#41  
Old 03-09-2023, 04:17 PM
Formulajones's Avatar
Formulajones Formulajones is offline
Ultimate Warrior
 
Join Date: Jan 2012
Posts: 10,796
Default

Quote:
Originally Posted by 25stevem View Post
I have a question for a lot of you, especially in regards to the above post where it’s stated that the 744 cam is fairly mild.

I have had all the factory cams in one of my 9.5 to 1 400 motors but for the 744 cam.

Ok so now I need to ask about my info I posted here from old HO racing recommendations.

As you can see they called for 3.90 gears to be run with the 744 cam in a 400.

How many agree that in a 9.5 400 motor the 744 needs a 3.90 gear to get it done right?

When I stuffed the 041 cam in my 400 above I used Rhodes lifters due to my 3.55 gears I had in the car and the motor performed well once oil temp came up.

The 068 cam was fine without the Rhoads lifters and with the 3.55 gears.
I think it's all relative Steve. Install position and tune will radically affect how any particular cam acts in an engine.
The 744 cam is relatively mild in my opinion for a 400, and the 068 is small. In fact, I run the 068 in my 400 and with 3.31 gears and stock converter it's perfectly fine, idles baby butt smooth, 16 inches of vacuum, and makes power right off idle, however it's all done at 5000 rpm. That particular engine is 10.13:1 compression. I suspect 9.5:1 wouldn't make much of a noticeable difference.

However I will say when it comes to rear gears, these cars always benefit from more to a point. For instance the 3.31's aren't even near enough gear for any decent 1/4 mile work. I barely even get into 3rd gear at the 1000 foot mark and lug through the finish line in 3rd at about 4000 rpm. A change to something like a 3.73 or 3.90 would certainly help and the car would absolutely gain some ET and MPH. For sure help in the 60 foot department. Ideally I'd like to see it crossing the finish line at least 5000 to 5200 rpm.

It's all a matter of what you want to put up with and what the car is intended for. On the street where the car is used 99% of the time, 3.31's are fine, it cruises nice and returns 17 mpg. It's just not optimum for any drag racing. It does okay for what it is, just not it's full potential.

__________________
2019 Pontiac Heaven class winner

https://youtu.be/XqEydRRRwqE

Last edited by Formulajones; 03-09-2023 at 04:22 PM.
The Following 2 Users Say Thank You to Formulajones For This Useful Post:
  #42  
Old 03-09-2023, 04:53 PM
geeteeohguy's Avatar
geeteeohguy geeteeohguy is offline
Ultimate Warrior
 
Join Date: Dec 2009
Location: Fresno, California
Posts: 5,313
Default

Quote:
Originally Posted by Formulajones View Post
I think it's all relative Steve. Install position and tune will radically affect how any particular cam acts in an engine.
The 744 cam is relatively mild in my opinion for a 400, and the 068 is small. In fact, I run the 068 in my 400 and with 3.31 gears and stock converter it's perfectly fine, idles baby butt smooth, 16 inches of vacuum, and makes power right off idle, however it's all done at 5000 rpm. That particular engine is 10.13:1 compression. I suspect 9.5:1 wouldn't make much of a noticeable difference.

However I will say when it comes to rear gears, these cars always benefit from more to a point. For instance the 3.31's aren't even near enough gear for any decent 1/4 mile work. I barely even get into 3rd gear at the 1000 foot mark and lug through the finish line in 3rd at about 4000 rpm. A change to something like a 3.73 or 3.90 would certainly help and the car would absolutely gain some ET and MPH. For sure help in the 60 foot department. Ideally I'd like to see it crossing the finish line at least 5000 to 5200 rpm.

It's all a matter of what you want to put up with and what the car is intended for. On the street where the car is used 99% of the time, 3.31's are fine, it cruises nice and returns 17 mpg. It's just not optimum for any drag racing. It does okay for what it is, just not it's full potential.
I agree 100%. I run an 068 cam in the 9.3 CR 400 in my '67 GTO convertible with stock Q jet and points distributor with an 1800 stall converter with a 2.56 rear gear. Terrible combo for the quarter mile, but great response from idle to 5000 rpm. Car will not even pull redline in top gear as that equates to 158 mph and the aerodynamics of the car limit the top end to 135 or so max. It's a cruiser and road trip car, so I enjoy 21 mpg at 75-80 mph all day long and a cool running engine loafing along at 2450rpm or so. It's all about what the car is being used for.

