572 N/A Builds
 

I'm changing the direction of my 572's. They started life as Keith Eickert 1000s that had 10-71's on them. Sold the 10-71's due to hatch clearance issues with the 38 KV Scarab I was building at the time. I then purchased a set of Whipple quad rotors. So I began to buy all the parts to build around the whipples.

Then last week I threw in the towel on the 43 Scarab I was rebuilding, and now it looks like I'm going back to a 38 Scarab Thunder. With all that said, I do not need 1300 hp a side in a 38 Scarab. So I sold the Whipples and I'm wondering what else I may need to change. I'm thinking the cams may be a touch large for N/A so that is the real question here.

First the specs of the engines:
Dart Big M blocks with steel caps
Callies Magnum Cranks 4.375"
Carrillo Rods 4.56"
CP Pistons (these will be changed)
350 Canfield heads. Worked over by Valako flow 385/308 @ .65
TD Shaft Rockers
.903 Morel Ultimate Solid Lifters
Then the new cams I bought for this set up are 262/268, with .663 lift, 112 lope separation

Again the cams were designed around the whipples not an NA application. If I can run these great, if not then I don't have an issue with having new cams ground if I really need to go that route. I was going to run SM 3 manifolds, but I'm pretty sure I'm going to sell those and go back to the Thunder and Lightning headers. Thoughts on the cam? I'd like to end up at 750 hp. I think that power and the SSM 6's I have will make a nice combo for the 38.

As far as the fuel system goes. I'm not sure If I'll go carb or the Fast Multiport EFI set up. I'm leaning toward the fast set up.

So what are the opinions on the Cam for this engine. All of the parts to top of the line, so RPM limitations don't really matter here.

Are these short or tall deck? Just curious because of the 4.375" crank.

Tall Deck

my thought? It is so bad you sold the restored scarab hull and worked on this 43 to go back scarab! you would be pretty close finished if you would have kept the 38 ! I feel so bad for you reading all this!
but I will definatly follow your progress wichever way you take!

good luck and keep it up !

While I loved the 38 KV as a kid, I ended up not really liking the flat deck when I owned one. Yes they look cool, but the cabin was totally impractical. Even bent over as far as I could practically bend over, I would still hit my back on the bulk heads. When sitting on the seats in the cabin, my head would hit the ceiling. When at the helm, the freeboard was far too low, and while the race hatches look cool, again totally impractical. The 38 KV in my mind is a cool boat to look at, but not to spend time in. The Gen 2 38's with the different deck fixed all of these problems plus MUCH better construction in the Thunder series. I really like the 43, but I don't like the amount of time I'm limited to, to fix it.

Yes I spent a lot of time on both of these boats, but I also learned a lot. So it wasn't a total waste.

positivity is always good ! That's how I keep up with my chriscat resto too ! :)

If the cam is ground for a boosted engine it will not be optimal for a NA application.
I believe a cam for a NA engine usually has more lift and duration than one for a boosted engine.

Keep them supercharged! Seriously

I'm just exploring ideas right now. I'm in liquidation mode, as I'm going to buy something different, as the 43 project is done. When I decided to sell off all the stuff I've accumulated over the past year, the only things I told myself I was going to keep were the long blocks, and SSM 6 set up. Everything else is going.

At some point though I need to have the blocks rebuilt, as that is never a quick process. When I need to do that I need to know NA or blown. If I stick with blown, it has to be Whipple or ProCharger, as I'm not about to have scoops.

I have the dyno sheet from this cam, blown. VERY similar set up as mine, 572, Brodix heads instead or Canfields but same runner size, similar valvetrain, Whipple, The engine made peak power at 6500.

I'll probably stick with the blower set-up. I already had the exhaust, cams, pistons, heads. It's fun to throw around ideas, but everything is already there, and its all great stuff. I'll just go with something a bit more tame than the quad rotors.

HA- Is that why I haven't been able to sleep this week?

I wouldnt be afraid to run that cam. I assume its a solid roller. Is it a tight lash grind?

wide lobe separations work well with small blowers/small carbs , that are limited. Narrower lobe separations can not only make more power, they also help cool the chambers and valves down because of the fresh cool air charge being blown thru when valves are in overlap. If you have enough blower, to compensate for the small loss of boost psi, they work well.

lot of variables to whats the right LSA for a blower. Gasoline, alcohol, endurance vs drag race, emissions concerns, and so on.

