Need help tuning a 273.

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trebor75

trebor75

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This winter i switched out the slant 6 to a 273 in my Duster. The 273 was previously owned by a friend of mine and ran really good in his Dart, strong and quick little engine.

I haven’t really done anything to the engine besides cleaning and panting it, changed filters, oil etc. I had to remove the carb and distributer when we pulled the engine, so that and the headers is pretty much the only thing that’s been removed and put back.

It does run now and idles fine, but it is nowhere near as strong, quick or alert as it was in the Dart last summer. It has a stumble and hesitation if you stomp it when idling and taking off. If I am in neutral and rev it, it feels somewhat alert, but from idling it kinda feels like it’s not running on all cylinders. I pulled each wire though and it does run on all.

It has headers a 4 bbl edelbrock and the previous owner said it had a somewhat ”wilder” cam.

I hope it is a tuning issue. Any suggestions on how to start tuning it? I used the coil from my old slant six, could that be an issue? How would you set the timing? I don’t have that much experience so please help out if you have advice.
 
Check the difference in the gear ratios between the car it came out of and the car you put the engine in. Sounds like it could use a little advance or maybe have a vacume leak. The old coil could be an issue as well.
JMHO, Rat:read2:
 
Thanks. I will check this today and get back. Any more suggestions anyone?
 
Well I'm not sure how to set the timing with my setup. The manual suggested 10 B for a 1965 stock 273. But mine is not stock.

Here are a couple of questions and sorry if my english is a bit weird, I’m from Sweden 

The vacuum hose for the distributor can hook up to two places on my edelbrock carb. Not sure which one to use, but I believe it used to be to the right side if standing in front of the car. What’s the difference?

At what rpm should it idle when I set the timing and what timing would you suggest?
 
My .$.02

All extra vacuum lines on the carb should be plugged. If you have two open for the distributor, either put a Y on the distributer line to both vacuum openings, or put a plug on one of them. I know my 273 has a Y prior to going into the 2 vacuum lines on my carb.

Be sure distributor line is disconnected from distributor and plugged before timing.

Normal timing in on mine is 12-14 BTDC, even though the manual says lower.

Set Timing at 800rpm or less. Less is better as anything above 900 and the advance weights will start to change it timing automatically.
 
You should set the timing with the vacuume advance hose off of the distributor. Plug any vacuume ports on the carb. The advance hose from the distributor goes on the timed port. This port shoud be the higher of the two on the base of the carb. The lower is full vacuume and the higher one is timed. You can go to the the carb manufactures website and get instructions in PDF format to learn more. As stated it sounds like timing to me!

John D. Beckerley
Austin, Texas
 
Thanks for the advice. Much appreciated! I'll get to it today and get back with the progress! (I've done reading about tuning in other topics on the board also. Very useful!)
 
Yesterday I warmed up the motor. Plugged all vacum ports on the carb and set the timing to aprox 12 BTDC. The motor idles at about 500rpm. Is that a little low maybe?

I then attached the vacum hose from the distibuter to the higher of the two ports on the carb like you suggested "Fishthatkills". I could only feel vacum in that port when I reved the engine.

It runs much better now, there is still some hesitation if you stomp it from start though.
I dont know the total timing either, the scale runs out, so How do I set it?
A friend checked with the timing gun when I reved the enginge and it stopped climbing around 3000 rpm but it is just a guessing game where it was.
 
trebor75 said:
Yesterday I warmed up the motor. Plugged all vacum ports on the carb and set the timing to aprox 12 BTDC. The motor idles at about 500rpm. Is that a little low maybe?

I then attached the vacum hose from the distibuter to the higher of the two ports on the carb like you suggested "Fishthatkills". I could only feel vacum in that port when I reved the engine.

It runs much better now, there is still some hesitation if you stomp it from start though.
I dont know the total timing either, the scale runs out, so How do I set it?
A friend checked with the timing gun when I reved the enginge and it stopped climbing around 3000 rpm but it is just a guessing game where it was.
Click to expand...

So your timing is set to basic now.

Need to put a vacuum guage on either the base carb vaccum line (usually to PCV valve, or off the intake vaccume tree. Then and adjust the Idle to about 650-700 if manual trans. Not sure which carb you have, but if its the old Carter, you adjust center Idle Air screw to best vacuuum, then the two idle mixture screws, then re-verify center screw and lastly re-verify the 2 mixture screws.

Once set, then test drive to check again for the hesitation. If still there, move back to the timing. Add a couple degrees and check again. If worse, reduce a couple degrees and check again. Continue till it moves and takes off like you want, OR until you get best response.

If you get to a point where you ping, then you're definitely too far advanced.
 
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