89fast5oh

It is pretty smooth but has a chop. More than I expected with the small cam.

ULTM8Z

I'm surprised it has that much chop to it...

My 212 cam in my 350 idled much smoother, but it had essentially the same idle vacuum.

What vacuum are you getting in neutral and at what RPM? That video looks like you were in neutral.

I was planning to get the EFI cam

https://www.compcams.com/xfi-218_224...all-block.html

A little wider LSA, but with the same duration and lift as yours.

ULTM8Z

Have you thought about raising the idle speed a bit? Also what spark timing are you running? These short runner manifolds like quite a bit of timing at idle...

skinny z

Can you post a link to where I can find your build specs? I'm working through a pile of build options (although the short block is finally sorted) and am interested in the heads, compression ratio and cam specs (seat to seat if you can).
A little surprised the idle vacuum is low although that is only 575 RPM. What's your idle timing (and that compression ratio question again)?

89fast5oh

Idle timing is about 8 btdc. Compression ratio is 9.8-10.1 depending on calculator used.

This cam installed 4 degrees retarded to shift power band up a few hundred rpm. With 1.6 rockers for more lift.

https://www.compcams.com/xtreme-ener...oller-sbc.html

Can find most info in this thread and also this one: https://www.thirdgen.org/forums/engi...uild-swap.html

skinny z

I'd say those two are what are principally responsible for the somewhat low idle vacuum.
The IVC is delayed so some of the cylinder pressure will be lost (as would be demonstrated by the proper DCR calculation).
As for timing, there's not an SBC I've met that didn't like at least 14 degrees of idle advance. Or more. The stockers are spec's with less but that's not for performance.
If it's working for you though, then that's the good thing.
I'll check those links.
Thanks for info.

ULTM8Z

Ahhh, yeah... like SkinnyZ, yeah that makes sense now.

89fast5oh

To those asking about vacuum, what do you envision it should be making and what is the pros/cons? I truly don't know. I have always heard to low vacuum and brakes can suffer. But mine feel fine.........actually scratch that...I changed my tires today and before I did, I did a big brake stand. It pushed the car forward 10-15 feet, I don't know if the wheels skidded or rolled.

skinny z

Have you done a compression test? A properly done test, even on a couple of cylinders, will reveal a great deal on how the engine is capturing compression pressure. More pressure generally equates to more idle vacuum.
A first quick calculation on your combination suggested 15" Hg idle vacuum. But there are too many variables to say conclusively if that's accurate or not.
I'll try to back into a better answer with a few "calculators" that I use.

FWIW: A quick calculation using 10:1, a 5.7" rod and an IVC of 66 degrees ABDC (your cam has a spec IVC of 62 ABDC) gets about 195 PSI cranking pressure at sea level. If you live on a mountain, this will be less of course.

89fast5oh

I shampooed the interior today. Came out very nice.

DynoDave43

iTrader: (11)

The engine looks and sounds great!

QwkTrip

iTrader: (22)

13 inch Hg vacuum is roughly 56 kPa MAP which is kind of lousy for a moderate cam, but enough to run power brakes.

Bump up idle speed to 700 rpm and see what happens. I idle at 1050 RPM and you'd never guess so by sound.... Just give the engine what it wants.

How do you guys with old school distributor set idle timing? Timing that creates the most vacuum at idle is also creating the most torque. And torque is good.....

If this was modern EFI then I would hunt for spark advance that creates max vacuum and then back off a few degrees to give the engine some range of spark idle control. In other words, give the EFI some ability to add and subtract torque (with timing advance) to control idle. Do the old school distributors have a form of idle spark timing control? Or do you just aim for max vacuum and call it a day?

skinny z

Idle timing is one of those things that is particularly unique to each engine. Now while that may be stating the obvious consider that engine x is perfectly fine with 14 initial. Engine y however will run with the distributor locked out at 36 degrees. Cam timing is the major player here.
Idle speed is set with a various combination of idle mixture (via the carb) and idle stop screws. After the carb is adjusted, it might be found that the engine will continue to absorb as much advance as you care to throw at it. Keep in mind that this would involve revisiting the mixture and stop screws.
​​​​​​In my particular case, I've a base initial timing of 16. Runs ok. Vacuum a little low (but then again the engine in question is basically worn out). To that I add another 14 using the distributors vacuum advance. So I idle at 30 degrees. Much better. Throttle blades are closed almost completely and vacuum is peaked. Off idle response is immediate, engine idle temps are low and drivability improved overall. This is with a 288/294 cam with 71 degrees of overlap. Idle vacuum is about 11" and idle speed speed at 750-850.

89fast5oh

There is something that could partially explain my low reading. I have Tuned Performance doing the tune. He told me I may have to close the throttle body a bit to get the IAC counts down. Maybe the blades are open too much and not creating as much vacuum as it should?

skinny z

The problem with closing the throttle blades is that it slows the engine speed even more. So the net gain might be zero. Now, if you can bump up the idle timing (without increasing the overall total), then that will typically increase speed. That then allows you to close the throttle some.
Now your vacuum goes up.

QwkTrip

iTrader: (22)

I didn't realize this was a TPI engine. Maybe the 8° advance is for engine cranking during startup, and then the ECM takes over timing after that. Either way, you're not the person solving it so it doesn't really matter. Tuned Perfomance will take care of you.

89fast5oh

Since last time, I have installed a probuilt automatics street/strip transmission with a Edge street 9.5" 2600 stall converter. That really woke the car up even with the 3.23 gears that Dana told me to keep. I also pulled the engine to put a different timing cover on. The cheap 2 piece was leaking like a sieve.






I wrapped part of the y-pipe that runs under the oil pan, hopefully to reduce some heat transfer.




I also recovered my factory steering wheel by myself.





And I have ordered a FiTech 38350 TPI EFI system. Although it was supposed to ship on July 9-10, but nothing and no response to an email...

https://fitechefi.com/product/38350t...ne-efi-system/

89fast5oh

Spring is coming fast and I have a few things to do to the car.

I am going to change over to the EBL FLASH-2 system. I'm hoping it will allow me to fine tune a few areas of concern. Last year I was all set for the FITech 38350 TPI system. But after placing the order and being lied to for months about when it would ship out I cancelled the order.

I have a Derale 13950 Atomic transmission cooler to install.




I also have a set of Nitto NT555R2 drag radials.

DynoDave43

iTrader: (11)

I always enjoy a good EBL tuning thread. Hope to make the change myself, so there's always a lot that I can learn.

89fast5oh

Originally I bought fabricated aluminum valve covers for the build but it wasn't until final assembly I found out they wouldn't work because they hit the AC compressor. I ended up using some old junkyard 1980s GM covers that I quickly painted silver. They worked okay until I put a high volume oil pump in and they started leaking near the rear flange surfaces.

I decided I wanted new valve covers and wanted them to be diecast aluminum so they would seal well. I couldn't use center bolt style because of the large comp roller rockers so that left perimeter style. I ended up with the cheapest plainest covers I could find on purpose. They are billet specialties short style covers. They look like they will do the trick.

DynoDave43

iTrader: (11)

So you have center bolt heads, and will need an adapter to run the perimeter bolt covers? I've seen the adapters, but never seen a thread here with anyone using them.

89fast5oh

The AFR heads have provisions for center and perimeter bolts. No adapter needed.