For what its worth, a GM ZZ572 uses a 254/264 112 hyd roller, that peaks at 5500ish. The 720R version has a 266/274 112 .714/.714 solid roller that peaks at 6300ish.

those are both 4.375 stroke 572's like yours.

Good plan man! Looking forward to seeing you in the water soon!

Joe I got this right off Chevrolet.com. Shows slightly higher duration on the 720 hp. Possibly a typo. Seems like I've seen some variations on specs with this engine before. What's deal on the heads also. When I looked up the part number on the heads they show a 310 int runner left intentionally smaller for porting. Just wonder if the heads are untouched on the 720 or if they are cnc' or what. Head P/N 88961160. Are these edelbrocks and are they rec or oval port. They come up as oval port 310 cc however as you can see the specs show rec port for the advertised on the site. I would think there is a bunch of power left on the table especially with the CR and cam used. Just in the heads alone. Intakes appear to be the same on each 620/720. Look pretty similar to edelbrocks.

Just some conversation.

good call . If you look the cam part # from the 720R up on some sites, it shows the durations I mentioned earlier. But in the GM literature for the 720r, it shows 278/282 @ .050

ill bet the 720 heads are as cast , just different part numbers due to the 720 having different valve springs than the 620hp version.

[QUOTE=endeavour32;4657921]I'm changing the direction of my 572's. They started life as Keith Eickert 1000s that had 10-71's on them. Sold the 10-71's due to hatch clearance issues with the 38 KV Scarab I was building at the time. I then purchased a set of Whipple quad rotors. So I began to buy all the parts to build around the whipples.

Then last week I threw in the towel on the 43 Scarab I was rebuilding, and now it looks like I'm going back to a 38 Scarab Thunder. With all that said, I do not need 1300 hp a side in a 38 Scarab. So I sold the Whipples and I'm wondering what else I may need to change. I'm thinking the cams may be a touch large for N/A so that is the real question here.

First the specs of the engines:
Dart Big M blocks with steel caps
Callies Magnum Cranks 4.375"
Carrillo Rods 4.56"
CP Pistons (these will be changed)
350 Canfield heads. Worked over by Valako flow 385/308 @ .65
TD Shaft Rockers
.903 Morel Ultimate Solid Lifters
Then the new cams I bought for this set up are 262/268, with .663 lift, 112 lope separation

The 6 degree split may hold a lot of heat in the motor.

I really don't think so. The guy that designed the cam knows what he is doing, and this cam has run well in all his engines he's used it in, lol and no- it's not a Marine Kinetics cam. The Eickert cam that they are replacing, only had a 4 degree split.

Just my opinion by what I saw on the EGT gauges in the boat while trying different cams,

I was running wideband 02 sensors, it was EFI.

Hijack all you like

Gpm, what were the cam specs between the two? Curious if the reduced egts were from exhaust duration, or overlap, or exhaust timing events .

good topic

I've lost track of how many cams I tried in my motor, 10 or 12, all solid rollers, 112 or 114 ls, either in my boat on the dyno or both. Not a lot compared to an engine builder. All were custom grinds from Crane, Comp, or Bullet. I tried between 4 and 14 degree difference between intake and exhaust. Ranging from 266 to 276 intake, 270 to 286 on the exhaust.

598

So the question is was it worth the hassle and expense in changing cams? was one eventually so much better then the rest?

Mine isn`t optimal, i`d like to know if changing is worth it.

For my 598, M5 Procharged, CNC BB2xtra or CNC Big Duke head, the 112 lsa and 8 to10 degree split worked the best. The 4 degree split limited the rpm and ran higher egt's, the 10 degree split just kept going. I didn't notice much difference with the 14 degree split from the 10. The 276/284 @ .050 with BB2xtra ran the same RPM range as the 272/280 @ .050 Big Duke. The good ports on the Xtra's at .700 were 404 intake and 315 exhaust, Big Dukes were 453 and 333. Bullet and Comp seemed to like the 10 degree split with the blower. The last cam I ran was the 268/278 @.050 .758 lift. it idled nice and seemed to do alright on top end. My combo was different than yours, it's hard to say what will be best for you. I was experimenting for my own knowledge.