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Crane 168731
Going thru and freshening up. Rings, bearings etc.
Gen 4 454 .030 over Speed pro 2465 (9.5:1) Block set up for cam thrust plate. Rectangular 188 heads, Ferrea valves, Merlin intake. Blue 800 Holley Gil manifolds with long risers(dry to 6" from transom). It did have a Crane 134241 in it with a lode going flat so time for roller. The 731 seems to be a decent option. Other suggestions? |
Originally Posted by convincor
(Post 4615439)
Going thru and freshening up. Rings, bearings etc.
Gen 4 454 .030 over Speed pro 2465 (9.5:1) Block set up for cam thrust plate. Rectangular 188 heads, Ferrea valves, Merlin intake. Blue 800 Holley Gil manifolds with long risers(dry to 6" from transom). It did have a Crane 134241 in it with a lode going flat so time for roller. The 731 seems to be a decent option. Other suggestions? I chose the 791 (168791) cam. Same basic specs but has 114 degrees lobe separation instead of 112. It brings up the power curve about 200 rpm and will offer a more stable idle. But the major benefit is less chance of exhaust water revision. I don't know if they make the 791 for gen 4 but... |
After all the searches and reading I ended up going with the 731. Seems to be the most recommended.
Was running a cam with 112* and with the length of the risers had no issue. I believe the 791 in gen IV would be the 139771. My block has the provision for the gen VI thrust plate so went the the 168731 and gen VI timing chain. |
What exhaust are you running? The 731 cam is good for around 5200-5400RPM in a 454. If you want to be more in the 5600-5800 peak power range, the 741 would work for that.
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Gil manifolds with custom risers which are dry to about 6" from the transom.
Rather be in the lower rpm range being bottom end is just stock rods with stock 7/16" bolts.https://cimg5.ibsrv.net/gimg/www.off...20427161c3.jpg |
Your safe either way. I've even ran stock BBC 3/8 rods with arp bolts for years at 5,800 plus rpm's. Just an FYI. btw your right those some custom risers. Well done! |
Crane recommends 99896-16 springs and steel 7° retainers and keepers with the 168731.
These springs have a 528 lb spring rate. Others here recommend comp 949 with 437 lbs or isky 8005a with 400 lbs. With 10° retainers. What do you guys think? |
I got my info directly from a crane rep on the tech line. I went with all crane parts. Same springs. Less pressure will help your valvetrain last but could also affect hp. Closed seat pressure is also very important. Be careful not to mix up retainer and lock geometry. I'm not a bbc guru but mixing manufacturers is typically a bad idea in most cases. |
https://www.offshoreonly.com/forums/...e-springs.html
This is one of the threads I found regarding springs for the 168741 which Crane recommends the same springs. Seems like a lot more spring than the 8005A. From the Crane catalog 99896-16 1.540 1.140 0.760 150 lbs @ 1.900 560 @ 1.150 1.135 0.755 528 lbs/in. "Various Big Block hyd roller apps. Harmonics optimized for sustained high RPM marine use. Solid flat tappets with tall assembly" |
I used the Crane recommended springs when I did my 731 upgrade. They are on the heavy side for the 731 cam, but I never had any issues.
Knowing more now though, I'd probably choose the Isky's. |
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