Stop in for a cup of coffee

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straightlinespeed said:
I've read and read, but its really the one thing on the car that I have never really understood.
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Lets start with this part. We can dig up some illustrations later but the basics are this:
Timing can be thought of as time. Literally time for the mixture to get lit and develop pressure.
The faster the engine is turning, the less time there is for maximum pressure to be developed.
Also the better the mixture quality and cylinder conditions get hotter, things burn faster.
All the above explains why we need to give provide for more time as rpm goes up.

A hot rodded engine often has idle conditions with less compression and exhuast dilution. So more timing is needed because its not going to burn as wel as typical stock engine.

straightlinespeed said:
I changed the timing in my car at the request of Edelbrock due to a major bog (almost kill the car bog going WOT) with the new AVS2 carb. They got all my specs of the car and according to them I had way to much initial timing (20*) and wanted me to change it to 14* initial and add more mechanical from 14* (Im now at 18* mechanical)=32*total. Timing curve starts @ 1400 and all in by 2500. So I tried it, the bog is still slightly there but nothing like it was, which is way better. However I noticed my engine temp is about 10* warmer. It was 180* and now 190*.
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Tell us what we got here.
Engine, Cam duration, compression if you know it. Trans and gearing.

20* at what rpm? 1400?

edit: Are you using vacuum advance?
 
straightlinespeed said:
Ok, stupid technical question of the evening.

I changed the timing in my car at the request of Edelbrock due to a major bog (almost kill the car bog going WOT) with the new AVS2 carb. They got all my specs of the car and according to them I had way to much initial timing (20*) and wanted me to change it to 14* initial and add more mechanical from 14* (Im now at 18* mechanical)=32*total. Timing curve starts @ 1400 and all in by 2500. So I tried it, the bog is still slightly there but nothing like it was, which is way better. However I noticed my engine temp is about 10* warmer. It was 180* and now 190*.

Im stupid when it comes to timing. Thoughts?
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Yes, lower initial can cause an increase in engine temp. You say WOT, but at what rpm starting from, idle?
 
Ddaddy said:
Yes, lower initial can cause an increase in engine temp. You say WOT, but at what rpm starting from, idle?
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I'll say 60mph @ 2700rm and I go WOT. Although the same bog is through the entire speed and rpm range. Doesnt seem to change if Im going 30, 45, 60 or ??? Same bog
 
straightlinespeed said:
Ok, stupid technical question of the evening.

I changed the timing in my car at the request of Edelbrock due to a major bog (almost kill the car bog going WOT) with the new AVS2 carb. They got all my specs of the car and according to them I had way to much initial timing (20*) and wanted me to change it to 14* initial and add more mechanical from 14* (Im now at 18* mechanical)=32*total. Timing curve starts @ 1400 and all in by 2500. So I tried it, the bog is still slightly there but nothing like it was, which is way better. However I noticed my engine temp is about 10* warmer. It was 180* and now 190*.

Im stupid when it comes to timing. Thoughts?
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PM Hoppy @halifaxhops
 
So the mechanical timing looks like this:
14* initial at 800 rpm
14* at 1400
32 at 2500

Without vacuum advance, that should be OK. It could be tweaked but that should be close enough to be workable.
As Dave mentioned, decreasing timing can put more heat into the engine. Nothing wrong with 190*. In fact arguably that's better.

I'm with Dave. Its prob carb tuning time. Isolate the conditions if possible.
 
straightlinespeed said:
I'll say 60mph @ 2700rm and I go WOT. Although the same bog is through the entire speed and rpm range. Doesnt seem to change if Im going 30, 45, 60 or ??? Same bog
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How 'bout off the line - or rolling start off the line?
 
Mattax said:
So the mechanical timing looks like this:
14* initial at 800 rpm
14* at 1400
32 at 2500

Without vacuum advance, that should be OK. It could be tweaked but that should be close enough to be workable.
As Dave mentioned, decreasing timing can put more heat into the engine. Nothing wrong with 190*. In fact arguably that's better.

I'm with Dave. Its prob carb tuning time. Isolate the conditions if possible.
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Yes correct on what my timing looks like.

Originally I thought carb tune but since the AVS2 is so new Edelbrock didnt have tuning sheets out yet (really still dont). So I called them for advice on which way to tune the carb and they told me to mess with timing. Car ran fine prior to changing the timing just that extreme bog. Now the bog is mostly gone and I thought maybe increase my mechanical 2* more. So is it recommended to use the vacuum can or not? I can tweak it so it only pulls so much more but I dont know how much is to much or if it will benefit anything..
 
Well darn it! Left side slid on out no issues. Right side not so lucky. Have to order a removal tool. Should be here Thursday. Unfortunately looks like I’ll be missing Mopar night at the Fosters Freeze on Monday.
 
straightlinespeed said:
So is it recommended to use the vacuum can or not? I can tweak it so it only pulls so much more but I dont know how much is to much or if it will benefit anything..
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Generally yes. For drag racing, not really. Depending on the distributor, its easy or a PIA to use it. With the timing you have right now, I wouldn't use it. I'd work on the carb, then come back to reworking the mechanical curve. Then test it out. Once that seems good, its time for vacuum advance.
 
straightlinespeed said:
Havent really tried it but once and I the back end broke free and I was sideways going around a corner, wife screaming in my ear and about made me turn the car around.. So I didnt try it after that.
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:rofl:

I'd say it didn't bog much!
straightlinespeed said:
I was thinking of adding 2* more but I have the Mallory MP distributor so its pretty easy to change.
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Easy and also difficult because adjustments change two things at once.
To use the vacuum advance we need to slow the curve around 2000 rpm, so it not all in until 3000 or higher.
Not so easy with that distributor, but its doable. Lets come back to that after you've solved the bog.

I suspect its the secondary opening too quick or too soon.
 
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You could. I'd only change one or the other; especially since that's 3 changes.
Upping the initial would be my choice.
16* initial at 800 rpm
16* at 1400
34 at 2500
 
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