Profile Picture

Y block Roots blower

Posted By dennis22 3 Months Ago
You don't have permission to rate!
Author
Message
dennis22
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)

Group: Forum Members
Last Active: 2 Months Ago
Posts: 84, Visits: 17.6K
Hi everyone,

I’m going to put a Weiand 144 blower on a 272 y block and I’m just trying to work out correct estimated boost. I have used the formula on Weiand’s tech pages (see pic below) but I’m unsure what the 25.58 factor relates to. If anyone could help me out with a formula that would be great. Any other recommendations/experience blower related would also be welcomed.(I have had a search and found nothing specific)

The engine will be just a cruiser, nothing too serious. The project is happening, I just need to figure out how far I will dig into the engine. I am hoping to run a low PSI to keep the engine close to stock and comp down below 12:1.

Here is a list of things that I have planned/thinking about.

- new 1.54 rocker assembly + stiffer springs (still not sure how stiff)
- stock grooved cam or custom grind favoring exhaust (although I have read custom grinds have marginal gains over stock cams <5000 rpm.
- ecz-c heads or G not sure yet.
- head studs
- forged pistons

And all the usual little y block rebuild mods and all bearings changed out, also I have the manifold sorted out too.

I have probably missed some things but oh well.




Thanks, Dennis.

56 F100 - 272 Y Block
Sydney, NSW, Australia.



LordMrFord
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)

Group: Forum Members
Last Active: Yesterday
Posts: 675, Visits: 9.0K
Pistons and connecting rods breaks first. Comp ratio with pump gas should be something like 9:1 not 12:1. Stock engine can handle 6psi quite long.



Hyvinkää, FI
Sandbird
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (301 reputation)Supercharged (301 reputation)Supercharged (301 reputation)Supercharged (301 reputation)Supercharged (301 reputation)Supercharged (301 reputation)Supercharged (301 reputation)Supercharged (301 reputation)Supercharged (301 reputation)

Group: Forum Members
Last Active: 8 minutes ago
Posts: 109, Visits: 494.3K
I believe the 25.58 is a figure they chose for an approximation of Barometric pressure.  One inch of mercury equals 0.49 PSI. The last step subtracting 14.7 converts the answer back to PSI. They probably wanted to keep things simple.
miker
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (2.9K reputation)Supercharged (2.9K reputation)Supercharged (2.9K reputation)Supercharged (2.9K reputation)Supercharged (2.9K reputation)Supercharged (2.9K reputation)Supercharged (2.9K reputation)Supercharged (2.9K reputation)Supercharged (2.9K reputation)

Group: Forum Members
Last Active: Yesterday
Posts: 1.4K, Visits: 90.1K
I ran a 9:1 static comp. Yblock with a Paxton centrifugal, blowing thru a 1406 Edelbrock. Only saw 5lbs at 5000rpm, and nothing until 3000. Used a 270 Mummert cam. That set up liked a 2 degree ignition retard, which came in at 2lbs on a Hobbs switch to an MSD 6 something ignition. Premium 91-92 with some ethanol. Initial and total timing was pretty much standard performance Yblock, 10-12 initial and 36 or so total.

I’ve got an OT car with a small Eaton charger, makes 7lbs right off idle. It too likes a bit of retard from 3000 rpm up, even though it’s still at 7lbs.

So you might consider that when you put the ignition system together. Hot weather and a long pull put me into light detonation, and that’s not good even with forged pistons.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ
charliemccraney
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)

Group: Moderators
Last Active: 47 minutes ago
Posts: 5.6K, Visits: 84.0K
Even with G heads, a 272 will not have much more than low 8s;1 compression with flat top pistons so I probably would go with Gs of the two choices.

A custom ground cam should produce far more than marginal results, if you answer all of the grinder's questions honestly and take what they give you (unless you actually do have enough experience to specify the dimensions).  The reason being that it will be custom tailored to the whole package.




Lawrenceville, GA
dennis22
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)

Group: Forum Members
Last Active: 2 Months Ago
Posts: 84, Visits: 17.6K
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
Sydney, NSW, Australia.



charliemccraney
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)Supercharged (8.8K reputation)

Group: Moderators
Last Active: 47 minutes ago
Posts: 5.6K, Visits: 84.0K
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
dennis22
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)Supercharged (208 reputation)

Group: Forum Members
Last Active: 2 Months Ago
Posts: 84, Visits: 17.6K
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
Sydney, NSW, Australia.



LordMrFord
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)

Group: Forum Members
Last Active: Yesterday
Posts: 675, Visits: 9.0K
charliemccraney (7/10/2019)
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.

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
LordMrFord
Posted 3 Months Ago
View Quick Profile
Supercharged

Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)Supercharged (1.2K reputation)

Group: Forum Members
Last Active: Yesterday
Posts: 675, Visits: 9.0K
dennis22 (7/10/2019)
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!

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


Hyvinkää, FI


Reading This Topic


Site Meter