Hi all,

I could not find an answer to my questions in the numerous threads regarding the factory (emissions) retarded timing sets and cam swaps. I have a stock 400 in my 1979 F-150. The motor runs well, has good, even compression and is sporting rebuilt heads from ATK. I have deleted the EGR. The harmonic balancer has been replaced. The distributor and carburetor have been replaced with rebuilt units and there are no performance mods. Yet.

I'll be pulling the engine soon in order to replace some weeping freeze plugs, so I'll have the engine on the stand. While it's accessible, I'd like to enhance the low/mid range torque, while maintaining an eye on expenses. I drive 100% off road at low speeds and would like to augment the pull off idle up to 2000rpm's. I have zero interest in high RPM power. It won't serve my needs.

My simple questions are:

* If I replace the timing chain, which I suspect is original, would it be worth it to spend another $150 for an RV cam, lifters and intake gaskets? Are there pitfalls to consider? What are some low speed torque cam numbers to look for?

* If I do attempt to fit a new cam, do I need to be concerned about the cam bearing dimensions, or is it a simple case of swap one in? I did not uncover any discussions about oversize bearings or undersize cam journals, so I thought I'd mention it to the trust! It would not be too big a deal to pull the stock cam, only to refit it in the case of a incompatibility, but I'd like to hear from y'all first.

Thanks in advance,

Rick

 

. This prolly belongs down in the '335-series' engine forum...

. Your cam came retarded about 4 degrees or more, I'd suggest a new timing chain set that allows you to advance it 4 degrees, instead, for more low RPMs power...

. Most cams offered will be bigger than what you have, which is going in the wrong direction... don't know if any smaller ones available off the shelf... might call Comp Cams and ask them...

http://www.summitracing.com/parts/su...FYo-MgodKlYAMw

. These 400's were rather low RPM engines to start with in '79, torque peak around 2,000 RPMs, so the stock cam may be sufficient once the timing is fixed...

. Long 1 5/8" primary tube headers and true dual exhaust may also help...


. And some higher compression ratio TMI pistons if willing to go that deep into the engine...
.

 

Thanks Buzz,

Nah, I won't pull the heads again for fitting pistons. I'll probably follow your advise and go with a timing set and leave the cam.

Do you or anyone else have an answer to my concerns about a cam swap? Those questions would really impact my consideration of the project and I'd appreciate any wisdom.

Thanks,
Rick

 

On the cam swap... an "RV" cam often has more lift and a bit more duration for mid RPM pulling. Wrong direction. More lift will need better valve springs... stock 400 springs cannot handle more lift. Also, more duration will reduce low end torque. I think the timing set alone is best for your needs.