Holley Tuning for E10

[kryptik]

Hello Guys,

My engine has had intermittent running problems which seem to point to fuel delivery. The carburetor is a quickfuel 680cfm which should be set up just right for my engine (zz383). The timing is correct. I feel as if the recently mandatory E10 gasohol is the culprit.

I have read in a publication that when tuning for E10 one should:

"lower float levels 1/32 from original specifications increase main metering circuits’ fuel flow by 10 percent, increase idle jet diameter by 0.002 inch."

The publication is found HERE.

What do you think? The engine is low on power, is quite hard to get a consistent idle with the mixture screws, and just runs flat out STRANGE compared to a couple of years ago when straight gasoline could be purchased.

Thanks in advance for the assitance.

Cheers,
Matt

[Shaker455]

Matt,
How long has it been since you did a complete tune up?

More than likely you could use a new fuel filter and brake the carb down fo a cleaning.

Also, you could use a new cap & rotor.

How's your engine timmed & what dist you running?

[68Formula]

Either the terminology is wrong, or the technique. E10 requires enrichment of the mixture (the amount varies by circuit). Lowering the float level can delay the activation of the main metering circuit coming off from idle. So this would be exactly the opposite of what you would want. You should be raising it. BTW, 1/32" is one Hex rotation of the nut.

For idle and cruise, you only need a 5% increase in fuel. There should be enough adjustment on the idle screws to compensate for that circuit. If you've adjusted the float level up that 1/32", and you're still not getting the response from the mixture screws then something else is probably going on. E10 has a slightly slower burn rate, so you might need a couple degrees more static initial timing (don't forget to take the same amount back out of your centifugal to keep the same total timing). This might help make the screws responsive.

For the primaries, going up 2 jet sizes would probably be enough. Best way to check it would be to set the float level, followed by the idle mixture (highest rpm), then go up one jet size at a time, and cruise on a flat road in top gear at about 2200-2300 rpm to see if it reduces stumble.

On the secondaries, you'll need to increase it even more. Make sure you've already adjusted the primaries first. I'd probably start with 2 jet sizes higher. Don't try to adjust for stumble, you just looking for maximum power after any fuel from the acceleration circuits has been consumed and you're running off the primary/secondary jets only.

For acceleration, try a larger squirter size to eliminate heavy throttle tip-in hesitation. Do this after you've set the secondaries.

The exact amount of adjustment is going to depend on how close your calibration was back on straight gasoline.

[kryptik]

Shaker:

The carburetor is basically brand new (500 miles on it). The filter was cleaned when it was installed. The rest of the fuel system is brand new so there is no gunk. The cap and rotor are brand new MSD units. The engine is timed to GMPP specfications (10 degree initial, 32 total, all in at about 3200rpm...no vacuum advance as required by the manual [which btw shocked me because I have NEVER heard of a street engine not requiring vacuum advance!])



68Forumla:

Yes they recommend lower in the float level but at the same time recommend enriching the jetting, both idle and main metering.

I DO have adjustment in the idle mixture screws. I will try to play with the initial timing...maybe bump it to 14 initial and see what it does. By the way the idle is set with a vacuum gauge for highest and smoothest vacuum...so that SHOULD be ok.

I already have a 10 point jet split between my primaries and secondaries...so I don't think a PVCR change would be necessary...what do you think?

I'll try the increasing the squirter size, I have more experience from tuning an automatic transmission car so maybe having to slip the clutch more when getting in gear IS a stumble from lack of pump shot...I just wasn't aware. The arm is adjusted properly BTW.

Let me know what you guys think...thanks in advance

Cheers,
Matt

[Nessumsar]

It sounds to me like your timing may be the culprit; 10* initial is quite low, as well as the 32* total @ 3200. I would recommend trying 14-16* initial, with 34-38* total @ 3000. I would try that first. Hopefully that will help significantly; and maybe you can hook up your vacuum advance as well (if equipped).

On my 388 I have 18* initial and 38* mechanical total by 3000, plus vacuum. Granted our engines have different heads and cams.

[kryptik]

That timing specification is straight out of the manual for the GMPP ZZ383 with Fastburn heads, which allegedly require far less timing.

[Shaker455]

Shaker:

The carburetor is basically brand new (500 miles on it). The filter was cleaned when it was installed. The rest of the fuel system is brand new so there is no gunk. The cap and rotor are brand new MSD units. The engine is timed to GMPP specfications (10 degree initial, 32 total, all in at about 3200rpm...no vacuum advance as required by the manual [which btw shocked me because I have NEVER heard of a street engine not requiring vacuum advance!])

68Forumla:

Yes they recommend lower in the float level but at the same time recommend enriching the jetting, both idle and main metering.

I DO have adjustment in the idle mixture screws. I will try to play with the initial timing...maybe bump it to 14 initial and see what it does. By the way the idle is set with a vacuum gauge for highest and smoothest vacuum...so that SHOULD be ok.

I already have a 10 point jet split between my primaries and secondaries...so I don't think a PVCR change would be necessary...what do you think?

