FAQ |
Members List |
Social Groups |
Calendar |
Search |
Today's Posts |
#41
|
||||
|
||||
Quote:
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. 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
|
||||
|
||||
Quote:
__________________
Jeff |
The Following User Says Thank You to geeteeohguy For This Useful Post: | ||
#43
|
||||
|
||||
Sounds like mine, all stock with an 068, 2.93 gear lopes along at 70 just great.
__________________
I'm World's Best Hyperbolist !! |
#44
|
||||
|
||||
Quote:
|
The Following User Says Thank You to Kenth For This Useful Post: | ||
#45
|
||||
|
||||
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
|
||||
|
||||
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.
__________________
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
|
||||
|
||||
Quote:
A 2.93 still gives excellent highway cruising that's effortless, but has more grunt around town.
__________________
Jeff |
#48
|
||||
|
||||
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
|
||||
|
||||
Quote:
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
|
||||
|
||||
Quote:
__________________
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
|
||||
|
||||
Quote:
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
|
||||
|
||||
I think this Horse has been beat to death now!
__________________
I do stuff for reasons. |
#53
|
||||
|
||||
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 |
#54
|
|||
|
|||
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
|
||||
|
||||
Quote:
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
|
||||
|
||||
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
|
|||
|
|||
Ignition timing
Quote:
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
|
||||
|
||||
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
|
||||
|
||||
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.
__________________
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
|
||||
|
||||
"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 | |
|
|