Setting timing on a non stock engine? - Team Camaro Tech
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post #1 of 15 (permalink) Old Jun 28th, 14, 06:00 PM Thread Starter
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Don
 
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Setting timing on a non stock engine?

Trying to set the timing on my 350 which has about everything different than it came with except pistons and such. Cam dist,intake,carb, heads all different.

Does that change timing specs?

Related question,,, what do you use for idle speed on such a animal? Is that the high or lowest on the lope?
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post #2 of 15 (permalink) Old Jun 28th, 14, 06:09 PM
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Re: Setting timing on a non stock engine?

Cam duration determines initial base setting. Google Barry Grant Demon Carb Selector and look at the table there. When you dial up the initial, you might have to limit how much mechanical advance you have in the distributor. Better read Timing101. If you don't have a distributor that has bushings to dial in certain amounts of advance, you will have to make a advance limiter. Nothing difficult, could be a self tapping screw in the slot of the advance mechanism. Google that too. Its a balancing act between initial, mechanical, and vacuum advance. READ up on the subject so you understand it well before doing anything. Good luck.
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post #3 of 15 (permalink) Old Jun 29th, 14, 12:20 AM
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Re: Setting timing on a non stock engine?

Quote:
Cam dist,intake,carb, heads all different.

Does that change timing specs?
Yep

Quote:
If you don't have a distributor that has bushings to dial in certain amounts of advance, you will have to make a advance limiter. Nothing difficult, could be a self tapping screw in the slot of the advance mechanism.
What limits the cent in points and HEIs is the shape pf the counter weight on the anvil...filing around 0.5 to 1mm off adds enough cent to dial in the timing for Hei on a non EGr engine.. u will also need to limit the VA with tags on the VA mounting screws
If u happen to remove a little too much on the counter weight tails , THEN u can tap the hole in the counter weight carrier, ad a grub screw , and file flats on several sides... each falt different distance from center... this now gives u an adjustable cent ...
Careful also, u can end up having the counterweight fall off the edge and jamp full advance... If u require that much cent, then u will have to replace the pads the counter weights slide on

There are many older threads i have discussed , talked ppl thru and detailed instructions on modding Points , HEI dizzies and VAs ....this also applies to Dodge dizzies.

It sound complex, but once u have the dizzie in front of u, and the rotor off it is a very simple process...

Any changes are made AFTER the idle , power and cruise circuits on the carb have been ball park dialed in, the sec butterflies set correctly...
Then establish the idle advance requirement , the total requirement....then mod the dizzie so u have a initial between 8 and 12 degs idle (non EGR) initial +VA mild cam 14 to 16 degs, lumpy street cam 16 to 18 degs , wild street / track upto 22 degs
Total (initial +cent ) ball park 32/ 34 @ 3000/ 3200 ball park , and all up initial +cent +VA do not exceed 40/42 degrees unless dialing in with a knock sensor..

make use of the search function for more detailed info how to etc.

My Spelling is not incorrect...it is creative

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post #4 of 15 (permalink) Old Jun 29th, 14, 09:49 AM
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Re: Setting timing on a non stock engine?

"What limits the cent in points and HEIs is the shape pf the counter weight on the anvil"

I'm sorry but that is incorrect. Shape and weight of the counterweights control how fast the advance comes on. Has nothing to do with the amount of mechanical. You have to limit how much the counterweights can travel and that is either by replaceable bushings in the slots the pins of the weights travel, a self tapping screw in same slot, or some other method.

BTW, not too many guys with performance running EGR so you should probably stop mentioning that when a guy is talking non-stock engine.
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post #5 of 15 (permalink) Old Jun 29th, 14, 02:27 PM
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Re: Setting timing on a non stock engine?

Quote:
Originally Posted by onefiness View Post
"What limits the cent in points and HEIs is the shape pf the counter weight on the anvil"

I'm sorry but that is incorrect. Shape and weight of the counterweights control how fast the advance comes on. Has nothing to do with the amount of mechanical.
Not necessarily. The shape of the weights (including their "tails") and the shape of the "football" on the mainshaft work together with the stop bushing and the length of the slot in the autocam plate to determine the shape of the advance curve, and the springs determine when the centrifugal curve starts and at what rpm it's maxed out.

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post #6 of 15 (permalink) Old Jun 29th, 14, 03:57 PM Thread Starter
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Re: Setting timing on a non stock engine?

The Demon carb place is so big and full of stuff I cant find any ignition or timing info. goggled several times and came away empty.

