Timing and heat ported as opposed to full and effect temps - Page 2 - Chevelle Tech
Performance Our High Performance area

 12Likes
Reply
 
LinkBack Thread Tools Search this Thread Display Modes
post #16 of 21 (permalink) Old May 19th, 19, 7:30 AM
Lifetime Premium Member
Marcus
 
Join Date: Sep 2005
Location: Sweden
Posts: 5,855
Garage
Re: Timing and heat ported as opposed to full and effect temps

Quote:
Originally Posted by Gtogeoff View Post
In the 70s after ported vac adv had been in use for a few years & emissions got tighter- & engines ran hotter- manufacturers incorporated a temp switch into the cooling so that once temps reached a critical temp, ported VA was switched to manifold VA to cool the engine. I doubt the manufacturers would have gone to this expense if this didn't work....

This is the description in my Motors Manual 1973-78 models, for GM cars. Others are similar. " ...the thermo vacuum switch is added to the system on some engines. The switch senses engine coolant temp & if temp reaches 220*, the switch valve moves to allow manifold vacuum to reach the dist & advance the timing to & allow the engine to run cooler."

The Crane adj vac adv unit will work down to as low as 5~6" of vacuum which will cover most peoples needs.

You cant compare a 70`s smog engine with a engine built for performance. Those 70`s smog engines didnt have enough initial timing to start with some had redicilous low initial like 2-4 deg and lazy curves so total wasnt all in before 4500rpm.

Most with a performance engine run 16-18 initial some like me even more Im running 25 initial. Some even uses looked out distributors.

There are GM cans that start as low as 2 hg of vacuum.
I tried both them and the crane and none of them where fully activated at 8hg that I have in D wich resulted in unsteady timing. You need a can that is fully activated atleast 2hg lower than the hg you have in gear on a car with aut transmission. Both a couple of GM and crane cans worked at idle in P since I had 10hg in P put it in D and 150 rpm drop and 2hg drop was enough to not get the vacuum can to work with manifold vacuum with my combination.

Same thing can happen if you use To light springs so your mechanical curve has started at idle in P but not at idle in D because of the rpm drop between P and D.

My car runs same temp with 16 deg initial as with 25 at idle in line up traffic no matter of time and outside temps of 90+ deg, used 16 deg initial with my Hei and now 25 deg initial with my msd pro billet both had a total of 35 deg all in by 2500. Still ran 175-180 deg in the head or 155-160 in the intake with a 160 deg thermostat with both settings.

So my experience is that if your cooling system is marginal from the begining it may have effect if you use ported vs manifold but if it has some extra cabability no difference to write home about.
mr 4 speed and Chevelle 1969 like this.

Chevelle Malibu ss 64
489 BB with parts from Lewis racing
Alumitech radiator with dual spals
Th 400 Edge 9.5" converter
57 3/4 wide 12 bolt: Eaton posi, Us gear 3.31, Toms KA 33 splines axles
Malibu ss 64 is online now  
Sponsored Links
Advertisement
 
post #17 of 21 (permalink) Old May 19th, 19, 7:41 AM
Tech Team
 
Join Date: Jun 2009
Location: Home
Posts: 229
Re: Timing and heat ported as opposed to full and effect temps

Quote:
Originally Posted by richr View Post
Thanks - How do you determine "correct" with the cam I mentioned and a stroker. My total is at 34, and no pinging and no hard starting, and runs nicely. I assume if anyone of those are an issue then I would have to back it down. I certanly can't set it at a stock application as there are no settings for it.
What heads? Some modern combuation chamber heads like 32-34 more old school 36-38 some even 40-42 total.
Was your engine dynoed? If at what total Did it produce most power?
If not dynoed and old school heads I would use something like 18-20 initial and 36-38 total with medium springs so all is in at 2500-3000 rpm with additional 10 deg from the vacuum can on manifold vacuum if engines seems to like that best. If modern Chambers same initial and 32-34 total and 10-12 deg from the vacuum can.
Chevelle 1969 is offline  
post #18 of 21 (permalink) Old May 19th, 19, 7:44 AM
Tech Team
 
Join Date: Jun 2009
Location: Home
Posts: 229
Re: Timing and heat ported as opposed to full and effect temps

Quote:
Originally Posted by Gtogeoff View Post
In the 70s after ported vac adv had been in use for a few years & emissions got tighter- & engines ran hotter- manufacturers incorporated a temp switch into the cooling so that once temps reached a critical temp, ported VA was switched to manifold VA to cool the engine. I doubt the manufacturers would have gone to this expense if this didn't work....

