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  #76 (permalink)  
Old 07-08-2010, 01:49 PM
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Quote:
Originally Posted by sooper
The 270 HR cam has a peak of 5000 rpm and we all know if they advertize a cam from idle to 5000,thats really 1500 to oh say 46-4700.
In addition, you have a 383 stroker- all the manufacturers use the 350 as the "yardstick", so the power peak will be lower than advertised w/the 383.

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I think I'll sit on the bomb for now, she just running to good.
Bomb's away!!

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Last edited by cobalt327; 07-08-2010 at 01:55 PM.
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  #77 (permalink)  
Old 07-08-2010, 03:26 PM
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cool rockin'
I found a link to the full length "original" article which was written by Mike Goble....
(John Hinkley's name is listed as author on 454's link,,,he did work for GM,,,he is a respected vette guy,,,who knows why)

http://webcache.googleusercontent.co...&ct=clnk&gl=us

it's only the "abbreviated" (introduction section) version that keeps getting posted on this board which IS just a preface statement...

I would definitely write that first section different to explain what is to follow!!!!
BUT....
then he does go on to explain the how/when/why to use manifold,,,, covers both the do's and don't's all the way to what are the vac unit calibration differences....

darn good article when read "in total" for performance tuning centered around vac adv on GM motors....

about me???
LOL,,,I wasn't ignoring your question,,,took awhile to figure out how to reply?????

it was my good fortune that my business/work history path allowed me to learn electrical and mechanical engineering directly from many of the very best in the world working on new products development in many many different industries including automotive....

if that is what you want to know???
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  #78 (permalink)  
Old 07-08-2010, 03:38 PM
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Quote:
Originally Posted by cobalt327
In addition, you have a 383 stroker- all the manufacturers use the 350 as the "yardstick", so the power peak will be lower than advertised w/the 383.

Bomb's away!!
Thats true but I've found even when you were using the intended or "cam designed for" engine the power band started to tire before the manufacturer said the cam would. Not by scads but some
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  #79 (permalink)  
Old 07-08-2010, 04:29 PM
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sooper,
27" tires with 3.73 gears at 5000 rpms (cam peak) is approx 133mph from this calculator...

http://www.wallaceracing.com/calcmph.php....

you should not be crapping out at only 80mph....

all that the tan plug tells you is that the overall average A/F mix ratio is good and the plug operating temp is good...

yup,,,"bombs away"
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  #80 (permalink)  
Old 07-08-2010, 04:40 PM
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Quote:
Originally Posted by sooper
Thats true but I've found even when you were using the intended or "cam designed for" engine the power band started to tire before the manufacturer said the cam would. Not by scads but some
You still running the Edelbrock heads?
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  #81 (permalink)  
Old 07-08-2010, 04:59 PM
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Quote:
Originally Posted by cobalt327
You still running the Edelbrock heads?
Yes and lovin em. best bucks I ever spent. Lots of gues up here cheaping out. Sorry trying to cheap out the vortex route. By the time all the works done they got near the same bucks. Buy the eddys and bolt em on
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Old 07-08-2010, 05:02 PM
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Quote:
Originally Posted by red65mustang
sooper,
27" tires with 3.73 gears at 5000 rpms (cam peak) is approx 133mph from this calculator...

http://www.wallaceracing.com/calcmph.php....

you should not be crapping out at only 80mph....

all that the tan plug tells you is that the overall average A/F mix ratio is good and the plug operating temp is good...

