Joel5.0

Nope... it means that in the 180° rotation of the downward stroke movement in an Otto piston engine ...... 90°, or 50% of the stroke rotation â‰* 50% of the piston stroke in the cylinder..... it is more more on the 60%+ side......[sm=WTFsgign.gif] .... for a person that versed in the R:S topic and lateral loading you should know this engine 101 fact.

An please...... no excuses on the possible rhetorical nature of that question....... a direct 1:1 relation as you used below.....

Does not apply to piston location/crankshaft degrees......

86GreenMachine

Dont mean to be a thread stealer.But i have a comp xam XE264HR cam.Im not a roller block,i have flat top pistons,will this cam work in my engine?

Joel5.0

'86 w/E6 heads it may clear..... but I wouldn't even bother to add a cam with those heads.

'86 with any other style heads (TFS TW would be the exception)..... it won't clear.

Hamutoff

If you do nothing but change your RR you will affect the lift AND duration...

5spd GT

Joel, you seem to be taking some past post personal. I am done with this thread now...

Mustangkiler

Again i know peak lift has nothing to dowith ptv clearancei have said that 3 times, i said lift not peak lift again i know peak lift is nowhere near tdc, and howcould a 1.6 to 1.7 roller rocker change duration too? All im asking is if lift has absolutely nothing to do with it at all then why once he changed to 1.7's it didnt clear? The only answer i have gotten is that he had to do be doing something wrong which i doubt cuz hesolder wiser and been involved in 5.0s since back in the day.

midasmustang

im so confused!!!!!!!!!! lol

Joel5.0

[quote]ORIGINAL: 5spd GT

Nope..... calling it as I see it and here is why, so you don't assume anything "negative".......

1. In order to understand the dynamics of a piston enclosed in a cylinder, you need to understand the statics..... statics in a sense of taking some snapshots of the cycle.

2. Taking #1 as a basic rule (similar to the "you need to learn to walk before your run" cliché) you need to understand and visualize the piston cycle in a static mode....... this helps determine and ID position and stroke motion curve.

3. After #2 above, you then start adding all the vector forces involved in its simple up-down motion.....velocity, acceleration, etc

4. After #3, then you begin working all the friction coefficients and all the elements that affect piston speed, acceleration, points of mechanical stress, etc.....

5. Then you add the flow characteristics of a specific cylinder-piston-rod setup (no cylinder heads yet)..... the effects of piston C/H, piston crown surface, seal efficiency, wrist pin position, etc, etc.

6. Then add the cylinder heads and all their characteristics and effects on the cylinder/piston setup.

7. Now add the valves timing effects (cam + valve train), seat diameter, angles, weight, stem length, stem diameter, position, angle, etc.

6. Etc, etc

7. More etc.

If 1-2 are not understood....... how can anybody talk about #3+ ?...

Since you're done at the other thread, again, you're taking things too personal..... oh!.... and regarding your conclusion of......

Wrong assumption....... or did you forget that I also have customers?... have I spent a dime yet? (which was the question)...... nope. Have I had to play the "customer" role for my customers?....... what do you think? .... wouldn't that give me the factual data and experience to answer as I did, w/out being "ironic"?......

Joel5.0

The only way to explain that, is doing a PtV measurement with both rocker ratios. If you look at the lift @.050 during the overlap, using the intake opening and exhaust closing events (when the piston is very close to the partially opened valves)..... you're looking at valve lift differences in the .005" - .020" range/valve...... if you have a 1.6 rockers setup with a PtV clearance near .020", it would explain why they will not clear with the 1.7 rockers..... reason for the importance of the measurements.

"Seat-to-seat" valve duration is not affected with the rocker ratios, if you look at the duration of valves lift with the 1.7 rockers, and compare it against the same lift figures with 1.6 rockers, you have the same lift at a different duration...... OR ..... the time the valve is open past a specific lift point will be longer with 1.7 rockers when compared vs. the 1.6 rockers.

Mustangkiler

ya well thats basically all i was saying to begin with just not in such smart words it seems, eventhough its not at peak lift its still at a higher lift with 1.7s than it would be with 1.6's at the point in which it would cause ptv issues when they are slightly opened and piston is near the top which the extra lift would be causing the ptv problems which would mean it has something to do with ptv clearance.