351w cam

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Apr 1, 2022 | 12:20 AM

1975f250custom

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351w cam

Hey y’all, pretty new here and new to cams. To start off I have a 1974 351w. I’m taking it out of my truck to go over all the gaskets but while I’m in there I plan on putting in a new cam. Most likely going hydraulic roller conversion. But regardless of wether I go flat tappet or roller, what the hell is my max lift and duration? Cylinders are .60 over so It’s gotta have oversized pistons (duh). But what’s a safe lift and duration? How stiff springs should I use for said lift and duration and what rockers? I should mention it’s got stock heads. Im pretty overwhelmed since I’ve never really looked into it till now and can’t really find a straight answer. Or is this a waste of time, I’ve got a 650cfm edelbrock and performer intake, and don’t wanna change that any time soon as I am very broke and don’t feel like putting another $700 for a new carb. Give it to me straight doc 🥲

Apr 1, 2022 | 08:51 AM

DaveMcLain

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In a totally stock engine in a truck I'd keep the duration short. 200-208 or so at .050. Your compression is low as is your usable rpm range. Max lift is mostly irrelevant unless you start to run out of clearance between the retainer, the valve seal and the guide. Most cam lobes with that sort of duration will have around .460 or so lift with the stock 1.6 ratio rocker arms.

A good set of stock springs would probably be adequate for a flat tappet hydraulic cam. Be very careful that the loads don't get too high or the life of the cam will be very short. I'd recommend keeping the open loads under about 250lbs.