yup,,,"bombs away"
My tires are less than 26" dia and dont get me wrong when I say starting to crap out I mean certainly not the pull you got at say 3-4000 rpm. Thats a neat calculator. I come up with 126 mph. Geesus do you guys suppose maybe I aint been in third gear yet
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  #83 (permalink)  
Old 07-08-2010, 05:08 PM
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Quote:
Originally Posted by sooper
Yes and lovin em. best bucks I ever spent. Lots of gues up here cheaping out. Sorry trying to cheap out the vortex route. By the time all the works done they got near the same bucks. Buy the eddys and bolt em on
Any indication the springs are letting the valves float/bounce/loft?
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Old 07-08-2010, 05:15 PM
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OK enough with the monkey business,I'll serious up. I gotta ,too much to pay for engines. Let me get this straight. Are you trying to tell me I can be pulling good clean plugs, showing good A/F on gauge and still be fouling things to the point of damage? I hate to be taking over this post so please pardon me if I am but you have my interest. My builder says no vac. Personally I've had bad luck with vac, but by the same token I dont want baby croking either. The vac cannister on my hei is frigged anyhoo. You put vac to it ,it will pull open for a nano second then drift closed, but if you all figure I'm friging things I'll try to dig up an accel adjustable and throw it on
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Old 07-08-2010, 05:17 PM
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Quote:
Originally Posted by cobalt327
Any indication the springs are letting the valves float/bounce/loft?
No the builder tested the springs and didnt like their pressure so shimmed them to give them enough and a pinch more for the roller cam, cause he said they didnt test any where near their rating
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Old 07-08-2010, 05:36 PM
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Ported vs vacuum

I have checked these with a vacuum gauge and found that manifold vacuum drops when you open the throttle and gradually increases as the rpms come up whereas ported vacuum is zero at idle and comes on as soon as you open the throttle . So the question would be : "Do you want vacuum advance at idle and high rpm or as soon as you open the thottle and through the whole off idle rpm range?" My personal use is ported vaccum for the distributor and manifold vacuum for the vacuum shift modulator. As others stated previously . Try both and see what works best for you . I hope I didn't confuse anything .
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Old 07-08-2010, 06:02 PM
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Red65mustang
A quote from your article (which I read and liked BTW) says the following

" Anything less than 52 degrees produces less than optimum fuel economy at cruise speed."

My builder tells me that anything more than 38 degrees total of timing from all forms and I may has well have my wife follow me with the truck and car hauler when I go out for a spin cause donut pistons are a certainty

So how do the two scenarios gel?
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Old 07-08-2010, 06:07 PM
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Quote:
Originally Posted by sooper
Red65mustang
A quote from your article (which I read and liked BTW) says the following

" Anything less than 52 degrees produces less than optimum fuel economy at cruise speed."

My builder tells me that anything more than 38 degrees total of timing from all forms and I may has well have my wife follow me with the truck and car hauler when I go out for a spin cause donut pistons are a certainty

So how do the two scenarios gel?
I was mainly wondering if the springs may be causing the engine to falter above 5K RPM.

The only time the engine sees the vacuum advance added in is under light throttle cruise conditions (and at idle- if using manifold vacuum for the vac. advance). If you're hard on the gas, the vacuum drops as does the vacuum advance. This is either manifold OR ported vacuum. The only difference between the two is ported IS NOT seen at idle, manifold IS seen at idle. Otherwise they're the same thing.

I gots no dog in the ignition advance fight.
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  #89 (permalink)  
Old 07-08-2010, 06:15 PM
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No dogs

Just checked . My dog is asleep in her bed , LOL . However it runs best is always best .
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  #90 (permalink)  
Old 07-08-2010, 06:21 PM
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Sooper and adantssr,

Have read the article that Red65 linked?

Sooper, it will explain why 52-54 degrees if timing is a good number for best economy on the street. Say your running a HEI. That distributor has 20 degrees MECHANICAL ADVANCE built into it. Let's say that you have your INITIAL TIMING as seen with your timing light at 16 degrees. This is 36 degrees TOTAL ADVANCE. Now most non-adjustable vacuum cans on distributors will add 15-16 degrees advance at part throttle when vacuum is highest to help burn the air/fuel mixture. 36 degrees TOTAL ADVANCE plus 16 VACUUM ADVANCE equals 52 degrees of timing. Depending on your compression ratio, gears, cam duration your engine might not be able to handle all of that timing. You will either have to dial back the INITIAL, limit the amount of MECHANICAL, or get an adjustable vacuum can and dial that back.

Adantssr, of course your vacuum gage will show no vacuum at acceleration. That is normal. Read the article. You can also find many other timing articles on the web that will state that manifold vacuum is the best. I think is you 100% understand what is happening at these events you will concur that manifold vacuum is the way to go.

This is my last post on the subject. I sure didn't mean to take up 6 pages of band width when I made my original post. I am like Cobalt, I don't have a dog in this fight. My dog is very fat and happy running full manifold vacuum.

Last edited by cool rockin daddy; 07-08-2010 at 06:28 PM.
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