I guess it counts as a viper

[DavieStone]

I have a DCB (Dave's Custom boat) that has two Viper motors that a company named Ilmor developed into a 725hp motors each. The challenge I am having is that I have two motors that have blown over the last year (one that the prior owner blew and the replacement motor that I blew)...that I took the time to open up (unlike the old owner) and look at what was the issue.

The issue so far seems to be a stretched out cam chain. Both motors lost the valves in the number 5 cylinder (they typically run hotter) when one of them tagged a piston. So the question...is there a geardrive cam setup for the Gen IV motors that anyone knows of??? Belt system, cam tensioner chain errr whatever???

So picture of said boat for reference. :-)

[commandomatt]

Dont have the answer to your question but I really like the DCB's.

Awesome and Beautiful boat you have there

Seems like Ilmor would have the answer for you as they really know how to make power with these engines while keeping them NA

[DavieStone]

Dont have the answer to your question but I really like the DCB's.

Awesome and Beautiful boat you have there

Seems like Ilmor would have the answer for you as they really know how to make power with these engines while keeping them NA

Thanks...love the boat and the motors if I can figure them out. Ilmor has never heard of the cam chains stretching out and doesnt have a fix for it.

[Viper Specialty]

I cannot possibly see a chain being stretched, and have never seen that issue in any Viper engine, including Gen-4/5. You would rip the cam gear off the camshaft before you stretched the chain enough to matter... and trust me I have seen that, with the resulting chain still good!

Are you sure there isn't something else going on here? Perhaps accelerated timing chain/gear wear masquerading as a stretched chain? Cam/Crank machining error from the start?

We specialize in that version of the engine platform... so if you have any questions, let me know.

[DavieStone]

cam chain.jpg

This is a shot of the cam chain as it sat in the motor and will look at the Cam gears a little closer. Good call thou and I will call ya tomorrow. Thanks

[ssgsnake]

I have friends who have the motors in there boats and are rock solid, DCB boat are awesome.

[jaxtk]

It's normal for the chain to get slack after being run. Unless the chain skips a tooth, it will never cause the piston to hit the valve. Possible incorrect cam timing, or piston to valve clearance to close.

[Viper Specialty]

cam chain.jpg

This is a shot of the cam chain as it sat in the motor and will look at the Cam gears a little closer. Good call thou and I will call ya tomorrow. Thanks

OK, that is a Gen-3 based timing set. Those OE timing chains are always loose as hell, even brand new. It is a design flaw IMHO, and we do have alternatives. What you are looking at is actually normal... albeit sad! This issue is only normal for 2003-2006 engine blocks using OE timing sets. It is not seen elsewhere in the Vipers, and is easily correctable.

So, knowing that, we have to find your ACTUAL problem...

[gfviperman]

Dolph has (maybe had) a boat just like that .. Twin Ilmors ...