[charlie66]

So im trying to change to 3/8" push rod diameter . Im getting .025" of clearance on the intake side at the bottom of the hole when on the base of the cam. Is this too close . What is the minimum clearance that you guys would leave? I will be running hight boost presures in this engine and at around 6500 - 7000 rpm. I already milled out .090" of material on the intake side of the hole.. I thought it would be enough..

Thanks..

[steve25]

I don't grind them out anymore as it's too time consuming!
I use a 1/2" drill bit in good size drill ( as in big!) and drill down in from the top side 1" and then in from the bottom side 3/4"

If need be after that then grind some on the bottom side to flare that out more.

If you care to what I do when I sleeve the push rod hole to open that area up as much as possible is to just drill all the way thru and then sleeve it with 1/2 OD Aluminum tubing.

Once the tubing is sealed in place you can still easily grind a flare in the bottom.

But in general I think your just fine with .025" clearance now as long as your not running a solid type Cam with lash, if so I would want .035" just to be safe.

[charlie66]

Thanks steve.

I dont think id have the nerve to drill all the way through but ill do the 3/4" in the bottom . I was surprised that it was the closest when on the base of the cam. I thought the problems would occur as lifting .

The cam is a solid roller. .580 lift.

[steve25]

It can be crap shoot, as different Cam base circle heights produce different effects as can lifter plunger heights in concert with the base circle.

One other thing I would do is to check the contact area between the lifter end of the push rod and the push rod seat in the lifter.

Clean them both up from any oil the color the ball/ lifter end of the push rod with a black marker, then set it in the lifter and spin it enough to see the contact pattern.

The ball end of the push rod might be too big for the cup in the lifter plunger and making the push rod sit up too high.

Ask me how I know this some day, lol!

That motor when running should be enough to scare you pretty good Charlie, enjoy!

[charlie66]

Thanks Steve, ill check that ..

Yes it has gaven me the pucker effect in the past ..

Should be better this time around . I just received my Moldex billet crank and Carrillo rods. Now i can push it alittle more..

Thanks!

[gtofreek]

Usually at rest on the base circle is where I see the closest also. Get as thick wall of a pushrod that you can. I believe 3/8" can be up to .136" thick wall. That will reduce the risk of pushrods flexing[especially on the exhaust side]. Can't have too stout of a pushrod.

[charlie66]

Originally Posted by gtofreek

Usually at rest on the base circle is where I see the closest also. Get as thick wall of a pushrod that you can. I believe 3/8" can be up to .136" thick wall. That will reduce the risk of pushrods flexing[especially on the exhaust side]. Can't have too stout of a pushrod.

Mine is .130"

Thanks

[steve25]

What helps big time to having push Rods not flex is running a good valve spring that can control its own mass, as in no surge.

Loss of control even at only 4500 rpm can lead too issues, it just takes a little longer to see the bad results then at 7000 rpm!

[charlie66]

My springs are 295lbs on the seat and 680lbs open...

[steve25]

Yikes! I think your covered then, lol!

[charlie66]

Ive been running it like that for awhile now. Seems good.

But now i have to control my urge to turn the boost up having this new improved lower end because the block is now the weak link..

[steve25]

Control Luke, you must learn control!

[charlie66]

[QUOTE=steve25;6108036]Control Luke, you must learn control![/QUO

Lol. True!

[charlie66]

I bought a 10" 3/8' round file. I got 4 done so far. This takes alot of time . Its nerve racking to me. I dont what to break through. A 1/2" drill bit fit through . So i decided to do it by hand slowly ..

[steve25]

Don't fear breaking thru , if you do you can fix it, it will just be more time input.

Since your running 3/8" push Rods if you do break thru then use Brass tubing to sleve it since its thinner wall then Aluminum tubing.

If you have the hole bigger then 1/2" where it passes the runner area then you will need to slit open the Brass tubing lenght wise so you can bend it into the bigger radius needed to load against the hole wall.

I do this with a cut off disc , but the very sharp edges left can be deadly so be super careful!

[charlie66]

I got them all to fit. Took me 7 hours.lol. I wound up cutting all the push rod guilds in two because all my rocker tips fell off center of the valve tips. Once lined up i welded them back together. Doesn't look like i broke through.. I was skeptical on the end holes by the threaded water outlets.

Now i can finally drop my new crank in to see how it fits... I have to say Joe at Moldex really did a dynamite job on this crank . Its a work of art.

[73 TRANSAM]

Good job Charlie! I am sure she's going to hurt some feeling this summer.

[charlie66]

Originally Posted by 73 TRANSAM

Good job Charlie! I am sure she's going to hurt some feeling this summer.

Thanks Edwin, hopefully not mine.lol-

[steve25]

So you got 3/8" push Rods to fit into stock guide plates made for 5/16" push Rods?

[charlie66]

Originally Posted by steve25

So you got 3/8" push Rods to fit into stock guide plates made for 5/16" push Rods?

Yes. I ground the slots to fit the push rod .