Andy

Well summer is almost and I need advice for next season. I have installed two sets of reworked Vortec heads on my 330 hp BB chevs. 2.18 intakes and stock exhaust both stainless. No porting just mild bowl work. Edelbrock 2.0 oval port manifolds ported to the nuts to fit my heads. Crane cam .515/.520, 268/280 dur. lobe sep 110. When my heads where off there was quite a lot of cylinder scoring so comperssion is down. I also picked up two sets of Stainless marine exhaust. Holley 750's with 1 inch spacers. My problem is this, cant hit 4800 rpm in a 1984 8200lb Formula with Cobra drives and 21p Michigan props? 57 mph.

Vinny P

Is that duration advertised? It sounds like alot for .050". That lobe seperation looks way to tight as well.

KAAMA

iTrader: (1)

Are the cams a flat tappet hydraulic or a hydraulic roller? Also, what is the duration of your cams at .050" lift??? Were the Stainless Marine exhausts installed on your boat when it could only turn 4800rpm? Are the Vortec heads a rectangle port design? Is your 8200lbs Formula a 302?

cooltoys61

Somethings not right. BAMs Go-fast.com website says your boat with 660 total HP should hit 64MPH and my experience with a heavy 30' Scarab agrees. If you added better heads(and you did, I gained 80 HP with them and the roller cam)and more cam you should be faster. Like the others said what is the duration at .050? Also if you changed to vortec heads your Comp ratio should be up about a 1/2 point, can you confirm this? What total timing are you running?

rmbuilder

Andy,
Neither the intake or exhaust lobes you listed is in the Crane Master Lobe Catalog. However Comp Cams does have an exact match for the cam you described. It is a hyd-flat:
Part # 11-242-3
CB XE268H-10
268*/280* @ .006”
224*/230* @ .050”
134*/138* @ .200”
.515”/. 520” Lift @ 1.7
110* ICL
Cam card
http://www.compcams.com/Technical/Se...umber=11-242-3
Is it possible this would be your cam?
Bob

Pat McPherson

Cooltoys is right, you should be running better than that.

I have heard about 30° total advance is as far as you want to go with the Vortec heads. Good place to start...

If you are running the cam rmbuilder is showing, I would think your engines would make near 400HP...

1BIGJIM

iTrader: (1)

I put that exact cam in my ride this year. Got the idea out of Dennis Moore's BBC book. I bumped the compressing to 9.2, set of 781 heads, same intake manifold, and new Edelbrock 750 carb. Picked up 100 RPM. My thinking was not enough compression. I am in the 145 range. I was thinking of advancing the cam 4 degrees to bump the compression up. Anyway cam is going in the trash next year. Time to join the roller cam club

Andy

Sorry the cam was a Comp cam part # ending with 242-3. Total timing at 30 deg. Oval port heads and intake.

Andy

The boat is a 1984 302 Formula. Heavy at 8200# but a sweet ride in the rough stuff!

KAAMA

iTrader: (1)

Andy,

Back in the mid 1980's, a friend of mine had a 302 Formula with TRS drives. It originally had a pair of stock Merc 454" 330hp engines in it. He modified the engines with Holley 800cfm carbs, single plane intakes, bored them to 461 cubes (.030" over bore), forged pistons, ARP rod bolts, flat tappet hydraulic cams, 9.0 comp ratio, took the stock GM oval port (049 castings) heads and modified them with larger valves (2.19" intks, 1.88" exsts), hardend seats, bronze valve guides and replaced the stock junk Merc exhaust manifolds with an aftermarket GIL exhaust system with dry tailpipes. The engines turned up to about 5500rpm or so with something like a 23" pitch 3-bladed cleaver. The boat ran something like 75-76mph back in the day------and he smoked A LOT of other boats back then with that thing!

I think you are in the ball park----and if that cam is what rmbuilder suspects it is (224*/230*) then that's a pretty decent cam for your engine. My cousin took some junk oval port heads and had JimV do some pocket/bowl porting to them with larger valves and put them on his 461" engines with a dual plane intake manifold, 800cfm Holley (750cfm is all you need), the exact same duration of cam that you most likely have (226*/230*), 8.6 comp ratio, and the engines made 461hp @5100rpm. Torque was something like 510 foot lbs @3400rpm and stayed within 15 foot pounds until about 5000rpm.

I don't know why your speed is still would be down. You SHOULD be in the ball park----especially adding the Stainless Marine exhaust system to all those mods you mentioned. Something that throws a bit of a RED FLAG up is that you said that the comp ratio may be down. It sounds as if you don't know even what it really is-----and you mentioned that the heads didn't have any porting done to them, but rather just some "minor bowl work", which is fine but usually the way I have always known it is when modifying a set of oval port GM heads with larger valves then you MUST open up the bowl and venturi areas for the larger valves being installed. Otherwise, it will not most likely flow well. Also, the short side radius's are very important to have a nice smooth transition of air flow in the bowl area. It doesn't take a ton of metal removal to do this and you also don't want to grind into the water jackets, but the flip side is that you just can't leave it in a bone stock configuration after installing larger valves either. Hopefully, the guys who modified your heads with larger valves opened up those bowl/venturi areas a little.

Please understand this is my opinion based on what I have experienced in the past---I am NO professional!!! Best wishes.