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I am building a 78 x 100/2400cc engine. Heads were built by Bothers Machine with 44 x 38 valves/dual springs. 186/86b cam w/ 104 lc. Static compression measures at 10.2:1. 5.325” H beam rods
In the mock-up of the bottom end the #4 rod is hitting the cam. It is a smaller base circle cam supposed to be good for up to 78 stroke. Glad I am measuring everything 3 times.

Could I retard the cam timing by 4-6 degrees vs clearance the rod ends? I believe this would move up the power band by several hundred RPM. That would be ok for my application. Engine is replacing a Porsche 616 that made power 3000-6000 RPM
Any input appreciated

Correction
Cam is 163/86b

Hi Druck1, 1 question. What journals/rod bolts are you using? My little experience is that retarding/advancing is helping a bit, but does not give you millimeters more clearance. Only tenths.

Ps. Is cyl nr 2 not causing any issues?

also have you got the piston and cylinder supporting the rod in its normal position when assembled .

These are H beam T1 rod ends with 5/16 bolts.
Seems like the “ears” have enough meat to allow clearancing.
#2 ok, but will recheck

I think that 55mm t1 journal in combination with your (short) rod length is causing your issues. A chevy 2" or 2l 50mm journal would give you more clearance. But because you already have the parts id try to make it work. (If you do not have to remove too much)

Mark

Belt sander, meet rods, once you have triple checked the cam orientation... piston sans rings in bores.
make up and end-to end balance rig and make them match, if not, send out.
DIY clearancing a nitrided cam can cause issues, and make certain to take the super hard edges with a diamond hone...
(the existing edges at the sides of the lobes, not around the clearancing...)

Web likely has jigs for cam clearancing and can check,straighten as needed after the deed.
Use Webcam if it comes to that.

Thanks for the help here
Rods will meet sander at my local machine shop
They do a fair amount of race engine work so are right for this job
All fitting has been done with pistons in the barrels