IDLE Vacuum issues - Need Assistance

[odise.carr]

Hello gurus!

I've just finished a build, and am having suspected vacuum issues. I'll list a little about the build below:

TA Block, stroker, stock bore size
Champion Heads/Intake
230/236 roller Cam (grind from TA)
75/76 PT
160lb Holley injectors
E85 fuel, -10 feeds/-8 return
Fuel pressure mechanically regulated to 43psi w/o vacuum
Cruz Holley ECU and Harness
Cruz Vaccuum Delete kit (dedicated vacuum to booster, MAP sensor, PCV valve and fuel pressure regulator)

While running and tests i've done:
Lowest I can get IDLE to is 75 kpa (should be somewhere around 40-60)
Injectors were tested, found one leaking, replaced
Vacuum smoke test, found one vacuum leak - sealed it, made no difference.
fuel pressure at idle is about 41 psi (i suspect because of the vacuum)
-i've played with timing and base fuel, (played with range from 15- 30 degrees, and lowered VE table (in idle zone only)) and it just purrs a lot better, or increased the AFR, but again, has no impact on idle vacuum.
PW is 2.5ms and 1.8% duty cycle.

When warm, i can get idle down to about 800 RPM (but this does not change IDLE vacuum even a little bit)
I'm also having an issue keeping idle during warm-up, but this is secondary to me right now. I can play with target idle and lower as it warms up. and do the TPS reset dance 20 times.

Cruz has been super helpful and helped me diagnose alot of the smaller stuff above, and we both feel that maybe the injectors are to blame, but before i drop any more money, i was hoping to lean on some of the Gurus' knowledge on what may be the issue.

 

[Chuck Leeper]

Post the terx file... tune.
Zip it before posting.
PCV valve & booster... Take them out of the plumbing, plug the ports, and look at the MAP.
Do this 1 at a time.
Cam in where it belongs?
Lifters too tight?
Leak down and comp tested?

 

[PSID6]

What are the other cam specs, lobe separation degrees of overlap?

 

[odise.carr]

Chuck and PSID6, thank you for your response.

CAM SPECS

• Valve Lift with 1.6 Rockers: .560"/.560" (i'm using 1.55 so i'm at .543")
• Duration: 297° intake / 306° exhaust
• Lobe Centerline Method used for installation (believe i had to retard 4 degrees)
• LSA 113

PCV Valve and Booster/All Vaccum Sources will be plugged today and checked. ( did check the booster as well for a leak, none)
I did do compression test, all checked within 3% of eachother.
I'll perform a leakdown tommorow and post results (i'm waiting for the tool to come back after lending out)

Lifters, New Johnson short travel. One was found tight during assembly. Honed and had proper movement.
I triple checked lifter preload after seeing one rocker hitting the poly lock a little, did some clearance, and triple checked all again.

Heads are GN1 Champion. Milled .005". Valves done, seats freshened. All valves held 50 psi on vaccum test (off of motor). Using Cometic .043 gaskets. Using head studs.

 

[Chuck Leeper]

Sorry, used the wrong program...
Looked at the timing map. What's the big "hump" right at idle speed?

 

[PSID6]

Chuck and PSID6, thank you for your response.

CAM SPECS

• Valve Lift with 1.6 Rockers: .560"/.560" (i'm using 1.55 so i'm at .543")
• Duration: 297° intake / 306° exhaust
• Lobe Centerline Method used for installation (believe i had to retard 4 degrees)
• LSA 113

PCV Valve and Booster/All Vaccum Sources will be plugged today and checked. ( did check the booster as well for a leak, none)
I did do compression test, all checked within 3% of eachother.
I'll perform a leakdown tommorow and post results (i'm waiting for the tool to come back after lending out)

Lifters, New Johnson short travel. One was found tight during assembly. Honed and had proper movement.
I triple checked lifter preload after seeing one rocker hitting the poly lock a little, did some clearance, and triple checked all again.

Heads are GN1 Champion. Milled .005". Valves done, seats freshened. All valves held 50 psi on vaccum test (off of motor). Using Cometic .043 gaskets. Using head studs.

So with the duration you have and the lobe center at 113 I’m sure you have a decent amount of overlap which is not helping your cause but to be realistic 18 in. of vacuum or 40 kpa is a little out of reach in my experience with your combo. But if you had 10-12 inches or 60-65 kpa that would be acceptable. Idk hopefully you don’t have huge piston ring gaps.

 

[BEATAV8]

As you mentioned, plug off everything that is unnecessary like pcv and brake booster.
How well is crankcase ventilated? Make sure breathers are wide open & unrestricted.

 

[Chuck Leeper]

So with the duration you have and the lobe center at 113

I'm wondering why there's 4* adjustment required.

 

[odise.carr]

Wow, thank you, everyone.

CAM comments -
I agree the overlap, would make vacuum a little on the higher side. but at it seems 75 kpa just a tad too high. But i'm no expert at Buicks, so i was turning to you all.