__________________
Jeff
The Following User Says Thank You to geeteeohguy For This Useful Post:
  #43  
Old 03-09-2023, 05:10 PM
dataway's Avatar
dataway dataway is offline
Ultimate Warrior
 
Join Date: Jan 2012
Location: Saratoga NY
Posts: 8,922
Default

Sounds like mine, all stock with an 068, 2.93 gear lopes along at 70 just great.

__________________
I'm World's Best Hyperbolist !!
  #44  
Old 03-10-2023, 05:12 AM
Kenth's Avatar
Kenth Kenth is offline
Ultimate Warrior
 
Join Date: Feb 2003
Location: The Kingdom of Sweden
Posts: 5,458
Default

Quote:
Originally Posted by 25stevem View Post
I have a question for a lot of you, especially in regards to the above post where it’s stated that the 744 cam is fairly mild.

I have had all the factory cams in one of my 9.5 to 1 400 motors but for the 744 cam.

Ok so now I need to ask about my info I posted here from old HO racing recommendations.

As you can see they called for 3.90 gears to be run with the 744 cam in a 400.

How many agree that in a 9.5 400 motor the 744 needs a 3.90 gear to get it done right?

When I stuffed the 041 cam in my 400 above I used Rhodes lifters due to my 3.55 gears I had in the car and the motor performed well once oil temp came up.

The 068 cam was fine without the Rhoads lifters and with the 3.55 gears.
You don't get it. OP has a 468 engine and I have a 462.

__________________
1966 GTO Tri-Power
1970 GTO TheJudge
http://www.poci.org/
http://gtoaa.org/
The Following User Says Thank You to Kenth For This Useful Post:
  #45  
Old 03-10-2023, 02:32 PM
scott70's Avatar
scott70 scott70 is offline
Ultimate Warrior
 
Join Date: May 2002
Location: maine
Posts: 2,220
Default

If I didnt run my engine on the dyno or didnt run my car at the track I probably would set my total timing at around 33 degrees,,,,no vac hooked up. Shouldnt be too little and shouldnt be too much for most pontiac street engines

__________________
72 lemans,455 e-head, UD 255/263 solid flat,3.73 gears,,,10" 4400 converter,, 6.68 at 101.8 mph,,1.44 60 ft.2007
(cam 271/278 roller)9"CC.4.11gear 6.41 at 106.32 mph 1.42 60 ft.(2009) SOLD,SOLD
1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.64 @ 87.3 mph on slippery street tires.Bad 2.25 60ft.Owned since 86'
  #46  
Old 03-10-2023, 03:36 PM
Radman's Avatar
Radman Radman is offline
Chief Ponti-yacker
 
Join Date: Jan 2010
Location: Tippecanoe, OH
Posts: 765
Default

1961 389 Tri-power with the 61 steel heads. I have an MSD distributor with the 6AML box. I use a dial back timing light to set my timing at 3000 RPM. The light gives funky readings with the MSD multiple sparks under 2500 RPM. Not on a dyno or at the track but driving on the road. The distributor comes with different weights for the mechanical advance. I ended up using the two heavy weights. Here are my results.
Attached Thumbnails
Click image for larger version

Name:	timing curve.jpg
Views:	160
Size:	80.4 KB
ID:	608652  

__________________
If you built it, drive it.
red 62 Tempest total stock restoration.
white 62 Tempest modified, 61 389 Tri-Power, and a conventional drive train.
  #47  
Old 03-11-2023, 08:18 PM
geeteeohguy's Avatar
geeteeohguy geeteeohguy is offline
Ultimate Warrior
 
Join Date: Dec 2009
Location: Fresno, California
Posts: 5,313
Default

Quote:
Originally Posted by dataway View Post
Sounds like mine, all stock with an 068, 2.93 gear lopes along at 70 just great.
IMO, the 2.93 is optimal for a 400 powered GTO-weight car with a TH400 trans. The only reason I went with a 2.56 is because it was a limited slip, and it was free.
A 2.93 still gives excellent highway cruising that's effortless, but has more grunt around town.

