Cam question

[ameristar1]

Justin, the timing of the cam and the specs are what makes the engine work. The heads controll the power of the engine. As much air as you can get through the heads, that is where the power comes from. Now, the cam is the heart of the engine. It opens and closes in reference to where the piston is in the cyl. (BTDC) and opens a certain height (lift) and stays open for a certain amount (duration). That is for the intake. The exhaust uses timing of the valve for a partial scavenge effect. You can effectively move more air into the cyl. if there is overlap between the exhaust and intake. This allows the exhaust to be evacuating the cyl. until there is negative pressure and the intake will open. It pulls air from the intake in. Now, the more overlap you have, the engine will want higher revs to run within the power band. There is a TON more to it than that...but that should get you close.

Ameristar, do you sell cams too?

SWS

Not yet, just know a person or two that can get the job done. I may do like Agnem and put together a line of 2 or 3 grinds for the IDI's with the guy I work with and market them. There's a need for this. Once I find a source for fresh cores, I could do it. Regrinds wouldn't be a problem, it's just that with the reduced base circle, depending on how far you go with it, you'll need to get custom pushrods to preserve the geometry in the valve train.

You guys tell me what you want your motors to do and we'll work it out.

 

[ameristar1]

Did the factory turbo IDI have the same cam? Does anyone have cam specs for the 1st series of Powerstroke, and would those specs be a decent start for a turbo specific IDI cam?
Travis..

Cam in the factory turbo was is the same as the NA, and the same problem that afflicts the IDI affects the PSD. I think as far as IH is concerned, that the cam design philosophy is to not leave any room for growth; either that or they are guessing. Makes you wonder.

 

[Agnem]

Unfortunately an interference engine such as ours also limits your options on scavaging. Our exhaust valve must close before the exhaust stroke has even ended, so the first thing the intake air does when the intake valve opens is run into a **** of hot exhaust gases. It's almost like you'd need a little lob on the cam to re-open the exhaust valve just a hair so the turbo fed air could scavange on the intake stroke. Certainly not something that is going to work at higher RPM's.

 

[ameristar1]

Unfortunately an interference engine such as ours also limits your options on scavaging. Our exhaust valve must close before the exhaust stroke has even ended, so the first thing the intake air does when the intake valve opens is run into a **** of hot exhaust gases. It's almost like you'd need a little lob on the cam to re-open the exhaust valve just a hair so the turbo fed air could scavange on the intake stroke. Certainly not something that is going to work at higher RPM's.

So the running clearances are tight between the valve and piston? How much room is on there?

 

[dyoung14]

So the running clearances are tight between the valve and piston? How much room is on there?

wouldnt you get more clearences with milled pistons and(or) custom valve releifes cut?

 

[ameristar1]

wouldnt you get more clearences with milled pistons and(or) custom valve releifes cut?

Absolutely. It's just a matter of putting the time in to make it work. There's only .380" lift and nothing for duration to start with, there's got to be more room in there.

 

[crashnzuk]

Cam in the factory turbo was is the same as the NA, and the same problem that afflicts the IDI affects the PSD. I think as far as IH is concerned, that the cam design philosophy is to not leave any room for growth; either that or they are guessing. Makes you wonder.

What about the cam timing of other turbo diesels? Would the IDI vs direct injection make cam specs mutually exclusive, or would the theory be interchangeable between the two. I'm sure the more modern engines have had lots of R&D on cam design.
Travis..

 

[ameristar1]

The things needed to design a cam properly for a 4 stroke engine are the same regardless of fuel type and injection system type. The OEMs do spend a lot of time doing what they do, but most of the time it still is a compromise, and lets be real; the people who count the money don't want the motor running too good. I've seen this happen over and over. The engineers come up with an excellent design, but can't get it produced. So instead, they are told to only go so far and not any further. When it comes to truck engines like the 6.9/7.3, they just put enough cam in there to make it run and not break.
With almost 30 years of advancements since this engine was produced, we can now have cam profiles that can wake these older engines up and make them live up to their potential. I would like to see an IDI hit 200-250hp before a turbo gets brought into the picture. I believe the heads, compression and fuel are already there to do that, but the cam has not been up to *****, not by a long shot.

 

[crashnzuk]

I don't doubt that they come with compromised design elements, but the newer engines run cleaner and make good power. I would think there are some cam timing tips in the newer stuff that could be made to work in our engines.
Travis..

 

[icanfixall]

Newer motor have 4 valves per cylinder plus they are completely an all electronically controlled motor. Some of them actually have as many as 8 fuel pluses per combustion stroke....

 

[david85]

Yeah and some of them come with extra valve stem side loading free of charge

 

[ameristar1]

Yeah and some of them come with extra valve stem side loading free of charge

Oh the joys of modern technology.

 

[seawalkersee]

Roller rockers cut down on that a bit. Seriously though, for the question about the milling/valve reliefs, yes, you can cut reliefs in the pistons. Not sure how much you want to cut though. The gross valve lift is 1.7 (or is it 6) times that of the TOTAL lift on the cam. Knowing the difference in depth needed is determined by the lift at TDC and/or the duration of the piston as it is "parked" at TDC. Now, that being said, you need a certain amount of clearance between the piston and valve. There are people in gassers who have kiss marks on their pistons from the valves which did not hurt the engine. With the diesel, the deck of the piston must remain fairly thick for two reasons. 1)the extreme pressures that the diesel makes in the cyl. and 2)closely related (directly) for the heat. If the therma efficiency of the piston is compromised in the valve reliefs, the pistons will crack or they will develope holes.

SWS

 

[ameristar1]

Roller rockers cut down on that a bit. Seriously though, for the question about the milling/valve reliefs, yes, you can cut reliefs in the pistons. Not sure how much you want to cut though. The gross valve lift is 1.7 (or is it 6) times that of the TOTAL lift on the cam. Knowing the difference in depth needed is determined by the lift at TDC and/or the duration of the piston as it is "parked" at TDC. Now, that being said, you need a certain amount of clearance between the piston and valve. There are people in gassers who have kiss marks on their pistons from the valves which did not hurt the engine. With the diesel, the deck of the piston must remain fairly thick for two reasons. 1)the extreme pressures that the diesel makes in the cyl. and 2)closely related (directly) for the heat. If the therma efficiency of the piston is compromised in the valve reliefs, the pistons will crack or they will develope holes.

SWS

According to Russ, the rocker ratio is 1.5 to 1, Gary gives the lobe lift at .253, so total lift at the valve is .380". I got a chance to see the ports on the heads, and like one other poster said, they are huge. This cam doesn't tap the full potential of airflow available with the stock heads and induction system.

 

[seawalkersee]

If you look at Agmen's photobucket, you can see the cutaway version of the heads. We could use some 1.7s for these heads...but I think the cam will be WAYYYY less expensive.

SWS