OSOUSMC

Hello, I'm new to being a member here but not new to gathering info here. Question, I have a 454 Gen 6 from a 1997 Scarab 22 that I'm rebuilding. I have Vortec heads and a stock cam. I'm interested in the Comp Cams XM270HR cam and have read about other mods to do as in intake, valve springs/retainers, carburetor etc. What I need to know is on the Comp Cams website for that cam P/N 01-445-8, on the spec sheet says that the "Heads need to be machined. Question; what on the heads need machined. I'm thinking valve spring seats but the ones I ordered are supposed to fit the Vortec heads. I'd appreciate any help. Thanks!!

1BIGJIM

iTrader: (1)

Probably valve guides and springs for increased lift.

doubleduecedonzi

The valve guide runners need to be machined down for extra clearance. Anything 500-510 I can't remember which. Competition products sells a tool to do this. Can be done using a drill. Assuming you have the 454 non mag 310hp version. I had hat same motor rebuilt for my boat a few years ago keeping everthing stock and reusing the fuel injection system. Long story short that was a huge waste of time money. Loose the efi and go carbed. You pick up a few mph by just doing that alone even without the cam. The intake is doesn't flow enough make decent power. Read somewhere that even Tyler crocket couldn't more than 375hp. Install some good valves while you at it.

OSOUSMC

Thank you for the replies. I have a Holly 750 Dual P. No EFI. Yes, 454 Gen 6. I was told it was 330 HP with the Vortec heads. I do have a marine intake, large oval (not peanut), aluminum Torquer. I'll look into the tool that you mentioned for trimming down the valve guides. Lift on the XM270HR is .510 intake and exhaust so I shouldn't have to remove much. Thanks!!

doubleduecedonzi

Do some searches on here there's lots documented build's to reference from. Unless there's a particular reason you wanna use that cam. If you already have to mill down the guides you might as well go to a bigger cam. Why not... personally it wouldn't be worth it to me. I would either throw in the 502/454 mag cam(simple swap no parts or head work needed) ! Or I would take take full advantage of already having to machine the heads for clearance , buying new spring's and cam.

tpabayflyer

Yes..... I rebuilt my gen6 7.4 using the vortec heads and the minimal gains are not worth sinking a lot of cash into..... I rebuilt mine with forged Pistons and h-beam rods on the stock cast crank. Heads were new with bowl porting but the ski jump intakes just are not made for big power. I also used the bigger 2.19/1.88 valves and the 510/540 marine HO cam....... No mods needed to run that cam and it has a little ruble at idle but I am using stock exhaust so again, minimal gains........ I would go with better heads for sure if you want to spin the motor faster. My wellcraft cruiser only turns 4,400 rpm but will go 51mph..... I gained 4mph but I never cruise that fast so it was all a wash for me......... I am using the stock FI setup and it works good but I did have to increase the fuel pressure to get the A/F ratio right....... If you are not in salt water maybe the edelbrock heads would be a good choice? I would not try to get more power from the vortec heads, they do make awesome torque lower in the Powerband.... TBF

OSOUSMC

Great!! I appreciate the info. Thank you.