JD33

I've been told these 525SC engines should have the valve springs replaced at around 400 hrs., is this true?

If so can somebody recommend what springs to use; maybe a good aftermarket replacement?

I have both engines out to take care of a couple of anoying minor oil leaks so if I should be replacing the springs I'll do them now.

Griff

Since they are out, you should really do complete top end refreshes. Valve jobs, head gaskets and valve springs.
The stock cam is a Crane 132561 and pretty sure the stock springs were Crane 99839-16.

Knot 4 Me

I'd go ahead and swap the cams over to rollers while you have the motors out.

MILD THUNDER

iTrader: (3)

That would be a nice upgrade. However, probably looking at 800-900 per engine to convert to a hyd roller.

IMO, that 1600-1800, would be best spent on getting some slightly larger blowers, like a 250-256 blower. Run 6-7psi and they will wake up big time. Blower shop 250 would be really nice.

IF the blowers havent been rebuilt, and have 400 hours, i'd get them gone thru now.

Griff

It will cost at least $1200 more per engine to change to roller cams.
Having the blowers gone through is good idea.

mcollinstn

Thise are pretty mild cams. If you weren't already taking the engines out, I would say to not worry about the springs yet. Since they are coming out and you're putting fresh gaskets and such on, go ahead and put new springs. If you were planning on pulling the heads off, go ahead and bore notch the cylinders and lap the valves. Costs no extra money, just a few hours of your time.

MC

JD33

I really don't want to tear into the engines too much, they both run perfect and the compression checked out very good as well as a cyl. leak down test. The previous owner was very good on his maintenence, they've seen a pretty easy life so far. My plans are to go through both of them next winter and do some upgrades; roller cams, better rods, etc. but right now I'm limited on the budget since I just bought the boat this past Sept. and still need to buy a bigger lift and some dock modifications.
The blowers look like they have been apart before, they showed no signs of fuel in either of the gear cases.

MILD THUNDER

iTrader: (3)

The stock rods arent bad. Unless your going all out with lots of boost and gonna try to make 800HP, the stock rods are fine with good bolts.

Roller cams are a nice upgrade. you will be limited to about 575-600HP with the stock blower. Bigger blowers, like a 871, its not that hard to make 700+ out of the 454 blocks.

supermx96

I am in rebuilt now of mine, I have swap the rod for Callies Compstar H Beam, .030 oversize with block valve notch, Speed Pro forged piston, new aluminum Hedelbrock Performer RPM head 45 cfm more than the stock head, Crane costom grind 114lsa with less overlap 67 deg than the stock one 74 deg to keep the boost in the cylinder, estimate comp ratio at 7.5:1 - 7.6:1.

I will possibly get a porting job on the head for an extra 30 cfm or so.

I estimate at least 650HP possibly 700hp if i am lucky.

I think i will be able to keep the boost at 5.5 with the stock pulley due to less overlap on the cam and smaller intake runner 315cc instead the 325 or 335 stock.

The stock cam is very not good for this surpercharger setup.

I keep the comp ratio low for a bigger blower in future and boost arond 7 with a 250 or 671 blower.

MILD THUNDER

iTrader: (3)

If your going to the aluminum head, I'd get the compression up. The stock 7.5 or so to one is pretty dismal. 8.5:1 with the aluminum heads is good.

Sounds like your on the right track, but no way 700HP with the stock blower and 7.5:1.

I can tell you this. I ran 460CI, dart race series alum heads, mild port work, 308cc intake runners, hyd roller 236/245 114LSA, compression was about 8.3:1. With the 177 blower, I was turning the blower at 2:15:1 overdriven. Making about 4.5-5psi. I then went to a 250 blower, drove it at 1.68:1 overdriven, gave me 5psi. 1.8:1 gave me 7psi.

On my engines, if i wanted 7psi, I probably would have had to drive the small 177 to 2.3:1. Turning the engines to 5500RPM, thats almost 13000 rpm blower speed. Talk about a heat pump. The bearings probably wouldnt last long, and the added boost would really do nothing for power.

The more cam, better flowing heads, will drop the boost psi. Once you start getting into that stuff, you outgrow the small blower quickly.

To get near 700HP, I'd say 250/256 blower, up the compression, 7-8psi with a chiller. Im currently rebuilding mine, H-beam rods, JE pistons, and adding 8-71s. If i get 700-725HP at 5500-5700rpm I'll be happy.