__________________
Jeff
The Following 2 Users Say Thank You to geeteeohguy For This Useful Post:
  #48  
Old 03-16-2023, 10:37 PM
SD421's Avatar
SD421 SD421 is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Concord,CA
Posts: 1,147
Default

For the OP, I have found this pdf file called Timing 101 to be very helpfulwww.camaros.org/pdf/timing101.pdf

__________________


1966 GTO

1966 421-9.3-1 comp-Race Tec 23cc Pistons
1966 Tri-Power
1967 670 Heads
Pontiac "Highlift" TriPower Cam by SpeedPro
DUR 214 Int 224 Exh @.050 - 107 ICL
LIFT .445" Int .465" Exh
Tri-Y-Headers by Tribal Tubes w/ Goerlich Mufflers
1966 Muncie Wide Ratio 4-Speed
1968-72 Chevy 12 Bolt Rear End w/ 3.73 rear gears
The Following User Says Thank You to SD421 For This Useful Post:
  #49  
Old 03-17-2023, 09:51 AM
chiphead's Avatar
chiphead chiphead is offline
Ultimate Warrior
 
Join Date: Nov 2004
Location: Aiken, SC
Posts: 5,182
Default

Quote:
Originally Posted by geeteeohguy View Post
I agree 100%. I run an 068 cam in the 9.3 CR 400 in my '67 GTO convertible with stock Q jet and points distributor with an 1800 stall converter with a 2.56 rear gear. Terrible combo for the quarter mile, but great response from idle to 5000 rpm. Car will not even pull redline in top gear as that equates to 158 mph and the aerodynamics of the car limit the top end to 135 or so max. It's a cruiser and road trip car, so I enjoy 21 mpg at 75-80 mph all day long and a cool running engine loafing along at 2450rpm or so. It's all about what the car is being used for.
What's your timing curve? My car currently has 256s and I slowed the timing curve way down to avoid pinging near peak torque. I didn't hear pinging I was just being careful. I'm wondering if that's really necessary with stock compression in a 69 400?

As far as 64 speeds original question, I didn't see mention of static compression or heads used. That's kind of critical to understand of 27 total is within the ballpark.

__________________
I could explain all this to the girl at the parts store, but she'd probably call the asylum.

White '67 LeMans 407/TH350/Ford 3.89... RIP
Red '67 LeMans. 407/TH400/Ford 3.25
  #50  
Old 03-22-2023, 10:29 PM
bankbook's Avatar
bankbook bankbook is offline
Ultimate Warrior
 
Join Date: Jun 2007
Location: New York City
Posts: 1,456
Default

Quote:
Originally Posted by SD421 View Post
For the OP, I have found this pdf file called Timing 101 to be very helpfulwww.camaros.org/pdf/timing101.pdf
Good read, Need part 2.

__________________
DOC'S TA





Turbo 535, CV 1 heads.

Built by Cerralli Competition Engines

Tenth Anniversary (Van Nuys) restored.
Tenth Anniversary Barn Find (Norwood)
Both 4 speeds!
The Following User Says Thank You to bankbook For This Useful Post:
  #51  
Old 03-22-2023, 11:35 PM
Shiny's Avatar
Shiny Shiny is offline
Ultimate Warrior
 
Join Date: Nov 2008
Location: Centennial CO
Posts: 1,899
Default

Quote:
Originally Posted by SD421 View Post
For the OP, I have found this pdf file called Timing 101 to be very helpfulwww.camaros.org/pdf/timing101.pdf
I also just read through this and find it useful. Thank you.

I think, however, the author's adamant dismissal of ported vacuum may not be great advice for everyone and is clearly contentious.

Knowing next to nothing, I try to digest whatever is in my food bowl. It seems if a carb is set up to idle with a very lean mixture or has a big cam with a lot of overlap and "mixture dilution" by exhaust, then adding vacuum advance at idle may be helpful.

But if a carb has been modified to add fuel at idle, has a mild cam, and seems to idle well with reasonable base timing, why would it need that vacuum timing goose?

I just read another thread (link) where other perspectives are shared.

I'm at level zero on setting up my timing and plan to start with ported vacuum. If my engine seems to like base timing beyond 20 degrees or something similarly unexpected, I'll revisit.

