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Old 11-12-2008, 09:50 AM   #31
Michael Mayben
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Default Re: engine overhoul

Quote:
Originally Posted by charles brown View Post
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
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!
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Old 11-21-2008, 01:22 PM   #32
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Default Re: engine overhoul

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.


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.

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.
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Old 11-21-2008, 02:03 PM   #33
Heath
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Default Re: engine overhoul

Ok if I do all this and take .030 off the heads will valve to piston clearance be ok.
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Old 11-21-2008, 02:50 PM   #34
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Default Re: engine overhoul

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
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Old 11-23-2008, 05:01 PM   #35
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Default Re: engine overhoul

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.

Last edited by 71 Scout 2; 11-23-2008 at 10:40 PM..
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