Can you guys help me summarize some of the thoughts I've gotten from reading all the posts on building up 351M's? I've read BubbaF250's website and a ton of posts on this forum and right now this what I'm thinking about doing to my 79 351M. It's in a 79 Bronco with a 4" lift and 35's.

I don't really want to get into doing a cam and lifters right now. But, do I understand it correctly that I can set my STOCK cam at straight up timing for better performance? Is this just a matter of taking all the stuff off the front of the engine to get to the timing chain and then basically unhooking it and putting it back on at the straight up timing mark? Then what do I need to do at the distributor? Trial and error for best driveablity without pinging?

The second part of the plan is to put on a Weiand 8010 intake and a 600/650 cfm 4-V carb of some sort. Not sure on brand yet.

I already have headers and dual exhaust. Everyhting else is stock on the engine.

Can I do these things in combo with each other, and will I get better power out of the engine? Any negative effects? Do you think I would actually feel any increase or would it just be better on paper?

Please let me know if this is a stupid idea. I'm just trying to think of ways to get a little more oomph without really tearing things up and without spending a lot of $$.

I'm planning on re-gearing the axles too.

Thanks for any advice yo can give me!

 

wel alot of the prob is the low compression ratio smog equiment and poor timing
you cant do really anything about the cr so timing is a good place to start
i think please correct me if im wrong the motors where timed 4 deg retarded
at the factory. run a non egr intake with a good carb i try to run ebock on trucks holleys jus tdont seem to like steeper grades for me.

but listen to theese guys they really know their stuff.

soory i couldnt help more

 

you can't get rid of the factory 4* retard using the stock timing set unless you drill the dowel hole in the cam sprocket and use an offset bushing, that's old school stuff. you could probably use a new timing set anyway? aftermarket timing sets don't have the retard built into them, you just install an aftermarket set at "0" or "straight up".

 

If you're going to have the stock timing set off, and the intake manifold off, that's just two bolts and a good tug away from having the cam out too...

 

real good point 84

hey at least youll save on the cost of gaskets lol

 

The cam in a late 351M/400 is a decent cam. It just needs to be timed right. I degreed a cam for another engine and it was a real learning experience. I'll never install another cam without degreeing it. I had two new 'stock' timing sets and neither one was even close.

If I were you, I'd get a RollMaster timing chain and have a shop degree it. If you've taken the EGR off, you need a new distributor, tuned for a non-EGR engine. If you can get one from a 70 351C, that should work. Once you've done that you should be in pretty good shape.

 

Thanks guys. I guess you're right, if Ihave all the other stuff off, it would make sense to just do the cam at the same time. Duh.

I do already have the EGR removed because the EGR spacer had holes burned right through it. I replaced it with phenolic spacers. I didn't realize though, that I need a different distributor because of the EGR being gone. What's happening with my current dizzy now that the EGR is gone? Does this really mess up engine performance? Good info for a newby driveway mechanic, thanks.

I guess right now I'll just back off to doing an intake and a 4-barrell and see how that goes. I'm not sure where to find a '70 351C distributor around my parts. Not too many junkyards with stuff that old around here that I know of. Hopefully if I re-gear I'll get a little performance back as well.

Thanks again!

 

You don't necessarily need a new distributor you just need to make sure the advance curve is modified. There's a good tutorial on recurving Duraspark distributors at the Reincarnation Automotive website. It's a 385 series specific website but the info should be good for just about any modified engine since they use the same dist at the 351M/400.

Here's the link:

Duraspark Recurve Instructions

 

doing the cam at the same time is kind of a no brainer, but the trick is to find a cam that you like that will not require any spring seat work if you aren't planning on taking the heads down. some M/400's have retainers and rotators that don't allow hardly any additional lift over stock. it wouldn't be hard at all to figure out how far you can go by using a dial indicator and a light test spring to find out where she bottoms out. then figure in the safety allowance and start looking at cams. or get different retainers and springs to allow for more lift, but then you are going to have to check installed heights. it can become a bit of a nightmare doing all this at home, the shops have stock on hand to rial and error the right combinations of retainers, shims and keepers.

 

Before you dig real deep in your wallet, a good double roller timing chain without the built in 4 degree retard will help alot. Just the fact of a new chain without all the slop of an old chain is a big improvement. If you decide to replace the cam, stock valve springs won't support a lift of more than about.510 without binding, especially if they're old. Your Bronco probably has 3:50 gears in it, same as my 78 F-150. I also have a 4" lift with 35's , and it's not enough gear. I plan to switch to 4:56's to make effective ratio approx. 3:73. Should make for much better throttle response.

 

There was a thread on max lift for stock springs in this forum several years ago and IIRC the final calculations came out to +/- .480" of lift on stock 351M springs so any cam which has more lift than that will run the risk of coil bind resulting in bent pushrods, wiped cam lobes, etc. When installing a new cam it's always best to get new springs matched to the cam. Cheap insurance in my book.

Effective final gear ratio is certainly going to affect performance and changing the diff gear ratio to match the intended tire size is a very good suggestion although generally not cheap.

 

I've ran 35's with 3.50 gears and I had plenty enough torque to pull those gears. Than again I have a 400 and not a 351M. I recently swaped out my 268H and lifters to a puny grind/stock lifters, advanced 4.5 degrees for a total of 5.5 degrees. It worked though and I picked up about 5mpg. With a new torque converter I'm hoping for 16-17mpg. Yes the comp cam had alot more top end, but I can only tell the differance if I have my foot shoved in it. But with part throttle acceleration, I can't tell the difference. All being said, a stock cam timed straight up with other mods works fine. I'm running a 600cfm edelbah carb with matching manifold, 4V valves undercut and tuliped, strait cut timing gears, headers and dual flowmasters with a crossover pipe. I'm also running around 9.5-1 compression, a remanufactured points distrbitor with pertronix II points and coil. For a 4600lbs truck she is pretty damn spirited with a stock cam.

 

Hey Eric...
I Played with alot of cams and timing settings and found that the motor ran like a raped ape when the cam was set 6 degrees ahead of the crank. My sister had an escort (I know...laugh) and the timing was offset on that cam and it burned the tires big time. Ask some performance engine builders and they will confirm this. I live near a 1/4 mile track and talk quite a bit to the techs in the pits....brings back alot of memories but now I'm old and lazy! Thats why I have this keyboard now!!! lol

 

I agree, timing the cam adv lets the engine see more of its displacement, raises the dcr, and brings in the power band earlier. I beleave for every 4 degrees adv it lowers the power range 200rpm.

 

i'd think that after the first 4* advance the next 4* would have significantly different results than the first 4* jump. lookingsmaller says 6* is still a "go" for him, i'm guessing any much more than 6* may be past the point of driveability improvement and might see some issues? i did an experiment where i purposely set up a timing set one camsprocket tooth advanced. at the time the way i figured it to be 10*? ran great at idle and off the line but gave up real quick, way before 55mph.