huskyrider

iTrader: (1)

Mike, thanks for the equation.

I remember speaking with you on the phone a few years ago when I was searching for the right boat and one was your previous boat by another seller. Thanks for your insight then and now.
All your reply's these years I've read have been full of hands on knowledge.
Your numbers are impressive for sure.
I was targeting high/mid 600's max on hp/tq while on boost, I like the sound of docile down low.
My boat is heavy out of the gate and still runs the original B-1's on extension boxes, I come up easy and don't want to bust a drive.
Dave told me that when the boat was rigged they estimated about 600hp on each when they campaigned her.
I now have a sweet set of very low hour new style B-1 sweptbacks I'm going to use when I upgrade.
I know I've heard my stock heads have smaller valves and wont flow like some others. Tim doesn't know which ones are stock on my engines and neither do I. I'm hoping you or another member might.
I'm wondering if they'll be adequate reaching my target. He said that for the coin I'd be better off having Nickens Bro's just rework mine and get a slightly more aggressive roller cam. I sure don't want to outfit new heads and purchase new blowers.
I just don't know if my munchkin blowers are capable of that level of power production without making to much heat even during short blasts of higher rpm's.
I appreciate any and all imsight from y'all and am open to reasonably priced alternatives, can you say that in the same sentence in this sport, LOL!!!

Thanks,
Kelly

Griff

What size upper pullies and how much boost are you running?????

I highly doubt that just the chillers and increased boost would get you 600hp. Maybe 560-570hp.
I ran a Crane 731 cam and about 7.5# of boost in my 525SC with no chiller and never had any issues.

The stock 525SC heads are GM rect ports with inconnel exhaust valves. Cleaning up the heads some and using a well matched roller cam should put you just over 600hp,
You will have to run 7-8#'s of boost, and spin the 177 close to its max rpm rating of 13,500. It creates a lot of heat so change the SC lube every 25hrs or so.

MILD THUNDER

iTrader: (3)

Honestly, it all boils down to how much you want to spend on these engines. As far as your friend who doesn't understand why mercury put such a large carb on a 454, he has to realize its a roots blower. I am running a pair of 850s on my 468s. They definitely aren't hurting power or causing a lack of throttle response. In regards to the 177s, they work great on a stock 525sc, at that power level. However, once you start modifying them, you start running out of blower. Boost is just a measure of restriction, and although the smaller pulley might show more boost on the gauge, its just not doing a lot for power, because its just heating the air up, and making the blowers wear faster.

What you might want to consider, is listing the 177 setups for sale, with the chillers, carbs, etc. You might get lets say around 3000-3500 for the pair. Then, for a few more grand, you can pick up a pair of B&M 420's, which are out there usually pretty reasonable. You'll go from probably spinning the blowers at 115% over, to 5% under, which is a major reduction in heat and parasitic drag. You will then have the option to run 5psi, 6psi, 7, or even 8psi, with good returns in power, as the large blower isn't working anywhere near as hard. The twin carb setup has much better fuel distribution, and once tuned with an 02 sensor, can net economy as good if not better than your stock setup.

As far as the engine itself, a set of aftermarket heads would be a improvement, but a pricey one. To meet your goals, you really don't need them. A roller cam upgrade is the way to go. Griff ran the 731 cam, I run close to the 741 specs, except a 114lsa. On the dyno, I pulled it to 6000, and never saw a drop in power, but it was getting real close to peaking out. At 5500, I was making 754hp, at 6000 798hp. A bit large, but I am propped around 5600-5800 currently.

To sum it up, I'd do basic rebuilds, hyd roller upgrade, larger blowers, and spin the engines to 5500ish. At minimum, upgrade the rod bolts to ARP wavelocs, if you need pistons i'd consider a flat top to get the compression up to around 8.25, cometic or felpro MLS gaskets, and ARP headbolts or studs.

If new blowers just aren't in the equation, I'd probably at minimum get the compression up a little to help them out, and do the cam upgrade. Bob Madera can set you up with the right cam lifter spring combo.

I had the following setups on my 454 based engines, all in the same boat.

