Cam selection and install

I question the lift on the EX it seems a shade high, but regardless your getting new heads so have better springs installed or spec before you buy the heads.

Just be judicious with the spring pressure else you decrease the odds of the flat-tappet cam surviving.

Follow break-in to the letter; worse thing you can do is to let the engine idle at first start.

Suppose you must have an oj prop to get that 3000rpm launch? That was my experience, its like a high-stall converter on a car and a kick in the pants. The acme was very 1:1. predictable and linear, but screwed up my flat wake.

That kit may be best for you, but beware jets are only $5 a pair, and its a fair bet you have 66's in the primary now. The kit is good value but you'll have a bunch of sizes you will never need unless you have another vehicle with a 750 or 850 holley.
You will have to gauge whether to spend that money on the kit, or just on the sizes you predict you may need and a couple sets of blue non-stick bowl and metering plate gaskets.
I suppose for about a dollar a pair thats not a bad deal at all.

To jet the secondaries consider the 4150 conversion kit that adds a metering block to the secondaries in lue of the metering plate...its the only way to smartly tune the secondaries. The metering plate you have now does not accept screw-in jets.

Thanks for all the replies, they are very helpful!

Gottaski, the prop is an Acme 470 (12.5x15 3-blade). Acme says it has as much surface area as a 4-blade, and I believe it with how much bite it has. With 1" less pitch I turn it 200 RPM more than the 4-blade OJ that I replaced. With just the DUI distributor, my otherwise stock motor can keep right up with my dad's '03 196 with the Excalibur (330 horse) out of the hole. He pulls on me at 35+ MPH though. Ski wake is still great.

AWhite, I asked the Comp Cams tech if he had springs that matched the cam, and he said they have something "that would work."   TFS and Crane both have spring kits that the mustang guys on corral.net seem to like with the GT40p's. I do see your point about having all the components match, though. Do you have a part number for the springs you're using?

I also got a few tips from an accomplished engine builder:
- A cam with a little more duration might be desireable.
- He said that the valve springs should NOT be shimmed.
- He also suggested installing an "over the counter" (non-Ford) roller chain and sprocket, as the stock parts have ~9 degrees retard built in. I am not familiar with this at all.

Can anyone add to these comments?

I think I will get the jet kit from Summit. As long as im buying 4-5 pairs, Im within a few bucks of the kit anyways. Ill be glad I have the extras if I ever get a Barry Grant carb- they would be interchangable, correct?

Quick update:

On Thursday I ordered a cam based on the suggestion from Cam Research Corp. I came across this company on one of the Ford message boards- either Corral or Ford Truck Enthusiasts- and decided to give them a call. All they work on are Fords, and they know their stuff. In addition to being thoroughly familiar with my exact engine and heads (much more confidence inspiring than Comp Cams), the guy I spoke to had also sold a number of cams to people with ski boats. He was familiar with the short setups that sometimes exist on private lakes and knew the name "Ski Nautique" (which is more than I can say for any of the other cam companies I called).

He suggested a cam with the following specs:
RPM Range: 2500-5200
Duration @.050" (I/E): 218/222
Lift w/ 1.6 Rocker (I/E): .490/.490
LSA: 110 degrees

Since everything they do is custom, he said he could make whatever I wanted. However, I went with his exact recommendation based on his experience and the following points he made:

-He said that 110 deg LSA was plenty safe on a ski boat (no real danger of reversion), and it would give better midrange power than one with 112 deg.
-He said any more lift (especially on the exh) would not be beneficial with the GT40P heads. While they would flow well up to .500 of lift, going up to and beyond that would decrease runner velocity (hurting torque).
-He said that any more duration would put me on the verge of hurting my holeshot. While comp cams said their cam would be good from 1300-5500 RPM (with a more aggressive grind), he didnt see how they could make that claim based on my specific components.

Also of note, their prices were better than Comp Cams! For $60 more than the cam/lifter kit ($240 total) I opted to have them break the cam in on a special machine. Naturally, all lifters will be carefully marked. I ordered springs at the same time that match the cam, and do not require machining on the GT40p's.

