Finally time to start tuning!

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KnuckleDuster

KnuckleDuster

Well-Known Member
Joined
Nov 9, 2005
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Location
Texas
410 ci stroker

NGK FR5 7373 plugs
Stock Mopar old style electronic distributor recurved with FBO plate (think I used 2 light springs)
MSD 6AL
750 Proform Street Mechanical Secondary
RPM Air Gap (fully ported, center milled .40)
RPM 60779 63cc heads (fully ported by Larry Smith to 300/210 on a 4.150 bore, my bore is 4.040)
Comp Pro Magnum rockers
Comp XE285HL (241/247 .0545/.0545)
Crane Hi Intensity Lifters
Wiseco Pro Tru 20cc dish pistons (.007 below deck)
Felpro 1008 head gaskets
(10.1: SCR)
SCAT H-beam rods
SCAT cast 4" crank
ARP main studs, head bolts
Melling M72HV
Edelbrock 1720 Fuel Pump (110gph, 6psi)
3/8 fuel supply line, 5/16 return with three prong filter
Kevko oil pan M302 (no windage tray)
Hedman 1-5/8" headers
Jegs 2-1/2" exhaust
Flowmaster 40 series mufflers
727 TCI Streetfighter
Turbo Action 17805ST 10"convertor
Stock console shifter
3.23 Sure Grip 741 case
15x8 Cragers with 275/60/15 Cooper Cobra radials

Here's the timing curves as of today-

20181031_142252.jpg
 
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Here's three videos of the tach and AFR readings.

Surface streets, leaving the garage, up to about 35mph-



Getting on the access road and then freeway up to about 65mph-



Wide open throttle from about a 20 mph roll-




Stock carb settings. Haven't opened the carb, but confirmed bleed sizes on the air horn.

20181030_175304-1.jpg
 
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Just a couple engine pics.
Some of you may remember the carb throttle shaft was whistling. I changed the return spring setup so there is now no tension on the shaft at rest.
Idle is pretty steady now. Pulls about 9hg, that's as high as I can get it. I switched to manual brakes and plugged the vacuum bung on the intake.
I hooked up the v-can to full vacuum, and loosened the tension on the pod until the engine seemed pretty happy.

I sprayed water with a squirt bottle, soaked the heads /intake gaskets and carb base. Rpms never budged, so I don't suspect any vacuum leaks.

20181031_140155.jpg


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I am running rich at highway speeds, and WOT, as you will see in the videos.
Would like advice on how to best go about fixing that, to start with, (jets or bleeds?), and generally hear what some of you guys are seeing and how you would go about tuning it.

Thanks!
@TXDart
@yellow rose
@moper
@IQ52
@Mattax
@Rapid Robert
@318willrun

Just to name a few off the top of my head. There are so many good minds on here!
 
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Here are a couple kits I have to work with, and micro bits to check bleeds and such.

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20181031_154744.jpg
 
I wouldn't be afraid to open up the primary high speed air bleeds .002 at a time. it might need as much as .037. How are your metering blocks set up, as far as emulsion holes?
 
This is my setup on my Proform 750DP. I live at sea level.
340 10.3:1, IMM ported heads, 25* initial, 34* total, 50* ported vac advance highway cruise, 93 octane, XS274S SFT 236@.050, NGK FR5 7373 plugs, MSD 6AL, OEM recurved distributor, AZ e-coil Ford style, 4.10 gear with gear vendor OD, cruise temp 180-190 in summer heat.
Eddy airgap 1" open spacer divider top rounded. Dual snorkel scoop sealed to air cleaner, 14x4 with filtered lid.
IAB .067
IFR .035 moved to the bottom of the metering block.
all 4 idle screws 1 turn
PV 9.5 PV channel .052 I drilled and tapped the metering block for 6/32 brass set screws.
MAB .028
Primary jet 73 Sec jet 81 (hot summer 1 size down)
both nozzles are .033 Primary white cam #2 cam and throttle (launch car at 2K at the track), secondary pink cam #1
Metering blocks have 4 bleeds
#1 .028
#2 blocked
#3 .028
#4 blocked

I run a carter mechanical pump, 6.5 psi dead head regulator, 5/16 fuel pickup no screen, 3/8 to pump. I also use demon fuel bowls since they hold more fuel.

