4.1 stock block build

What kind of mods did you have to do to the rods? Any pictures? I am very interested in doing something like this.
 
The rods have to be ground down on the side that comes close to the cam, and usually the bolts have to be ground down also. It depends on the cam. Roller cams come closer to the rods. Molner rods have more clearance than all the other H-beams, but it still has to be checked. I give them .060 rod to cam clearance measured with a feeler gauge through the cylinder with the crank, cam, and timing gears and chain installed and degreed. Only three rods have a clerance problem, but they all have to be ground to keep the weights close. Changes in cam timing affect clearance. You also need a nuetral balance damper and flex plate. Here is a photo of a set of rods modified by Chris Hogeland. The area needing clearancing is where the bolt threads come through the rod on the cam side. The bolt is ground down on the threaded end.

uty3esed.jpg
 
ek02 said:
I have built three 4.1's with stroker cranks. Custom pistons and modified rods for cam clearance, if using H beam rods, are needed. Rod to cam clearance needs to be checked in any case.
Click to expand...
what was the cost of pistons?which crank?external or internal balance?thanks
 
I think I will be looking for a 4.1L block now. A 4.5L stroker would be awesome. Any strength issues that you have run into ek02?
 
Yes. My # 2 & 3 main webs cracked all the way to the cam bearings. This was N/A on Nitrous with some detonation. Any V6 production block will fail in the main webs if you detonate it enough. Most builders use billet caps at least on the # 2 & 3 mains. The caps have to be fitted to the registers and the mains line bored and honed. I went with an RJC girdle after that failure, and a better tune with a progressive controller. No problems since. The girdle involves machine work on the block and caps, and line honing. The other issue is the head bolt holes cracking into the water passages. Countersinking the bolt holes like a 109 block helps that problem. Some 4.1 blocks have a lot of core shift and thin cylinder walls. Sonic testing is not a bad idea. Also, final bore size is dependant on the rings available for that bore size. Custom pistons can be made any size, but rings may not be available for that bore diameter. Follow Mike's build in this thread if you have a good machinist and you will be OK, or find a vendor on here that knows how to build one.
 
Ordered up the full rotating assembly from Mike and Marianne. Also will be changing cams to a custom roller in the 220ish range. Wasn't a build I was planing on but should be fun ;)

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Undercover, let me know how things go. I won't be ready to dive into this until August at the least..
 
Zack, if you are going to do this, you might want to start looking for a block now so you can have it checked out. I only know one guy in this area that had one and he had issues with the threads in the block cracking.
 
ZNix said:
Undercover, let me know how things go. I won't be ready to dive into this until August at the least..
Click to expand...
Will do. My block looked ok, no cracks in the deck, old school felpro 1000 gaskets looked perfect. Possibly upgrading to a bigger turbo like a 67 or 71hpq. Keep in mind more cubes will probably loosen the converter stall a bit.
 
Last edited:
Pronto said:
Zack, if you are going to do this, you might want to start looking for a block now so you can have it checked out. I only know one guy in this area that had one and he had issues with the threads in the block cracking.
Click to expand...

Good thought Pronto, I will be on the lookout for one. I think Intercooled88's might have a few I could look at.
 
FYI,if anyone wants to clearance their rods,Weber offers this service. It includes grinding the material off of the rods while held in place in a fixture that removes the exact amount of material needed. They also cut the threaded end of each bolt that is associated with the relieved side of the rod. They cut it into a conical shape which creates more clearance between the bolts and cam.
 
Oil pan ideas
In dredging up my 4.1 after couple years of abuse
Shout out to full throttle for quick shipping of my new king bearings

The 4.1 oil pan is different than the turbo one and does not have the thicker bottom flange area where it bolts to the block
This causes some warping and leakage
Rjc sells a nice deeper pan with the reinforced area but that's not in my budget right now

What are the other 4.1 guys doing??
I'm thinking about creating my one reinforcements to help spread the load in each of the 14 bolts



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