Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - problems with running my supercharged 351w
View Single Post
  #22 (permalink)  
Old 10-17-2012, 03:10 PM
cobalt327's Avatar
cobalt327 cobalt327 is offline
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Posts: 5,031
Wiki Edits: 1616

Thanks: 128
Thanked 616 Times in 565 Posts
Originally Posted by mustang 671 View Post
guys this is great thanks so much . i have this weekend to get all of these tips in place for next wednesday .

ok compression ration is 7.48 to1
i have a 14 psi max ratio on the pulleys . ( so weiand say )

i had to have a new pulley machined to fit over my rattler harmolnic balancer to save space so thats why the top one it larger than normal . bottom pulley is 45 and top is 51 teeth so its 0.88 so its being underdriven.

i can regulary get hold of 98 octane gas .

thanks t bird for the tech stuff . just what i needed. i have 6.5 power valves . so they must be getting pulled open all the time ?

so my .72 in the primary also seem to rich ?

will check my plug gaps . i have just been sold a cooler plug from champion and i havent gapped them . i wonder what they are factory set at ?

i have larger headers and also nice elderbrok victor heads . so feel confident on them . what about my air filters and scoop . i hope i am not restricting air flow ?

i have a ecu so will have to speak with them regarding boost and timing retard box and how that will work with it ?

what about colour for fuel squirt cams ? and colour of spring on sec's ?

also the vac sec's have 2x air tubes coming out of them and are fixed to the manifold "below " the supercharger !! is this where it should be plumbed in to read vacum to open the vac sec's?

thanks guys . good job !!
The carbs are referenced for secondary opening if connected to each other. Could be boost referenced if connected below blower. The vacuum would need to fall below 6.5 in/Hg to have the power valves open, so there's almost no chance they're opening all the time unless there are other problems. Take a vacuum reading below the blower and use that to see what power valve you need. If the vacuum is excessively low, there could be other issues that need attention. If the carbs aren't boost referenced, the power valves will stay shut.

You have secondary metering blocks w/changeable jets, I take it?

If you are .88 underdriven, w/a 355 cid engine, and a blower displacement of 411, I'm getting about 11 psi. Still a good bit of boost for a street vehicle. With the static CR you have, that puts the effective compression ratio at about 13:1 at max boost, so you may well need to blend in race gas. Remember no detonation, else the pistons will fail.

Boost formula I used:
[(25.58) times (Blower Displacement) times (Blower Drive Ratio)] minus 14.7 divided by the engine displacement in cubic inches equals the theoretical boost in psi.

Last edited by cobalt327; 10-17-2012 at 03:40 PM.
Reply With Quote