HP 500 carb + Gill + Silent Choice = Reversion?
09-15-2003, 11:34 PM
#11
Charter Member
My last motor:
HP465 (same thing as the HP500, except for cam and intake)
Cam upgraded to the Crane xxx741 cam. a bit bigger than the stock HP500
Merc manifolds, Gil risers and SILENT CHOICE.
Dry as a bone, Never any signs of reversions.
HP465 (same thing as the HP500, except for cam and intake)
Cam upgraded to the Crane xxx741 cam. a bit bigger than the stock HP500
Merc manifolds, Gil risers and SILENT CHOICE.
Dry as a bone, Never any signs of reversions.
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Last edited by US1 Fountain; 12-02-2011 at 11:17 AM.
09-16-2003, 10:25 AM
#12
Guest
Posts: n/a
Cord,
how do you raise the idle speed to 800 rpm? With the Thunderbolt V ignition, the idle speed is controlled by the ignition module and always seeks 700 rpm on my HP 500 carb motors. You can raise it is when the pur/wht wire on the distributor is grounded, as when you are checking or adjusting the timing by turning the idle speed screw on the carb linkage. But as soon as you unground the wire and put the system back into normal mode, the module takes over and lowers the idle speed back to 700.
Rich
how do you raise the idle speed to 800 rpm? With the Thunderbolt V ignition, the idle speed is controlled by the ignition module and always seeks 700 rpm on my HP 500 carb motors. You can raise it is when the pur/wht wire on the distributor is grounded, as when you are checking or adjusting the timing by turning the idle speed screw on the carb linkage. But as soon as you unground the wire and put the system back into normal mode, the module takes over and lowers the idle speed back to 700.
Rich
09-16-2003, 12:03 PM
#13
MarineKinetics
Platinum Member
From the Stainless Marine FAQ on their web site
Hope this helps,
Bob
Can I use the short risers and silent choice on a high performance engine?
Maybe. To avoid reversion, the cooling water must be dumped far enough away from the manifold that it does not get ingested while the engine is idling. One of the camshaft parameters is duration. For use with a stock length riser, duration should not exceed 224 degrees @ .050" lift. As duration increases, the risers must be lengthened in order that the water is dumped further away. In the worse-case scenario, the cooling water must not be introduced into the inside of the riser at all, but rather dumped overboard via a dump tube.
Hope this helps,
Bob
Can I use the short risers and silent choice on a high performance engine?
Maybe. To avoid reversion, the cooling water must be dumped far enough away from the manifold that it does not get ingested while the engine is idling. One of the camshaft parameters is duration. For use with a stock length riser, duration should not exceed 224 degrees @ .050" lift. As duration increases, the risers must be lengthened in order that the water is dumped further away. In the worse-case scenario, the cooling water must not be introduced into the inside of the riser at all, but rather dumped overboard via a dump tube.
09-16-2003, 06:52 PM
#14
Guest
Posts: n/a
I was told that there was a reversion problem with the HP500 carb engine running Gills. Originally the HP500's had a short stainless riser. After there was found to be a reversion problem, Gill supposedly offered/came out with a taller riser as a replacement, and as I understand it, some later 500 carb engines came with the taller riser. This was supposed to help with the reversion. I would guess thats why the 500efi came with CMI's to totally eliminate this problem.
I would also make sure the internal flappers are installed in the exhaust pipe that runs thru the transom, as this will help in preventing water from running up the riser back into the engine when comming off plane, especially with boats with the exhaust exiting under the swim platform, like Sonics. The flapper will also help when backing up and prevent water from backing up the riser, and back into the engine. Over time the flappers wear/burn out and you have no protection from water backing up into the riser.
Just relating info as it was related to me by marine mechanics.....
I would also make sure the internal flappers are installed in the exhaust pipe that runs thru the transom, as this will help in preventing water from running up the riser back into the engine when comming off plane, especially with boats with the exhaust exiting under the swim platform, like Sonics. The flapper will also help when backing up and prevent water from backing up the riser, and back into the engine. Over time the flappers wear/burn out and you have no protection from water backing up into the riser.
Just relating info as it was related to me by marine mechanics.....
09-16-2003, 07:54 PM
#15
Registered
Join Date: Mar 2001
Location: ohio
Posts: 2,558
Likes: 0
Received 0 Likes
on
0 Posts
I also remember the service bulletin saying to increase the idle to 800. On my T4 ignitions, the idle is controlled by the carb, the module has nothing to do with it. I didnt think any of the carb engine idles were controlled by the module.
