Holber race car gets a new engine. Progress Report
08-13-2008, 05:13 PM
#241
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The GT vs S3 cam comparsion shows that the GT at the same crank angle is now in the accelerated angulation of the lobe for the 20 degree crank movement. that makes sense. However, this doesnt explain the difference in the differences of distance for cam settings between 928 models. GTs .3mm, S4 .2mm, 85s .4mm (differences betweek passenger and Driver)
So, Im not too worried about it, as i did a lot of these tests and measurements with the holbert car after the cam change.
since it worked on that car, i trust it will work on this one. as a note, the holbert cams were more GT like in the sense that they had an intake cam more advanced than the intake on the 85s. BUT, they were both timed from the factory at 2mm for 20 degrees crank movement.
as another note, my compression for all cylinders were all right around 190psi, with the driver side having the highest compression by a couple of PSI. High was 195 and the lowest was 190. this was done hot.
mk
So, Im not too worried about it, as i did a lot of these tests and measurements with the holbert car after the cam change.
since it worked on that car, i trust it will work on this one. as a note, the holbert cams were more GT like in the sense that they had an intake cam more advanced than the intake on the 85s. BUT, they were both timed from the factory at 2mm for 20 degrees crank movement.
as another note, my compression for all cylinders were all right around 190psi, with the driver side having the highest compression by a couple of PSI. High was 195 and the lowest was 190. this was done hot.
mk
Oops, 1.05 mm is not right, here are the precise measurements for 2°.
Top row of 32V'r holes - 1.408 mm
Bottom row of 32V'r holes - 1.384 mm
Top of belt (74.5 mm from cam center) - 1.298 mm
Remember, GT intake cams are advanced 8° versus S³ (open at 3° ATDC) so you are checking at a different lobe thickness.
S³ and S4 intake valves open at the same point, 11° ATDC. GTS open a little later, 13° ATDC, and the (cold) difference between banks is .25 mm.
Checking (with the 32V'r at TDC#1) with a hot engine is the ideal.
Top row of 32V'r holes - 1.408 mm
Bottom row of 32V'r holes - 1.384 mm
Top of belt (74.5 mm from cam center) - 1.298 mm
Remember, GT intake cams are advanced 8° versus S³ (open at 3° ATDC) so you are checking at a different lobe thickness.
S³ and S4 intake valves open at the same point, 11° ATDC. GTS open a little later, 13° ATDC, and the (cold) difference between banks is .25 mm.
Checking (with the 32V'r at TDC#1) with a hot engine is the ideal.
08-13-2008, 05:41 PM
#242
Under the Lift
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A suggestion.... Don't get too wound around the axle on the initial cam timing settings. Ball park is good enough now. Once the engine is running, and the rings sealed, take compression with the engine hot. Both sides should be the same. The side with higher compression has cams advanced (intake valve closing sooner) with respect to the cams on the other side. You can use Ken's tool to take a reference cam timing setting when you get equal compression. After that, use Ken's tool to advance, or retard both sides an equal amount to get the torque curve you want. Mark is expert at figuring torque under the curve between the shift points he wants. Time the cams to get the best compromise for those shift points. I'd anticipate, he'll want his cams set 5 or more degrees retarded from the WSM specs.
Thanks!
08-13-2008, 05:54 PM
#243
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The GT vs S3 cam comparsion shows that the GT at the same crank angle is now in the accelerated angulation of the lobe for the 20 degree crank movement. that makes sense. However, this doesnt explain the difference in the differences of distance for cam settings between 928 models. GTs .3mm, S4 .2mm, 85s .4mm (differences betweek passenger and Driver)
GTS, S4, and S3 cams all have different amounts of lift, and so have different ramps to reach that lift.
At 20°, each type will have a different lift measurement compared to the others, and each type will have a different lift measurement at 20° versus 22°.
So you're saying the driver's side is advanced...
08-13-2008, 06:40 PM
#244
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No, im saying that all the cylinders were equal and by chance, one was a little higher, by 5psi. I think it was a random cylinder as 2% variation is pretty good for any engine.
again, why wouldnt the passenger side be higher if i had the cams indexed equal? Driver side was 2mm at 20degrees after tdc. By the way, the compression was the same with the holbert cams as well. The only time it wasnt, was when i skipped those 3 teeth in that world challenge race practice session.
mk
again, why wouldnt the passenger side be higher if i had the cams indexed equal? Driver side was 2mm at 20degrees after tdc. By the way, the compression was the same with the holbert cams as well. The only time it wasnt, was when i skipped those 3 teeth in that world challenge race practice session.
mk
08-13-2008, 08:27 PM
#246
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If in doubt, go with the 32V'r! The 32V'r measures the angular relationship of the exhaust cam to a fixed point on the head, like the water pump pointer does with the balancer. It does this regardless of belt length, or block/gasket/head thickness. As long as the cams are stock, IE. the LSA has not changed, the reading will always be what the factory intended. Period, stop, shhh.
