Need some advice for rebuilding 77 350 please

I would tune the idle mixture screws at the front of the carb... My method:

Block all 4 wheels and have a friend sit in the drivers seat...

With the engine off screw both of the idle mixture screws in till they LIGHTLY seat, then screw them out 1.5 full turns...

Connect a vacuum gauge to a manifold source (one that gives vacuum at idle)

Start the engine and put it in gear with foot on brake....

Set idle speed to about 700 rpm in gear

Take a note pad and record the vacuum readings.... Try turning both screws out a half turn, record the readings, and if the vacuum readings go up then you are on the right track... If the vacuum readings go down then return the idle screws to the 1.5 setting and then try turning them in further....

Some trial and error will get you the max vacuum readings.... Keep in mind that you will have to lower the idle speed as you get closer to the optimum tune...

 

Thanks Sean, I will give it a shot and note if it makes any difference.

What is the max vacuum I should expect to get out of the TA 212 at idle with no load on the engine?

The engine is mated to a 4-speed.

Thanks!

 

does it sound like this ? also mated to a 4 speed Super T-10

https://www.youtube.com/watch?v=akRnco8yIwE

 

I had a 212 cam in a low comp 350 and it was 17 inches of vacuum.

 

I'm just wondering if the carb I have on there is screwed up. It's off an Oldsmobile 403.

Here are a few videos of the engine running. Please let me
Know what you guys think. It's a little loud because I don't have mufflers on it at the moment. Thanks for everyone's help. It's much appreciated!

http://youtu.be/9xvWoN4lJDU

http://youtu.be/QnIIwdtpM0E

http://youtu.be/Kn4_FNW_g6E

 

Chances are good its carb.and olds uses a different setup for timing on some engines. You set timing at 20 degrees at 1800 rpm with advance disconnected. So your advance could be affected by the old carb

 

I know that the idle air passages will be a different spec than a Buick 350 carb so that may be an issue... The safe bet is a BUick 350 Q jet on there.

 

So how is the engine running now that its broken in?

 

What everyone here that has some kind of cam in their car should hook up a vac gauge and take readings at idle in gear and neutral and post it and tell everyone what cam you are using.

This will give some kind of database for the cam used and this may give you an idea which one you can use, especially if you use power brakes.

Make sure car is fully warmed up at 180* then take readings.

My TA 510 cam had 5 in neutral and 3 in drive. Even though this low the car would idle all day long in drive.

Lunati Pop Mechanics cam 230-245@.050 502-507 lift 13 inches neutral 10 in drive.

 

Good Idea. (truthfully, no sarcasm)
I've always viewed idle vac as an indication to the "finished product" in tuning.
Can't think of a better way to compare apples to grapefruit though.

It's going to be hard to really set a baseline.
For example, I typically see a differences of 1.5" or more just changing a Qjet to a Holley 750, from a dual to single plane, or with drilled primaries to tune in a wilder cam vs. a 4500 when appropriate.
I've also seen machining specs like quench distance change things a bit along with the extent of head porting, header type and certainly differences in combustion chambers or installed centerline.
That's in neutral. Think of all the things I haven't mentioned.
Drop in gear is going to be near impossible to baseline, simply for timing/tuning and converter differences. Internal converter specs would be a huge unknown factor as available torque in different atmospheric conditions might vary wildly.
I've been able to tune 400" pump gas engines with 270* @.050" to barely operate brakes, only with a dual-diaphragm booster though. That one would read better with locked timing.

If these are similar spec'ed mostly stock and mild cam engines a useable standard might be established.

 

My GS 350 with 413 cam pulls 7" of vacuum in gear hot @750 rpm. I can idle down to 450 rpm in gear:shock:

 

Only hope to be of use to anyone is if the RPM is also posted. And it must be from a tune up style tach NOT an in dash, hood mounted, or cheapo aftermarket tach.

A 100 rpm increase could change vacuum a couple inches. Then your relying on how well it's tuned which can skew the numbers even more.

My Crower level 3 is 16"@800 rpm.

 

I was just thinking general idea and you guys are right this is usually after you have tuned in the carb and got down to a reasonable rpm. The higher rpm will change the vac. I was just thinking a general idea of the vac on a particular cam. I know othther variables will change the reading. Demco's 413 cam is in the 7 inch range. He should state the rpm in neutral and in gear and the vac readings. we do know if the readings are low there needs to be changes made to the carb since the lower vac readings will affect how the carb performs. Again I am just thinking a general reading from your cam in neutral and in drive. At the proper rpm with carb idle jets adjusted. I do not want to be that technical with this. This will give everyone a chance to know ahead of time what readings you may get with a particular cam.

I happen to have a Craftsman engine analyzer and it has a big wide sweep for the rpm, it even has a high and low setting. It is old old enough to tell you if your points are good or bad. It has a real nice dwell meter and has amps volts and ohms. I think I paid around 130 bucks for it around 1980 or so. I will use this in conjunction with the vac gauge to set the carb. The rpm scale is in 25's works really nice.

 

But what is the vac reading in neutral and what rpm is it at, and are you using one of those chepo tachs Steve was talking about.:laugh: