Boring the FPP

Foximus

Foximus

CFL Cheapass.
Location
Oviedo, Fl
Searched around a bit and I know that you need to bore the B pipe to 47-49mm, however I cant find specifics...

I measured the manifold, and the opening is at 46mm, but just below that is a taper down to 44mm. I figured it is obvious this needs to be bored out to 47 or greater.


But then I checked the headpipe. That measured in at 42mm. WTF?


Obviously I could bring out the headpipe to match, but with that aggressive curve through the pipe I could only get so far and then it would most likely taper back down again before opening up.

So someone enlighten my situation.
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
That's the older FPP manifold with a measurement of 42mm, the new ones are around 46mm in diameter.

Most people port the exhaust opening and head pipe around 47mm to 48mm and if you're running more displacement 49mm to 50mm will work well but you need to make the stinger tip smaller in diameter but not too small that you'll melt the pistons.

Also if you go bigger then 50mm there a great risk of going through the water jacket at the rear of the exhaust manifold, so on the larger sizes make the port oval with the bigger ends going toward the front and rear of the engine.
 
Foximus

Foximus

CFL Cheapass.
Location
Oviedo, Fl
Well mine is still not here, so I havnt measured it, But the headpipe was 42, not the manifold. This was on my buddies, CarterB.


And Ill be running a Blaster mod, So.... hrmm How to make the stinger smaller... lol
 
Dustin Mustangs

Dustin Mustangs

uʍop ǝpıs dn
Location
Holland, MI
I'm glad you made this thread fox, I was just about to post something similar. I'm sure each pipe will vary, but boring out the manifold if the head pipe is already smaller is waste of time and will actually decrease flow. I personally wouldn't plan on anything until you get a chance to measure your actual pipe.



If you don't mind, I'd like to add a few related questions to the thread:

-Is it safe to bore the headpipe to 47 or 48 to match the manifold? I'm thinking water jacket conflicts here...

-Other than what's mentioned here, the dual cooling mod, and polishing the manifold, are there any other worth while mods for a B-pipe? I've got mine just sitting here waiting for the weather to warm up and quite frankly I'd like a few more excuses to go hide from my wife in the basement.
 
Frosty

Frosty

New York Crew
Location
Western New York
I have an older one that i sent to Chuckie at Team Scream. He opened up the head pipe and manifold, and cut a gasket to match as well.

I have a brand new FPP B-pipe now... and was also wondering whether to open it up a bit more or just leave it?
 
SJ Thumpa

SJ Thumpa

SJ THUMPA
"Most people port the exhaust opening and head pipe around 47mm to 48mm and if you're running more displacement 49mm to 50mm will work well but you need to make the stinger tip smaller in diameter but not too small that you'll melt the pistons."

#0, At 50mm. What diameter would you recommend at the stinger tip? Restrictor or control valve OK? Thanks.
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
SJ Thumpa said:
"Most people port the exhaust opening and head pipe around 47mm to 48mm and if you're running more displacement 49mm to 50mm will work well but you need to make the stinger tip smaller in diameter but not too small that you'll melt the pistons."

#0, At 50mm. What diameter would you recommend at the stinger tip? Restrictor or control valve OK? Thanks.
Click to expand...
The stinger tip on the mod and limited pipe is about 2.00" O.D with a .060" wall, making the inside diameter 46.23mm. There's a computer program that you use to figure out what size stinger tip will work best with your setup but you can just experiment with different size inserts till you find what works the best for you. (Note) "This should only be performed on head pipe diameters larger then 49mm". I wouldn't go under 40mm because you'll be taking a chance of overheating your pistons at WOT. Both a restrictor and flow control valve will keep the waterbox from loading up with water and are recommended.
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
That's the stock inside diameter of the FPP stinger tip.

This trick only seems to work well on ported, larger displacement engines, where the head pipe diameter is opened up larger then 49mm.

I have a few sets of Wiseco pistons that the domes are collapsed and the edges are burnt off on the exhaust side if you'd like to try not going WOT. :hitwithrock:
 
Dustin Mustangs

Dustin Mustangs

uʍop ǝpıs dn
Location
Holland, MI
I just measured my blaster mod pipe and the manifold, headpipe and chamber exit where all right at 47 as delivered. Both the manifold and the headpipe got pretty rough and lost some size about 5mm in. The gasket from fp measured 46 so that should be hogged out.

I measured the chamber too, I'll add that to eel's thread...
 
Foximus

Foximus

CFL Cheapass.
Location
Oviedo, Fl
Well I guess I'll have to wait till the damn thing gets here, then go from there. Dont know if my head pipe will be tiney or not.
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
Dustin Mustangs said:
I just measured my blaster mod pipe and the manifold, headpipe and chamber exit where all right at 47 as delivered. Both the manifold and the headpipe got pretty rough and lost some size about 5mm in. The gasket from fp measured 46 so that should be hogged out.

I measured the chamber too, I'll add that to eel's thread...
Click to expand...

What measurements did you come up with for the blaster mod pipe?
 
Mouthfulloflake

Mouthfulloflake

ISJWTA member #2
Location
NW Arkansas
Bump from the dead.

Ive got a B chamber, it appears to have been modified from stock and has a 42.xx stinger diameter.

is this going to roast my junk or what?

i was working the manifold and headpipe to open them up when I realized the stinger was made smaller.

any ideas on this?
 
Speedfreak

Speedfreak

Location
So. IL
Well it looks like you have to build your motor from the stinger up. So your stinger is 42.XX so you need to open the manifold to 50mm or larger.. Just go 51 for simplicity. Then you need a larger displacement motor. Go with the 91mm seadoo pistons and a medium length stroke of +7mm and that will net you 975.58cc's. That is a larger displacement motor which you need to compliment your stinger...

Tell the wife that you need this motor work because you already have the pipe for it. Problem solved.. your welcome
 
Mouthfulloflake

Mouthfulloflake

ISJWTA member #2
Location
NW Arkansas
it helps alot!

this chamber came with a manifold and headpipe that were still the OLD 42mm opening, but im not sure they were ever actually ran together.
 
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