As we continue to test, we have observed a common situation:
The brake specific value usually falls in the range of between .42-.45 under a full throttle run up to the rpm where the hp peaks. After peak hp, the brake specific number rises substantially for the rest of the run and climbs to...
The balcony looked very good, but we didn't jump yet.
The more testing we do, the more the issue points toward the problem with reversion and lack of power and rpm potential being in the cylinder head itself.
It doesn't respond well to cams, pipes, type of carburetion, ignition timing, valve...
In the past, with an earlier version of this motor design, we did rig that one with dual carbs and ir manifold. We did that test to understand whether the reversion was due to interaction between front and back cylinders or just confined to each cylinder. The reversion and lack of high rpm...
Engine sounds fairly responsive, not the best it's ever been, but not terrible. On the dyno, you can tell that the engine is not pulling hard on top where is should and seems to labor
No hydraulic pucks - shim under style buckets
The current cam grinder has no recommendation for us on the...
Some more tests have been done.
1. Completely new style ignition system - revoved electronic module and replaced with a more conventional inductive pickup with weights for advance.
Result - no change, so ignition is not an issue.
2. Looked at A/F between front and back cylinders and saw that...
Automotivebreath,
The current thinking on the smaller camshaft selection is to be able to detect whether or not we do actually have the wrong sized ports. We believe that if 213 duration works in increasing power and reduced reversion, then that may point in the direction of port sizes being...
Couple of things tried, again with no different power results:
1. Replaced the spring tensioned cam chain shoes with solid adjusters. These were tightened after the engine came to temperature and there is very little play or room for chain to deflect. Thying to rule out cam timing changes as...
Did the run at intake and exhaust cams set to 112 centerline and basically nothing changed form other settings. Hp, torque, and rpm peak we all within about 5% of other cam settings.
It sure seems that there is something far overshadowing the normal tuning options here. No matter what tuning...
No detonation except when we radically change the ignition curve (very high advance rate). Normally, we run around around 26-28 degrees total advance with no problems.
The plenum size I have scoped out will mount in place of the existing carb on the end of the manifold and will be made to be...
With the currrent set up, we will swap the o2 sensor between cylinders to check for lean and rich conditions.
Good to hear confirmation that the plenum will make carb seem bigger.
More than one ignition system has been looked at. Also, we looked at the timing marks during a pull to 6K and it...
Did the 112 and 112 intake /exhaust cl test yesterday. As usual, this made almost no difference in the peak power or rpm where it made it. The reversion did seem to be a bit less as compared to other cam settings in the past. Still, though, during a pull on dyno, your hand will get wet with...
I should be able to try the following tommorrow.
Going on the idea of opening up the centerlines, I'll try with the cams at 226@050 intake at 112 cl and 234@050 exh at 112.
If this shows improvement (reversion and power), then probably go even further with lowering the overlap. What would be...
In my mind, the reversion is a problem because at the rpm it is noticed (visually) coincides with where the power seems to drop off. As the rpm's come up, the reversion gets worse and never goes away. It makes me think that the rpm potential of the motor will not be achieved until the reversion...
Pat,
Very much appreciate your suggestions.
The a/f ratios are being read by an oxygen sensor on the front headpipe.
The next step for me is to try the 112 centerline intake and exhaust.
On the plenum idea, I think a "box" can be made up to bolt onto the existing intake manifold flange...