I'll try the increasing the squirter size, I have more experience from tuning an automatic transmission car so maybe having to slip the clutch more when getting in gear IS a stumble from lack of pump shot...I just wasn't aware. The arm is adjusted properly BTW.

Let me know what you guys think...thanks in advance

Cheers,
Matt

Matt,
What filter you running that you cleaned and reused?...a glass one with a white net inside???

If so that filters nothing and you need paper element a filter in-line that filters 10 microns.


10 degrees is too low as others have posted and you need to be about 18 degrees initinal.

Problem is with the fastburn heads you only neeed about 32 total as you stated so you need a custom bushing that will only give you about 12 to 14 degrees.

I have made a few for tuning customers cars here.

Also you posted a 10 jet spread so what is your jet sizes?

Instead of playing with the squiter you may simply be under jetted on the primary.

[kryptik]

I am running an aftermarket Earl's 35 micron sintered bronze filter -8in -8out (with a brand new element) which for years has never given me trouble...all this started with the introduction of ethanol.

Actually...10 degrees initial is specified for this motor directly out of the GMPP manual (I am running about 11 right now). I can understand bumping it up a few degrees to 12-14...and I do trust that the GM engineers know what this motor requires.

My jets are 68 primary/78 secondary.

Thanks guys,
Matt

[Shaker455]

Wake up Matt your being stubbon.

If you do not accecpt advice or suggestion then why post?

Contact your GM dealer and have them advise you properly because you not accecpting advise here.

At 35 microns your sintered filter will not filter dirt and will allow it to enter the carb....take the bowls off and carefuly look for yourself.

Also that rock you call a filter will hurt fuel flow and performance.

Go get yourself a Summit or Jegs brand filter with a paper element that does 10 microns.

Your under jetted in the primary for your combo.

Your not the first ZZ engine I've encountered so you will find your GMPP manuals not up to date with today's fuels.

Maintain your total but bump your initinal.

The E -content in gas has hurt Performance but not all the mods listed by Jon at The Carb Shop in MO are nessary.

[kryptik]

Alright Shaker, wasn't trying to be stubborn. I appreciate the advice and will purchase a 10 micron paper filter, and I will play with the initial timing and see what it does. Would you suggest I change the PVCR's and ONLY increase the primary jet size?

P.S. Is cellulose the filter material I should purchase? Because that is what the Summit filters use. The only one with 10 microns and a paper element (with -8 in/out) is a Russel found here: http://www.summitracing.com/parts/RUS-649000/?rtype=10

[Nessumsar]

As far as what GM recommends for the engine, it is probably on the conservative side so that even with a misjetted carb you won't be able to do any damage; I'm sure thats why they don't recommend vacuum advance, so you can't burn a piston while cruising.

[68Formula]

Increasing the float level should help during the transition from the idle circuits to cruise.

For the timing start with 14 degrees initial, if it likes more than of course you can increase it (you'll know you've gone too far if the engine has too much starter load during hot cranks). Increase the total to 34 degrees with fast burn heads, but no further. Have it all in by 2800 - 3200rpm.

I suggest you work on the timing curve first, and the carburetor settings second. You may find you don't need as much (or maybe any) carb adjustment.

[kryptik]

Alright guys I will get the car nice and hot tomorrow and start with about 14 degrees initial. I can't go much farther because the smallest bushing that the MSD has advances mechanical timing by 18 degrees. I really don't want to push it because the 91 octane is detonation prone. I will also try using the vacuum advance after because I do not see a reason not to (my unit is adjustable so i should be able to dial it in).

Thanks guys I REALLY REALLY appreciate the time and patience...this problem has been discouraging me because I spent so much time building the car and it just does not run how it should.

I will try these two things individually and report back.

Cheers,
Matt

[68Formula]

Definitely hook up the vacuum advance to ported if you have it available. Remember to do all your adjustments to static and mechanical before hooking up and tuning the vacuum. Let us know how it works for you.

[kryptik]

I'm guessing you mean before hooking up the vacuum advance? I'll let ya guys know.

Thanks a lot!
Matt

[Shaker455]

Alright Shaker, wasn't trying to be stubborn. I appreciate the advice and will purchase a 10 micron paper filter, and I will play with the initial timing and see what it does. Would you suggest I change the PVCR's and ONLY increase the primary jet size?

P.S. Is cellulose the filter material I should purchase? Because that is what the Summit filters use. The only one with 10 microns and a paper element (with -8 in/out) is a Russel found here: http://www.summitracing.com/parts/RUS-649000/?rtype=10

Matt,
No need to increase the PVCR at this time.

Bump primary jets to 72 and count the amount turns your mix screws are out.

Using Vac advance is fine like others suggested but do that very last as you have other issues to tackle first.

And the vac adv should only give you another 10 to 12 degrees, if it give you more than that it willl need to be limited.

I made a custom MSD bushing that gives about 12 to 14 degrees so if you find your engine likes more initinal and shuts down okay I can hook you up.