I get the general concept...Just looking for a starting point to tinker with
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post #7 of 15 (permalink) Old Jun 29th, 14, 04:34 PM
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Re: Setting timing on a non stock engine?

Sry I didnt post the fuel ball parks
idle looking at low to mid 15s AFR.. thu with that combo high 14s maybe the best stable idle u will get
Cruise, same as idle.. which with the combo should improve as the rpms get higher.. faster
Power low 12s to 13s max... mid 11s acceptable

Quote:
I'm sorry but that is incorrect. Shape and weight of the counterweights control how fast the advance comes on. Has nothing to do with the amount of mechanical.
That doesnt make sence...HEIs are sold off the shelf for EGR engines with small cent degs lot of VA..which means the need MORE degrees and all u describe is reducing????
So how do u increase the cent degrees?

I started with needing to mod an Aussie Holden dizzie back in the 70s before internet...using the dizzie calibration machine it was not clear what stopped the advance .. I messed with moding rotors , all sorts of stuff, til when i started changing counterweight of different profiles... different tail shapes....
Up to that piont most of my mods where on British/ European stuff.. all had their own methods...
Since then . IF U BOTHER to do any research, some Dodge guys in resent years have played with similar results.. except they used different anvils, and change the anvil shape, which works just as well....I prefer the counterweight because easier access and far more similar and more accurate in proportion of changing the shape than modding the anvil
I have spent over 40 yrs doing this a for petrol LPG , cng, British pool fuels , pre war unleaded and post war leaded, and engine technology going back to 1912
All hands on experiance, like John (independently with similar results, sometimes different approaches to a common result)
Quote:
BTW, not too many guys with performance running EGR so you should probably stop mentioning that when a guy is talking non-stock engine.
most prberly because as I have often mentioned, and wil do so again since u miss the piont... HEIs off the shelf have small cent , big Va for EGR engines, and as u say most guys have non EGR engines... I consider this basic information essential , espec when we get marketing propaganda BS saying " Ready to run..."
No new dizzie in an engine is Ready to run.. it has to be recurve to THAT engine to get enough advance for the flame to max cylinder pressure at a GIVEN deg ATDC between 12 and 18 degs for a given load and rpm

My Spelling is not incorrect...it is creative

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post #8 of 15 (permalink) Old Jun 29th, 14, 05:15 PM
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Re: Setting timing on a non stock engine?

Quote:
Originally Posted by Orange 69 Camaro View Post
The Demon carb place is so big and full of stuff I cant find any ignition or timing info. goggled several times and came away empty.

I get the general concept...Just looking for a starting point to tinker with
Yeah, site's are big but you gotta do some exploring. You haven't even told us the specs on the cam, how do you expect us to steer you in the right direction? Then you can't even be bothered to look on the site recommended. It is your car, right?

Right from the Demon site. Carb selection chart. You size a Demon by how much cam duration you have at .050. Base timing recommendations are on the right hand side. https://www.demoncarbs.com/Tech/DemonSelectionGuide.asp

As far as the guy saying HEI are EGR distributors, whatever. Maybe from the factory they are timed for that. Most people mod them. Most people who do mod them ditch the EGR unless required for smog inspection. 21st Century, man, 21st Century.
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post #9 of 15 (permalink) Old Jun 29th, 14, 09:01 PM Thread Starter
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Don
 
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Re: Setting timing on a non stock engine?

I didnt post cam info because I dont know it. I bought a new cam for it as guided by the guy installing it. By the time it was ready to install that cam was not going to work. So he bought a different one,,,and he is 120 miles away and not talking to me at this time,,,but i will try to find out and get back to you.

I did search that site several times to no avail. Guess I am too old for all this techy stuff
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post #10 of 15 (permalink) Old Jun 29th, 14, 10:03 PM
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Re: Setting timing on a non stock engine?

Quote:
Originally Posted by Orange 69 Camaro View Post
I didnt post cam info because I dont know it. I bought a new cam for it as guided by the guy installing it. By the time it was ready to install that cam was not going to work. So he bought a different one,,,and he is 120 miles away and not talking to me at this time,,,but i will try to find out and get back to you.

I did search that site several times to no avail. Guess I am too old for all this techy stuff
Did you click on the link I provided? There's three pages, mild cam profile, performance cam profile, and radical cam profile. Nothing "techy" about it.

