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Is it possible to add variable timing to a big cam I ?

Posted By shredator Sunday, March 22, 2020 5:36 PM
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shredator
 Posted Sunday, March 22, 2020 5:36 PM
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I recently got a K100 that has a big cam I 400 in it. The cpl is 310. I live in a cold place, and it smokes the whole town out when I start it. I'm wondering if it feasible to add either MVT or STC to this engine? Which would be simpler? Any guidance is appreciated.

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Newto
 Posted Sunday, March 22, 2020 11:03 PM
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Hi Shredator,

That CPL is a California spec supposedly an anti pollution mother but with .081 timing its no wonder the town hates you!!!

Simplest fix would be to advance the timing to .070 to .075 by pulling the cam boxes and adding gaskets.

Also check the set on the injectors.....even tho its got top stops fitted if the set is slack its only going to make things even worse.

Seriously.....re-time the cam boxes to .070 and remove the injectors, remove the stops ,refit them and adjust the injectors to .072 in/lb on the outer base circle of the cam and you'll have plenty of cash left over (and no cold start smoke) to buy everyone a drink rather than trying to go down either the MVT or STC route.

And lastly....if you're in a really cold place....(we don't have that here).....maybe add a block heater as well.

hope that all makes sense...

Newto
shredator
 Posted Monday, March 23, 2020 4:21 AM
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Thanks! I'll advance the timing, and add a block heater, and see how it goes. Out of curiosity, are there any other differences to the California models that are worth noting?
Newto
 Posted Monday, March 23, 2020 10:39 AM
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That CPL had the 14.5 : 1 pistons so the only other differences I know of were in the fuel pump settings and injector flows.

Usually the AFC is set to give poor throttle response to minimise acceleration smoke & fuel pressures are not over exciting.

jimfols on here could give you more info on pump & injector specs......he's the fuel guy!

Newto
jimfols
 Posted Monday, March 23, 2020 5:10 PM
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Hello Shredator,

To answer your question the main difference is the fuel system.


Like Newto said, CPL-0310 was a nightmare for cold engine smoke.
Take CPL-0393 for instance, the injector flow is 176BK and the 0310 is 190BK.
The 0310 pump flow is a little less to make up the difference but not much.

These two CPLs have the same Cam, Pistons, and Turbo.
The timing on the 0393 is -.070.
You could set the injectors at 90 in lbs on the outer base just to see if it helps the smoke.

The early STC injectors used the same type cup and you could go to 90 in lbs per Cummins Spec.

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Jim
Newto
 Posted Monday, March 23, 2020 5:30 PM
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Thanks for the backup Jim........I knew you'd have those fuel figures readily available!!

Newto
Geoff Weeks
 Posted Wednesday, March 25, 2020 1:15 PM
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Another option is an Espar or webasto coolant heater if you park where plugging in is not an option.
I use this method on my engine that smokes bad when cold, I just don't idle it cold!
Geoff Weeks
 Posted Thursday, March 26, 2020 2:29 AM
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Jim, what about CPL 324? It seam they share all the same FF numbers of cam and pistons, Again the injectors are flowed different but it is timed much more advanced. I have one, and while it doesn't start well in the cold (none of the old 400's did) doesn't smoke on cold idle. They start fine cold with either being pre heated or with 5cc of ether injection.
jimfols
 Posted Thursday, March 26, 2020 2:59 PM
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I just chose 0393 because it was a nice round number and a very popular 400.

Probably the reason for the fast timing on 0324 was not as strict certification at the time.
Think more cylinder pressure making more NOX.


Getting away from the subject of white smoke and going to long crank times.
Who can we name that ever tests the pressure and flow of the gear pump?
The minimum flow for a gear pump is 1050 PPH at 350 PSI. A good one will do the 350 PSI at 1200 PPH.

A well used gear pump will do ~950 PPH. So a guy (or girl) can easily jack this fuel pump up to 400 or 500 HP
with buttons and springs. But the buttons and springs have no effect on the cranking fuel pressure.

Just a little rant on getting back to basics.

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Jim
444xtmike
 Posted Thursday, March 26, 2020 3:37 PM
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So pressure is resistance to flow, just remember to always set the flow then read the pressure! I've spent enough time behind a Hartridge I could probably change a button, sorry! idle plunger, in the dark with two nails!

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