408 tuning with a Wideband sensor

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Loosenutz

Loosenutz

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Figured I would share this experience with you all in the hopes we can learn something. I installed an Innovative wideband sensor last night to make tuning the Holley 750DP much easier. Cool part is that the gauge fits in the ashtray so I can easily hide it when it's not in use. Checked my manifold vacuum at idle and it's around 5". Since the stock power valve opens at 6.5 that would explain the overly rich condition the car has. I swapped it out to a 2.5 PV. I managed to get the idle to 13.7 on the wideband. Any leaner and the car would stall. Took it for a cruise afterwards and getting mid 12s at 60mph. Running pretty rich on the stock 71 primary jets. I think the 2.5 PV is slightly too low because when I accelerate lightly on the freeway the wideband hits about 16 before the PV opens to richin things back up. Gonna try 69 primary jets and a 3.5 PV next

Here are my engine specs:

• 360 bored and stroked to 408ci
• 10.3 to 1 compression
• Eagle forged stroker crank with ESP armor
• Eagle forged H beam rods
• Keith Black forged pistons
• RHS 2.02/1.60 cylinder heads
• Hughes 1.6 roller rockers
• Comp Cams 306S camshaft
• Edelbrock Victor Jr intake
• Holley 750DP carb
• MSD ignition
• Dougs ceramic headers
• 3” dual exhaust with X pipe
 
Loosenutz said:
Figured I would share this experience with you all in the hopes we can learn something. I installed an Innovative wideband sensor last night to make tuning the Holley 750DP much easier. Cool part is that the gauge fits in the ashtray so I can easily hide it when it's not in use. Checked my manifold vacuum at idle and it's around 5". Since the stock power valve opens at 6.5 that would explain the overly rich condition the car has. I swapped it out to a 2.5 PV. I managed to get the idle to 13.7 on the wideband. Any leaner and the car would stall. Took it for a cruise afterwards and getting mid 12s at 60mph. Running pretty rich on the stock 71 primary jets. I think the 2.5 PV is slightly too low because when I accelerate lightly on the freeway the wideband hits about 16 before the PV opens to richin things back up. Gonna try 69 primary jets and a 3.5 PV next

Here are my engine specs:

• 360 bored and stroked to 408ci
• 10.3 to 1 compression
• Eagle forged stroker crank with ESP armor
• Eagle forged H beam rods
• Keith Black forged pistons
• RHS 2.02/1.60 cylinder heads
• Hughes 1.6 roller rockers
• Comp Cams 306S camshaft
• Edelbrock Victor Jr intake
• Holley 750DP carb
• MSD ignition
• Dougs ceramic headers
• 3” dual exhaust with X pipe
Click to expand...


Not necessarily. I've run cars with 8" of vacuum and 10.5 power valves, no rich idle condition.

That's a pretty good sized cam. I'll guess the idle timing is low. If the initial timing is less than 20* it's not enough IMO. Might want to run closer to 25*. I'd bump the timing up and see if you can get the idle settings to come around a little better.

If the carb has adjustable bleeds, etc, it's much easier to get it closer.
 
I have the initial set at 16 and I'm running the black bushing on the MSD for 18 degrees of advance. Total timing is 34. I guess I could make my own bushing so I could have more initial timing. Do you happen to know the dimensions of a 10 degree bushing so I could fab one up?
 
Yep...

I've seen measurements from .393 to .406. I'd go high side at .406.

You may have to flat side the bushing to fit in the opening or open the width of the window it fits in (that's what I do).

You could try tuning the idle before making the bushing, twist in some timing and see how the carb/idle/vacuum reacts. Just don't drive it with your total number being out of bounds.
 
Setting up the CNC lathe to pump out a 10 degree bushing tonight. I'll probably have it make a dozen or so while I'm at it. Hard to believe 4secondsflat.com sells them for $35 plus shipping! If anyone wants one, I'm thinking $5 shipped.
 
I have that same cam in my 410 stroker with an 850dp but locked my dizzy to 36 degrees it's a little rich but never hooked up a sensor . Want to to get it tuned up better has hesitation off idle put pretty responsive when cruising .
 
Why in hell can't MSD fix this problem? A quick Google shows this is "all over" the internet. Here was a response!!!! from msd in 2004!!!!
 

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I think I may have located an off the shelf bushing to get 10-12 degress of advance for only $2. The through hole is small at 0.172 but could easily be enlarged. OD is .388-.398 which should match the 10 degree bushing made by 4secondsflat.
 
Loosenutz said:
I think I may have located an off the shelf bushing to get 10-12 degress of advance for only $2. The through hole may be just a tad small at 0.172 but could easily be enlarged. OD is .388-.398 which should match the 10 degree bushing made by 4secondsflat.
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i have the bushings made by 4secondsflat. your going to have to file 2 parallel sides of the bushing to get it into the slot in the dizzy. it will end up being like a oval. just a heads up.
 
Ok.

I found these on McMaster.com

Bushing - 92871A072 $2
Bearing - 7804K106 $7

The bearing is dead on the dimensions for a 10 degree advance so I ordered one.
 
younggun2.0 said:
i have the bushings made by 4secondsflat. your going to have to file 2 parallel sides of the bushing to get it into the slot in the dizzy. it will end up being like a oval. just a heads up.
Click to expand...

I was told this is one way to do it. Another member said he increased the size of the slot which is what I have planned.
 
Loosenutz said:
I was told this is one way to do it. Another member said he increased the size of the slot which is what I have planned.
Click to expand...

that would work well with the bearing. i just wonder about it being heavier than an alum. bushing. that rotor is gonna be spinning pretty damn fast.
 
Good point. Widening the slot should remove some of the added weight. Plus a bearing has empty space in it to cut down the weight also. I'm giving it a shot.
 
Loosenutz said:
Good point. Widening the slot should remove some of the added weight. Plus a bearing has empty space in it to cut down the weight also. I'm giving it a shot.
Click to expand...

i will be waiting to see how it works for you. I have the msd pro billet dizzy in my car right now. i will be switching to the bearing you listed if it works like it should. curious how exact the advance limit will be.
 
Mad Dart measured that one and he said it was .406 IIRC.
 
They will be here in the morning so I'll test tomorrow after work. If they work you should be able to find them cheaper than McMaster prices.
 
Hmmm. I found a post on another site that said the 10 degree measured 0.394. Guess I'll find out tomorrow.
 
Nice awareness,at least you have a clue.FWIW,My 9.7 (actual)compression, 408 [email protected] hydraulic flat tappet ,106 l.c.,liked 22 initial, to start. Food for thought.
 
Received the bushing from McMaster. It measures right at .3935. I'm going to machine a bushing at the .406 spec listed above as well. I'll test them both tonight to see what advance they yield.

20130516_083717.jpg
 
Loosenutz said:
Received the bushing from McMaster. It measures right at .3935. I'm going to machine a bushing at the .406 spec listed above as well. I'll test them both tonight to see what advance they yield.

20130516_083717.jpg
Click to expand...

Jaime, if you are going to do a run of these I will take a few no problem!
 
I would def. take a 10* bushing if you're going to make a bunch for that price.
 
First one. Hot off the machine. I'll figure out the size of the flats tonight when I install it.

20130516_152738.jpg
 
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