525sc's Rebuild
 

I am doing a complete rebuild on 96' 525sc's. All new internals, Dartcast iron heads, cam, etc. Need suggestions. What size heads and cam? Looking for aprox 75-100hp. Can not do intercoolers. Anybody have any success putting reliable power into these motors?? Motors r being done locally on Long Island.

Re: 525sc's Rebuild
 

Who on long island?

Re: 525sc's Rebuild
 

There are people on here who are a lot more expert than me but, from what I have read on OSO: Don't increase the boost with that blower without adding an intercooler. It is a Weiand 177 and will cause to much intake heat. You may want to sell that one and move up to a 250 or even a 420 mega blower.
The AFR 305 heads seem to be the way to go. With a good porting job, you won't need to raise the boost any. With a good roller cam, that combo should give you what you are looking for.

Re: 525sc's Rebuild
 

thanks for the info. Anybody have some more suggestions??

Re: 525sc's Rebuild
 

Who's doing the work on the motors?

Re: 525sc's Rebuild
 

JC, i do have somebody to do the assembly. basically buying all new, sending out the block, etc for bore, balance. Also plan on having them dyno tuned. i am sure you have experience with these motors. Any suggestions would b appreciated.

Re: 525sc's Rebuild
 

Install Crane 741 hyd roller, upgrade to B&M 250's, dual Nickerson/Holley 750's and add 5 1/2 psi boost = 600+ TRQ & 600+ HP. Baby the bravo's and it will be reliable. Idles at 750rpm with max hp around 5400 rpm. B&M 250's have the same height as the Weiand 177's.

Re: 525sc's Rebuild
 

Here's an old thread about cam choice. Cam choice will also depend on the flow numbers of the heads you get.
http://www.offshoreonly.com/forums/s...w%2Fwieand+177

I put the Crane 731 cam in my 525SC last Spring. It was the only performance upgrade I made. I picked up 50 -100rpms on the top end over the stock cam. I am/was running 7lbs of boost with no cooler. I did a top end refresh last Spring and everything looked fine.

If you are not boating in salt, I would go with aluminum heads.

Re: 525sc's Rebuild
 

thanks Griff, .. Heads, carb jetting, cam. I ill be keeping the stock 525sc carb, intake mani, 177 blowers and crank. Block will most likely be 30 over. My head is spinning...nite nite

Re: 525sc's Rebuild
 

I have used the 741 in a blown 454 with 420 mega blower with great results..690hp on dyno @ 5psi. A good friend used a similar comp version with 174 B&M and dominator carb on a 454 @ 7psi , dynoed 675hp. Both these engines had 8.5-8.75 compression and ported square GM heads with larger valves. I like the added static comp especially with the smaller blowers. The first engine mentioned going on 6yrs and over 250hrs, lots of oil changes and timing never over 30deg total also now at 7psi boost. Just my .02, good luck.

Re: 525sc's Rebuild
 

thanks for the info....any body else ? Gotta keep this post at the top

Re: 525sc's Rebuild
 

Greencard, what heads on your set-up.

Re: 525sc's Rebuild
 

I am the "friend" Greencard is talking about I can Email you the cam specs and possibly the dyno sheets if you give me your address. My heads are stock GM square port. Gil exhaust 1050 dominator B&M 174.

Re: 525sc's Rebuild
 

Why can't you do innercoolers???

The whipple coolers are pricey but only add an inch or less in height. Upping the boost, and adding a cooler, and changing the cam should get you to 600hp.

Re: 525sc's Rebuild
 

dont want to cut into the hatch, not even with the kit that fis into the sunpad foam. Flame arrestors r about 1/2" below. Also, want to rebuild motors completely to keep for next 2-3 yrs. Only so much $$$$ to spend

Re: 525sc's Rebuild
 

cfd12... my e-mail address : [email protected]

thanks

Re: 525sc's Rebuild
 

I rebuilt my 525 Hawk Blower motors-- used all the same components as the stock
engines had, they had 405 hrs. on them. ran 4900 at 72 mph.Everything is new but the block 30 over 468 cu----- now 5300 at 76 mph. with 25 inch props.
Put a set of 27's on an went back to 5000 rpm's at 76 mph I can give you the name of my engine builder if you want + he gave me a 1 year guarantee. So far so good Have 43 hrs. an I'm thrilled ! They are in a 38 Top Gun--Carbon Fiber Boat.

Lucky Strike

Re: 525sc's Rebuild
 

Lucky Strike, did they do any head porting or valve work .

Re: 525sc's Rebuild
 

bringing back to top..............

Re: 525sc's Rebuild
 

You say Dart cast iron heads. I assume you already have a deal found for these?

You are on "a budget", too? The small blower is NOT your friend in this endeavor. You will need to keep boost pressure low, to combat heat, but you can spin it as fast as you need to in order to keep 4-5 psi. In other words, with good flowing heads and a matched cam, you can make your hp goal with no trouble with the little blower, but it would be easier AND CHEAPER to get there with a larger huffer and more boost.

Re: 525sc's Rebuild
 

No special head or valve work, probably should have.

Just stock high performance heads from the Chevy store.

Incanel severe duty valves.

When it comes time to do the heads, probably in 150 hrs, thats the next trick.

L.S.

Re: 525sc's Rebuild
 

Ls, did you have the blowers rebuilt? if so, by who.

thanks for the info

Re: 525sc's Rebuild
 

The best is the Blower shop for rebuilds.

Re: 525sc's Rebuild
 

Mcollstn, i am using Dart or possibly merlin 310cc.with mild econo port. But i will need to stick with current 177 blowers. Are u saying that i will have trouble spinning the little weiand's fast enough(with my stock 3" pulleys) to get back my original boost of 5-6lbs. If that is so then can i raise the static Comp. to maybe 8:1. They r currently 7.5:1.

