New 4.1 Stroker Build

ek02

Well-Known Member
Joined
Jan 31, 2008
I decided to build the best 4.1 block I have. It's an unusual 044 block. It seems to be one of the last 4.1 blocks cast. I already fitted it with a RJC girdle. I sent the main caps to RJC and they machined them for me and sent a shim kit. I just got a RPM 3.625 stroke 4340 crank just like the one in my spare motor. It balanced with almost no weight removal on the spare. Next I will need a set of H beam rods, 11-1 custom JE pistons, rings, wrist pins, and spirolocks. I'm in no rush and will get the parts as my budget allows. It will have a 4" bore to make rings easier to find. I tapped the oil galleries for TA allen head plugs. A few photos attached of the progress so far.
 

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ek02

Well-Known Member
Joined
Jan 31, 2008
Yes, NA with a 150 shot of N2O. The engine in my truck now is a 484 4.1 casting with a roller cam, GN1 heads, RJC girdle and pan . I also have a spare stroker motor, 291 casting engine with flat tappet cam and iron heads. I'm looking for rods next. Probably Molner stock length if I can find someone to machine the side clearance. Molners are too tight to use as delivered. I used them unmachined in my spare engine and the side clearance was only .006. Double that would be ok.
 

ek02

Well-Known Member
Joined
Jan 31, 2008
I scored a set of stock length Molnar rods for a great price. Most places I called said they were on backorder. The place I found them at said they had them in stock. The funny thing is they were drop shipped right from Molnar in Michigan. I bought them from a place in W. Virginia. They will probably need to ne narrowed for more side clearance. I haven't checked it with a feeler gauge yet, but using a dial caliper on the crank and a mike on the rod big end, they look pretty tight. I may need to get more cam clearance also. The Molnars are made for stroker builds with more clearance on the sides compared to most other rods, but It has to be checked. I can also now clearance the oil passage where the rod bolt hits with a stroker crank. I have a standard bore stock piston I use for that job.

IMG_3491 (1).jpg
 
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WarWagon

Caustic Cacophony
Joined
Mar 10, 2007
Odd how that is, My set of rods were drop shipped the same way right from Molnar. Nice score
 

ek02

Well-Known Member
Joined
Jan 31, 2008
I mocked up the block using a stock bore piston so I could grind the block for clearance at the oil passage. I've done 4 blocks this way over the years, but it still makes me nervous. My Chinese sonic tester says I have .179 of thickness left, but I would say it's more like .125. I ground the head of the bolt slightly and ended up with .060 clearance. I measured the side clearance on the rods and they were all .010-.011. Molnar must have machined a little more side clearance in their rods or my RPM crank is different than my spare engine. It only had .006 side clearance. It may be a while before I can get my JE spherical dish pistons made. It's going to be expensive.

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Pronto

You can't knock them up with spit.
Joined
Dec 9, 2002
Seen that area ground through and a thin brass tube slipped into the oil passage. That was on a 109 block.
 

ek02

Well-Known Member
Joined
Jan 31, 2008
I guess that's the biggest thing, not grinding into the oil passage there?
Yes ,for sure. I have done 4 blocks this way with no problems. Weber Performance grinds all the way through and puts a tube in the passage. I found a GM front cover I bought new years ago to use for this build. The block it was on cracked the main webs. A bit too much N2O and timing. I also have another brand new GM cover that has never been used. Saving that one for later. I can't use the front cover from my current engine because it was machined along with the pan rails for the girdle. Some machine shops don't like to mess with shims, so they cut the pan rails and front cover so the girdle lays flat on the main caps and block.. Then the oil pickup surface has to be machined also. I had to wait 9 months for that girdle to be done. This new engine has the caps machined by RJC and the shims used to get the clearance between the block and girdle to .005. Girdles are a pain, but after cracking my main webs, I have not had a problem with my current engine that runs a girdle. Also, my MSD ignition box cuts back on the timing when the N2O hits.
 

ek02

Well-Known Member
Joined
Jan 31, 2008
I got the RJC crank scraper and oil pickup spacer yesterday. The scraper is not made for a stroker crank. I had to widen the reliefs for the rods on 2,4,&6 to get the.060 clearance I like to have. The rods on 1,3,& 5 clear fine . With a girdle and a RJC deep oil pan an extra long extension is needed to put the pickup at the right height in the pan, or the pickup can be extended. The spacer is easier, but I had one come loose once so I always use red Loctite on the threads.

IMG_3496.jpg IMG_3498.jpg
 

liquidh8

Active Member
Joined
May 17, 2006
Nice! I plan on doing a girdle also. I have to contact rjc to get the caps machined. I'm not sure my local machine shop had done girdles, though they ha e built some high hp drag and circle track engines.
 

ek02

Well-Known Member
Joined
Jan 31, 2008
RJC can machine the caps and weld the spacers to the rear main cap. Then whoever sets up the girdle will have to shim it. I built my front cover today. All the threads were helicoiled from the first time it was built, a carry over from my motocross days. Don't have to worry about stripped threads in the aluminum. I used the Kenne Bell oil pump booster plate and adjustable pressure regulator I had from the first time I built it. I had stainless allen head bolts already that were 1/8" longer than stock due to the booster plate. The end play is .0015 with new gears. Packed the gears with Vaseline and put it on the shelf in a plastic bag for later.

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ek02

Well-Known Member
Joined
Jan 31, 2008
I put some cheap disposable cam bearings in the block and slid a flat tappet cam with the same lift and specs as my roller in to check rod to cam clearance. I took a little more material off the cam side of the rods and tapered the bolts more. I decided to have a cam ground to the same specs as the one in my truck, but I may do a reduced base circle. I wont have to worry about rod to cam clearance and maybe I can do a little more lift. It may be the end of the month when I order it because I plan to be out of town for a while in early August and don't want any deliveries. Same with the pistons and rings.
 

ek02

Well-Known Member
Joined
Jan 31, 2008
I called Comp to get an order started. They told me no cam cores for 8 months. I wanted to get the cam degreed with my Rollmaster chain and make sure the rods have enough clearance. I'm pretty sure they are OK but just wanted to be sure since I used a flat tappet cam to check it. My only other option is to use the roller cam from the engine in my truck. It kind of puts this project on hold. I can still order the JE pistons, pins, and rings though.
 

626gn

Well-Known Member
Joined
Feb 15, 2009
I feel your pain... Duttweiler ordered a custom ground cam for my build back in October 2020, Comp said it would be about a week or two. Over 2 months later Comp said cam cores were still on backorder. Prior to that there was another lengthy delay for custom Diamond pistons since they had closed their factory due to COVID. Luckily the pistons eventually showed up but we ended up just reusing my old billet roller cam so the build could be finished.
 
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