weld works well enough and can be found anywhere. Just make 100% sure you never use that 5-minute JB Weld crap!

 

[douglee25]

I don't know why, but I feel like I can never trust JB weld. I feel like I can never trust it's holding strength. I've seen it literally fall off like welding slag for some reason. It just doesn't sit well for some reason.

Doug

 

[SkiDaddy]

If you fill the entire passage in one shot the curvature will prevent it from coming loose even ifit breks free from the walls. Rough up the walls & clean well w/Acetone (in a well ventilated area) & it'll stick well.

Yes, it makes tuning considerably easier (go leaner).

I have one for sale, if someone needs it PM me.

 

[Sanford]

I've seen it literally fall off like welding slag for some reason.

The reason is most likely bad prep work. I like to sandblast then use a coarse 1/4" carbide grinder. Sometimes I use a 1/16" drill bit to make shallow holes in all directions...it really give it something to anchor into.

 

[douglee25]

The reason is most likely bad prep work. I like to sandblast then use a coarse 1/4" carbide grinder. Sometimes I use a 1/16" drill bit to make shallow holes in all directions...it really give it something to anchor into.

I'd agree with that.

Doug

 

[aqua]

ok....i filled the manifold tube last night. how is this going to change my jetting?

 

[douglee25]

You may be able to tune it with the screws or you'll have to go richer one size or so.

Doug

 

[sjetrider]

You should be fine by simply turning the screws, if not you may want to bump to next jet size up from where you were. The crossover allows fuel to pass from both carbs if need be, with just 38mm carbs you may starve the motor of fuel especially at top end if you do not run somewhat richer IMO. I have never done this with 38's before, just my thought proccess, wich has been wrong once before.

 

[SkiDaddy]

I had to lean out my ported cylinder, maybe one size on both high & low, don't remember. YMMV.

 

[sjetrider]

I had to lean out my ported cylinder, maybe one size on both high & low, don't remember. YMMV.

WOW, that is interesting.
I would be curious to see what you end up with. Please update this post once you get the non crossover mnfld. tuned.

 

[Matt_E]

I would expect to have to lean it out. :dunno:
You're reducing intake volume, and speeding up airflow through the intake tract.
You'll need leaner jetting.

 

[jura]

What is the advantage of this mod?
Is it good for freestyle or racing?
Why does it come out of the factory with a crossover?
What can you expect from this mod?
Is this also good on a stock engine?

Thanks.