A reputable engine builder said this could be achieved just by increasing the rod length slightly???

Any one care to advise

Re: 525sc's Rebuild
 

He must be on dust!!!!

Re: 525sc's Rebuild
 

hey jc....care to explain why??

Re: 525sc's Rebuild
 

He wants to change compression height by putting a longer rod in.The right way Dwayne is to put the right piston in the motor to make the compression you want.Adjust compression without changing your deck height.Blower motors like the piston in the bore about .015-.025 in the cylinder.Your merc motor is about that now.

Re: 525sc's Rebuild
 

Rod length will not increase or decrease compression ratio.

Re: 525sc's Rebuild
 

Thanks for the info Jeff, i guess the question is, will i be able to maintain 5-6 lbs boost with my current blower set up while maintaing 7.5:1 comp?

Re: 525sc's Rebuild
 

no problem.

Re: 525sc's Rebuild
 

even with new perf heads??

Re: 525sc's Rebuild
 

What make heads are they?

Re: 525sc's Rebuild
 

A little side not question.

I've been told a 454 will show a lot of benifit from a .030 or even a .060 overbore as it will unshroud the valves. Will you still see just as much benifit with a blower and a slight overbore?

Re: 525sc's Rebuild
 

JC, they r either going to b cast iron Merlin or Dart

Re: 525sc's Rebuild
 

Go with the dart iron eagle 308 heads.They will work fine with 7.5 compression@5-6 lbs. of boost.I would run 8.5 compression instead for two reasons:You will not have to spin the blower as fast to make the boost you want which means less heat.Less heat going into the engine equals more power and less prone to detonate.The second reason is when your cruising you motor wont be in boost. For ex.4000 rpm making no boost[0].This will all give you longer life and reliability.

Re: 525sc's Rebuild
 

You can spin the 177 up to its "safe speed". I'm not sure what this is, but above that the rotors will either sling the teflon strips out or explode. Like I said, I'm sure you are in the safe zone still.

Above a certain flow rate, the rotors start whipping the air. Sort of like any pump that is starving on the incoming side. Like a cavitation. All blowers have an efficiency curve. And it depends on the pressure differential as well as the flow.

On one hand, you can flow say 2000 cfm into a given blower (without falling out of the efficiency curve) at 2 psi differential (into say an intake manifold)...

Same blower may flow 1000 cfm into a 6 psi differential (within the efficiency curve).

And at a certain pressure differential, the flow rate drops dramatically. Say for the example (which is an imaginary blower), you may drop to 400cfm at 20psi.
And 1cfm at 28psi.

Keep in mind, that these numbers are considered to be in the "EFFICIENT" range of operation. You can pulley PAST this efficient range and still get what you're after, but when you operate outside of the efficient zone you are building more heat from the cavitation or "whipping" and your results will not be as good as if you upsized the blower.

And remember, it ISNT what pressure you can ram into the motor - it's what quantity of molecules you can ram into the motor. Hot charge has less molecules than cool charge.

With your 177, I would GUESS than you could still spin it hard enough to see 4psi on a very modified free flowing 454 without falling out of the efficiency curve. 6 psi would yield benefit, but would be generating enough heat to require less than optimum spark lead - or higher octane fuel (both being bandaids).

And yes, longer rods (with nothing else changed) will raise your compression ratio. It will also put your pistons into the heads unless your "builder" can find you some rods that are .020-.030" longer than stock (I ain't never heard of any..). Typically, longer rods are matched to pistons with relocated pin (compression) height.

Re: 525sc's Rebuild
 

The original B&M compact blowers were limited to 12,000 Blower RPM.

Just for the sake of friendly interesting discussion. Not an online argument. :)

A .020 - 030 longer rod is not going to happen.

But with noting else changed a longer rod would make the volume at TDC less and also the volume at BDC less due to the piston being raised in the bore (deck height). So in effect would not both volumes decreasing cancel each other out to some degree?

I am getting a headache thinking about something that could never happen. LOL

Re: 525sc's Rebuild
 

Of course he's not gonna find .030" shorter rods. His "builder" needs to stop talking while he's ahead..

But no, you're missing the obvious on the volume comparison. You're thinking too much (yet not enough!). At TDC the long rod makes the volume less. Yep. At BDC the long rod makes the volume less. Yep again. BUT:

Whenever a small change is hard to visualize, then picture an extreme case. Since rod length (with no other changes) changes the position of the stroke within the bore, then picture a cylinder about three feet long with a "zero cc" chamber bolted on it. Start with a short rod that only moves the piston in the bottom 4" of the cylinder. BDC you got about 33" to the deck. TDC you got 29" to the deck. Veeeery low CR. Now use a long rod that uses only the top portion of the cylinder: BDC you got 4" of volume. TDC you got none. Veery high CR.

And if you are familiar with running the math on a gasket and deck ht stackup to figure exact CR, then you alredy know that the deck height and gasket thickness make a Beeg difference in the CR. So you already knew this stuff..

Re: 525sc's Rebuild
 

i will call the "reputable engine builder" to qualify exactly what he suggested to me?
maybe i misunderstood him. (quite possible ) Or maybe he just aint reputable!

infomniac, r u sure that 12,ooo rpm's r max on the weiand 177? I guess i could do the math to determine what my stock pulleys r spinning it. I assume the stock 525sc set up was within the optimum efficiency. Measure the pulleys and divide the top into the bottom @ 5,200 ????????

Re: 525sc's Rebuild
 

HES not my builder...just someone i happened to speak to... thanks for the info though!!