Engine load from auxiliary equipment

[Wietse]

Hey guys,

I've seen many video's of engine dyno's (i.e. Nick's Garage) where engines with a similar cam or bigger compared to mine can idle smooth and have a decent vacuum. (my cam is 238/244 @ .050" .572/.576" lift and get 7-8" vacuum at 900 rpm idle)
Only realizing that those engines on the dyno are not pulling any other auxiliary equipment other then the oil pump.
So I wonder how much power would be drawn from the engine at idle by the oil pump, radiator fan, cooling water pump, alternator and power steering pump?
My 440 has an HV oil pump (80 psi @ cold with 20W50), high flow 440 source cooling water pump, fixed 18" flex fan, 90 amp alternator and a saginaw power steering pump.

When the engine is at normal operating temperature it settles down and runs ok-ish, likely less load demand as the battery is charged, engine oil and power steering oil are warm and therefore easier to pump.
Obviously it is not an option to remove any of them, though I do want to test this by removing the belts and run the engine for a bit to see what will happen.
Could all these together add enough load on the engine to affect the idle quality?
Any thoughts?

Before you ask, I tried everything already that is known to man to figure out why this relative small cam causes such poor vacuum.
Vacuum has been same with 2 different carbs an currently on EFI, no vacuum leaks, cam is set as correct, ignition advance does not matter sh*t, new timing chain, pressure tested intake manifold (no external leaks and no leaks towards crankcase)

 

[AR67GTX]

I’m a little surprised you don’t have just a bit more idle vacuum than that based on my 427 Chevy. It pulls 8” vacuum with a .579/.600, 256/[email protected] cam. Could be the lobe separation or just basic engine design. But, yeah, all that takes a toll at idle speeds. For a relatively good sized motor in a Corvette with a 4.11/WR transmission it’s kind of weak knee’d off idle on city streets - takes a little more care with the clutch than I should think It should and I’ve tuned the heck out of it.

 

[69Bee]

Not sure why you think this is a "relative small cam" with those duration numbers at 0.050" lift; that is a a pretty radical cam. With 238/244 deg dur @ .050", the valves are open at the same time quite a bit. If look at the "Overlap", you will find it to be quite large, thus creating the low vacuum reading and idle quality. The limit for street engines should be below 230 deg of duration at 0.050" lift.

As far as removing power robbing items, a toggle switch in the field circuit for the alternator to switch it on/off will remove alternator load, and you could also use an electric water pump drive too. A good add would be a vacuum can to store vacuum for brakes boosters.

 

[Cranky]

Why are you running 20-50 oil? Loose bearing clearances? Where is your cam degreed in at? A cam that's say 2* retarded can idle a bit more lumpy than if it was 2* advanced and it's usually enough to notice the difference at idle. I also like to advance my cam some since it's moves the power down a bit lower in the rpm range. I also don't run 20-50 stuff anymore but run 15-40. What's your oil pressure hot?

 

[dvw]

Load is mainly cold oil, and if it's an automatic, the converter. It all boils down to carburtor tuning. Correct throttle plate to transfer slot location. If you're idle screw is turned further than 1 -1 1/2 turns from completely shut, the throttle plate to transfer slot location is most likely incorrect. Correct idle feed restiction and bleeds will help as well. Not to mention it probably needs close to 20-25 degrees intial timing. With the total timing to be determained by compression ratio, fuel quality, chamber design, and spark plug location.
Doug

 

[BSB67]

Hey guys,

I've seen many video's of engine dyno's (i.e. Nick's Garage) where engines with a similar cam or bigger compared to mine can idle smooth and have a decent vacuum. (my cam is 238/244 @ .050" .572/.576" lift and get 7-8" vacuum at 900 rpm idle)
Only realizing that those engines on the dyno are not pulling any other auxiliary equipment other then the oil pump.
So I wonder how much power would be drawn from the engine at idle by the oil pump, radiator fan, cooling water pump, alternator and power steering pump?
My 440 has an HV oil pump (80 psi @ cold with 20W50), high flow 440 source cooling water pump, fixed 18" flex fan, 90 amp alternator and a saginaw power steering pump.

