Which Cam?

[jefflock]

I've decided to change cams in my 340. Looking at either a Lunati 60403 or 60404. My motor is a 30 over 340 with stock type pistons, J heads with 2.02 intakes, 780 Holley(3310), 3200 stall converter and 4.10 gears. I will install an air gap in place of the Weiand currently installed. We cruise in it a little and goes to the track 1-2 times a month. The cam currently in the motor is a Lunati 60043.
Which cam do you guys think I should use? I'm leaning toward the 60403.

 

[rumblefish360]

I like the 404 cam better myself.

If it were my build, I'd be doing the 405 cam and porting my heads later on.

 

[moper]

Stock type pistons and J heads give you little static compression. I would stay conservative and go with the 60403 if it were me.

 

[jefflock]

How much cam lift can stock heads handle? Do you have to cut the guides down?

 

[rumblefish360]

Around the .500 mark. If you keep it around that, you'll be fine.

I think I remember people saying the purples .509 was OK.

 

[Baxter61]

Most of the factory SB heads Ive seen can usually take about .540 to .550 lift in stock form. How far out/in the hole are the pistons?

 

[vioperblue72]

Most of the factory SB heads Ive seen can usually take about .540 to .550 lift in stock form. How far out/in the hole are the pistons?

Not with higher compression pistons they can't, especially with a hydraulic that requires preload. A zero deck piston without valve reliefs would doubtfully even fit a mp 509. The heads will likely take it but not the pistons. Last time my dad ran the 509 he had 1 valve bottoming out and wiped a lobe. We need more specifics about the compression ratio to give you a good recommendation. Also what are the specs on these cams?

 

[Baxter61]

Not with higher compression pistons they can't, especially with a hydraulic that requires preload. A zero deck piston without valve reliefs would doubtfully even fit a mp 509. We need more specifics about the compression ratio to give you a good recommendation. Also what are the specs on these cams?

The pistons have absolutely nothing to do with what the heads can take as far as lift. They affect your PtV clearance, but thats not what I said. I said the HEADS can usually clear that much lift.

 

[vioperblue72]

I stood corrected if you read my post again. I agree the heads may take it, just not the pistons. He needs to realize that piston to valve clearance is just as much an issue in his case.

 

[jefflock]

I went to the Lunati website. I'm liking that 60404 grind. Spec are:
Advertised Duration (Int/Exh): 276/284
Duration @ .050 (Int/Exh): 234/242
Gross Valve Lift (Int/Exh): .513/.533
LSA/ICL: 110/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2200-6400

Anybody else have a favorite grind from someone else they like better?

 

[vioperblue72]

I think that cam would fit your needs. I like that the cam apparently has a fast rate of lift, judging by the adv. duration and .050 duration and the lift is about as high as you would want to go. Check your clearances too.