Sorry this post is a little long but I thought describing the mods to get the PC heads to work might be of interest.

Current Engine Build

DOAE-L block filled with Hardblock to within 1 in of deck
Race prepped factory crank
Eagle H-beam rods
TRW 2348 dome pistons
ARP Main and rocker Studs
Smith Bros 3/8 pushrods, Manley guide-plates
Jomar stud girdles
PC aluminum heads - reshaped chambers, extensive port grinding, milled .050
Crane 99890 springs, Titanium Retainers with 10deg locks, Crane gold rockers
HV oil pump & ARP drive
10 Qt Oil pan with trap doors & windage tray
Water cooled Oil cooler, Oberg filter , External Oil returns - head to block
Crower cam 272/276 @ .050 lift .668/.675 LCA 108 In at 104
Unilite dist locked up timing and MSD Digital 6 with 20deg start retard
Modified Runner Tunnelram with 2 670CFM TBI's and Holley 4DI ECU
Basset boat headers are 2" primary 32" long into 4" collector with internal muffler and curved extension - noise level is legal here

Background:

I have loved building fast fords and boats for quite a few years now. I had a 1966 fairlane with a 427 medium-riser in it. That was seriously fun drag racing.

I Started building boats in the 70's first with FE motors and then in 74 I put a 71 C Boss motor in a home-built tunnel boat. That ran pretty darn good for it's time. I wish I still had that rare motor, but over time everything broke and got upgraded and changed.

A few years ago we acquired a 1985 19ft Cougar tunnel boat that was originally equipped with a 454 chebby and a pump. Well the motor was long gone and I hate pumps so we converted the drive system to a V-drive which is by far more efficient and seriously faster than the jet. I still had many 351C parts so we started developing a current C motor for this boat.

The basic motor consisted of a 4 bolt block, basically stock crank and rods, 2348 Dome pistons and a set of "high-ported" pro-stock prepped heads from the late '70s. It was cammed up pretty good with a 264/272 @ .050 camshaft. On top we used a Tunnelram initially with a matched pair of 650DPs. Later we changed to 2 - 670CFM TBIs and a Holley 4Di ECU programmed from my laptop. We spent about 4 years getting the Fuel maps to work, but finally the motor went about 20mph faster and used 30% less fuel than the carbs. Well worth the development effort. Even though there are better FI systems, this works surprisingly well.

The C motor ran 100mph in this boat. It was seriously fun to blow past many 454 pump guys who never will believe they had just been beaten by a small block ford!

Then as always happens sooner or later, things break. One of heads developed a crack the full length of the head at the bottom of where the slab was milled out for the port plate. I was sick. These heads had run so well but this size crack was just un-repairable.
And these port-plated heads are a little hard to find now so the boat sat while we pondered what to do. And we missed a few races.

Then the unthinkable happened. My buddy acquired a pair of aluminum head castings from a parts trade. Yes they were ProComp. (I thought ...Yuk)

Since our high-port iron heads were now out of business, we wondered just how much work it would be to get them to flow well enough to be competitive. Never would have even considered buying these "knock-offs" but here they were in a pile of parts just lying there....

The Head Project

The short story is it took a lot of work ...................but

The thing is, the raw material was there so the big job looked like the grinding. The first obvious step was to grind the valve seat transition to the bowls. They were pretty bad so a fair amount of grinding was needed. The bowl shape actually looked pretty good so not much was done inside of the bowls.

Next we un-shrouded the valve area in the chambers a bit and fitted our 351C size Severe-Duty valves. These castings would normally use slightly smaller valves but we had a lot of $ tied up in the parts from the old heads. As it turned out, the valves, springs and cups were fine but we needed to use a higher retainer on the intakes to get the right installed height.

The as-cast chamber shape looked pretty good so we decided to try it with flat-top pistons first. It ran pretty good, but more on performance later.

