I've heard that the biggest thing I can do to my 351w SD EFI is to add 1.7 rockers. Now here is my set up 351w bored 40 over, slight cam for torque, 1978 HO heads, stock EFI truck intake, and stock manifolds.


Can I find the 1.7 rocker arms in the junkyard? Off of a roller 5.0 or possibly a 7.5? I plan to add long tube headers, but how much will the rockers help with the stock manifolds? Will the SD EFI need any tuning?

So far as exhaust I currently have true duals, 2 1/4" pipe, no cat, thrush welded mufflers. I need a new exhaust cuz mine is starting to leak alot, but I'm trying to wait until I get my longtubes.

Thanks guys for everything!!

 

the rockers add more lift which might com in contact with the piston sincce you have a mild cam

 

78 heads? No... swapping something(anything) else on there to replace those boat anchors is probably the best thing you can do. What cam you got?

 

Im not sure what cam, it came with the old engine before I built it. It can't be much more than the stock cam. it sounds alittle different than my stock 5.0 but not much.

And if I read the date codes right it was 1978 heads. They had the smog holes in the just like the E7's.

 

I just realized I read the date codes wrong. Lol. The heads that are on my engine are the ones that would have came on the 1985-1987 351w HO 4bbl. And the cam I have might be stock, it doesn't lope, I believe its just a slight over stock cam.

 

Doesn't matter that engine got the same large chamber smog head as everything else from that era so CR is down around 8.3:1, and ports and valves are the same as later heads so they're nowhere close to appropriately sized for this displacement. The 351HO cam was pretty much a flat tappet version of the 5.0HO roller cam though so you're in good shape there, bolt on a set of GT40s and you get a bump in compression up to 8.8 to 9:1 and bigger valves and ports so you'll see healthy gains across the board.

 

Now, If I do a head swap will I have to build the bottom end again?

How much compression do you think I have with my engine being bored 40 over? I don't want to do a head swap and have to run mid or high grade fuel. and I also don't want to have to rebuild my bottom end. I only have 10,000 miles on this engine.