Pump gas with 11:1 compression?
07-20-2016, 10:23 PM
#21
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NewbVetteGuy (07-20-2016)
07-20-2016, 10:38 PM
#22
I had the same problem with my original crane SR cam 232/238 383 @11.2
I used octane booster and dorked with everything. I actually had very light ping at freeway cruise without booster. I had the crane cams adjustable vacuum can on my Unilite dizzy. I finally gave up and went to a bigger cam and wrote it off as a learning experience.
I would have told that cam of yours would not work
I used octane booster and dorked with everything. I actually had very light ping at freeway cruise without booster. I had the crane cams adjustable vacuum can on my Unilite dizzy. I finally gave up and went to a bigger cam and wrote it off as a learning experience.
I would have told that cam of yours would not work
I'm very happy with the cam so far. Your welcome to check it out if your ever down this way.
07-20-2016, 10:48 PM
#23
I've been happy with an 11.5:1 406 small block on 91. I tried to optimize the details. AFR heads, zero deck with reasonable quench, 243-251 @ .050 hyd roller, 110 LSA installed with two degrees advance, full time cold air, 160 thermostat. The first ignition curve I tried was very happy in the first four gears but it did not like being in fifth below 2400 rpm. I slowed the curve and on flat ground you can now get below 2000 rpm in fifth.
07-20-2016, 11:27 PM
#24
Melting Slicks
I've been happy with an 11.5:1 406 small block on 91. I tried to optimize the details. AFR heads, zero deck with reasonable quench, 243-251 @ .050 hyd roller, 110 LSA installed with two degrees advance, full time cold air, 160 thermostat. The first ignition curve I tried was very happy in the first four gears but it did not like being in fifth below 2400 rpm. I slowed the curve and on flat ground you can now get below 2000 rpm in fifth.
Unless the really low advance @ 2 degrees and the super low temps are staving off detonation...
To me this just sounds like a car that would drive down the streets like a diesel- powered by compression-based detonation with no spark required...
Adam
07-20-2016, 11:34 PM
#25
Melting Slicks
How the heck does vacuum advance create cooler running temps and better MPG? That blows my mind...
I'm planning an EFI install this winter and from what I can tell that means I have to give up distributor vacuum advance and either move to a dual sync electronic distributor or an electronic distributor AND a crank sensor; does that mean when I make the swap I'll have higher engine temps and lower MPG?
I honestly don't understand why vacuum advance works or how it works or how these benefits are provided...
Adam
07-20-2016, 11:36 PM
#26
Well, it's official; I do NOT properly understand the factors that determine detonation... I thought I was starting to get it...
Unless the really low advance @ 2 degrees and the super low temps are staving off detonation...
To me this just sounds like a car that would drive down the streets like a diesel- powered by compression-based detonation with no spark required...
Adam
The two degrees of advance refers to the relationship of the cam to the crank. It is very common for a sbc cam to be installed with four degrees of advance for optimal "overall" power. By taking out two degrees of the advance (installed two degrees advanced) the intake valve closes later in the cycle. This reduces cylinder pressure at lower RPM. Less cam advance typically trades low RPM power and gains a bit at high RPM.
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NewbVetteGuy (07-20-2016)
07-20-2016, 11:38 PM
#27
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The advance in an EFI distributor is controlled by the computer. It is also monitoring vacuum and can adjust timing to what is set in tables for each driving condition. You have way more possibilities with EFI.
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NewbVetteGuy (07-20-2016)
07-20-2016, 11:56 PM
#28
Melting Slicks
The two degrees of advance refers to the relationship of the cam to the crank. It is very common for a sbc cam to be installed with four degrees of advance for optimal "overall" power. By taking out two degrees of the advance (installed two degrees advanced) the intake valve closes later in the cycle. This reduces cylinder pressure at lower RPM. Less cam advance typically trades low RPM power and gains a bit at high RPM.
Adam
07-21-2016, 07:26 AM
#29
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George, I'm pretty confident that I can tune this condition out. I just have not got around to it yet. It could also be related to the stumble that I often get at both idle and cruise speeds due to the 7530 Team G. I've played around with squirter sizes, but not acc pump cams. I can tell you AFR does lean out briefly, so I attribute this to a combination of a brief lean condition and vacuum advance.
I'm very happy with the cam so far. Your welcome to check it out if your ever down this way.
I'm very happy with the cam so far. Your welcome to check it out if your ever down this way.
Last edited by resdoggie; 07-21-2016 at 07:29 AM.
07-21-2016, 08:14 AM
#30
Melting Slicks
Thread Starter
I've been happy with an 11.5:1 406 small block on 91. I tried to optimize the details. AFR heads, zero deck with reasonable quench, 243-251 @ .050 hyd roller, 110 LSA installed with two degrees advance, full time cold air, 160 thermostat. The first ignition curve I tried was very happy in the first four gears but it did not like being in fifth below 2400 rpm. I slowed the curve and on flat ground you can now get below 2000 rpm in fifth.
In comparison my 355 got 17 mpg with the same gears, but running a 2000 stall. Now I run a 3000 stall with the 3.70 gears.
07-21-2016, 10:58 AM
#32
Team Owner
I don't think that it is practical for a street car.
Years ago some outfit was selling a water/meth container that bolted on top of the intake. It was simple, heat from the motor caused it to boil. The lid had a 3/8th rubber hose that you plugged into full manifold vacuum like your carb port. Under motor vacuum it would boil at lower temps. It was designed to add the most vapor under highest vacuum like cruising down the free way. My buddy swore by it in his hot rod Dodge.
Last edited by gkull; 07-21-2016 at 11:08 AM.