Overall I was very happy to find a company that was so knowledgable and I highly recommend them based on my experience so far! I will make sure to update this thread once I get everything installed.

FYI, I asked if they had access to reverse-rotation blanks, and unfortunately they did not.

Thanks Munday, I think the package will come together nicely. I was all set to order the Comp Cam before I found this company. Their knowledge was extensive and the price was better so it made my decision easy! I actually ordered a timing set from them as well- a double roller billet set with a nice German chain. I was going to go with a Cloyes True Roller, but this was only a few bucks more.

Id be curious to hear what kind of performance increase you saw from just the cam- I have a reasonable idea what to expect from the heads and intake manifold, but no one else I know of has changed a cam on this hull.

TRBenj,

Here's a link where a guy added cam, gt40p, manifold and ignition and claims a a huge increase.

Caution he's an MC guy so you really never know

http://www.skiboathelp.com/ubb/Forum1/HTML/000352.html

Amazing, that cam will probably get you 20-30 HP with right heads. Be sure you know how to figure lift also you can change to 1.7 rockers to gain lift. However without the knowledge you can gain zero. CC hulls use about 20+ hp to gain more speed, go figure. With the roller timing you also can retard or advance 4-8 degree the cam. Also you should degree the cam to find dead center in relationship to the cam. Cam grinder have their own querks ,etc build in advance or retard.
If you don't understand you have to PRELOAD the lifters, if not lot's of power will be lost. cam should come with the lifter how to.
The deck clearance will figure in the lift factor,etc.
Lot's of things to know, good luck.

True,with the 1.23.1. You have a handel on everything. Good Luck.

your going to have to check the pushrod length regardless, I would go with the stud mounts and if you use roller rockers you are going to have to use guide plates. I'm going to use scorpion billet roller rockers 3/8 stud mount, guide plates and .080" walled pushrods.

You want the pro magnum RR, the magnums are junk stamped steel. You'd be better off using the pro comp aluminum rockers on e-bay if cash is an issue.

Top of the line are Scorpion or Crane Gold billet RR. I can get a better price on the Scorpion's so that's why I'm using them. From what I have read shiming the heads isn't the way to go.

$400 would include the RR's themselves- the machine shop can do the conversion for $150. I wasnt planning on cheaping out if I do the conversion, if Im going to bother at all, Ill do it right. The Pro Comps or Scorpions are what I would go with if I bought new.

I have a line on some lightly used (1000 miles) Crane gold RR's (7/16") for under $200, so thats a decent option.

If I go this route, Ill have ~$1000 into the heads (used heads, cleanup/valve job, springs/retainers/locks, stud conversion, rockers) which is WAY more than I wanted to spend on them. Oh well.

Whats a grand or so amongst friends anyhow, I spent about 700 or so I think on the GT40P head and RR upgrade but that was with no machining on the castings other than for the larger valves and getting a deal on used scorpion pedestal mount RR. I also got lucky and didnt have to replace the pushrods, or the valve covers. Chris which castings are you starting with over there?

79, I have some more questions for you, if you dont mind (Or Bill or anyone else who wants to chime in)!

I see there are several lengths of studs available from Summit. Do I want the 1" rocker arm nut thread length like these from ARP?

With the stud mount rollers Ive heard it is necessary to run hardened pushrods. Since the stud mount setup is adjustable, is it possible to order pushrods before getting everything installed and checking the length? Probably not, but just checking. It would be nice to place only one order.

As far as guideplates go, anything I should be aware of? These from Ford Motorsports should work on my GT40p's, right?

Chris; Once again I have no idea what you guys are talkin' about but I think I like the sound of it.

Now you know why the '80 was bone stock when you looked under the cover. And here I thought all ya had to do under there was change the oil, impeller and the plugs once-in-a-while. Silly me.


john

Good info Bill, mine turns just under 6k when I'm by myself that's why I'm going with the 3/8 and billet. I've been thinking of removing the mufflers for a while so I guest when I change the heads I'll run new exhaust hose too.