Set the cams to:
¼ | ⅝ New belt, cold
-1 | 0
When the belt stretches, it will end up something close to:
¼ | ⅝ 1K mile belt, cold
-3 | -1
When hot, they will be -1°, which is a good starting point for max HP.
Going from +3° to -1°, I gained >15 rwhp, same dyno session. Remember, you lost 20 somewhere...
There is at least 1 mm of movement, there.
1.3mm at the belt surface = 2°. The tooth is 2.5 mm lower, so it takes even less.
08-14-2008, 04:19 AM
#249
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Mark hasn't reported in yet, but the motor is in the car. We are not getting more that 4-5 hours a night to work on it, so it will be a couple more days. It seems we became clutch num-nuts tonight as we spent most of the time after dopping the motor onto the mounts putting the clutch in, getting stuck on one step or another then restarting. First the shaft would go into the bearing, then the arm would not go over the ballcup. Then... Anyway, we've both done enough clutches that we were just stupid tonight. But that's done. Next, it's the headers from hell. Maybe we'll finish tomorrow night, but, believe it or not, I've slowed Mark down to a sane pace.
Last edited by Bill Ball; 08-17-2008 at 09:07 PM.
08-14-2008, 04:27 AM
#250
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We worked on the F'n clutch 'til just a couple of hours ago. Like a couple of rookies, we forgot or ignored the need to put the clutch lever arm on the bushing first. we tried to do it so many different ways, i lost count. I think we did the equivilant of 4 full clutch jobs tonight! 
The car has never beaten me, but tonight Ill call it a draw! Not much done EXCEPT, the STROKER ENGINE IS IN THE HOLBERT CAR, and the clutch is in and much of the wiring is ready to be plugged back in side.
The dreaded headers are next, and then the fun stuff. alternator console, radiator, solder a few broke connections, and put the colder plugs in.
Ive already backed out the fuel regulator by 1.5 turns, so it should be down to near stock fuel pressure.
Still a chance this thing might be lit by the weekend!
Bill has all the wide band O2 sensor equip so we can monitor what the car is doing through all of the WOT rpms. (when it is time to go WOT
)
mk
Mk
The car has never beaten me, but tonight Ill call it a draw! Not much done EXCEPT, the STROKER ENGINE IS IN THE HOLBERT CAR, and the clutch is in and much of the wiring is ready to be plugged back in side.
The dreaded headers are next, and then the fun stuff. alternator console, radiator, solder a few broke connections, and put the colder plugs in.
Ive already backed out the fuel regulator by 1.5 turns, so it should be down to near stock fuel pressure.
Still a chance this thing might be lit by the weekend!
Bill has all the wide band O2 sensor equip so we can monitor what the car is doing through all of the WOT rpms. (when it is time to go WOT
)mk
Mk
08-14-2008, 09:13 AM
#252
Burning Brakes
OK, when you say fuel regulator...this thing is still CIS, right? Because if it is, the CO setting that's where the distributor is does close to nothing everywhere but at idle. The one to mess around with is the warm up regulator (once you unplug it and get one that has the vacuum enrichment if you don't already).
08-14-2008, 09:25 AM
#253
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08-14-2008, 09:51 AM
#254
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Fuel injection baby! 
Good job boys. Clutches can suck if you miss one step. I remember once when I forgot to put the guide tube on and then there was something else later... in and out 3 times before I finally got it right. I feel your pain.
Good job boys. Clutches can suck if you miss one step. I remember once when I forgot to put the guide tube on and then there was something else later... in and out 3 times before I finally got it right. I feel your pain.
08-14-2008, 11:17 AM
#255
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the LH cars have a fuel pressure regulator, but the Holbert car has the risng rate adjustable fuel pressure regulator. 1-2 turns drops the pressure by near 20psi. (as i was up near 72psi with the 5 liter ) . with the 30 lb injectors, i think I wont need more than stock fuel pressure in the mid 50psi range.
It should idle and run like it did before, as we are not changing really anything other than the pump
mk
It should idle and run like it did before, as we are not changing really anything other than the pump
mk
OK, when you say fuel regulator...this thing is still CIS, right? Because if it is, the CO setting that's where the distributor is does close to nothing everywhere but at idle. The one to mess around with is the warm up regulator (once you unplug it and get one that has the vacuum enrichment if you don't already).