392 supercharged cilinder heads what to do

I'm working on my 392 hemi have a 6-71 @ 14 PSI 8.5-1 compresion ratio.cam lift .519 adv duration 290 int 290 exh
priopane powerd.
would it be worth the $$ and time to do some mods on the heads?
larger exh valves I already removed as mutch material as I could to open up the heads.
With this boost and compresion it is not a realy wild 392
what would a conservative HP gues be?
I need to select the propane injectors and the trottle body's.
I will use a megasquirt ECU
Regards
Remco

 

Just a gasket match on the intake and exhaust ports, make sure the chambers are smooooth - you don't want any hot spots - and your biggest gains will come from working on the exhaust ports since you've got so much boost on the intake.

As for power - it's going to make a lot! I won't even venture a guess, as the cam and fuel injection tune will make all the difference in the world. Probably 850hp give or take 200.

 

I'm thinking about 2 inch exhoust valves.
Will use 3 throttle body's but what to use 75 , 80 or 85 mm
what`would the max hp be with optimun throttle body's
Than i can calculate the injectors.
I will use 16 propane ( gasious) injectors
With only 8 injectors the pulswide ad idle and part throttle will be verry short.

 

The 92 head is very good as cast. Do a good valve job and if the valves are sunk, put new seats in. The 92's exhaust was the best part of the head. I would recommend not touching it. I ran them on a blown fuel setup with just orings and good valves.

 

It will most likely be faster than a DAF...what else do you need to know??
Really an interesting engine...is the propane fuel for legal emissions, for economic purposes, or for a performance reason?? That is unusual and intriguing.

 

It should not only be faster than a DAF but also a LOT faster than my neighbours BMW M serie's his car is limited at 155 mph (250KMH) only.
The car the hemi is in is a 1957 imperial. brakes and suspension is all altered. Have a set of porsche diskbrakes with 4 cilinder calipers.
still need to build a 4 link rear setup.
from the outside it loks like a 50 year old car with first paint and it will stay that way. If there is a hole I weld in a new piece of metal and paint it with hamerite paint.
I use a megasquirt ECU to controll fuel , spark and with the soon to come GPIO board the 4L80E GM trany.
ignition is 8 coils in waist spark mode
would the 850 hp be a good gues to calculate the throttle body's and injector's ?
When adding nitrous should I than use the max HP for calculating the throthle body's.
If the 850 is a good gues I will surely ad some nitrous to get to the 1000 number if the 850 is realy over estimated I'll keep it as is.
The hemi has all the parts to be able to stay in one piece with 1000 hp.forged pistons 4 bold mains dry sump oil system and all the other bla bla bla .
I use propane becouse it's 1/3 of the price of gas overhere .
And propane has a high octane rating around 110 octane.
It is not a traditional engine build overhere there is a lot of experiance with propane but not with V8's and superchargers.
at first I was looking for liqued propane injection but at this moment that is not possible

 

I wouldnt say that this engine would fall into the mildy built category. it sounds gnarly to me.

 

I'd say that you should expect somewhere between 700 - 800 HP. A good friend of mine just built a blown 392 with HotHeads heads, fairly stout cam and a Hilborn 6-71 injector converted to EFI by RetroTec . . . put out about 650 - 700 at 8 lbs boost. His heads don't flow that much and he was running those ****py shorty headers that everybody sells. The dyno man said that with a good set of equal length headers, that it would probably make 50 - 100 HP more. So, if it was mine -- I'd probably size the injectors for 800 to 850 HP, which will give you some room.

Hope this helps.

Dale