07-21-2016, 11:23 AM
#33
Burning Brakes
Thanks.
I have a NOS Holley unit in the box, but no plans for it. I think better "fast burn" style combustion chambers have harshed the allure of these kits.
I could see them in certain truck applications being useful.
I have a NOS Holley unit in the box, but no plans for it. I think better "fast burn" style combustion chambers have harshed the allure of these kits.
I could see them in certain truck applications being useful.
07-21-2016, 11:26 AM
#34
Drifting
Temp Control?
Forum: I posted on something similar a while back.
Say an engine was on the border line of detonation.
Wouldn't CAI, lower temps on fuel, oil and water make the difference?
Not sure how much difference this would make?
R
Say an engine was on the border line of detonation.
Wouldn't CAI, lower temps on fuel, oil and water make the difference?
Not sure how much difference this would make?
R
07-21-2016, 11:46 AM
#35
Drifting
Motorhead, Diehard, and myself are running 250 ish solid roller cams in our 427's and I think 11 or more compression. very doable on pump gas with higher stall or even better manual tranny.
I worked on locked out magneto ignitions @ 30 years ago. The old salty guard had been using them for 20 years and couldn't see why you would change. We showed them that optical triggered or crank triggered ignition and changeable race battery with some advance was far superior.
Modern chambers like these AFR's tend to make the most power at sea level @ 32-34 degrees. I'm a fan of 18-20 initial and adding 12-14 degrees mech advance and limiting vac advance to 10 or less more like 6-8 degrees.
The point of when to have the all timing in VS rpm is a war that will rage on the internet for a long time. But this is the facts, so I did not make it up and a reasonable person should be able to grasp it.
It comes down to volumetric efficiency, period. Flame travel does not do well in a exhaust diluted poor stock gen 1 chevy chamber design. small cam, poor intake, restrictive exhaust, EGR 80% cylinder filling.
Of course you need all the advance you can and all in at sub 2800 rpm.
As volumetric efficiency and flame travel increase the less timing required. Period.
In real race engines they actually pull timing out as the rpm increase because the flame travel increases with highly atomized fuel
I worked on locked out magneto ignitions @ 30 years ago. The old salty guard had been using them for 20 years and couldn't see why you would change. We showed them that optical triggered or crank triggered ignition and changeable race battery with some advance was far superior.
Modern chambers like these AFR's tend to make the most power at sea level @ 32-34 degrees. I'm a fan of 18-20 initial and adding 12-14 degrees mech advance and limiting vac advance to 10 or less more like 6-8 degrees.
The point of when to have the all timing in VS rpm is a war that will rage on the internet for a long time. But this is the facts, so I did not make it up and a reasonable person should be able to grasp it.
It comes down to volumetric efficiency, period. Flame travel does not do well in a exhaust diluted poor stock gen 1 chevy chamber design. small cam, poor intake, restrictive exhaust, EGR 80% cylinder filling.
Of course you need all the advance you can and all in at sub 2800 rpm.
As volumetric efficiency and flame travel increase the less timing required. Period.
In real race engines they actually pull timing out as the rpm increase because the flame travel increases with highly atomized fuel
If Tony has not change my cam from his engine then it is not a Solid Roller, It is hyd roller. It is not 250 duration, it is smaller, and it is in the 10 to 1 compression ratio sir.
07-21-2016, 12:50 PM
#36
Team Owner
I was thinking Diehard was also solid roller. Only relatively few of us on the forum actually have 420+ ci small blocks motors
07-21-2016, 02:07 PM
#37
I'd be interested to know your timing curve. At some point I would like to address my locked out timing, but for now it just flat out works. No stumble, or bog what so ever. Easy starts hot or cold, and no ping at any road condition. The down side.....I lost a few mpgs and at the present time get maybe 12 mpg if the wind is in my favor.
In comparison my 355 got 17 mpg with the same gears, but running a 2000 stall. Now I run a 3000 stall with the 3.70 gears.
In comparison my 355 got 17 mpg with the same gears, but running a 2000 stall. Now I run a 3000 stall with the 3.70 gears.
I built a 10.7:1 377 for a friend with similar set up. It had something like a 3.4 ring an pinion with the same .64 OD (mine's a 4:11). We could get down to 1500 RPM in fifth with his. By 1800 you could ease in the throttle and start pulling quite well. His cam was similar but 112 LSA vs my 110 LSA, installed with four degrees advance vs my two degrees. His also had a Performer RPM Air Gap vs my Victor JR with a 1" spacer.
I think his typically gets 2-3 more MPG than mine. I get about 14 consistently. I'm in the Ozarks and the hills hurt the mileage and are a factor in the ignition curves. I've tuned cars that are pretty happy right up until we try to climb a hill in OD.
07-21-2016, 02:16 PM
#38
I think those factors can make a difference as well as spark plug heat range. On iron head engines I have found deburing sharp edges in the combustion chamber can make a difference too.
07-21-2016, 03:19 PM
#39
Melting Slicks
Adam
07-21-2016, 03:23 PM
#40
Melting Slicks
Related question: When you've got a high compression engine that's right on the border of knocking like this, does EFI help to reduce knock risk?
When you are at cruising speed and only push the pedal slightly you're thinning out the AFR and can get that knock- but an EFI is supposed to keep a constant configured AFR AND EFI injectors maintain the same level of fuel atomization at high and low air velocities, unlike a carb, right?
Adam
When you are at cruising speed and only push the pedal slightly you're thinning out the AFR and can get that knock- but an EFI is supposed to keep a constant configured AFR AND EFI injectors maintain the same level of fuel atomization at high and low air velocities, unlike a carb, right?
Adam