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I bought a 76 F350 dually but is has a 77 400 swapped into it. I'm currently building out the engine and am looking for some advice. It has previously been bored .030 over but as far as I can see that is the only change made to the stock configuration. The mods I have already purchased include Edelbrock 4bbl intake, 650 cfm edelbrock carb, Long tubes, new distributor (old didn't work). Also some normal maintenance stuff while I'm at it like plug wires, spark plugs. I need advice on the cam. I've read that the stock cams have very delayed timing and aren't that great. I'm thinking a comp cam magnum 224/224 k-kit (K32-224-4) so I can upgrade the valvetrain too. Can I use the stock pushrod/rocker setup? I would buy new ones as the current ones are very worn. Or would I have to buy a different style? any and all advice for the whole build is welcome. Thanks in Advance. (it is an NP435 so torque converter things don't matter)
The Comp kit will be complete for what you need, but probably more cam than you might want really. I don't see it being a good fit in a dually truck, even with a manual. What is your intended purpose for the truck? Horsepower goals?
What is your intended purpose for the truck? Horsepower goals?
Mostly just driving it. Little bit of hay hauling. I don't know what this engines capable of I just want to fully utilize the other parts I've bought so far and not be limited by the stock cam. I also love a little bit of a rough idle.
With that cam, I doubt you can use the factory pedestal mount rockers you just torque down and forget
Think
Screw in studs and pushrod guide plates
Think
Bronze wall valve guides
If your rockers are worn, I can assure you your valve guides are worn beyond the wear limit
That valve guide wear limit is .001 for the intakes and .0013-.0015 for the exhausts IIRR
Basically, any perceptible movement in a valve guide is a fail
Please forgive my lack of knowledge. I'm 16 and this is only my second project and my first time really getting into an engine. My plan now is to replace the valve guides and put in either the comp magnum roller rockers or the equivalent summit racing ones. What studs am I looking for. (I am keeping the stock heads) Also with these I plan on installing guide plates and new pushrods. With the pushrods would the geometry change be drastic enought for a different length or is the stock 9.500" good? Thanks for all your help.
By the time you're my age you'll be twice as smart
The stock pushrod length should work with the adjustable valve train you will have after the machining
You will be looking to have your stock heads machined for a 7/16 screw in stud
It's great to see a young enthusiast getting into this hobby, especially with a classic truck! That rig looks solid and should serve you well.
Now, about the cam. Like @manicmechanic007 mentioned, the K32-224-4 might be a bit much for your setup. Many people go for a “choppy” cam, but they’re not always the best fit. You’ll want strong low-end torque and a responsive mid-range for smooth power through the gears. Here are two better options:
More lope, strong mid-range, and works well with your intake, carb, and headers. This cam is in stock as a kit (CCA-K32-242-4).
Gearing & Drivability
From the factory, these trucks should have 4.11 or 4.30 gears. A cam focused on low to mid-range power and torque works well with these gears and the NP435 transmission. This combination will make for a fun and usable setup. It’s great for farm work, towing, or even daily driving.
Rockers & Pushrods
There is mixed info about the limit of stock rockers for the 400. Yours already sound worn, so we’d recommend:
Break-In (Crucial!)
Use assembly lube (typically sufficient amount comes with a cam). Also, use break-in oiloradditive and follow proper break-in procedures. Skipping this risks premature wear or failure. We don’t say this to scare you. We just want to make sure you enjoy the truck for years to come!
You're on the right path. Keep at it, and we can’t wait to see this build come together! 💪
Update: I was looking at my heads a little closer and the casting numbers didn't match. D5AE-A2A and D5AE-BA one has a 74.5cc chamber the other a 78.4cc. This along with other problems with the heads I decided to get some different ones. I found a nice set of D3AE-G2B that have been sandblasted and don't have any components with them. My plan now is to put some SBI valves, valve guides and seats in them. I decided to go with a summit cam SUM-K5201, Comp pushrods CCA-7837-16, trick flow spring components TFS-16972-16, TFS-31400443, TFS-51400423 and a summit double roller timing set. I am also planning on using some comp magnum rollers CCA-1411-16 and arp studs. What length stud am I looking for?
.
Good call on getting matching heads. You never know what surprises can come with a used engine or vehicle. We appreciate your support with the purchase of our SUM-K5201 cam and lifter kit! That setup will give you a noticeable idle and shift the powerband more toward the mid-range and top-end.
If you're running 4.11+ gears, they'll help keep you in the powerband where this cam really shines. As for rocker stud length, there's no one-size-fits-all spec—that's something you'll want to confirm with the machine shop handling the head work.
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