You're not going to be able to do a thing to that engine until you know what is in it. Hope you are able to get the info or you're stuck. What kind of distributor is in it? What kind of heads are on it? Can ball park the timing if we know that.
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post #11 of 15 (permalink) Old Jun 30th, 14, 01:11 AM
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Re: Setting timing on a non stock engine?

Wdont actually nee the cam specs
When dialing in one establishes around 14.7 to 15.5 AFR milder the cam higher the AFR
Then disconnects the Va, lock the cent with rubber bands and finds with the intial the best stable idle advance... note NOT the best idle, otherwise will be over advanced.. and note the egine vaccuum u will nee that number later
Simple...
It is done THAT way simply because the cam is unknown and if the secondaries and / or the AFRS are way off uit may appear to be a far more lumpy cam than it really is...
And a general guide line
stock to mild with good AFR and secondary adjustements ...around the 12 deg mark....little more lumpy, 14 to 18... a wild track cam that should be on the track gets up around the 22 degs

Once the idle spec has been established , the total is estblished the same way road testing moving speed, set distance and times
u now have idle spec and total, u want no more than 40 to 42 degrees all up
Say the total (intial+ cent) is 34 41 minus 34 = 7 degs . put that in the VA
And adjust the VA so u have it all in at the idle vaccuum , noted above

Now sort the idle (intial + VA) if the idle spec was say 16 degs 16 minus 7 (the VA degs) is 11.. the intial s 11 degs
now sort the cent (intial + cent)
34 minus 11 intial= 23 degs.. that what u put in the cent curve...

u now have an intial of 11
total of 34
VA of 7
and all up under 42 of 41.
So there is no need at all to know what cam....
And it is not only the cam that determines idle intial whatever, bore , stroke, compression carb all play huge parts....as do each individual parameters of a cam.. which are not always listed... have mild duration big overlap or lift the cam becomes flaky, the ramp rate will also effect thing unexpectedly.

To dial an engine .. establish the tuning specs one doesnt need to know what is inside at all... and usually better not to know and have preconceived ideas screw u up during the process

My Spelling is not incorrect...it is creative

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post #12 of 15 (permalink) Old Jun 30th, 14, 06:21 PM
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Re: Setting timing on a non stock engine?

The short answer is no, you cannot run the factory timing. Well, you can but it certainly will not be optimal. You are likely leaving a lot of power on the table if you do.
Need to know a few things.
1. What distributor are you running?
2. Does it still have the vac advance?
3. Do you have the skills to reset your distributor curve? It really isn't that hard, and we can walk you through it.
3. I know you don't know what cam you have, but you did mention a lope. If it is a street car, you should still get a fairly smooth idle between 900 and 1000 rpm. Even if you don't know what camshaft you have, hopefully you can tell us what heads you are running.

4. Do you know the compression ratio as told to you by the builder?
5. Stick or auto trans?
Answer those questions the best you can and I can give you a recommendation on where to start.

Do you have a "dial back" timing light? It isn't absolutely necessary, but helpful. If you don't have one, you will need to buy a timing tape to put on the balancer (unless, and this is unlikely, your balancer is already marked in increments up to 40 degrees advanced).

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post #13 of 15 (permalink) Old Jun 30th, 14, 10:31 PM
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Re: Setting timing on a non stock engine?

Quote:
The short answer is no, you cannot run the factory timing. Well, you can but it certainly will not be optimal. You are likely leaving a lot of power on the table if you do.
exactly.
The original specs where for an original engine , on leaded fuels and never had a rebuild.. std deck heights , heads bore etc and cam... even then factory where rather conservative in their tuning specs...which is why some simply knocked the initial up on their points dizzies , often a slow death to the engine, and others a little wise lightened the springs a little.
u can put 2 identical engineers side by side, then when dialing in the engine end up with slightly different tuning specs... ad to that change the humidity or altitude or temp of the day...will change things slightly... eg high altitude slower burn , more advance.

My Spelling is not incorrect...it is creative

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post #14 of 15 (permalink) Old Jun 30th, 14, 11:54 PM
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Re: Setting timing on a non stock engine?

Quote:
Originally Posted by Orange 69 Camaro View Post
The Demon carb place is so big and full of stuff I cant find any ignition or timing info. goggled several times and came away empty.

I get the general concept...Just looking for a starting point to tinker with
Try here: https://www.demoncarbs.com/Tech/DemonSelectionGuide.asp
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post #15 of 15 (permalink) Old Jul 1st, 14, 12:19 PM
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Re: Setting timing on a non stock engine?

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Originally Posted by Cdminter55 View Post
that link was posted 5-6 posts ago.
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