When the engine is at normal operating temperature it settles down and runs ok-ish, likely less load demand as the battery is charged, engine oil and power steering oil are warm and therefore easier to pump.
Obviously it is not an option to remove any of them, though I do want to test this by removing the belts and run the engine for a bit to see what will happen.
Could all these together add enough load on the engine to affect the idle quality?
Any thoughts?

Before you ask, I tried everything already that is known to man to figure out why this relative small cam causes such poor vacuum.
Vacuum has been same with 2 different carbs an currently on EFI, no vacuum leaks, cam is set as correct, ignition advance does not matter sh*t, new timing chain, pressure tested intake manifold (no external leaks and no leaks towards crankcase)

You failed to tell us three key cam elements. Is it hydraulic or solid, the seat or advertised duration, and the LSA.

 

[4mulas]

What’s the Centerline? Lsa?

 

[Nxcoupe]

Not sure why you think this is a "relative small cam" with those duration numbers at 0.050" lift; that is a a pretty radical cam. With 238/244 deg dur @ .050", the valves are open at the same time quite a bit. If look at the "Overlap", you will find it to be quite large, thus creating the low vacuum reading and idle quality. The limit for street engines should be below 230 deg of duration at 0.050" lift.

As far as removing power robbing items, a toggle switch in the field circuit for the alternator to switch it on/off will remove alternator load, and you could also use an electric water pump drive too. A good add would be a vacuum can to store vacuum for brakes boosters.

Overlap depends on LSA.

 

[Wietse]

The cam is 282/291 @ .008" duration, LSA is 108 and is hydraulic FT.
Most people mention it should give more vacuum than it currently does.
I tried everything in regards of carb tuning, swapped from a 750 double pumper to a 770 vac. secondary and am now on Holley Stealth Sniper EFI.
I can adjust the target idle AFR by touch screen and make it run lean to pig rich and I have been all over the chart just to find the best spot.
I recently installed a new 3000 stall converter to reduce the load applied to the engine at idle which helped a bit compared to the old one.
Just thinking I made a mistake going with HV oil pump and high flow cooling pump, it's all adding up I guess.
There was a HV oil pump installed when I bought it so I simply replaced it with a new one.
Oil pressure is solid, 80-90 psi when cold and 55-60 when hot. I am not aware of the clearances as it was rebuild by a PO.
Using 20W50 is what was recommended to me to stick with it, didn't bother asking the specific reason but from what I know it is good oil. (Kendall Racing Green GT1)
Changing the oil pump to a standard version, or dropping in viscosity should be possible with those pressure to reduce some load.

Ignition timing is currently at 20*, adding the v-can gives another 6* but does not change anything.
Increasing initial to more does not help the idle and makes it harder to start.

Load is mainly cold oil, and if it's an automatic, the converter. It all boils down to carburtor tuning. Correct throttle plate to transfer slot location. If you're idle screw is turned further than 1 -1 1/2 turns from completely shut, the throttle plate to transfer slot location is most likely incorrect. Correct idle feed restiction and bleeds will help as well. Not to mention it probably needs close to 20-25 degrees intial timing. With the total timing to be determained by compression ratio, fuel quality, chamber design, and spark plug location.

On the 2 carbs I had I (not knowing) opened the throttle blades that far indeed to just keep it running, obviously it ran pig rich all the time. (that's where it all started actually)
CR is about 10.5 and I am using 98 octane fuel only with 906 heads.
You would guess the oil pump is the biggest power robber between them?

When I get home I will remove the belts and run it for a bit without to see what it does.
It is just strange this thing has such poor manners when it comes to idling.

 

[AR67GTX]

I would have been suspicious of idle and transition slot calbration on a Holley carb too. But if you are running a fuel injection system now with no improvement, that kind of eliminates it as an issue. With that much initial timing I would think it would handle off-idle response fairly well. Is the vacuum advance can hooked to manifold vacuum? Does the 7-8” of vacuum bring the vacuum advance timing in at idle? That 427 Corvette I mentioned earlier, I run 16 to 17 degrees initial timing and about 6 degrees in manifold vacuum advance timing at idle. In that case the vacuum advance does help make my idle a little stronger.

 

[Don Frelier]

It sounds like you are not set up to allow the sniper to control the timing.
If so you really need to set it up so it can.
I think you'll find much higher advance at idle will make a big difference.

