6Time's Stroker build ...Round 2

[6TIME]

So after a set of mangled cam bearings and some odd bottom end vibrations from round 1, I've decided to make some changes for round 2 of this stroker project. I have decided to keep the stock cam thrust pin setup for one more try before calling it quits. The main differences are going to be the crankshaft weight and higher compression from a different 7120 head that I had previously running on a healthy 4liter. It's basically all an experiment that hopefully creates a smooth reliable runner. Thoughts? Here's the list:

*93 HO block reused, zero decked, .030 overbore, mains and cam tunnel checked for straight.
*Balanced 321723 12CW crankshaft going in, Previously balanced 4CW short snout crank coming out.
*Reusing 258 rods, 26cc 677cp pistons, and rings.
*New rod, main and cam bearings.
*Reusing 63500 Lunati Voodoo cam. Machine shop did micropolish journals, as they did find the surface nowhere near acceptable for optimal bearing life. Lobes and cam gear wear looked excellent.
*New lifters
*Reusing Romac timing set.
*Swapped 7120 heads to another ported one I had laying around with 57 cc chambers vs the 65cc chambers on the previous LS valved head. the compression should jump from (8.6SCR and 7.4DCR) To (9.4SCR and 8.0 DCR) with the smaller chambers. It has Stainless undercut 1.94/1.50 SBC 11/32 stem valves, 3 angle grind, and LS beehive springs and hardware. Hopefully it'll still happily drink 87 octane......

[6TIME]

Parts are starting to go together!


12cw crankshaft shot peened and polished


Crank in block with end bearings in to check for runout in center journal.


My machinist swears by angle knurling the rear main surface on 2pc seals. He threw that in for free


Same Pistons and rods goin' back in..


Bottom end all together. Had to space out the girdle a bit more because there was some casting nubs that stuck out a bit further than the 4CW crank. Shoulda checked it before the cleanup and balance job..


Hopefully this doesn't happen again!!!!

[604rail_king]

looks good! in past experiences ive always run new rings when reusing pistons. rings are cheap, and its easy to flex hone the cylinders if needed.

did you machine off the snout on the 12 wt crank and re-mill the keyway, or just going with the collar method?

[6TIME]

The shop turned a bit of the snout off up to the end of the keyway slot. I had to space it out about .250" or so with a thick washer. I also had to grind a notch in the washer to clear the keyway.

[604rail_king]

ah ok. i kept a hb off a 258 so i could make a collar from that if needed.

what oil pump are you using this time around?

[SilverXJ]

Angle knurling is the way to go.. but I though it came stock with that already? I would rethink using the stock pin and spring setup though.

[6TIME]

Silver, The crank had a smooth seal surface to start with. I have no idea if they started angle knurling from the factory at some point or not? As for the factory spring and pin setup...The motor is already in so I'll consider it one more experiment in finding out exactly what had caused my cam bearing wear.

[6TIME]

It's running and all is good! The power is being sent thru an Ax15 5speed, 31" Duratracs, and 3.73's. The bump in compression really makes a huge difference at lower rpm's. The motor is waay more torquey under 2500rpm. I can drive all day long shifting at 2k. Pretty impressive torque curve for a 4.6 liter motor! It's pulls hard up to about 4800 or so, but it feels like it could use a bit more cam with the increased stroke/displacement. I used Melling jb-2011 lifters this time and I already have a couple noisy ones on cold startup Pulled the cover and found 3 that were soft enough to push down with my hand. Bleeding down too fast? I recently found that Melling and Sealed Power are starting to box lifters made in Mexico....

[SilverXJ]

I would run it a bit more before you consider the lifters having problems. Could be a bit of dirt or some air in them still.

[6TIME]

I would run it a bit more before you consider the lifters having problems. Could be a bit of dirt or some air in them still.

I'm giving them some time but they seem to be getting worse. It now misses a bit on startup instead of just clacking. If they pump up solid while the engine's running I think all of the oil is being bled out when they don't have oil pressure. I wouldn't think that air was trapped in them because it'd compress and make noise while running right? The head will come off in another month or so. I'm planning to reaming out the pushrod holes so I don't have to pull the head when dealing with cam/lifters. I had a similar issue with a set of Comp lifters and few years back...