I trust the info I find on this site, that being said i want some sound advice on what direction to go on upgrading a painfully stock 351. The engine is out of 1977 LTDII, stock spec rebuild (as far as I know anyway) and in a 1982 f150.

The engine has an anemic 2 barrel motorcraft carb on it, runs good but not much power.

Does anyone have solid recommendations on what direction to go as far as what heads I should use. I'm leaning toward a set of good used gt40 heads, since budget is the biggest concern.

Any help is greatly appreciated.

 

Yes GT40 heads would be a very good upgrade and even E7 heads would be better that what it's got now, then you need to put a cam in the motor that actually opens the valves.. loads of possibilities here but even something like the Comp 35-235-3 would be a hugh upgrade.

 

I've also heard that upgrading to 1.72 ratio rockers provides a huge difference.

I don't one really want to put a new cam in it, when it was rebuilt 25,000 ish miles ago a new and different cam was put in it. I'm assuming it's not much more than stock.

 

No.. it's about the same as adding a few degrees of ignition advance.. noticable but not dramatic. This was a 150hp motor back in 1977 and most of that was due to a grossly undersized stock cam that artificially limited air flow through the motor, with no other changes(yes even without changing the heads) you could potentially add 100hp to this thing.. something that only requires a cam that produces around 0.450-0.500" total lift and 260ish degrees total duration which is not radical at all.

 

With that much lift would it not have a rough idle and have no intake vacuum at idle?

 

Lift is not the issue for idle or vacuum. Duration, overlap, and timing are the concerns for idle and vacuum.

 

It's all in the details, a cam this size is not large at all in the big scheme of things, the key to high vacuum and a smooth idle is to keep the 0.050" duration at 205-210 degrees max and the LSA a conservative 110 degrees. The cams that have a rough idle and low vacuum all have 220+ duration at 0.050" lift and 105-107 deg LSA.

 

Thank you for clearing that up for me. I always hear all these terms thrown around and never paid too much attention to them. Now I need to learn more.

I checked out comp cams website and found a cam with the specs listed above and was shocked at how cheap they are.