 

[gtxrt]

have to go by advertise duration. if your cam is 238*-244*@.050 and 294*-302* advertise and Nicks cams are 238*-244*@.050 and 282*-286* his will have a better idle and more low end power. and of coarse LSA will make a difference.

 

[dvw]

The oil pump, water pump, alternator are not causing your issue. I'm assuming the Holley Sniper uses a map sensor? Low vacuum can drive them nuts as well. It sounds like your carbs were exposing the transfer slot. They needed more airflow with the blades shut down. Either a touch more secondary blade opening or holes in the throttle blades. Can't give any info on injection as I haven't used it.
Doug

 

[lewtot184]

i run a [email protected]" with 110lsa (seat timing 290+) solid in a 9.8:1 440 and it does about 14" at 900rpm.

 

[BSB67]

1. The cam is not small. If measured at 0.006, which most Hydraulic cams are, it would probably be 286/295. That’s 74 degrees overlap.

2. Is the 900 rpm in gear, or neutral? Can you give us the rpm and vacuum reading for both neutral and in-gear idle?

3. Have you changed intake manifolds through this process?

4. Can you explain how you confirmed that there is no vacuum leak?

5. I agree with Doug, it’s not the load from the ancillary stuff.

 

[Wietse]

Does the 7-8” of vacuum bring the vacuum advance timing in at idle?

Yes it does pull about 6* more in as it is on manifold vacuum. (it is the stock v-can that came with the MSD RTR distributor)

It sounds like you are not set up to allow the sniper to control the timing.
If so you really need to set it up so it can.
I think you'll find much higher advance at idle will make a big difference.

It does not indeed, for that I will have to change over to the complete Hyper spark setup.

have to go by advertise duration. if your cam is 238*-244*@.050 and 294*-302* advertise and Nicks cams are 238*-244*@.050 and 282*-286* his will have a better idle and more low end power. and of coarse LSA will make a difference.

Below is what I mean, others with similar cams get more vacuum.

i run a [email protected]" with 110lsa (seat timing 290+) solid in a 9.8:1 440 and it does about 14" at 900rpm.

They needed more airflow with the blades shut down. Either a touch more secondary blade opening or holes in the throttle blades

Yes, the transfer slots were exposed
I tried drilling holes, installed a Wagner adjustable PCV valve to be able to control the air I am adding but nothing real successful.
The EFI has the IAC valve (Idle Air Control), when the engine is cold (coolant below 160*) it supposed to bump the idle to high idle.
With the IAC at 100% open it cannot even reach the normal (low) idle of 900 without me nursing the throttle. (I already know to hold the throttle at 2-3% open to maintain it, can see it on the EFI screen what the throttle position is)

I bought an Accell adjustable v-can I want to try setup once the weather becomes better and see if I can let it pull in a lot more vac. advance as I am stuck with total timing.
Currently have 18* initial and 18* mechanical advance so total timing is already on the limit for a BB, I want to reduce the initial to 16* but will need more vac. advance to do so.

 

[BSB67]

i run a [email protected]" with 110lsa (seat timing 290+) solid in a 9.8:1 440 and it does about 14" at 900rpm.

What cam specifically? I know you know it can make a big difference. And, is that in neutral or in gear vacuum?

 

[justcruisin]

Here's a comparison for you, 10.2:1 440 3.75 stroke, 850DP pulls just over 13" @ 900 with an xe275hl Hyd (231/237 @ 50 275/287 seat timing .525 lift).
Same engine with a EX282S solid 244/252 @ 50 282/290 seat timing with .520/.540 lift - pulls around 11.7" @ 900. Both on 110LSA.
The 275 cam had 1.5 rockers while the 282 has 1.6.
Apples to apples I would put the solid cam with the 1.6 arms around 235-236@50 as a Hyd cam. You do have a tighter LSA so that is going to drop your vacuum.
The 282 cam provides enough vacuum but is border line for vacuum brakes in my application, if the rpm drops to 800 or so it wont supply enough vacuum to keep things happy.

 

[gtxrt]

on a solid lifter cam you have to minus about 5*-7* duration @.050 to equal a hyd cam.

 

[BSB67]

on a solid lifter cam you have to minus about 5*-7* duration @.050 to equal a hyd cam.

On a tight lash cam maybe. 8 to 10 degrees is not uncommon.