177's @ 5psi =78MPH
250's @ 7psi =83mph
420's @ 6psi=88mph (engines were freshened prior to this and got a fresh valvejob and all new seats).

huskyrider

iTrader: (1)

Thanks for your reply.
I'd have to measure the pulley.
I was told that when they rigged the boat that this was about what they anticipated.
The boost is a solid 7psi, the whine is fantastic but in spite of the chillers I'm just scared of heat.
As this is my first I'm still very green in my knowledge of high performance boats.
While talking on the phone last night with another member he suggested aftermarket aluminum heads for better heat dissipation, flow, and less weight.
I was wanting to keep my engines as close to stock as possible so it looks like I may be lowering my expectations and just go with a roller cam and lifters.

I'm curious as to how y'all feel about this.
If the cost comes in around the same would the aftermarket heads be worthwhile in acheiving a little more power and parking my current heads on a pallet rack at the shop?
As always thank for the advise from you guys.

See ya,
Kelly
.

huskyrider

iTrader: (1)

Mild, thanks that is a lot of help.
It took me a friggin hour and a half to get my crews out this chilly morning while trying to reply to Griff
I just saw your reply.

I like the sound of this, one of the reasons I feel I come on plane slow is the lack of low end response due to low compression.

At what power point would you guys think that the drives may be at risk?
A bud with a 40OL told me that he's had better luck with the new style B-1 sweptbacks than he's had with XR's in his boats
Y'all ever hear this before, I thought regular B-1's weren't as heavy duty and my boat is pretty doggone heavy.

Thanks a bunch,
Kelly.

MILD THUNDER

iTrader: (3)

Probably the simple fact with planing is you have a heavy boat. I don't really know how your drives will hold up, Im not up to date on the bravo drive stuff honestly.

In regards to aluminum heads, generally speaking, yes, they do dissipate heat better, which is important in a supercharged marine engine. One thing that hurts with the stock heads, is while the intake ports move air decently, the exhaust ports suck. With a supercharged engine, the supercharger can over some inadequecies in the intake port, but the exhaust has to be able to move air. Going to an aftermarket aluminum head, like a Dart, AFR, Brodix, will indoubtedly gain you power. Theres tons of options there for cylinder head choices. If you boat in salt, you definitely will want the marine coating on the heads.

Few things I don't like about the heads you have. #1 they just don't flow that well. #2 they are heavy old iron castings #3 they are prone to dropping seats. Many times, when rebuilding these old heads, a new set of heads isn't that far off money wise. That's really a decision you'd need to make depending on the condition of your heads. Lots of these older GM iron castings can get very thin in the water jackets from corrosion also. Need to watch for that.

However, if the heads are in good condition, and you only have ''X" amount of money to spend on the upgrades, I still say cam/blower upgrade. I know of a couple 454-468 engines with 420/871 sized blowers, GM rect port heads, making 700HP with 6-7psi.

Guys who have the 575SCI's, which had a relatively small 256 blower on a 502ci, have seen substantial gains by ditching the 256 and bolting an 8-71 on. You can perform this test on a dyno, and may not see as much of a gain, because on a short dyno pull, the small blowers aren't heating up as much as they would on a long wot blast in a boat. The larger blower just runs cooler, and the rotors aren't beating the air to a pulp at 5000+ engine rpm.

Griff

If you are at a solid 7# of boost with the chillers, then you are pretty close to the max rpm of the 177's.

huskyrider

iTrader: (1)

I feel certain that they're topped out, the whine is wicked cool and that's what scares me as my motors are way old now.

Your absolutely correct, I saw the same gains on my bud with the OL boat last year when he swapped 871's for his 256's on his 575SC's which were rebuilt incorrectly by a blower builder from using leftover parts and having a catastrophic failure.
He had a replacement thread here and I think you might have participated in replys. It was a solid 5 to 7 mph reward, that had to be some major power gain for sure. His heads and cam are still stock.
Do you know if the heads on the 525SC are the same as the heads on the 502cid 575SC.
I was shocked at the price he paid for new, it was less than I'd of guessed.
I'm liking your 5500rpm target, cam and quality fasteners idea for sure.

Thanks,
Kelly

Old Navy

My 525sc had 088 heads originally. I don't know what the 575 motors had.

Griff

Same heads on 525SC and 575SCi. GM rect ports.
Not sure if the valve size is exactly the same though.