I found four Summit filters with 10 microns -8AN
http://www.summitracing.com/search/D...?Ns=Rank%7cAsc

[kryptik]

Alright I will try this. I have an Accel adjustable vacuum advance can on my MSD...in the instructions it says that when at only one turn from bottomed, it will provide something around 10 degrees vacuum advance. I also have a vacuum advance limiter plate still in the package if you guys don't like those adjustable vacuum advance cans.

If I bump just the primary jets wouldn't the primary barrel run richer than the secondary when I'm into the throttle?

I will try 14 initial w/ 32 all in and may even go to 15 w/ 33 all in. If the engine likes it and wants more, I will let you know.

I saw those summit filters but I found that the filter material was advertised as cellulose, not paper. I assume these are one in the same but I just wanted to double check. I have only 800 miles on this carburetor, do I really need to pull it and completely clean it out? Or do you think I'll be ok.

Thanks!
Matt

[Shaker455]

Matt,
In your first post you said your down on power so you may be lean on the primary side.

Your sec side has 78 jets so I'm not sure what you mean about the primary running richer than the Sec side seeing you are below that jet size in the front?

I've had the Accel can's too and I'm not crazy about them.

If you have Cranes limiter plate that's what I use: http://www.summitracing.com/parts/CRN-99619-1/

But save the Vac Advance for last....that's a taylor not needed to be introduced at this point.

Lets back up a bit, can you pull a few plugs and tell me what overall color they are?

Should be a light coffee color.

Tell me how many turns out your mix screw are?

How much vacuum are you getting out of gear?

Also, sometimes the engine wants more fuel than best vacuum so you may want to try to open the screws like 1/8 to 1/4 more than current.

If you take the front bowl off drain it with removing one lower bowl screw and catch the gas in a container.

Also, tell me what size squiter and color cam your running?

When you pull the bowl look with a mag glass in all the lower corners for dirt as well as the lower spots on the metering block.

Take a look at the gas you have in the container and see if dirt has settled.

On another note:
I looked at your other post about your idle dropping and I've been on Quick Fuels site to look up your carb and I see it came with Jet extensions.

Are they installed in the carb or are they in the box?

If they are in the carb then remove them.

That's whats causing your engine to die on decel.

They are "not to be used on the street" as they will uncover the rear jets during decel and will stall the engine.

I think you been thru enough with you other car.

I have a 70' Carmaro too.
Jeff

[kryptik]

I will jet up one point and see how that helps...or would you suggest two for starters?

The reason I say about the primary running richer is because if I jet only the primary, for example up to 70, then when the power valve kicks in (the PVCR's adding 10 points of enrichment), my front jetting would be 80 while my rear would be 78 still. Make sense or am I missing something?

I have a Crane limiter plate at home but I will play with that last as you say.

Now on to the plugs...two points first. I was told that California gas does not allow accurate plug reading, not sure if this is true. Also, I set the idle last on the engine before I turned it off and checked the plugs, so the readings may be skewed:

Cylinder 1:




Cylinder 2:




Cylinder 5:



Looks a bit lean but I'm not an expert.

I checked my mixture screws today as well. Three of them were 1/4 turn out from bottomed. The right rear corner was, for some reason unknown to me (probably had a brainfart when setting them), 1 or 2 turns out. I put them all back to 3/8 turn out to get smoothest idle; I set the idle by ear and feel this time.

With the idle mixture screws how they were I was getting about 15-16" out of gear vacuum @~900rpm (+/-50) with the electric fan not running.

I am running a stock 31-size squirter with a pink cam. The arm is adjusted by sight, not with a feeler gauge.

About the rear jet extensions (yes they are installed)...the idle does not drop specifically with hard deceleration, just when coasting and releasing the clutch the engine wants to die when it returns to idle. The timing helped, and I think it may just be an overly lean mixture. I'm thinking since it wants the mixture screws only ~3/8 turn out an IAB/IFR change may be necessary, but I don't know for certain. You're the expert. Furthermore, don't these jet extensions prevent secondary leaning on hard acceleration? Or would my car not launch hard enough to see the benefits...

Anyways, let me know what you think. Thanks again for the help Jeff!

Cheers,
Matt

[Shaker455]

Matt,
Yes some do look at bit lean so jet up two sizes to start in the front.

Yes you are missing a bit about the primary & the PV and it's really only about 6 sizes but your engine wants it so don't worry.

Your Cal gas is the same as it is here and you can see they did color up.

If your mix screws are only 1/2 turns open then you will not require an IFR resize.

You should be out about 1 full turn all corners.

With the accel pump arm:

With your fingertips on the the screw section that is exposed above the locking nut, try to pull up on the spring loaded screw and there should be no play between the arm, cam, or pump lever.

If there is you go only go CCW one nut flat at a time unitl there is no play.

Otherwise it can be set on the bench with the feeler gauge.

Please remove the Jet extensions...they can get you killed on the street.

No IAB or IFR changes are needed....do you know all the airbleed sizes?
Jeff