Next step, we made a template of the intake port and saw that the volume by my rough calculations was only around 205 or so and that would just not be enough. So we did a lot of grinding to remove most of the hump on the right side of the port around the stud boss. We were also able to remove quite a bit more on the right side down low and also some on the left side as well. The new template is kind of a strange shape but came in somewhere around our goal of 230. Volume is volume and there is a reason why we thought that opening up more down low might be fine.

We had had such good results running the Tunnelram intake with the high-port heads, we wanted to somehow match it to these heads. So we obtained a couple of pounds of Splash-Zone epoxy and filled the runners. We made a nice gradual curve starting at the top of the runner to 4 tenths of an inch off the bottom. It was also necessary to taper out the intake ports in the head slightly to get a good port match all around. When we finally got to putting the motor together the intake was a little high off the lifter gallery but the port match was outstanding. Looking into the intake plenum, it appeared that the fuel/air path would follow the slight upward curve off the bottom of the runner and it then would be a straight shot to the back side of the valves. The overall runner size was still a little bigger than the intake port so we figured the filling would not slow us down.

It took many hours of grinding to match all ports to our template. Buying a CNC'd head would sure be easier. But since we are just poor racers we did it the hard way.

We did some grinding in the exhaust port mostly on the sides to make the port a bit more round. But the size and shape was very similar to the high-port plated head already so not much grinding was really needed there. We already knew the port-plated exhaust worked darn good.

Now the question was how much valve to piston clearance would we have compared to the 4V heads. The depth of the valves in the chamber was .019 deeper on the exhaust and .030 deeper on the intake than our old highly modified iron 4V CC heads. So we bolted on a head and set up the valve train on cylinder number 1. Using clay on top the piston we found .200 clearance on the intake and .150 on the exhaust. The FT cam used was .640/.660 lift and 264/272 duration at .050. This was exciting because we really wanted a little more cam and there appeared to be room to do that.

At this point we felt that we had a workable combination and put the motor together for some testing. Now you have to understand that we are just poor racers and would rather put our available $ into parts than high-priced dyno work so our testing would be done on the water.

This motor is going into the 1985 19 foot Cougar Mod V tunnel boat that was designed from the beginning to go 100+ miles per hour. It's really like a Pantera of boats.

So there are 3 aspects of performance that are important to us. We pull a ski-racer and circle race so we need:
1. Off idle low end power to get a skier out of the water and gone.
2. Mid-range torque for pulling hard off the turns to try and pull ahead for clear water on the straights.
3. High-end power for the top speed needed to win just like a drag race.

And of course we need the motor to hold together for several laps at a time which means extended periods above 6000 rpm. So besides a strong performer, we also had to build a bullet-proof oiling system. Cooler, drains from the heads, etc. But more on that later.

So the first test was about 5 miles, 2� to a bridge and back pulling our speed skiers. Our primary competition is a 20 foot Chev 502 powered ski-race boat. These guys have won so many races we have all lost count. We are out of the water 7 seconds behind them. Not the best start so we are playing catch-up. About 2/3 of the way to the bridge we caught them. They can't believe what they are seeing. I glance at the GPS and we went past 90mph to do it. Pretty fast pulling a skier. This matches the old High-port Iron heads!
So we consider our first outing to be pretty darn successful. But we're thinking there might be a way to get more.

Head Mods round 2

Ok so with the flat top pistons we are calculating just over 10:1 compression. Runs fine on 92 octane fuel. We would like to raise compression to at least 11 where we could still use pump gas but get some more performance. So the next things we did are:
1. Fit 12cc dome pistons to our set of Eagle H-beam rods and rebalance.
2. Reshape the combustion chambers to match pistons. Looking for good quench.
3. Mill the heads .040 - bring the 85cc chamber back to 74. Compression now 11.1

With these changes we also add a Crower cam. Lift is .668/.675 and duration is 272/276 @ .050. Advertised is 310/316. LCA is 108 with the intake on 104, Overlap is 58 with nice smooth lobe ramps. Still have .060 clearance till bind in the valve springs (whew).
And cranking compression is averaging 195. About 6in vacuum at 1100rpm idle.

