Cam shaft help!

[SLDPULR]

Hey guys, I need the advice of a engine builder. I am currently running the comp cams XE294H cam (part number 12-254-3). The motor runs great and has TONS of power all through the rpm range. I do however have a few issues. First problem is my brakes. I can only pull about 6hg of vacuum at idle. I have tried a vacuum canister but after about 2-3 brake cycles I am out of vacuum. I have visited with a vendor about switching to a wilwood master cylinder to fix that issue but I am planning on going to a Fitech 600hp power adder EFI kit. Which brings me to another problem the Fitech EFI kit will not work with my current cam shaft due to the choppy idle.

So I am looking for a cam shaft that will keep me at my current HP/torque levels, work with a EFI kit, and possibly pull enough vacuum to run a brake booster. From the research I have done I have not been able to find a cam that will meet all of my needs. So does anyone know of a cam that might work.

Link to current cam
http://www.compcams.com/Company/CC/c...x?csid=89&sb=2

SBC 383
BORE: 4.030
STROKE: 3.750
DECK HEIGHT: .025
CYLINDER HEAD VOLUME: 72CC
HEADS: 190CC RUNNERS
HEAD MATERIAL: ALUMINUM
GASKET THICKNESS: .032
COMPRESSION RATIO: 10.03:1
PISTON: FLAT TOP SINGLE VALVE RELIEF
CAM: COMP CAM XE294H
TIMING CHAIN: DOUBLE ROLLER
ROCKER ARMS: COMP CAMS ALUMINUM 1.5
DIST: MSD PRO BILLET/MSD 6AL
INTAKE: RPM AIR GAP
CARB: 750 HOLLEY DP MANUAL CHOKE
TRANS:TH350C
CONVERTER:HUGHES 3000 STALL
HEADERS: 1 3/4 LONG TUBE
EXAHUST: 3" WITH X-PIPE
MUFFLERS: 3" BORLA OFFSET/OFFSET
GEARS: 3.08:1 (I think they are 3.08, I will be swapping to 3.73 or 4.10 gears soon)

Picture for entertainment.....

[PGSigns]

So why wont the efi work? I have a holley sniper on my 66 and have not found any reason it would not work with a big cam. You can run these things on a full race engine. Have you worked with putting timing in it to help the vacuum? is your pcv and brake vacuum off the same tap?
Jimmy

[toolboxchev]

So most of the guys that run into brake problems opt for a standard stock hydraboost unit. From a later model truck or van.

Any idea why you could not keep the current cam setup and just switch out the brake equipment?

[SLDPULR]

Originally Posted by PGSigns

So why wont the efi work? I have a holley sniper on my 66 and have not found any reason it would not work with a big cam. You can run these things on a full race engine. Have you worked with putting timing in it to help the vacuum? is your pcv and brake vacuum off the same tap?
Jimmy

Fitech says that the rough choppy idle confuses the EFI. Maybe I need to look at the sniper system. I'm running timing at 32 right now. I am not super knowledgeable when it comes to timing. I know that every motor is different but how much is to much timing?

[SLDPULR]

Originally Posted by toolboxchev

So most of the guys that run into brake problems opt for a standard stock hydraboost unit. From a later model truck or van.

Any idea why you could not keep the current cam setup and just switch out the brake equipment?

I can switch out the brake equipment. I am trying to do the most cost effective modifications.

If EFI will not work with my cam then I would like a cam that would pull enough vacuum so I wont have to do anything with the brakes.

[GASoline71]

32 total? or initial?

Gary

[SLDPULR]

Originally Posted by GASoline71

32 total? or initial?

Gary

Thats total

[geezer#99]

Originally Posted by SLDPULR

Fitech says that the rough choppy idle confuses the EFI. Maybe I need to look at the sniper system. I'm running timing at 32 right now. I am not super knowledgeable when it comes to timing. I know that every motor is different but how much is to much timing?

If your hei is unmodified it will likely have about 24 degrees mechanical timing.
If you have 32 total then you only have about 8 initial.
At elevation and with your cam and compression you need closer to 20 initial. You'll need to modify the mechanical to about 12 degrees.
Link here for that.
http://www.crankshaftcoalition.com/w...EI_distributor

And here's a link to figure out your optimum timing.
http://www.badasscars.com/index.cfm/...d=76/prd76.htm

[PGSigns]

I think you need to find a better efi tech guy. A good bit of the choppy idle will be gone with the efi as it does not need a good vacuum signal to work like a carb does. So you can get a lot cleaner idle. Lots of folks have bailed from FiTech and there some threads here. I think if you work on you timing curve and get it more where it needs to be you will have the vacuum you need. Also having the pcv and brakes on the same port will not help. Have you tried more timing? I think I would look at what you have at idle, 1500, 2000, 2500 and 3000 to see what the curve looks like. That will help us get you better setup. Also I would see how it runs with 36 total. and at least 15 at idle.
Jimmy

[SLDPULR]

Originally Posted by geezer#99

If your hei is unmodified it will likely have about 24 degrees mechanical timing.
If you have 32 total then you only have about 8 initial.
At elevation and with your cam and compression you need closer to 20 initial. You'll need to modify the mechanical to about 12 degrees.
Link here for that.
http://www.crankshaftcoalition.com/w...EI_distributor

And here's a link to figure out your optimum timing.
http://www.badasscars.com/index.cfm/...d=76/prd76.htm

Thank you so much for those links. That second one is a great read. Ill be saving that one. If it wasn't raining id be out there redoing the timing.

[SLDPULR]

Originally Posted by PGSigns

I think you need to find a better efi tech guy. A good bit of the choppy idle will be gone with the efi as it does not need a good vacuum signal to work like a carb does. So you can get a lot cleaner idle. Lots of folks have bailed from FiTech and there some threads here. I think if you work on you timing curve and get it more where it needs to be you will have the vacuum you need. Also having the pcv and brakes on the same port will not help. Have you tried more timing? I think I would look at what you have at idle, 1500, 2000, 2500 and 3000 to see what the curve looks like. That will help us get you better setup. Also I would see how it runs with 36 total. and at least 15 at idle.
Jimmy

I'm glad I posted on here. I still have so much to learn when it comes to timing and tuning a carb. I will be going out of town tomorrow morning but I will definitely post up the results at the RPM's you suggested when I get home.

Thanks guys

[Tom]

Pretty much every turbo car out there runs a vaccum pump and resivior to operate the brakes. I'd go that route with junkyard stuff.