Piston to valve clearance - 454 Mag short block
 

I tried to do some searching, but came up short.

Assuming a stock 365 short block, where does one start to run into clearance issues?

Let's say I were to run a Crane 731 roller... is it generally a matter of installing, degreeing it in per the cam card, and being done? I know that checking PVC is a must anyway (i know how and have the tools to do it), but the intent is to avoid having to go into the short block to make changes.

How much lift is safe and with what duration?

Thanks!

Anyone?

You really need to mock up a cylinder and "clay" a piston to be sure.
Actual deck height and if the cylinder heads have been cut any can change things up.

Yes, that would be the plan after a camshaft was in-hand. What I'm getting is in regard to parts selection beforehand. Looking for others experiences with this cam and similar.

I haven't removed the heads yet, but I have all the service records for the engine, and I'm dealing with a factory stock short block. I'll measure to be sure, but let's assume that the pistons are .020 below the deck, and dealing with an untouched cylinder head.

It's not really the lift an duration that's going to get you on a marine engine. When you go from say a 2.25 valve to a 2.3 with a 454 piston it will hit on the sides of the relief. Or if you go from a 2.3 valve to a 2.35 or 2.375 on the large bore Pistons. But that's a different story because with those kind of heads they are rolling the valve angle a couple degrees.

In this case I'm not changing anything like that. My heads have the factory 26* valve angle. 2.19 intake and 1.88 exhaust. 118 cc chambers.

You should b fine

Tom, I don't think you will have an issue with flat top or small dome pistons and a 731. I am running a cam with .596 / .612 lift and similar duration to the 731 with flat tops, and it wasn't even close to interference. No need to go larger than 2.19 / 1.88 with the relatively small bore of a 454 block, from what I have been told.

A big block is not like a small block when it comes to piston to valve clearance. I have .721@ the valve with no issues. That's with a 2.3 valve and a flat top.

Thanks for the responses guys. Much appreciated.

When I was talking to Bob Madura last week, we were thinking the lift would be in the lower-mid .600 range. I haven't made my mind up regarding the cam just yet (I'm in "inventory" mode right now), but I know the 731 works for a lot of people. Good to know that it will fit without too much difficulty.

Also, this is going to be a blown setup. I don't think the 2.19 intake will hurt it. Agreed that the 2.19 works much better on the smaller bore of the 454.

Tom knowing what I know in my opinion anyone building a marine engine if it be a max effort or a mild "warm up" would be foolish not to buy a cam from Bob. I've had some lengthy technical discussions with the man and believe me his depth of knowledge goes much farther than what most of us know. If you are trying to get everything out of the combination you have his camshaft is the only way to go.

Agreed. And he's done my cams before (I have one of his SBC cams listed in the Swap Shop). I was just looking at generailities. I know Bob will set me up the right way for sure.

Does anyone have any proven data that shows a 2.19 valve works better on a 454 than a 2.25? What cylinder heads are we talking about here? A small oval or GM rectangle port, or aftermarket rectangle port?

I read where a guy did some flow bench testing, and by simply moving the head over some on the stand was able to gain 12 CFM. The context being that moving even the 2.19 valve away from the cylinder wall picked up some airflow.