ChuckLeeper, 4* degrees is where it came out when using the wheel, and lobe center method. I double checked before making the adjustment, and triple checked after the adjustment, and I was at zero. (Chuck I may have mispoke, and it might be 2* degrees of adjustment, it was adjusted, and it was done with the Lobe center method.) I say all that to say, the cam wasn't installed straight up.

Also, in the idle zone I was just playing with Idle in that area. so there is probably a two-block cell where it's static at 22 degrees or something. Regardless, any change i made in the actual idle zone (75 kpa/1000 rpm) made no difference - in terms of vacuum. It did seem to generally "purr" better with higher timing.

CrankCase Comments - two big breathers and "high flow" PCV valve (with a check valve in between)

Piston Rings - total seal gapless rings, gapped to specs from total seal. I don't recall what they were at this time, but .027 seems to be at the top of my mind.

I will complete the leakdown test tommorow and post results for everyone's benefit. I really appreciate everyone taking a little time out of their day to help diagnose. However, maybe because of the agressive cam I just can't get the vacuum lower and this is where it lives and i have to get a vacuum pump or PS brakes!!!

Video of engine running: Video Link (Google Drive)

 

[BEATAV8]

some more thoughts.
I would lock timing at 10 or 20 degrees and check with an old school non adjustable timing light to verify the timing is right where you expect it to be. It might be way off retarded due to some defect.
Also I’m sure you have already verified she’s hitting on all six cylinders ignition wise, but something to mention. The ECU might have a diagnostic feature to let you fire coils with the engine off.

MAP sensor connected with a hose? Make sure it’s not kinked

 

[odise.carr]

Thank you BEATAV8. that's a good call.

There is in fact a diangostic feature. I've verified wiring is correct (coils are sparking on the appropriate cylinders).
I'll lock timing and check!

MAP sensor is a holley 3.5bar unit, threaded directly into the spacer. I did verify it's appropraitely calibrated.

 

[Chuck Leeper]

Has this engine been on a dyno?

 

[odise.carr]

No Sir

 

[PSID6]

No Sir

Ok I need to clarify a few things about cam terminology LSA is the lobe separation angle and ICL is the Intake center line these are two separate things.
LSA of a single cam… meaning not a dual overhead cam engine ….is a fixed number that is ground into the cam by the manufacturer and cannot be modified. ICL on the other hand is what can be moved by the way of your adjustable timing set. If your cam is currently installed @ 117 “ICL” you will have

 

[PSID6]

stupid fat fingers….as I was saying you have to go back and advance your cam. Typically the cam manufacturer will suggest an “ICL” number that cam should be installed at.

 

[CaptainTurbo]

Hello gurus!

I've just finished a build, and am having suspected vacuum issues. I'll list a little about the build below:

TA Block, stroker, stock bore size
Champion Heads/Intake
230/236 roller Cam (grind from TA)
75/76 PT
160lb Holley injectors
E85 fuel, -10 feeds/-8 return
Fuel pressure mechanically regulated to 43psi w/o vacuum
Cruz Holley ECU and Harness
Cruz Vaccuum Delete kit (dedicated vacuum to booster, MAP sensor, PCV valve and fuel pressure regulator)

While running and tests i've done:
Lowest I can get IDLE to is 75 kpa (should be somewhere around 40-60)
Injectors were tested, found one leaking, replaced
Vacuum smoke test, found one vacuum leak - sealed it, made no difference.
fuel pressure at idle is about 41 psi (i suspect because of the vacuum)
-i've played with timing and base fuel, (played with range from 15- 30 degrees, and lowered VE table (in idle zone only)) and it just purrs a lot better, or increased the AFR, but again, has no impact on idle vacuum.
PW is 2.5ms and 1.8% duty cycle.

When warm, i can get idle down to about 800 RPM (but this does not change IDLE vacuum even a little bit)
I'm also having an issue keeping idle during warm-up, but this is secondary to me right now. I can play with target idle and lower as it warms up. and do the TPS reset dance 20 times.

Cruz has been super helpful and helped me diagnose alot of the smaller stuff above, and we both feel that maybe the injectors are to blame, but before i drop any more money, i was hoping to lean on some of the Gurus' knowledge on what may be the issue.

Been thinking about this issue for a minute. Check the EGR valve if you still have one or the plate gasket.

 

[odise.carr]

I did the Leakdown. All cylinders at 2% loss. great seal.

 

[GNVYUS 1]

75kpa is roughly 11" of vacuum correct?

In my 400ci GTO when I had a 288/294 on a 110 I had the same 11-12" of vacuum, you have a 297/306, you're lucky to even have 11" IMO.

BTW, this cam seems huge for a possible 4.2 to 4.5L V6, and getting it to idle at 800rpm would be tough in gear in the real world on the street, you might find 900rpm is your new home with this cam to have stability when you tip in.

 

[GNVYUS 1]

Sorry I'm wrong, 75kpa comes out to 22" vacuum on a different online calculator.

 

[BEATAV8]

At sea level.
75kpa —> 25kpa vacuum —> 7”Hg vacuum