LordMrFord- yeah I did read an article the other day saying that intercoolers on roots style blowers (between blower and intake manifold) were pretty much useless. It said that because the air is already compressed once it passed through the rotors that cooling could not make it any more dense, no extra performance gains. it would just cool the air to help with detonation issues. I also read that fuel atomization cools the air by up to 50%. I thought that was pretty interesting.

Peg leg- yeah I was thinking something 112-114 with larger exhaust duration. If John gets back to me I’ll let you know.


Thanks, Dennis.

56 F100 - 272 Y Block
NSW, Australia.

Keep the cam mild with not a lot of overlap (fairly wide centers) . If you tell Mummert what you are doing and want he can recommend an effective cam. 

Frank/Rebop

Bristol, In ( by Elkhart) 

Yes. Intercooler in roots-blower is not that effective because roots-blower only moves air not compressing it.
Turbocharger, centrifugal and screwcharger generatates pressure and therefore heat in charger it self and air is hot already when going in intercooler.
Roots just moves air forward generates heat and pressure in whole intake system from charger to piston and thats why intercooler located in the middle, cools only 50% compared to other charger types.
Water injection cooling might work better with the roots-charger because it can be located closer to piston.


Hyvinkää, FI

Thanks LordMrFord and Miker,

Looks like I’ll just give it a run at 5-7psi boost and see what happens. I will get an ignition retard module too.

I’ll let you know how it goes. It will still be a while off yet until I get a few bits and pieces together.


Thanks, Dennis.

56 F100 - 272 Y Block
NSW, Australia.

I wouldn’t get too carried away with the “theoretical” boost calculations. You’re going to have some losses thru the carb, and more loss thru the intake ports, etc. I know on my blow thru’s there a couple lbs loss between the top hat and the manifold. How much pressure reaches the cylinder I don’t know, but certainly there’s more loss. If you have a static ratio between 8 and 9 to 1, and 5 lbs boost, you should be ok. My OT car with the Eaton on it is a “factory stated 9.4:1 static” ratio. Now it’s a whole different motor, dual oh cams, fuel injection, etc. with a blower sized for its 96 cubic inches. But slowing the Weiand down is a lot easier than rebuilding a engine. Less boost is less horsepower, but as Gaga notes, an inter cooler is a big effect. The heat increase in more boost causes some problem, and an intercooler on your set up is a lot more complicated than his turbo units.

Should be a fun project, and a gas to drive.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

I just specify, when I said 9:1 comp ratio, I mean static comp ratio.


Hyvinkää, FI

I didnt know the originals were forged.  :o
However, I dont know whats the serious boost but we dynoted a stock 292 with 0.7 bar boost with turbo and engine seemed be fine. (c2 rods)
That combination saw no highway use and were intercooled what makes a big difference. A long term heat will be hard for the pistons.
(Combination was destroyed with 1.5 bar boost when one cast piston shattered due the detonation.)


Hyvinkää, FI

Thanks Charlie! Not serious boost, just aiming for 6psi. Weiand’s stock pulleys are sized for about 5-7psi and according to the calculation, applying those sizes to the stock 8:1 272 would give me just under 12psi. so I will have to order a larger snout pulley and I’m going to have to go back to the drawing board to get compression way lower anyway. 6psi puts me up around 12:1.

Anyway thanks for the info. Appreciated!


Thanks, Dennis.

56 F100 - 272 Y Block
NSW, Australia.

Stock rods are forged and considering the 40ci diference between a 272 and an F code, unless you will be running some serious boost, stock rods or stock replacements will be fine.

If you do want something beefier, hunt down some C2AE 292 rods.


Lawrenceville, GA

Thanks everyone-

LordMrFord- Well I better get some forged rods. Thanks for the comp ratio info. I was under the impression that 12:1 was the max I could get away with but as you mentioned it seems that I’ll need to be down towards 9:1.

Sandbird- thanks, I received a reply from Holley stating that the 25.58 was a universal factor, however they didn’t elaborate.

Miker- thanks mate, yeah I will have to thing about ignition retard module. I’m not sure if there is any difference in fuel quality here in Australia?

Charlie- thanks, I did think the G heads would maybe be better with the bigger valves (even though it’s forced induction) but wasn’t sure if the C heads would be better with the lower compression.
I emailed John M with parts list and recommendation for cams.




Thanks, Dennis.

56 F100 - 272 Y Block
NSW, Australia.