factory head pipe not sealing

[Lsx5.3]

installed a factory mod pipe into my blaster, had to install over sized screws into head pipe, top screw someone had tried to removed and messed up the hole i got the over sized screw in but its not sealing completely with it tighten down it still leaks when pressure testing off a hose. ski is only turning 6650 rpms right now with a 13/17 prop, what else can i do to stop water on the top screw the chamber doesnt sizzle i can grab it even right after beating on it for awhile

 

[SteveC]

Has anyone ever cross-sectioned a head pipe to see what the pathway looks like where those screws insert? I imagine that'd help here.

 

[Quinc]

close the other screws and only run the top screw? jbweld or atv silicone the hole closed.

I think the bpipe makes its peak power around 6600-6700 rpms.

 

[Lsx5.3]

It's still to much water the pipe is cold, that's how I'm running it now, setup is mod pipe, ada head185psi, dual 44mm carbs 62t engine

 

[Pro-pulsion]

Try making a taper point screw. Just find a regular hex head bolt that is the same pitch as the over sized screw you have now and try to grind down a proper taper point. It will seat into the hole and should seal it. Either the over sized screw doesn't have the same diameter at the point as the original hole, or the hole has become slightly oblonged. An easy way to make a chuck ready mount for the regular hex bolt is to just thread a piece of aluminum tube, screw the bolt in and lock it with a nut, if the drill can chuck the tube then you can make a taper point on a bench style belt sander or take it to a machine shop and get them to turn a nice wide angle taper point on it. Shouldn't take them more than a few minutes to do that in a fixed 3 jaw lathe chuck. If you are certain you will never use the top screw and just want it 100% sealed, drill and tap the hole for a 3/8-16 bolt, belt sand the tip of the bolt as flat as possible and wrench that thing in there as tight as you can get it. Coat the tip with the highest heat silicone you can get...red or copper I think it the highest and it should seal it. I had to do that with my center screw. The hole did not line up after trying to drill out an old broken screw and redo it, the drill pushed off through the center of the old screw and double cut the original water hole by just the smallest amount, new screws wouldn't seal it at all. Had to plug it with a bolt at that point. The only other option was major work, cut the outside section of the head pipe out entirely to give an access window, weld the inside hole shut, weld the cut out back onto the pipe and redo the entire water injection hole. I wasn't willing to take it to that extent, or willing to send it out to do that either. The bolt works, and has been doing well since, this is about a year now with no further issues.

 

[Lsx5.3]

Thanks for the help man I just found a bolt to matched the threads today so I'll be trying that this week, hole is definitely oblong after looking at it better, but it's back together so I'm can ride on the 4th so I'll take it back apart Friday

 

[Pro-pulsion]

Here is a photo of what I did for my original replacement screws. I made them both identically to original at the point, and also with a taper point. I made an aluminum holder too at the time so I could thread the screws and have a holder to chuck in a lathe. It turned out well. I will try to find the holder and get a pic of it too. You can see the how the center hole drifted on me forcing the bolt method in the one pic, but it works.