This is the description in my Motors Manual 1973-78 models, for GM cars. Others are similar. " ...the thermo vacuum switch is added to the system on some engines. The switch senses engine coolant temp & if temp reaches 220*, the switch valve moves to allow manifold vacuum to reach the dist & advance the timing to & allow the engine to run cooler."

The Crane adj vac adv unit will work down to as low as 5~6" of vacuum which will cover most peoples needs.
Is that the way your Chevelle is setup? A smog 262 from 78? Must be much faster than you said in your pm`s to me then? Still not fixed the broken Camera so you can take some pictures of it doing a one wheel brun out like you promised me? Or was it a leyland you have?
Chevelle 1969 is offline  
 
post #19 of 21 (permalink) Old May 20th, 19, 5:06 AM
Senior Tech Team
Geoff
 
Join Date: Mar 2015
Location: Australia
Posts: 1,865
Re: Timing and heat ported as opposed to full and effect temps

Malibu,
I am very happy for you that your engine runs at the temp you are happy with. Not everyone is as happy as you are with their coolant temps, which was why the OP started this thread.

Vac adv connected to manifold vacuum is just another thing the OP can do to reduce idle temps, his choice if he wants to try it.

When I set up Crane VA units for low vacuum cams, I do the same as Dave Ray & move the stop to towards the diaphragm end of the unit. Works perfectly.
Gtogeoff is offline  
post #20 of 21 (permalink) Old May 20th, 19, 6:13 AM
Lifetime Premium Member
Marcus
 
Join Date: Sep 2005
Location: Sweden
Posts: 5,855
Garage
Re: Timing and heat ported as opposed to full and effect temps

Quote:
Originally Posted by Gtogeoff View Post
Malibu,
I am very happy for you that your engine runs at the temp you are happy with. Not everyone is as happy as you are with their coolant temps, which was why the OP started this thread.

Vac adv connected to manifold vacuum is just another thing the OP can do to reduce idle temps, his choice if he wants to try it.

When I set up Crane VA units for low vacuum cams, I do the same as Dave Ray & move the stop to towards the diaphragm end of the unit. Works perfectly.
Goat good for you but it didnt work for me with the crane can, the stop plate is the best part you get when you buy a crane can and imho if everything in you cooling system is correct the difference in temp between ported or manifold vacuum isnt anytning you will notice.
I prefer manifold vacuum but have my own experience to help others and afaik op asked if there was big difference in engine temp ported vs manifold in this thread? And I Said no if your cooling system is setup to work correct. If its marginal from the begining it may be different. But is it the timing thats wrong than? Or something in the cooling system?

This is how I use a crane stop plate


But a piece of metall works just as good and is cheaper.
Attached Thumbnails
Click image for larger version

Name:	CFB262D2-6998-4CB5-B62A-D692970C0E12.jpeg
Views:	4
Size:	67.1 KB
ID:	594088  
Jeff65SS likes this.

Chevelle Malibu ss 64
489 BB with parts from Lewis racing
Alumitech radiator with dual spals
Th 400 Edge 9.5" converter
57 3/4 wide 12 bolt: Eaton posi, Us gear 3.31, Toms KA 33 splines axles
Malibu ss 64 is online now  
post #21 of 21 (permalink) Old May 20th, 19, 7:13 AM
Lifetime Premium Member
Marcus
 
Join Date: Sep 2005
Location: Sweden
Posts: 5,855
Garage
Re: Timing and heat ported as opposed to full and effect temps

To take it one step further gm and other very well respected engine builders clearly says in that instructions not to us vacuum advance at all. Gm even on very mild 350s.
If gm thought they would overheat without vacuum advance I think they would change their instructions. No vacuum advance at all or ported is same at idle.

Ive installed a couple of those 350 and went against gm and used vacuum advance same with a zz502 I installed. If they not run cooler they get better mpg.
https://www.chevrolet.com/content/da...ifications.pdf

Im not saying you shouldnt run vaccum advsnce at all or use ported instead of manifold just that the difference in idle temp if everything is as it should is minimal and in most cases something else cause it to run to hot if.

Chevelle Malibu ss 64
489 BB with parts from Lewis racing
Alumitech radiator with dual spals
Th 400 Edge 9.5" converter
57 3/4 wide 12 bolt: Eaton posi, Us gear 3.31, Toms KA 33 splines axles
Malibu ss 64 is online now  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Mutha Thumpr Cam issues Please !HELP! stony Engine 48 Jun 21st, 14 7:42 AM
Poor mpg's jat70 Engine 65 Jun 8th, 13 4:07 PM
Vacuum advance or no?? dt Performance 20 May 31st, 13 7:17 PM
Distributor-Vacuum advance or not? Dale H Performance 21 Apr 24th, 13 8:10 AM
back to ported to "square" transition slots? dauber65 Performance 38 Oct 8th, 12 5:31 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome