engine overhoul

71 Scout 2 was king enough to pm me the cam specs he recommended. Again, this isn't a cam grind that ihon has used but if anyone is willing to try it and return with some feedback that would be great.

"the cam specs I posted have a brand new (for 2008) lobe, so no I don't have dyno results. Like I mentioned before I don't have the time nor the resources to test every possible combination.
Here is was my suggestion:

intake
rated duration = 256
duration @ .050" = 212
lobe lift = .305"
valve lift w/ 1.6 = .488

exhaust
rated duration = 260
duration @ .050" =212
lobe lift = .296"
valve lift w/ 1.7 = ..503"

the "off the shelf" comp cams 83-201-4 specs as such.

Intake and exhaust are the same lobes

rated duration = 260
duration @ .050" = 212
lobe lift = .293"

as you see they are really close. The profiles I recommended are just newer with quicker ramp rates.
 
Jeff,
thank's. I too had received the specs in a very kind pm from 71 Scout 2. Unfortunately I had not had the chance to post.
I think we could all gain from a real trial of this or a similar grind.

Robert
 
Heath,
I would put it in my engine if I was building one.

If you compare the old and new lobe profiles the lift integrals are much better now then before. More torque and a broader power band due to more lobe volume and higher lift velocities.

I agree with 71 Scout 2 that this cam with 212 degrees of duration will like compression to be bumped like it sounds like you will be doing. Advance it a few degrees. You can ask that the cam be ground with 4 degrees advance in it.

One other thing on lobe centers. I like 110*-112 for short duration cams like this. I save 108 and smaller for strict racing applications. Jmho. :gringrin:

Robert
 
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Ok I'am ready to build this beast will the silvolite pistons be good for this build if so do you carry them, or where do I get them
 
Ihon can get silvo-lites. They can also get everything else you need.

They are the best piston on the market unless forged are required. Imo.

Robert
 
Robert,
you definitely have a preponderance of real world experience regarding cam specs for various applications. All I know is what I remember from various hot rod mags over the years, and what I've learned from mayben and the like trying to keep my two geriatric IH's (occasionally) roadworthy. In any case, here's a thought with regard to "lobe seperation" and IH motor applications:

in general, I've been led to believe that the result of increasing lobe seperation is to increase idle vacuum and broaden the power band, but decrease peak torque. Conversely, decreasing lobe seperation will decrease idle vacuum and quality, due to the increased overlap, but improve peak torque. The powerband does become more "peaky," though.

In high performance use, where cam profiles May be on the ragged edge to begin with, I think it is common practice to increase lobe seperation on a given grind in order to increase "streetability." clearly, improved idle and possible computer interaction May be enhanced by this approach.

For IH applications, though, we are quite far from what a hot rodder would consider the "ragged edge." and rarely is computer interaction an issue. For that matter, IH engines are not well suited to revving far past the torque peak in any case. Thus my theory that an IH application might very well benifit from a cam grind with a relatively narrow lobe seperation. Your thoughts?

Charlie
 
Charlie,

fact's first. Generaly speaking "torque" is of a finite quantity and: small lobe centers mean power comes in later and falls off earlier but is bigger when it peaks Large lobe centers. power comes in earlier and falls off later but is smaller when its peak.

If I had to come up with an analigy: torque is like a cake. You can sit down and eat the whole thing at one sitting and get one big hit or have one piece after dinner every night for a week and savor it.


My thoughts on lobe separation angle are this for heaths Scout and any heavy car, truck or boat. Cam selection is the single most important piece of the engine building game. These are again my opinion based on the engines I have built and what I expect to get out of them. Since this is a thread for heaths build I would like to keep this blurb in that context not a “hotrod” context.

If I build an engine for a person I ask that they take a week and write down on paper what they intend to do with the vehicle. What is in there opinion the most important characteristic of the operation of there vehicle. This is what I use to gage the build.

In heaths case I have already expressed the duration window. 206-208 degrees @ .050 max. For this I recommended 110 lc based on my opinion of how much overlap tolerance the project had. Lc changes double the effect on overlap or lift at tdc. This controls scavenging and in a large part how the engine will respond to exhaust and header changes. I don’t think headers are in the cards. It also effects the dreaded exhaust reversion that causes a rough idle and low suction ( high manifold pressure) at idle.



We ask that the engine have a power band that comes in strong early and sustains it’s self over a long period of time. We need it to lug it’s way around at 1000-1200 rpm crawling over rocks. This is where I stress the point on over lap most. To much overlap and cylinder pressure won’t be a big help until it starts to clear out. The custom cam profile we talked about 212* has 4 degrees more duration than my initial recommendation of which 2* from each lobe will effect overlap or 4 more overlap. I moved my recommendation for lobe centers to really 112-110 for a compromise on power band width and overlap. Bumping his compression is more important with this cam to further bolster low end.

In this case I feel a good solid idle and nice off idle throttle response is imperative. Thusly wider lobe centers help reduce overlap and augment what he is doing.

This is not a simple question to answer. You can ask ed iskendarian, schneider, vic jr, nick arias, david crower, gayle banks, or bubby wilton etc etc and each one will give you a different answer none of which are wrong. That is why I like to see test data on stuff before I recommend it.

I will often times take weeks before I bite the bullet and commit to a grind. I honestly doubt all of my rambling will help but. What the hell.:gringrin: :smilewinkgrin:

Robert
 
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Robert,
that is an outstanding cam application analysis! Its great to have guys like you that know what they are talking about on tap to answer these questions. You properly zeroed in on heath's intended application. I was conjecturing generically, on my (likely mistaken) opinion that sv's by their nature operate in a relatively narrow rpm range. So the burning question is: when are mm and you going lock on some dyno time, and do a full on sv parts thrash on cam swaps, head porting, intake and fuel system combos, ignition variations, and headers and mufflers!

Charlie
 
charles brown said:
Robert,
that is an outstanding cam application analysis! Its great to have guys like you that know what they are talking about on tap to answer these questions. You properly zeroed in on heath's intended application. I was conjecturing generically, on my (likely mistaken) opinion that sv's by their nature operate in a relatively narrow rpm range. So the burning question is: when are mm and you going lock on some dyno time, and do a full on sv parts thrash on cam swaps, head porting, intake and fuel system combos, ignition variations, and headers and mufflers!

Charlie
Click to expand...

You got sum kinda inside gummint track on manipulatin' sumbodies lottery my way????

Maybe I need to do a daily stint up on the always popular "albertson's corner" with the "wil wurk fer dynotyme" sign???

In actuality...we May be able to do this but not real soon (the dynodeal!). But mos' likely will involve a stroker 152 or two...I know that will git chawlee's attention! Ya want in on this one??? Robert's a big gun on this and will lead the way, I got dave in my corner to grind cast outta holes in the head, no tellin' what kinda shit is gonna roll downhill when I git 'em both together! Robert's already spoutin' shit about using briggs and stratton rods with ceramic bearings from precision bearing, a 4-71 huffer, and four 1904 carbs...burnin' kerosene so it's IH appropriate.

But...that's a subject for a new thread real soon, don't wanna keep pollutin' this one!
 
Heath,
some more tips for your build.
The semi-closed combustion chamber cylinder heads (ex 359489-c3) should be around 81-83cc's like you mentioned. You lose just under 2cc's per .010" you take off the cylinder heads for the first .040" or so, than it starts to decrease very slightly.
Putting notches in the block will decrease your compression ratio. It'll add roughly 2-4cc's (304 and 345 is 4cc's) to your chamber volume.
Here is a picture of a notch for the exhaust. Notice that there isn't really much material removed.
notched_bore.jpg


Another thing about the closed and semi-closed 345 chamber is that in stock form the intake starts to stall (flow wise) around 210-230cfm. The older open style don't have this problem, neither do the 196e/392e styles.
The best way to crack 230cfm is to mod the chamber. Here is a picture of a simple mod to keep things flowing.
345_head_unshrouded_359489-c3.jpg

This mod will also drop your compression ratio by adding roughly 3cc's to your chamber volume.
With the mods I have listed in this post you will be in the 200cfm range and starting to stall at the higher valve lifts.
Just keep this in mind if you are planning on modding the block and unshrouding the valves. You May want to shave another .020"-.030" off your cylinder heads.
 
Heath,
depending in the cam you choose, you will have less than .1 lift @ tdc (between int and exh stroke)

on the sv heads the valves are up in the chamber a minimum of .375. Clearance should not be a problem if you run a flat top@ piston at deck height. (0 decked)

even if you/I think you have enough clearance, always verify valve to piston clearance is a minimum of .125.!!

Closest clearance will be 15 * btdc and 15* atdc.

Robert
 
Heath,
pretty much like Robert said.
In stock form the 304e and 345e are basically non-interference engines, meaning there will not be any piston to valve contact even with a timing set failure.
Granted, your engine will become an interference style engine when you are finished building it like you want.
Even with all the alterations done to the engine there will be no problems with piston to valve clearance in a flat-top piston IH sv engine under normal operation.
Myself, if the application needs a close piston to valve clearance because of some reason I set the intake to a minimum of .060"-.080" and the exhaust .090"-.120". It all depends on the type of cam (solid vs hydrailic), rpms turned, connecting rod material, the list goes on.
Here's my thought process on why I have two different specs. With the intake the valve chases the piston down the bore. The piston is in direct connection to the crank, therefore it pretty much has to follow the stroke of the crank down the bore and the clearance only has minimal change. With the exhaust on the other hand, the piston chases the exhuast valve. The exhaust valve has only the spring to pull it up into the chamber and nothing else. This gives the exhaust valve a little bit of freedom and the clearance can change quite a bit (especially if you float the valves).
Anyways, enough tech back to your build.
Just to reassure you (and others). You will not have any piston to valve clearance problems in a flat-top (emissions, "e" style) IH sv engine. You will end up with .300"+ on the intake valve and .350"+ on the exhaust for piston to valve clearance (even after all the milling).
So as you see, more can come off the cylinder heads if someone wanted a little more pop in the pipes.
Sort of getting ahead of the build, but something I always look into is cam lifter preload. Like a few other engines out there, the stock rockers don't allow for any lifter preload adjustments. In stock form IH sv's run more than enough lifter preload, and your build will most likely add to that. Myself I run .050"-.100" preload on the street (perferred closer to .050") because I don't want to be back into the engine anytime soon. On something really hot that you know is going to be a high maintenance engine I'll set them to something between .025" and .050" preload. It just seems to help stabilize the valvetrain at higher rpm.
 
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