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In 2017 Mike posted this reply about his SST 60 and Mod 56 OMC successes. Over the last few years several T boat people have built modified 56 powerheads both Bridgeport and oval port powerheads. I don’t believe Mike ever built an oval port mod 56.
I have seen the dyno sheets and raced against many of his SST 60 powerheads. As he mentioned in his post over 100 hp at the crank was common. The difference in the dyno sheets was the rpm the engine first developed maximum hp and how long the motor produced maximum hp. Mike’s best performance motors on the race course were those that developed 100 hp at 6500 to 6700 rpm and held that hp up to 7600-7700 rpm. Some of his motors made more hp but they peaked and only held that advantage over a narrow rpm range. Off the dock acceleration, strong mid range and good top end was key when racing on a 35 second lap race oval. Mike’s powerheads were always at or near the top finishers.

So here is the post from 2017
Mike Wienandt ...I have built over 15 national championship winning SST 60s. The last 8 years I have run been about 100 - 102 hp at the crank. We dyno with the exhaust housing and gearcase so we match correct exhaust back pressure. The mod engines I make for lake racers or X class inflatables are now up to 118 hp. This is with stock SST 60 carbs. I'm working on one right now that is very over due. Porting includes finger porting, Boost port reground, A lot of grinding in the transfer ports, Exhaust port reshaping and timing edges of all ports to my own specs. Stock head with welded smaller thermostat hole, then re-machine to smaller ccs and angled squish band added. SST 60 reed pedals and grinding in intake and matching the case. Bored to .030 over with Line2Line coated pistons from Pro Marine. Stock SST 60 tuner. We have over 350 dyno runs doing development work on these. Dyno all computerized so no bull crap. Can't argue with the win history.

Mike mentions a lot about how he modified the motors. He isn’t using different components but rather working with the original parts and just improving them.
It doesn’t sound like “bigger is necessarily better”. A common mistake with many new engine builders is being too extreme with the porting. And using non original parts.
You build enough of these motors and you know what works and what doesn’t. Certainly the in-house dyno is an advantage.

There are enough of Mike’s SST 60 motors on T boats in Ontario that you can compete with. I don’t know of any Mod 56 Mike motors in the area, but that could be because the people won’t say what they are running.

A 118 hp T boat 56’r and it has to run over 80 mph.

Got an email from one of the T guys who has been working on a mod 56 OMC for a few years. He said Mike W hasn’t been working on any 56 OMC powerheads for several years. There isn’t any demand.

I checked Mike’s Facebook website and couldn’t find anything related to OMC 56 powerheads.
https://www.facebook.com/profile.php?id=100057338234295

It would be an excellent learning tool if we could get our hands on one of Mike’s 118 hp mod 56 powerheads.
The purchase price will be a problem with the Canadian dollar at about 70 cents. I don’t know how much the mod 56 powerheads originally cost. I do know that Mike’s special sleeve, special crank SST 60 drop on powerheads cost $5000.00 US back in 2004-2008. Other SST 60 powerheads built by different builders were $2500.00. US.

SST 60 became a very expensive class to race back then.

Oh, just another comment. The 1987-8 omc fishing 56 powerheads are sometimes called “sandcast” by most people. They were not sandcast made...the term is “production” cast.
The inside finish is smoother and the block flows better than the later lost foam cast blocks. The production method was changed to lost foam casting because that process was less costly. So when you hear either term the person is telling you it’s the different block. Easy to see the glue lines looking in the ports if you don’t know the part numbers of the blocks.

At 118hp out of a 56ci that is very close to what the southern boys are getting from the mod 90 Yamaha motors! Would these 118 hp blocks be the “production” blocks with Bridgeport sleeves or maybe Oval sleeves? Thats a big jump in HP over the 105-107hp from the sst60 power heads! I wonder how long they last??

This was a thread from 2023
https://hpbc.ca/viewtopic.php?f=19&t=4440

My quote
I was asked for suggestions in modifying 56 OMC powerheads.
I have never modified a 56 OMC.
Those that have normally don’t want to tell their secrets.

Here is an update.
Years ago I purchased a very competitive Mod70 56 OMC. The porting was so extreme I never ran it. It was a production block with lots of tricks. I knew the crank would be perfect.
I had 3 new SST 60 sleeves and 3 new wiseco pistons.

Tim Topping and I decided to put the SST 60 sleeves and wiseco pistons in this block. It wasn’t as simple as we thought. Even though the sleeves fit and the block had lots of aluminum casting removed in the port areas, there was still aluminum showing in the SST 60 ports. The intake portion on the front , the reeds and reed cages had all been modified and or ground on. We couldn’t use the front half and we were lucky to have a replacement.

The powerhead had stock SST 60 sleeves....so I thought the compression should be 175-180 psi with a spec SST 60 head........wrong it was below 160 psi. Well I confirmed to myself when I said years ago the 160 compression rule work only be relevant on stock non modified motors.

I still had my notes that Dave Elsey and I made when we tested various sized heads on 56 non modified blocks so I knew the cc measurement that produced 155 psi on a stock SST 60. So we now had that cylinder head to test.

We will test this powerhead next summer.

Here is some of Dave’s notes from 2013....tested 12 different cc sized heads.
Remember the SST 60 head is likely the smallest cc head (28.5) that you can safely run 92-94 octane pump gas...your compression will read below 180 on modified motors but that doesn’t matter.

Stock factory heads vary from 30.5cc to 34.8cc, even a 42cc head for commercial use.

An SST-60 legal engine requires ~ 30cc head to average 160 lb.
Dave’s stock ported 70 requires ~ 26cc head to average 160 lb.
Erik’s stock ported 70 requires ~ 24cc head to average 160 lb.
Dave’s 70 with a 28.5cc head​~ 147 lb cold
Erik’s 70 with a 28.5cc head​~ 138 lb cold
Don’s SST-60 with 28.5cc head​~ 172 lb cold

Pocket Depth:
Pocket depth closely relates to head chamber cc’s.

21cc​=.405”
23cc​=.440”​SST60 minimum
25cc​=.470”
27cc​=.505”
28.5cc​=.525”​SST60 minimum including head gasket ??
30cc​=.550”
31cc​=.565”
32cc​=.583”
33cc​=.598”

No secrets on this post!
With head studs you can crush the gasket an extra .005” Result ~ 6lbs on compression test.
There is ~ 12 lbs less compression with the Sierra gasket.
Each engine is unique, the compressions varied ~ 7 lbs from engine to engine with the same head.
Both engines fresh, 77/80 Leak down (Good),
My compression gauge reads ~ 5 lb LOWER than Don’s
Carbs held open good for ~ 2 lbs.
All figures are my gauge, and averaged.

Here are the part numbers for the “D” jets
70-327769
71-327559
72-328546
73-327487
74-333669
75-327560
76-329411
77-333438
78-319002
79-329414
80-333298
81-330917

Here is an excellent example of two Mike W top SST 60 powerheads. The video is from Sam M boat. Number 44 is Sam L. The race is the Nationals. The video is just over 13 minutes. It’s the complete race from start to finish. Both these boats run close to 80 mph on these short straightaways and it’s a driving error by Sam L that costs him the win.

LISTEN to the sound of the motor. It’s quiet for an SST 60 and very smooth. That was the advantage of these powerheads. As they lap the field you can see the acceleration advantage and the top end advantage.

Just driving in these races was a challenge in concentration with so many laps and so much traffic.
That’s a river course on calm water and maybe 10 entries . Imagine racing on a lake with wind conditions and 19 entries.

https://www.youtube.com/watch?v=bvlaFpXI22c