LT4 hot cam manifold vacuum question
 

Trying to get ready for some plug checks and I was messing with carb today trying to set the idle mixture screws. Put a vacuum gauge on it and turned the screws in 1/8 turn increments until the motor died and best I could get was 8-10 on the gauge and is very erratic. I'm running a performer rpm intake and had the idle set at 700-800 rpm. Is this normal for this cam or do I have a problem. Before I drag it into town and put it on an evap smoke machine I was hoping for some input here. Any help would be great.

fixx
 

i should bounce with the idle of the cam.. also if the lifters are to tight it will give you less vaccume..timing will effect vaccume also..

Base timing is 8-9 degrees.

You should get a V6 module, a little more initial will give you a stronger idle. Back the screws out until it stops gaining rpm, then go in slowly until it just starts to affect the idle then go back out 1/8 of turn and do the other side. Once both sides are done wind them in and count the turns then wind them back to where they were set. They should be the same, if not try tweaking a bit more.

A v6 module would give me 18* base. Would it not be hard to start with that much advance? Would a v8-22 make enuff difference to worry about? I guess a v8-20r would be ideal but hard to come by. I'm gonna smoke this ***** tomorrow and find out what's really going on. If 8-10 is all it will pull I'm ok with that but I want to make sure it's not a leak causing it. However at 700-800 rpm this cam has a decent amount of lope. Hoping I don't have to take the top end apart. When does the v8-24 start advancing? Just curious so I can check base and full advance.

Have I mentioned this thing is a ***** to get started and warmed up?

18-20 initial would be great and you won't have any issues cranking. The higher initial timing will allow you to close up the throttle blades a bit which will make your mixture screws more active and give you better control. It will give you a stronger idle and smooth it out some too. I would definitely look for a v6 module.

Sounds good to me, I've found a few for decent prices but I may pull one from our boat graveyard if I can find one there and it give it a go. Can I do a trailer test with my 24* module? I know I can't run it with 18+24 but maybe see how it acts at idle with 18* at base with my current module before I buy a v6 module?

that vacume reading not right should be in the mid teens..you have a issue somewhere...

I just fired it up and soaked the base of the carb and the intake with carb cleaner and it didn't change anything. Looking like no leak