Now for some fun testing this combination...


OMG, What a ride! Prop cavitates more out of the hole due to more torque. Top speed with earlier setup was 102mph which matched the Iron High-ported heads. This also matches most 427 flat bottom boats we have run against.

So we added another inch of pitch to the prop. Top speed now 108 at 7650rpm! 0 to 70mph took about 5 seconds. I tried a few power turns....WOW - great mid-range.

I don't know about you, but I'm think adding 6mph is a really solid gain and it still runs on 92 octane gas. We love the Crower cam. It seems to complement the filled Tunnelram / aluminum head combination even better than our wildest expectation. A bit wider LCA than the iron heads turned out to be right.

The motor likes about 34-35 degrees of timing. We are still testing fuel maps but it is slow going because we are using an old narrow-band O2 sensor and making very small changes to avoid stressing the motor. Really need to invest in a wide-band setup. The Fuel map software does allow for recording a file of all sensors while running so that is very helpful to see what is going on.

So far so good.

Never would have expected these heads and combination to blow away the well-prepped iron 4Vcc heads. I know there is some controversy over these head castings but they sure can be made to work. We are matching boats with 600+Hp dyno sheets. Can't wait for the next race!
Cheers, Gary

Hey thats great. How much is it to set up my pro comps this way? IS that an off the shelft crower cam?

Hi Jim, well I really don't know quite how much time is really in the head project. I would not hesitate to do it again but not sure if buying CNC'd might be cheaper. I'll have to think on that.

The cam is part nbr 15378. Don't know if it's still a stock item or not. Their new listings are a little different. But you can still pull up the cam card.

Anyway good luck with your project. I'm happy to talk over any of my experiences.
Cheers,
Gary

For taking the time to write that up.
The results don't really surprise me... and confirms that they do have plenty of potential.
However as you mention, there is ALOT of time involved and I don't think people without some reasonable experience/decent tooling should try it?
Alloys actually "need" compression. Their higher heat coefficient means they suck alot more heat out of the combustion chamber than irons do.
What does surprise me is the amount of mods/work that was involved to get to 11:1? A huge amount must have been taken out of the combustion chambers... are those cc's quoted, actual or estimated?

Hey, I am happy to share. Everyone has been wondering what could be done.

There is certainly some hours involved. None of it is that difficult but a methodic approach lile making a template is a good idea. And the first time one doesn't know how far to go in some areas so it's a bit of trial and error. I use an air grinder with a 3/4" carbide bit and roughing it out went pretty fast. I think there was several pounds of shavings on the floor though...haha Then I use mostly a 3/4" 150 grit sanding roll to finish. Took quite a few of those.

I was a little surprised when I cc'd the chambers and they were that big but there is plenty of surface and valve clearance to mill the heads down. I used a calibrated beaker and water and did it several times with all chambers so they are pretty consistent.

My ratio would be higher but the pistons are still .020 down in the holes. We did not want to deck the block this time as it was ready to assemble but will at the next rebuild. I think it will be closer to 12:1 then which I think will still be fine with pump gas but we'll have to be carefull with the mixture and timing, etc. You are right about more compession is good. I can't believe the added power just raising this much.

Thanks for the comments, we are all learning.
Cheers,
Gary

great info, also thanks for posting. knew the heads can be made to work great. that mph increase is not easy to get in water. do believe you will find more power . nothing like the big block guy's getting beat by a small block Cleveland

Sounds strange Garry, open chamber irons are only around 74cc?? Did you cap-off most of the chamber with a piece of glass or something before you measured? Thinking of the "dome" water creates before it flows over might have something to do with the high measurement?

Anyway, won't spilt hairs over it... its your deal ... and obviously producing some good power.... but may I suggest getting it checked by someone with a burette before decking the block though... you may already be well up, compression wise.

Good luck and keep kicking that "fast" chevy's backside..