But it is definitely helpful to read both sides.

Mike

  #52  
Old 03-23-2023, 06:38 AM
25stevem's Avatar
25stevem 25stevem is offline
Ultimate Warrior
 
Join Date: Jan 2022
Posts: 1,744
Default

I think this Horse has been beat to death now!

__________________
I do stuff for reasons.
  #53  
Old 03-23-2023, 07:01 AM
Kenth's Avatar
Kenth Kenth is offline
Ultimate Warrior
 
Join Date: Feb 2003
Location: The Kingdom of Sweden
Posts: 5,458
Default

Quote:
Originally Posted by 25stevem View Post
I think this Horse has been beat to death now!
This info may be new to new enthusiasts, not necessarily to old hawks who never really learned the principles of things but instead stuck to fallacies for 50+ years and can't learn anything new, or how things really works.

FWIW

__________________
1966 GTO Tri-Power
1970 GTO TheJudge
http://www.poci.org/
http://gtoaa.org/
  #54  
Old 05-16-2023, 10:48 PM
uttergto uttergto is offline
Member
 
Join Date: Feb 2013
Posts: 34
Default ignition timing

I have been reading all of the comments about ignition timing. I have a 65 GTO, .030 overbore with an HO 744 cam, set 3 deg advanced. The tuneup specs say, with the vacuum advance hose disconnected, the timing should be 6 deg. advanced. My question what happens if it is set at 12 Deg. advanced. Does this cause the engine to overheat driving at 3,000 RPM and under a load?

  #55  
Old 05-17-2023, 02:21 AM
SD421's Avatar
SD421 SD421 is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Concord,CA
Posts: 1,147
Default

Quote:
Originally Posted by uttergto View Post
I have been reading all of the comments about ignition timing. I have a 65 GTO, .030 overbore with an HO 744 cam, set 3 deg advanced. The tuneup specs say, with the vacuum advance hose disconnected, the timing should be 6 deg. advanced. My question what happens if it is set at 12 Deg. advanced. Does this cause the engine to overheat driving at 3,000 RPM and under a load?

Depends on what your mechanical advance is at 3000rpms and how many degrees does your vacuum can pulls at that rpm as well. For example.

12 initial
30 mechanical advance (stock w/o a bushing)
= 42 degrees at 3000 rpm’s
Add a stock vacuum can = 20 degrees

42+20= 62 total timing at part throttle/cruise

Yes, it’s going to overheat

42 degrees under load (no vacuum) will also overheat and probably ping too

You’ll need to shorten your mechanical to 24 degrees (by adding a bushing) & vacuum advance can of 14 degrees

12 + 24 = 36
Then add a vacuum advance that adds another 14 degrees
= total timing of 50 degrees for part throttle/cruising. No more than 52 degrees

I’d make sure to get the mechanical advance dialed in to get your 36 degrees at 3000 rpm’s
Then get an adjustable vacuum advance where you can back it off until there is no pinging at part throttle/ cruising speed

Here’s a great article http://www.camaros.org/pdf/timing101.pdf

__________________


1966 GTO

1966 421-9.3-1 comp-Race Tec 23cc Pistons
1966 Tri-Power
1967 670 Heads
Pontiac "Highlift" TriPower Cam by SpeedPro
DUR 214 Int 224 Exh @.050 - 107 ICL
LIFT .445" Int .465" Exh
Tri-Y-Headers by Tribal Tubes w/ Goerlich Mufflers
1966 Muncie Wide Ratio 4-Speed
1968-72 Chevy 12 Bolt Rear End w/ 3.73 rear gears

Last edited by SD421; 05-17-2023 at 02:26 AM. Reason: Add quote
  #56  
Old 05-17-2023, 06:02 AM
steve25's Avatar
steve25 steve25 is online now
Ultimate Warrior
 
Join Date: May 2008
Location: Westchester NY
Posts: 14,638
Default

Without the vacuum advance hooked up, no the motor will not overheat, in fact many racers run a locked out timing such that once the motor is started the timing is well above 30 degrees.

__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
  #57  
Old 05-17-2023, 10:20 PM
uttergto uttergto is offline
Member
 
Join Date: Feb 2013
Posts: 34
Default Ignition timing

Quote:
Originally Posted by SD421 View Post
Depends on what your mechanical advance is at 3000rpms and how many degrees does your vacuum can pulls at that rpm as well. For example.

