adding it all up

[joe1975]

I'm researching my motor so far this is what I've came up with 350 L-82, cam 268, elderbrock performer intake holley 750 cfm with elderbrock heads ( I think still looking at these) looks like a stock dist. headers hooked to a B.W. 4 speed will barely run on premium @ 12 deg. with detonation coming on about 3700 r.p.m.I'm not even gonna check m.p.g. seems like alot of overkill. I'm new at this,but I'm trying to get rid of the detonation without losing any performance which I'm losing now I'm wondering about going to a stiffer spring in dist. but what I've read so far seems discouraging. Any input? HELP?

 

[JohnZ]

What does your advance map look like? Can't diagnose the issue without knowing what your centrifugal advance curve looks like - when does it start, how much advance does it add, at what rpm does it stop advancing, and what is your total timing (initial plus centrifugal, vacuum advance disconnected) at 4500 rpm (or at whatever rpm it stops advancing)? If you have a dial-back timing light you can dope this out in about five minutes. The initial advance setting doesn't mean much without knowing what the rest of the curve looks like.

 

[joe1975]

Is there any way I can get this info with a standard light? If not I'll have to borrow a light and get back with you.

 

[vette-dude]

Is there any way I can get this info with a standard light? If not I'll have to borrow a light and get back with you.

You can buy a timing tape to mount on your harmonic balancer. Make sure the balancer is clean per the install instructions that come with the tape.

Randy

 

[Fishman]

Joe,

The 750 Holley is too big for most 350's... I had to remove mine and put on a 650. All is well now.

I saw this posted on the forum several times, wish I would have seen it before I put the 750 on...

How To Calculate CFM:
Engine size (CID) x maximum RPM / 3456 = CFM
CFM @ 100% volumetric efficiency (VE)
(Example: 350 CID x 6000 RPM = 2,100,000 / 3456 = 608 CFM)
Approximately 608 CFM would be required for this engine. However, most Street engines are capable of achieving only about 80% VE; a modified street engine with ported heads, headers, intake and carburetor can achieve about 85% VE; a fully modified race engine can achieve 95% or greater VE. The CFM number arrived at with this formula must be factored by this percentage.

Good luck with everything else!

 

[JohnZ]

You can make your own timing tape so you can use a standard non-dial-back timing light. Measure the circumference of your balancer, and divide by ten - that will be 36 degrees. Cut a piece of masking tape that long, subdivide it with a Sharpie in 2-degree increments, and apply it to the balancer with the "0" end of the tape on the existing index line and the 36-degree end facing down (clockwise as viewed from the front). Whatever mark on the tape lines up with the "0" on the timing tab on the front cover will be your reading. Then you can map your advance curve.

 

[joe1975]

that sounds pretty easy I'll give it a try as soon as time allowes