I got the whole engine for free and its leaps and bound better than the stock 350 so I am going to enjoy it while I work on my 408 small block. I would not have spent money building this combination, just trying to make it work for now. I like how the 30-30 sounds, but I totally agree that more modern roller profiles are sooo much better at making power.

 

Absolutely love it for timing adjustments. Very easy to make adjustments. I only have a few hundred miles with it so I can't comment on long term reliability. I will start a new post on this.

 

Oh, it will work....and they sound good...it is just not what one would run today unless you had to have it....

Jebby

 

I just posted my review for anyone who is interested.

https://www.corvetteforum.com/forums...or-review.html

 

Well plenty of good info here and just would like to add a few ideas rather than flame anyone. And for a street driven car i favor a vacuum advance where the race only cars can run "locked out" and dont use the vac adv at all.

My view is that using vac adv with most street cams and 14"Hg or more vac u want the vac adv to do the "adjustment" for good idle. Lower initial timing allows for easier cranking. And using the correct vac adv for your motor to bring in enough adv for good idle, low speed driving and provide better fuel mileage too.

A lot of owners will just disconnect the vac adv and set initial timing adv to where the car runs best then lock that in. Then blindly add vac adv to that. Well many are happy with this but as air temp and press/density changes so will the idle of the motor. While operating vac adv will supply adv as motor vac/load needs it.

Well the problem with vac adv is finding a good vac can for your motor. And not all vac cans with same part number will be exactly the same either. U can start by measuring your engines vac at idle then at 2,500-3,000rpm. This will give u the vac can requirements for operation. U want a vac can that provides full amount of vac adv at somewhat less than full idle vac. A lot of owners use a 2" rule where if your idle vac is 16"Hg u want a vac can that is giving full vac adv by 14"Hg vac. Then u want the vac can to drop out/zero vac adv before the 3,000rpm vac number. Now the amount of vac adv is where the skill is required. Adjustable vac cans will change this amount of vac adv but not when it occurs. lars has been working on this issue for quite a long time and a good source of information.

So what im saying here is a well set-up vac adv can substitute for higher initial timing adv while provide low rpm control and change with air conditions. Take it or leave it.

 

I have set the initial timing (on an L-48) at 12* BTDC for many years. It works well. The factory says 8*. Temp at 70mph? About 190*F with a 180*F t-stat.

 

By reading this post, I assume you set your initial timing to 20*, where you have achieved the highest vacuum.

However, why did you customise your vacuum and centrifugal advance?

At idle the centrifugal advance doesn't come to play, but Manifold connected vacuum advance will advance timing as soon as you rotate engine!?

This means you have 20* initial advance and 10* vacuum = Total of 30* at idle!?

In essence,
If you look for the highest/optimum vacuum at idle, ideally you need to have Manifold advance vacuum connected and check your timing for the loss of/change of vacuum while your vacuum advance is connected!?

If let's say your vac advance is 12* and you found your sweet spot,( timing light reads 30*) subtracted the vac advance from the idle amount and you will be at 18* initial?!

 

You hook the vac advance to a "Ported" vac port. Which is above the throttle blades. So no vac advance until the throttle blade open a certain amount

 

 

The above post makes sense now.
I am running Manifold vacuum advance.

I was under the impression that manifold vacuum is more advantages then Ported!?

 

The advantage to running manifold vacuum is that you get timing advance even at idle. This is very useful for the automatic transmission guys. Soon as you drop your tranny into "D" you load the engine. If you have your timing set optimum for a no-load idle then add a load you are going to loose lots of RPM and maybe even stall the engine with a high-ish overlap cam.

If you use manifold vacuum then the vacuum timing advance remains in place and you reduce the rpm loss (lose fewer rpm's) by going into "D" and the engine will not die as long as the vacuum does not drop below your vacuum can's minimum vacuum required to get full timing advance.
So the key here is to know what you vac can's min vacuum for full advance is, and knowing how much vacuum the engine is pulling while at idle in gear (D).
Driving a manual you would not encounter these issues.

I currently run 19* initial timing advance. With the vac can it's 36* of advance at idle.
Once the vac can drops out at WOT I have 34* of timing advance.
During cruise I have 50* of timing advance.

 

The magic 36* works for most stock cars, once you get into modified engines it can very quit a bit the same with the timing curve and intial advance, depending on: a) the amount of fuel the engine is igniting, engines with more duration usually need more initial to ignite the fuel earlier due to there being more fuel, b) fuel, compression and combustion efficientcy ( chamber and piston design) help dictate the needs of total mechanical advance, vortecs seem to use 32* total and my afr heads seem to do best at 34*, higher compression or blown engines with faster burning fuel ( lower octane) will use less total and some time initial because the tighter you pack the fuel air mixture the faster it will burn, higher octane fuels burn slower. With my 400" I run 90 octane and 22* timing at idle which is like 11* initial advance with the the lightest springs which start to come in at idle and adds 11* at idke and another 12* by 2500 rpm. Timing needs are based on what the engine needs for efficiency, low impression, low duration and inefficient heads will use a 8 to 12 at idle and usually the middle or one light and one middle weight springs and be all in at 36* 3000-3200 rpm.