AFR readings
Idle in neutral 12.4
Idle in drive tight 3200 converter 13.4
Cruise 13.5-14.0
WOT 12.5

This setup works for me, street driven 50 miles to track. Best 1/4 mile run so far 11.77 1.65 60' DA 950 ft. Still waiting for fall down here to see what it runs in good air.

Hopes this helps you.
 
You're pretty close right now. Pump gas is tricky ****. The porcelain will be white and only the additive will show color most of the time you could jet up one size get a better handle on your idle jetting imo but it's the internet and I'm looking at it on a cell phone

The base ring will reflect the chamber to an extent, way down where the porcelain meets the plug casing will show the actual wide open throttle mixture look for a 60 to 80 thousanths Brown ring.
If it's fat spiking under load make sure you have the right power valve rating n pump cam. Keep in mind most of the time the changes are made in the primary side of the carburetor and it's normal to be a jet smaller/larger than out of the box.
 
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I agree, that it's fairly close now. You can lean just a "tad" on the primary. However, don't get caught up in chasing the "perfect" A/F reading on the gauge. At this point, it's trial and error to see what the engines wants/likes for timing, jetting, etc. Move one thing at a time, see how the car responds.
 
@Dana

I will get into the carb today. Got rained out to test and had other stuff I had to do yesterday.

I have played with the idle mix quite a bit, but haven't had a helper to adjust it in gear. It's pretty good, but probably tweak on it a little more.

My main concern with the AFR is the high 10's/low 11's on the main circuit on the highway and WOT. I am not strictly chasing AFR numbers, but that seems pretty rich. I am wondering how much that is affecting power. I need to get it to the strip, but want to get it closer and get familiar with what each change does first.
I may get a chance to run it the weekend after next, so I need to get it as ready as I can.
I wish I had the cash to go stick it on a chassis dyno for a day with a Mopar small block and carb expert, but highly doubt I'll ever get a chance to do that. I guess I'll have to learn to do it
myself, so I appreciate you guy's advice and patience.


I took it on a 200mi round trip last weekend and burnt about $50 in gas at $3/gal. That's about 12mi/gal, but that also included some freeway blasts and one good burnout, so milage is not much worse than I expected. I got 14 on one trip before, but that's the best so far.
 
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What should I change first in the carb?
High speed bleeds or jets?
One or two sizes if jets?
Bleeds it has .031 in it, next size I have is .035
What would you do first to get AFR closer to the high 11's-mid 12's at highway cruise and WOT?
 
KnuckleDuster said:
What should I change first in the carb?
High speed bleeds or jets?
One or two sizes if jets?
Bleeds it has .031 in it, next size I have is .035
What would you do first to get AFR closer to the high 11's-mid 12's at highway cruise and WOT?
Click to expand...
Pull the plugs and clean them.
Post a picture of the metering block.
Measure the IFR and PVCR holes.
Put 72 primary and go for cruise. Get off idle and primary dialed in first. WOT is jet the secondary for best mph at the track.
Here's a link to tuning. Follow this procedure and you can dial in the tune:
Carb Tunning
 
Plugs- carb cleaner? Brake cleaner?

This will be my first time pulling the carb apart, any tips on sequence and how to avoid damage?
I know to be careful prying the gaskets loose, anything else?

I have read that, and will be re-reading it.
 
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Carb is apart.
Emulsion holes are all threaded, but empty?
Gotta find my magnifying glass to see what size the PVCR's are.
PV is unmarked, but card shows a 6.5.
Should I look for an 8.5 now? If I need one, I will probably have to order it.

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20181101_075215.jpg
 
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KnuckleDuster said:
Carb is apart.
Emulsion holes are all threaded, but empty?
Gotta find my magnifying glass to see what size the PVCR's are.
PV is unmarked, but card shows a 6.5.
Should I look for an 8.5 now? If I need one, I will probably have to order it.

8.5 is fine for now.
What size are the emulsion holes?
Spray gaskets with wd40 when you put it together.
Click to expand...
 
KnuckleDuster said:
Plugs- carb cleaner? Brake cleaner?

This will be my first time pulling the carb apart, any tips on sequence and how to avoid damage?
I know to be careful prying the gaskets loose, anything else?

I have read that, and will be re-reading it.
Click to expand...
Carb cleaner
 
Nobody local has an 8.5 power valve, it has a 6.5 in it now.
I don't know what my cruise vacuum. Is yet, anyway.
 
