415 sbc cam

[younger]

Just bought and waiting for a new 415ci Bill Mitchell short block to go in my 16 classic. Was wondering what I should run for a cam. The heads are edelbrock rpm with rpm air gap intake and have a 750 vac or a 850dp holley on top. The heads are a bit on the small side @ 170cc intake runners, they will be opened up some on the intake and exhaust ports along with unshrouding the valves with the 4.125 bore. Compression will be 9.7 to 1. Reversion won't be a problem I will be running glm alum. manifolds with dry risers out the back. I was thinking of going roller cam with 234 deg. @ 0.050 on intake and 238 deg. @ .050 on the exhaust with .539 and .548 lift. Any Ideas how the combo will work?

[BUIZILLA]

alum or steel heads ?

[kd5cue]

alum or steel heads ?:confused::confused::confused::confused::confused ::confused::confused::confused::confused:

[Rootsy]

:confused::confused::confused::confused::confused: :confused::confused::confused::confused:

You can get away with more pressure in the cylinder with aluminum heads. Camshaft controls that to a great extent.

[ky-donzi]

Aluminum disapate heat better, so there are not as many "hot spots" like at the edge of the combustion chamber. These hot spots cause detonation when the compression ratio is higher. In some cases you can raise CR a full # with out detonation by just changing to aluminum heads

[BigGrizzly]

You said Edelbrock I don't think they make steel alum only.

[younger]

Yes these heads are aluminum with 64cc chamber. I'm hoping that I can make gobs of torque and twist some prop. I ran the top end mentioned on a 350 the last 4 years with a couple different flat tappet cams the best being a mellings 232 deg. @ .050 on the intake and exhaust with .512 lift on both intake and exhaust. It had 108 deg lobe separation. With this cam the boat ran 72 at 5600 rpm with 1.32 gear and 19 laser II prop. I still have this cam and wonder with the extra cubes it might be the ticket.

[BigGrizzly]

I run 108 lobe center in my Corsican. Of course everybody told me I was wrong except an old friend Babe Erson who made the cam for me. Most cam guys tell you to run 110 to114 for idle reasons. Oh well I was never for believing what They say. Like my Mom use to say " who are THEY"! The only thing I can really offer is, You don't know until you try it. The other thing is that just because it works on a 350 when you add 65 cid things may change. In this case I think the idle may improve and torque will go up but not as much as you think. Don't look for monumental gains off the new engine. Sounds to me like you hove too much inefficiency on the prop side. 72mph at 5600 with 1:32, is pretty poor effiency. Look at OSUR866 72.3 at 4,800 with 1:65 gears. What is happening is that prop is loosing bite around 5,000 RPMs Very typical with small pitch props. If you do a grapk wit speed and RPMs every 500 increments you will see what is happening.

[maddad]

Hi younger, I'm not a motor expert but I do run a similar set up.(413ci, close .050 #'s) I installed my cam straight up and close the intake valve too soon. With a 9.6/1 CR, a warm motor compression test gets me 195-198 lbs. Retarding the cam, or maybe better yet some more duration would get my cylinder pressure to a more pump gas friendly, and timing advance tolerant 180-185lbs.
The important part is making sure you get advice from someone who knows what they're talking about, and then listening to them.
Not like me. Who Rootsy told to retard that cam.

[MOP]

Hey Norm are you going to fess up to the water trick????

[blackhawk]

I'm confused. 72mph @ 5600 with a 1.32 ratio and 19 pitch prop is inefficient? If anything it sounds TOO efficient to be correct as it is about 5% slip.

[younger]

Yes mop I guess I will tell. One of the mods I made on my alpha GENII to keep it alive and cool is, I removed the upper housing rubber plug in the water jacket under the top cap to make some more cooling volume. Then I drilled and tapped the top cap above the water jacket put in a 90 deg. brass fitting pointing towards the top bearing. The resaults have shown that the drive runs much cooler. After a long run at 50 plus speeds I can put my hand on the drive after stopping quickly and it is hardly warm. The drive also has never shown any sign of mineral residue from heat. This is after 4 years of abuse behind my 350. As for the 350 being efficient I have tried many many hour of testing props from all kind of manufactures and the 19 gave the best top speed and mid range cruise. The mellings cam that I have run was a very peaky cam and the 19 laser was one of the few props that I tested that would get the motor into its power curve.

[MOP]

Norm I did like the water trick, constant cooling can't beat that. You old combo was spinning the 350 where it made its best HP for that cam, most do not like spinning the drives over 5k. A 16 being pretty light gives you more slack, good luck with the project and looking forward to you getting your Rooster Tail higher next year!!! Was fun running with you!!!

Phil

[smokediver]

the laser2 is a great prop on the 16 hull but ... when you start adding more horsepower it is really going to start running your slip % up ... I ran a laser 2 on my 16 and it was great for 300 - 350 horsepower ... over 350 not so great .. you are going to need more blade area,imho ... like a mirage plus .. the laser2 is i think 13 3/4 diameter or 13 1/2 ... mirage plus at 23 pitch is 14 5/8 .. at 19 pitch i think the diameter is even more ...

[BigGrizzly]

Younger I see What your doing and it seems to work for you. That would not have been my first choice both in props and engine cam. I too have done extensive prop testing, because of where I use to work and the fact that I test for prop companies and also sell props. I am actually surprised that that laser has less then 5% slip on that boat. Do you run a nose cone? Was that speed with a GPS? It would be nice if you could post pictures of the cooling of the drive for everybody, It could be a good source of information for Alpha users. That is hauling in a 16. with a standard drive. Of corse therer are a couple of old Volvo drive guys there too, right magic and Maddad.:wink:

[younger]

Yes that was gps speed. The lower unit is stock with the engine mounted as high in the hole as possible. I will try to get some pics of the drive mod in the next while. Another mod I have been beating around because of the rare alpha ss is to run a 3.0 liter sportmaster lower in place of the stock alpha gen II lower. I have had a couple of these in hand and the match up looks ok. I know it doesn't give the raised x, but that may come after the lower mod. I have thought of cutting 1.5" out of my upper and running an alpha ss shaft. With the resault being a gen II ss. But before I get to that what is the conclusion on cam specs, lift, duration, lobe separation. Some ideas would be a great help. Phil, nothing better than a bunch of donzi's heading in the same direction with everyone giggling.