12 initial
30 mechanical advance (stock w/o a bushing)
= 42 degrees at 3000 rpm’s
Add a stock vacuum can = 20 degrees

42+20= 62 total timing at part throttle/cruise

Yes, it’s going to overheat

42 degrees under load (no vacuum) will also overheat and probably ping too

You’ll need to shorten your mechanical to 24 degrees (by adding a bushing) & vacuum advance can of 14 degrees

12 + 24 = 36
Then add a vacuum advance that adds another 14 degrees
= total timing of 50 degrees for part throttle/cruising. No more than 52 degrees

I’d make sure to get the mechanical advance dialed in to get your 36 degrees at 3000 rpm’s
Then get an adjustable vacuum advance where you can back it off until there is no pinging at part throttle/ cruising speed

Here’s a great article http://www.camaros.org/pdf/timing101.pdf
Thanks for the reply. This is a stock distributor. According to tuneup specs, it should have 6 deg. advance with the vacuum disconnected. It should have 11 deg. @ 2300 mechanical advance at distributor RPM and 10 deg at 16 vacuum.
Crankshaft RPM would be double, it seems rather difficult to run at 4,300 RPM. What am I missing? This would be about 38 deg total.

  #58  
Old 05-18-2023, 04:11 AM
lust4speed's Avatar
lust4speed lust4speed is offline
Ultimate Warrior
 
Join Date: Jul 2002
Location: Yucaipa, SoCal
Posts: 8,684
Default

I think the important thing is the engine builder ran the engine on the dyno - and with that balancer installed on the engine and the timing cover that was installed, the engine made maximum power with an "observed" 27 degrees advance with his shop timing light. Way too many variables to just accept the number as gospel.

__________________
Mick Batson
1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon in progress.
  #59  
Old 05-18-2023, 05:52 AM
steve25's Avatar
steve25 steve25 is online now
Ultimate Warrior
 
Join Date: May 2008
Location: Westchester NY
Posts: 14,638
Default

This is what the timing curve looked like from a late 60s points Dizzy from a 350 hp high comp 400 4 bbl motor.

Note the 1" of Manifold vacuum at 4500 and full throttle indicating that the Carb is already a restriction.
Attached Thumbnails
Click image for larger version

Name:	IMG_0589.jpg
Views:	116
Size:	43.2 KB
ID:	612851  

__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
  #60  
Old 05-18-2023, 07:32 AM
Cliff R's Avatar
Cliff R Cliff R is offline
Ultimate Warrior
 
Join Date: Nov 2000
Location: Mount Vernon, Ohio 43050
Posts: 17,972
Default

"This info may be new to new enthusiasts, not necessarily to old hawks who never really learned the principles of things but instead stuck to fallacies for 50+ years and can't learn anything new, or how things really works."

+1, 2, 3, 4, 5 and 6.

You can't read a single thread on any Forum about this topic without someone copy/pasting information they Googled up someplace and some of it isn't even accurate. Since I custom tune for a living and have for decades you'd think by now poor running engines would quit showing up with those POS aftermarket "high performance" spring/weight kits in them trying to get ALL the timing in right off idle, plus they have disabled the VA, but no, I still see them just about every single time one shows up. STOOPID, just stupid, but folks still buy into all that crap and think a well thought out V-8 engine build needs a super-quick timing curve and no added timing at light engine load for improved effciency.

I'm really not complaining here as following poor advice and making poor choices have kept my wallet full for decades. Even though I'm retired at this point I still get calls every single day where folks are having tuning issues, carb and distributor and can't get it sorted out, neither can their freinds, beer drinking buddies, local "gurus" and shops in their area that still work on these older cars.

The fix is ALWAYS the same when these vehicles show up for "carb work". I attack the distributor first, amputating the POS springs/weights and crap that was installed, put stock parts back in them, modify the VA to add the timing it should, and low and behold the carburetor problem is mostly or often completely fixed!........

__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran!
https://cliffshighperformance.com/
73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),
The Following 3 Users Say Thank You to Cliff R For This Useful Post:
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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

Forum Jump


All times are GMT -4. The time now is 07:43 PM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017