68Nwprt's Engine Build

[70bigblockdodge]

The summit cam is 81% the Lunati cam is only 78% the summit is a better choice. A Mopar with their .904 lifter dia. should be around 85%+ resulting in good ramp speed and a advantage over ford and gm crap. Out of those two I would use the summit. You get those numbers from dividing the @.050 by the advertised duration BTW all Mopar performance cams are 85% so don't count out a Mopar 383/440 magnum resto cam. You can do worse.

 

[68Nwprt]

The summit cam is 81% the Lunati cam is only 78% the summit is a better choice. A Mopar with their .904 lifter dia. should be around 85%+ resulting in good ramp speed and a advantage over ford and gm crap. Out of those two I would use the summit. You get those numbers from dividing the @.050 by the advertised duration BTW all Mopar performance cams are 85% so don't count out a Mopar 383/440 magnum resto cam. You can do worse.

What does it mean that a cam is 81%?

 

[tallhair]

Picture of finished crank. About hour and a half work.
View attachment 51710

Looks fantastic. Have you mic'd it and if so what bearings do you need to use?

 

[70bigblockdodge]

What does it mean that a cam is 81%?

Perfect can lobe would be instantly to max lift, open fully, for the whole duration, or 100%. This is a impossible to reach number. The higher the percent the faster the ramp speed the longer duration at a high lift or further open valve. The perfect curve would be squared off the vertical sides = 100% so a ramp that is 85% of vertical has good opening speed for a given duration. I would draw a picture but I can't do that on my phone.

 

[68Nwprt]

Perfect can lobe would be instantly to max lift, open fully, for the whole duration, or 100%. This is a impossible to reach number. The higher the percent the faster the ramp speed the longer duration at a high lift or further open valve.

Makes sense now. Thanks.

 

[68Nwprt]

Looks fantastic. Have you mic'd it and if so what bearings do you need to use?

Standard bearings, .003 clearance mains and .002 rods. Clearance on the mains is a little on the high side, but... it is what it is. Rather have bit more clearance than be to tight.

 

[vdk2010]

The summit cam is 81% the Lunati cam is only 78% the summit is a better choice. A Mopar with their .904 lifter dia. should be around 85%+ resulting in good ramp speed and a advantage over ford and gm crap. Out of those two I would use the summit. You get those numbers from dividing the @.050 by the advertised duration BTW all Mopar performance cams are 85% so don't count out a Mopar 383/440 magnum resto cam. You can do worse.

Very interesting information! Do you have a link to a mopar performance cam you would choose?

 

[70bigblockdodge]

P445278 or P4286677 Jegs has a special on one of them right now and they run specials from time to time. I'm not sure how to get a link done on my phone but if you put in Mopar performance in the search box then click on cams and lifters.l

 

[vdk2010]

Thanks! I found it. When the time has come, I will ask again which one is good for which setup ;)

 

[commando1]

Perfect can lobe would be instantly to max lift, open fully, for the whole duration, or 100%. This is a impossible to reach number. The higher the percent the faster the ramp speed the longer duration at a high lift or further open valve. The perfect curve would be squared off the vertical sides = 100% so a ramp that is 85% of vertical has good opening speed for a given duration. I would draw a picture but I can't do that on my phone.

It's my understanding, the faster the ramp speed, the noisier the valvetrain. Yes?

 

[70bigblockdodge]

On a hydraulic there should be no noise something is wrong. It just gets the valve open further sooner and holds it longer for a "smaller duration/more livable or practical". In other words the 78% lunati cam will reach .300 lift later than the 81% summit can which will hold the vavle open at least .300 for a longer period than the slower lunati cam. Even though they both might have very similar specs duration and lift, the summit cam should have a advantage, is at .300+ ,arbitrary number under peak lift, for longer.

 

[vdk2010]

If someone is interested in a crash course, this Video helped me understand Camshaft specs a little better!

[video]https://youtu.be/zUnJXSOSRU4[/video]

I have to say, I still don't get it all but it helped..!

 

[70bigblockdodge]

I didn't have the patients to watch every minute but jumped around and waaaaay to much detail info. Lift is free, doesn't really matter how big you go on lift it will not effect drivability. But you will get to a point where your low duration/low overlap for nice smooth driving can not support the lift you want, example would be approaching the 100% number we were talking about for ramp speed, again impossible to get to that especially with a hydraulic flat tappet cam. Because the exhaust and intake are right next to each other the valves tend to "overlap" open at same time. On a can with a small duration number this overlap is very minimal and Suzy secretary is happy her car idles smoothly and has good pick up below 3500 rpm that she never goes over or stock. Add duration on intake and exhaust and the overlap increases, idle and vacuum get worse/less and the power range starts to go higher. If you want higher lift adding duration is necessary. With faster ramps you can move you lobe centerlines a little further apart (increasing lobe seperation angle) thereby decreasing overlap and having a bigger cam that drives/idles well, getting back some of the drivability that you lost. Hope that makes some sense lol. This is why modern roller cams in new cars idle smooth and make lots of power they have very fast ramps that you can't get with flat tappets unless your are out on the ragged edge and reliability suffers.

 

[68Nwprt]

Got some work done over the weekend. She's bolted in and patiently waiting for me to finish.

 

[70bigblockdodge]

Looking good.

 

[68Nwprt]

Looking good.

Thanks.

 

[68Nwprt]

Haven't posted in a while so here's a quick update. Engine fired up yesterday. Original start up I think I had the Oil pump drive 180 off if that's possible. Couldn't set timing. Got that resolved today.

 

[70bigblockdodge]

Slot in oil pump drive should be parallel with the cam when #1 is at TDC on compression stroke. Then drop dist in with rotor pointed to #1 on the cap.

 

[68Nwprt]

Slot in oil pump drive should be parallel with the cam when #1 is at TDC on compression stroke. Then drop dist in with rotor pointed to #1 on the cap.

Thanks Dave, I think I had pump drive off one tooth which put the rotor slightly after no.1, rather than slightly before. All good now though.
:3gears: :3gears:

 

[commando1]

Im happy its so far do good. Hope it stays up.