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i bought the C2 as is , with a aluminium flywheel in it. Clutch 11"
Now that all ignition is "new" and dialed in , the car is hesitating starting moving or driving below 2000 rpm , sure below 1500. I blame that alu flywheel.
Were can i buy a steel flywheel ? ( and perhaps new bolts as well as pilot bearing ? ) i'm not looking for the best price , but want best quality .
With as much torque as a 540 in^3 engine makes, it's hard to imagine the weight of the flywheel is the cause of the hesitation. If it were mine, I'd investigate carburetion.
With as much torque as a 540 in^3 engine makes, it's hard to imagine the weight of the flywheel is the cause of the hesitation. If it were mine, I'd investigate carburetion.
Jim , carburation ( tripower) seems good , i had a AFR gauge in it today test driving and 13.5 idle, 12___13 driving.
Seems to idle nice but no lower then 1000 rpm.
Jim , carburation ( tripower) seems good , i had a AFR gauge in it today test driving and 13.5 idle, 12___13 driving.
Seems to idle nice but no lower then 1000 rpm.
An AFR gauge is great! What you want to look for is a momentary lean spike in the AFR at the instant you notice a hesitation. Such a spike can be so brief that it's hard to notice while just glancing at the gauge. If you have a way to record a test drive on, say, a laptop computer it will be easy to spot when you review the data later.
i agree, but what could cause such a lean spot at 1000 to 1500 rpm ? idle ia already 13.5 ...
I don't know enough about your installation to answer that. BTW, 13.5:1 carburetor idle mixture is good. With Rochester FI, I can go in excess of 14.0:1. But that doesn't help you.
In any event, it's what happens during transient conditions which matters.
then it should be the center carb's pump not working enough . The outer carbs don't have that ... or they come in to soon working ( opening on vacuum ) which lean's total AFR to much.
Yes, my Innovate AFR gauge has a connection for PC recording ... but never did that . Must look what is possible and how.....
Perhaps i can turn the mix screw out richer to a 11 AFR at idle and see if it is better in transition. Did that once with weber carbs.
I've been tweaking my 3x2 on my new 496 and had poor performance off the line too.
What manifold vacuum are you getting at idle?
What power valve does it have?
What is your gearing?
Which accelerator squirter does it have?
Which accelerator pump cam and position?
then it should be the center carb's pump not working enough . The outer carbs don't have that ... or they come in to soon working ( opening on vacuum ) which lean's total AFR to much.
Yes, my Innovate AFR gauge has a connection for PC recording ... but never did that . Must look what is possible and how.....
Perhaps i can turn the mix screw out richer to a 11 AFR at idle and see if it is better in transition. Did that once with weber carbs.
With Rochester FI, I can't be sure I've eliminated all the "gotchas" unless I record and review each test run. If I were tuning a carburetor, it would be the same way.
I won't admit this often but I also have Weber experience.
For what you described, I'd look for an idle jet with a smaller air bleed or an emulsion tube which turns on the main circuit sooner. As you know, getting useful data about the properties of emulsion tubes is all but impossible. You end up trying first one and then another....
If so, to you ahve an H pipe right after the collectors?
if not, you may NEED an H pipe. You may be getting lean out reversion (most likely)
See the AFR graphs. This was on a chassis dyno, RW HP/TQ
In the first, we could not add enough fuel to get it to not hesitate.
In the second graph, just adding the H-pipe greatly increased the torque and also gave good AFRs. Thats all thatw as changed
As far as your flywheel, that isn't the problem. I have a 15# FW, which is too light for my 427 SB just because at very low RPM in 5th gear, you can get a trailer-hitching effect. It sure does wind up fast, though. a 20# FW would be a bit better.
yes, i have headers and side pipes. No H .
But my bug is lower in rev's , once above 2000 rpm it 's all fine.
Worst is when rev's drop to nearly 1000 rpm , when i not keep the clutch slipping above 1500.
I agree....flywheel isn't the issue. Is it a tripower setup? That's a LOT if cubes pulling on a small carb setup...so it needs to get air. Does it generally idle well off the one carb?
I've been tweaking my 3x2 on my new 496 and had poor performance off the line too.
What manifold vacuum are you getting at idle? I am around 7.5" hg at idle.
What power valve does it have? I put in a 5.
Which accelerator squirter does it have? Stock is 21, I increased to 25 and it helped.
Which accelerator pump cam and position? I had a RED cam on #1 position, moved to #2 with slight improvement.
I changed to an ORANGE pump at #1 position and got more improvement.
I'm still tweaking... dealing with a bigger cam and rectangular port heads requires all the tricks out there. I'm trying them all.
I have 2.87 first gear and 3.70 rear and can't cruise under 1500 except in first. It might be the nature of the beast.
I had my idle mixture screws open 2.5 turns, a lot, I know, but it helped the low end driveability.
It caused A/F to be 12 or so under light cruise. I backed off to 2 turns and it leaned out the cruise mixture.
In an effort to minimize opening the primary throttle too much at idle and not drill holes in the butterflys, I disconnected the
secondary linkage and made brackets that I can adjust the openings of the secondaries for now.
Since I'm breaking in the engine and transmission I don't need secondaries just yet.
I also inserted pieces of 0.031" guitar string into the idle air bleed holes and this showed improvement.
@AZDoug i could build a H , but would do it in front under the pan. As in your pic i would diminish my ground clearance to much.
I have now 140 mm under the belhousing , even "dia 63 mm equivalent" oval tube would already take 45 mm.
Under the pan i could mount the oval tube vertical as to stay away from the R&P as far as possible.
Should make a detour around the R&P support at passenger side , but that's only "welding" pieces.
Think i do it... if it doesn't help , it sure will not harm ?
Can you explain a bit "reversion/lean out" and how a H solve this ? thanks !
I agree....flywheel isn't the issue. Is it a tripower setup? That's a LOT if cubes pulling on a small carb setup...so it needs to get air. Does it generally idle well off the one carb?
JIM
yes, tripower carbs.
Idle's very well , from any rev driving , it comes down and idle's at around 1000 rpm.
I would not think the hesitation is caused by the aluminum flywheel.
FWIW, I've been running an aluminum flywheel in my 540 from day 1 and no hesitation. I initially had dual quads and now have Sniper EFI.
04-18-2023, 11:51 AM
2006 Merlin 540 flywheel
