4.6 stroker from Russia

[darkcorp]

Hi guys!

'99 Grand Cherokee
4.6 stroker
4.2 crank
stock 4.0 rods
+0.030" KB944s with molly rings
block decked 0,5 mm
.043 MSL head gasket
CR 9.6
Propane converted. No ping at all! Even on 87 octane.

Almost everything is new.
New 505performance cam with new lifters.
192F thermostat
Bosch 0280155849 injectors.
Viper coil.

Starts good, runs rich, drives almost an ordinary 4.0.
Idle is not rough but not smooth, with vibrations.
LTFT is about (-)15%.
Vacuum 17inHg (43kPa).

Cam is this one:

WhatsApp Image 2019-11-26 at 11.43.52(1).jpeg

WhatsApp Image 2019-11-26 at 11.43.52.jpeg

Might the cam be an issue?

I also have AEM FIC to tune engine but not installed yet.

[Cheromaniac]

The cam's OK but your vacuum measurements don't convert correctly (one of them is wrong).
Since the engine's running rich, check for a vacuum leak. The combination gasket between the intake/exhaust manifolds and the head is a common site for a vacuum leak. Make sure all the bolts are correctly torqued down.

[Cummins90]

What happens with the stock injectors installed? With the intake hose off and the engine running can you stall the engine by occluding the idle bypass port?

Also, I have JTEC extension harnesses if you dont want to hack your factory harness apart.

[darkcorp]

Cheromaniac, thanks for reply.
I might be wrong converting vacuum measurements from kPa to inches as we are used to metric system. Sorry.
I've noticed that the engine runs rich only when idling. When I open the throttle all fuel trims go to about zero level.
Also I see my TPS shows 15% while idling. I know that for our engine normal level is 10-12%, so this might be an issue. ECU thinks the throttle is opened and enriches the mixture. Or this might be not properly work of the idle air control valve.
I'm going to replace my O2 sensor too.

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Cummins90, I don't have stock injectors and don't think this might be an issue.
I will try as you wrote with occluding the idle bypass port.

Thanks for suggestion JTEC extension harnesses. I've already made my custom.

photo_2019-11-28_16-33-32.jpg

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[Cheromaniac]

A TPS of 14-15% is normal so that isn't the problem. However if your idle vacuum is only 43KPa (converts to 12.7inHg), that definitely IS a problem and indicates there's a leak.

[darkcorp]

Ok.
Today I've disconnected TPS connector first. The Jeep ran like a hell, wow! No CEL light, plus extra power but idle revs are 1200.
Ok.
Then I've checked throttle batterfly to close as full as possible and installed a spare TPS (I have 5 pcs of them). Checked obd2 diag, it shows 12% TB's initial position now.
Good!
Jeep runs like a hell, trans' shiftings are much smoother and less noticeable.
Very good!
Although MAP's low vacuum and negative fuel trims aren't gone.
Ok.
So next step is to check vacuum leaks by smoke machine. I've tried to use a brake cleaner but it didn't helped. I can hear a hissing sound but couldn't locate it.

[darkcorp]

So TPS is a very strange sensor. If you disconnected it, there will be no CEL light and your Jeep will drive well. You will have high idle only. Diagnostic shows like throttle is opened by 34 percent.
But your TPS doesn't work properly you will have artefacts like some power loss and bad transmission shiftings.
Very interesting. I guess an original TPS is best choice.

[darkcorp]

Could you guys please help me to find a good aftermarket cam setup instruction?
Although I could waste a lot of time advancing/retarding my cam trying to find the best position empirically, but the better way is to use cam specs numbers, a protractor, an indicating gage and my brain.

I need a good instruction how to find out current setup angles and whether to advance or retard my cam.

[darkcorp]

I've done some research and found CamCalculator. According to calculations my Bullet Racing Cam has following specs:

Specifications:
Intake duration 208
Exhaust duration 212
Lobe separation 114
Advance 4

Calculations: (these numbers calculated)
Intake open BTC -6
Intake close ABC 34
Exhaust open BBC 44
Exhaust close ATC -12
Intake center 110
Exhaust center 118
Degrees overlap -18

Those match cam labels above.

So what does it mean? Cam is 4 degree advanced. Does it mean that I should advance it one tooth or it is manufactured with advance?
How to check if my cam degree is correct?

[darkcorp]

Figures at @ .050 in. lift.

Расчет 1.JPG

Figures at @ .000 in. lift.

Расчет 2.JPG

Схема.JPG

[Cheromaniac]

Lobe separation 114
Advance 4
Intake center 110

So what does it mean? Cam is 4 degree advanced. Does it mean that I should advance it one tooth or it is manufactured with advance?

The advance is ground into the cam so all you have to do is install the timing set with the dots on the cam & crank sprockets facing each other.

[darkcorp]

Kirk from Bullet Racing Cams has answered me:

The cam you have is not big, vacuum should not have been an issue.
If cam is late in the motor then vacuum will suffer.
Did you put a degree wheel on this when you installed it?
You have everything you need on the cam card you have.
It shows at the bottom of the card to install at 110 intake centerline, if you check it and have to move it then you could go as tight as 108 without any problems.
More than likely the cam needs to be advanced.

So I'm gonna study all the cam degree instructions, make a degree wheel, buy a stand for indicator and check everything up.

Also I suspect my Airtex Viper coil might be bad. New spark plugs and wires but old coil.

[dwg86]

It will probably be easier to buy a degree wheel. They aren’t that expensive. You’ll also need a piston stop.

[The Beast]

If you have a reading of 45kpa you'll have about 16-16.25inhg of vacuum. Just so you know.

[Cheromaniac]

He said his vacuum reading was 43kPa which converts to 12.7inHg. If 43kPa was the manifold absolute pressure (MAP), the vacuum would be 17.2inHg.
One atmosphere = 101.3kPa = 29.92inHg