HP500/Gil Offshore/Reversion
 

Gen VI HP 500 Clone
111* Intake lobe centerline
169611
9.4/1
088s
Large oil cooler wo/thermostat (no room)
MSD
Gil Offhsores (Early short risers)

Getting ready for some heads, old ones had a very poor leak down #s, mostly on exhaust.

Like most early carb HP 500s I have a reversion issue with the exhaust.

Gil remedied the reversion problem by producing a taller riser (which will not fit under my hatch)

On some of the older short risers they changed the water dump to lessen the reversion issue.

Does anyone know how Gil revised the water dump????? Pics?

If I extend the inner dry tube a few inches (3 or 4) would reversion be reduced?????

Any ideas? I cannot run dry exhaust due to local laws :(

THANKS!

You can run dry exhaust and get some mufflers...

Extending the risers may help

Fixx
 

rick, donzi rite? did you install the tubburlators?

Its the cam that is the issue. Merc put a bandaid on it when the modified the risers to be taller with more angle.

You are talking about new Dart heads in the other thread. If you are going to spend that much coin, spend another $500 and get a new cam less prone to reversion that will match well with the flow numbers of the heads.

THANKS for the replies!
Mild
Never thought of Dry exhaust w/mufflers. Reversion is not that much of a problem. Mufflers would look kind of funky on a 22 Classic:eek:

mrfixx
Yep it's me ;)
Turbulators are installed. Reversion is minor. It's only an issue moving around the docks when engine is VERY cool i.e. start up and/or extended idle w/cold seawater temps.

Giff
I am trying to upgrade heads wo/pulling engine (recovering from a broken back :( ). I will upgrade to the 731 when I refresh the bottom end in a few years. I am using stock GM lifters and dog bones. I'm not sure they would work w/.610 lift cam. Do you know if the base circle is smaller on the HP 500 EFI cam? Do you know anyone with a HP 500 EFI takeout? What is the difference in overlap and timing between the 169611 and EFI cam? I was surprised when degreeing cam that the 169611s intake lobe centerline was 111*??????? (cam card states 105?????). That might be part of the issue also.

fixx
 

have you tryed a restrictor to the riser,another thing that will work is a through hull dunps for the riser but you have to be careful on how bit you go..

I don't know about the base circle diameter. You would be best to call rmbuilder.
It looks like Crane just redid their website and the 500efi cam (169621) won't display.

Here are the specs on the 500efi cam

292*/298* Adv
230*/236* @ .050
.598"/.610" @ valve
114* LSA
109* ICL
119* ECL

Extending the inner pipe of the risers will help some. If you extend it, be sure to put a small bell mouth in the end of the inner pipe. This will help the water to move away from the end of the pipe as the water and exhaust meet each other.
Eddie

Extending the riser's...And installing a simple x pipe should cancel reversion if it is not severe from the start.

http://www.carcraft.com/techarticles...ion/index.html

It does work...merc racing has done some on this too i believe