Help picking 525SC rebuild cam
 

I'm at the point I need to finalize my cam selection so I can get my short block together.

So here's where I'm at, + .030 on the cylinders so 461 C.I., went with 6.385" rods and JE 257969 flat top Pistons with -3cc relief, I'm estimating 8.0:1 to 8.25:1 compression depending on how far in the hole the piston ends up being in the hole. 5-6lbs boost from Weian 177 with planned upgrade tp 6V-71 down the road. I went with EQ320 heads, 2.25/1.88, no porting, just cleaning up the runners and shaping the Chambers, 11/32 valves. Hardin/merc/gil replacement manifolds with low rise Gil E-tops https://cimg9.ibsrv.net/gimg/www.off...422723e721.jpg
And I'm leaning towards Johnson 2112bbr lifters vs the morel 4603's and all of this on a 1994 27ft warlock world class, so around 3,500 to 4,000 lb boat with a bravo 1 behind it.

My goal is to run the motor 4,000 to 4,200 most of the time crusing/skiing, run it hard for an hour at 5,000 if I'm making time, and max out around 5,600 to 5,800 RPM. It's a river and lake boat so I won't be running it WFO very often.

I'm looking at 4 cams, 3 Lunati's and a comp, all with billet cores (Lunati is +$200 for the custom cut due to the billet core). I don't know enough to be dangerous so I could use some advice because I only want to do this once.
1) Lunati# 20110669 -ADV 293/303 [email protected] -234/244 lift 629/612. 114LSA 2* advance built in

2) Lunati# 20110670 -ADV 297/307 [email protected] -238/248 lift 640/629. 114LSA 2* advance built in

3) Lunati# 20110671 -ADV 301/311 [email protected] -242/252 lift 640/629. 114LSA 2* advance built in

4) Comp Cams# 01-446-11 -ADV 289/297 [email protected] -235/243 lift 610/627 114LSA ?* advance built in

What do you think I should go with and why?

Do I need the billet core upgrade on the Lunati's?

I like the #1 Lunati cam. Others are too big IMO for your wants/cubes/exhaust. Billet core is worth it vs cast. I assume the Comp is a cast core?

I'd use a 525EFI cam. Its a Crane 168741 with a 114 lob sep instead of the standard 112. If you had the higher risers, I'd say use the regular 168741.

Griff is the resident 525sc master....but my thoughts... with a good cam and heads, it flows better, so you may have to spin the blower a little harder to make your boost goals, And shooting for 5800 rpm is really going to have spinning. Im not sure you want to spin it that fast.

It's got the teague over drive kit, smaller pulley and super chiller, but your right, I'll be hitting 13k on the blower at 5,327 RPM so I'll just have to stay below 5,300 until I get the 6v-71 set up on there, but one step at a time. I still want to build for 5,600-5,800 max.

Griff, why the EFI cam over the 1st Lunati?

MT to the courtesy phone please, I'd appreciate your thoughts on this too :readinghelp:

Thanks

Probably not a lot of difference. BBC's heads are known to have less flow on the exhaust side, so I'd rather see the increased lift there than on the intake side.

The difference between the first lunati, the comp grind, the 741, and 525efi cam, will be negligible.

I would go with the billet core.

the cams in my engines are 236/245 , .629/.632 lift, 114 LSA. 468 cubes. Theyve been in there since day 1. What has changed, is cylinder heads, superchargers, intercoolers, ignitions, and compression ratio.

from the original setup, they were 9:1 with dart alum heads, 177 blowers with single carb and 5psi. Now they are 8:1 , EQ iron heads, 420 blowers with chillers, twin 850 carbs, 8.5psi, cams retarded 4* (114Icl). Same hull, same drive height, same props. Boat is a solid 20mph faster.

^^^^^^ That is impressive!

Thanks Griff & MT.

What about the melonized or "everwear gear", worth the upgrade? I'm running the original Merc ingition.

Thanks

went from barely being able to turn 28s to 5000rpm, to turning them 6200rpm.

cam choice is important, but its not the end all make or break like some would like you to believe. At least not with roots blown bbc. The power is in the heads , and blower setup. Unless of course the cam is way out in left field

is there a rev limiter ? Which merc ignition?

It's a TB-4, merc cap, MSD blaster 2 coil, MSD 6A (not sure if i need to run this), and not sure on the Rev limiter, what does it look like, or what's it marked?

I know there's a adjustable knock sensor module up by the cockpit too.

Thanks

The Crane cams can be run with the stock iron distributor gear.

Stock 525SC has rev limit at 5350-5400 rpms. Rev limiter is part #41 Genuine Mercury & Mercruiser parts. WIRING HARNESS AND ELECTRICAL COMPONENTS

Thanks Griff, I went through my dissassembely pics and I don't have one of under the ignition module... So I'm not sure if there was a Rev limiter on there or not..

Should I remove it when I put it back together or just wait while I'm running the 177, until I put on the 6v-71?

Also I'm running the original distributor, does that have anything to do with what gear I should get on the cam?

Thanks

From the RPMs I want to run, I'm assuming I'm going to remove the Rev limiter, wither it's on the initial rebuild or when I upgrade the blower.

So should I run the everwear/melonized gear on the cam?



So I noticed the crane 741 and the 525efi can both have higher lift on the exhaust VS. the Lunati's that have higher lift on the intake, running a low boost blower, what effects will going one way VS. the other will there be? For example will exhaust valves heat up more with more intake lift, will get more cylinder pressure with the higher intake lift, etc...?

Don't look into it much when exh valve has slightly less or higher lift than the intake.
When exhaust has higher lift than intake, it is usually because it is the next larger lobe in the catalog in the same lobe family.

Exh under much higher pressure when exh valve opens than intake when intake opens. Thus why more important to have larger int valve at the expense of a smaller exhaust.

Oh, please don'r compare exh valve and pressure escape to a soda can. That doesn;t work well. :)

Distributor gear
 

Ok I've done some more research and it seems to come down to 2 choices for the pressed on distributor gear on the cam. I'm running a HV melling oil pump, so whats a better combo

1) Get the "everwear" gear pressed on the cam and run the original melonized distributor gear
OR
2) Get the standard iron gear on the cam and run a Howard's bronze distributor gear?

Which combo will last longer pushing the HV pump?

Choice #1. Never had a problem. Never liked the idea of a bronze gear wearing and depositing that into the oil. Which then goes thru your bearings.

I've also done some more research and it looks like I can run a gen 6 step nose cam with retainer plate. I have 2 threaded holes at noon and 6, so I can run the retainer plate vertical instead of horizontal?

If I run the gen 6 step nose cam with retainer, I do have to run a gen 6 timing set due to the smaller Diameter cam gear bolt pattern.