To get the cruise AFR under control you will be leaning the primary side and increasing PVCR size.
With your cam the 8.5 should be good.
 
Went down 2 jets on the primary and one on the secondary to 78/70, AFR is now 13.5-14.0 on the highway, starts out 11.7 then leans out to 12.5 at 5000rpm WOT.

Put the 80's back in the secondary bowl and it goes as rich as 11.0 WOT.

Should I try changing bleeds on the secondary to get somewhere between 12.5 and 11.0 WOT, or put the 78's back in and leave it 12.5?
 
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KnuckleDuster said:
Went down 2 jets on the primary and one on the secondary to 78/70, AFR is now 13.5-14.0 on the highway, starts out 11.7 then leans out to 12.5 at 5000rpm WOT.

Put the 80's back in the secondary bowl and it goes as rich as 11.0 WOT.

Should I try changing bleeds on the secondary to get somewhere between 12.5 and 11.0 WOT, or put the 78's back in and leave it 12.5?
Click to expand...
I would run 71/78 nothing wrong with 12.5 WOT. You will find cooler air will lean the AFR a little, as in warm afternoon cool night air. If it cruises good with the 71 leave it alone. If you find in the future you are running lean at WOT in the front cylinders put larger PVCRs in. For example you currently run a .046 PVCR put a .052 in. Air bleeds change the fuel curve, smaller starts fuel flow sooner bigger later.
Tuning WOT is hard since you are only WOT about 5 seconds. Best to tune WOT at the track.
 
I didn't pull the plugs again yet. I will clean them this weekend, then kill it after a WOT run to pull at least two plugs and snap some pics.


I went back to 70p/78s and ran it one more time.
The weather cooled down from maybe 72` to 66°.
It's running good. No real hesitations anywhere. It's a handful from a 20-30mph roll, even with 3.23's!

It's pulling hard enough to send me straight to jail already, so I'm gonna leave it where it is until I get some runs down the track to see some real numbers. I will try to learn more in the meantime, so I can have some idea what to tweak at the track. Keep the input coming, I really appreciate all of it!

I am curious why the emulsion holes are all tapped but blank.
Anybody got any feedback on that?
 
KnuckleDuster said:
I didn't pull the plugs again yet. I will clean them this weekend, then kill it after a WOT run to pull at least two plugs and snap some pics.


I went back to 70p/78s and ran it one more time.
The weather cooled down from maybe 72` to 66°.
It's running good. No real hesitations anywhere. It's a handful from a 20-30mph roll, even with 3.23's!

It's pulling hard enough to send me straight to jail already, so I'm gonna leave it where it is until I get some runs down the track to see some real numbers. I will try to learn more in the meantime, so I can have some idea what to tweak at the track. Keep the input coming, I really appreciate all of it!

I am curious why the emulsion holes are all tapped but blank.
Anybody got any feedback on that?
Click to expand...
You can plug them off with a 6/32 brass insert if you want to change the emulsion.
Did you measure the emulsion holes in the metering block?
 
KnuckleDuster said:
I didn't pull the plugs again yet. I will clean them this weekend, then kill it after a WOT run to pull at least two plugs and snap some pics.


I went back to 70p/78s and ran it one more time.
The weather cooled down from maybe 72` to 66°.
It's running good. No real hesitations anywhere. It's a handful from a 20-30mph roll, even with 3.23's!

It's pulling hard enough to send me straight to jail already, so I'm gonna leave it where it is until I get some runs down the track to see some real numbers. I will try to learn more in the meantime, so I can have some idea what to tweak at the track. Keep the input coming, I really appreciate all of it!

I am curious why the emulsion holes are all tapped but blank.
Anybody got any feedback on that?
Click to expand...
Sorry man. I never got a notification even though you you did the @ thing.

Seems like you're doing pretty good.
Look in the bottom of the e-hole bores. Maybe these blocks have restrictions drilled at the bottom like the original Holleys.
If there is, and they are all say .022" or less, probably OK. If they are .026-.028", I'd block the middle one.
Even though it may mean some retesting, having a flatter more consistant AFR curve will be worth it.

Secondary main circuits are doing nothing while cruising, even at highway speeds. Mderoy may have mentioned that already.
 
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