Hello all. I know I should ask this in engine forum but more activity in this room. Working on the 351m/400. I believe I have the 400 but have not measured it. Based on the vin it came with the 351m but the valve cover is 400.

Onto the question. I need to have it rebuilt and have read that if I can afford it, make it a roller valve train and not flat tappet. The work that needs to be done, is it to the heads only OR engine block needs special work too? Not looking for all the details, just basic info to make a better decision. About what kind of cost to do this modification? Any links you can point me to, to learn more will be helpful.

Thanks all. Chris

 

Go roller , custom roller cam you won't regret it. I'd contact Brent Lykins at Lykins motorsports and have him spec you one for your exact needs and have it ground.

To go with a roller cam all you need to do is buy the cam, roller lifters with the correct springs, push rods and a bronze or hard steel distributor gear. no machine work or modifications needed.

I don't like roller rockers and you don't need them , but you can if you insist.

 

Agreed. Go roller. It's a bit expensive when the cost of the lifters, shafts, and rockers add up (along with the supporting equipment) but it's worth it to have a maintenance free system.

 

There are severe problems in the market of flat tappet cams these days. One wiped flat tappet cam, and you will regret not going roller in the first place.

I think the problem with flat tappets today is the lack of quality control on the manufactures part. It is very critical that the taper on the cam is correct and the crown on the lifter is correct. Get this off even 1/2 a thousandth, and bye-bye, cam.

If you are only rebuilding and your original flat cam is still good, you can just make sure the lifters go back the same hole and keep running it. Get one lifter in the wrong place and it can wipe the cam. Well-maintained flat tappet cams can go 300K miles.

 

If you're just going for a bone stock rebuild with boring grinds and weak springs a roller cam isn't quite as big of advantage but still a good idea. a custom grind is always a good idea and you can get that in a flat tappet as well. but either way the only reason not to go roller cam is if you can't afford it. end of story.

Unless the cam was really low miles and looked great I wouldn't reuse one. they can last a long time but they do wear out and it's not worth tearing an engine down again because you cheaped out on a $150 cam . anytime you have the lifters out is a good time to put new ones in, they wear out and there's no problem putting new ones on a used cam that's an old wives tale. but never used lifters on a new cam.

For the OP, check out Brent's site and talk to him if you're thinking about a roller cam. you won't regret it.

 

Go roller. And 351m/400 valve covers are identical. Throw in 351c also.

 

Flat tappets have done well for about 200 yrs....dating back to early steam engines.

Roller lifters have more moving parts and are WAY more prone to failure as compared to 20 minutes of flat tappet break in.

Cam research offers a pre-break-in procedure which is very affordable...far cheaper than a roller conversion which requires block machine work, custom pushrods..etc.

For a mild truck application it's not worth a 25% cost increase to say "I have a roller cam of which I will never use the benefit a roller provides in my 5k max rpm application".

Break it in per the instructions with the right oil, use the right oil, and enjoy.

 

You can't get the ramp profiles in a flat tappet you can in a roller, the difference in the way they run is noticeable. roller lifters in a new car are basically the same except for the simple crossbars and the failure rate is a fraction of the flat tappet lifter.

of course the roller cam and lifters are more expensive but you get what you pay for. you need new springs, pushrods, distributor gear, cam and lifters for your flat tappet set up anyway so it's not as scary as it sounds.

Buy you will miss out on the thrill of the break in and 5000 miles afterwards checking for metal in your oil. those were the days.

 

don't need crazy ramp profiles in a mild truck application.

the steeper the roller ramp the more prone to lifter failure...

Lots of engines that ACTUALLY UTILIZE roller tappet ramps are in fact race/max effort deals and lots of those engines also change out their lifters as preventative maintenance so they don't end up with roller wheel brgs in the oil pan.

Here's a thought...after the proper break-in of the flat tappet, why not ALSO run the proper oil and keep on truckin??

 

Did I mention you opened a big can of worms with this topic?

I agree flat tappets were rock solid until recent history. When I was young and ignorant and building engined on the cheap. I broke lots of push rods, pulled rocker studs, and broke rocker arms, but I never had a single problem with flat tappets. That was in the '80 and '90s.

I have a 460 with ~130K miles, and it runs as smooth as the day Ford made it. (There never was a roller 460 made by Ford.) I just change the oil every 5K miles.

Do your research. There have been A LOT of problems with flat tappet cams and lifters in the past decade. You will find many of the most experienced engine builders swearing off of them entirely now because they've been burned too many times in recent history.

There's enough information about the modern problem out there; I won't build another engine with them. But I won't throw away a good one, either. It's not hard to inspect and measure a cam for wear.

Here's a good video on what you need to know if your new flat tappet cam and lifters are good to go:

 

If I cross this bridge again, I'll likely do as I always have ... flat tappet hydraulic lifters. I've seen rollers come apart, it's not good either. I do like the idea of roller lifters, but I always put extra effort into my cam break in. Twice I've had a wiped lobe or two, both times were on factory cams that come in the car. One was a '80 Plymouth police car with 360 & one a '79 Malibu with 305. Both times, the cam and lifters were replaced and oil pan was flushed out followed by fresh oil and filter.

I've put cams in Chevrolets, both small and big blocks. I've swapped cams in Pontiacs, my '69 Dart's 340, Plymouth 383 and 440s ... and I get the "being nervous for that initial start" feeling. I very liberally coat my cam lobes and lifter bases with thick dark grey high moly cam lube, I pour some good, rich high zinc 20w50 Kendall GT-1 down over the whole deal before putting the intake on. Once started. I remove my valve covers and set the crank at TDC on #1... first thing, then mark the distributor rotor to body and body to block .... before I even loosen the distributor hold down. Once started after a cam swap, I will keep it running at minimum 2500 rpm for 20 minutes ... that does not mean drive it .... it means hood open, watching, and not letting rpm drop once. You can twist the distributor, you can hand hold or screw the idle stop open, watch the temps. I'll even keep running water on the radiator fins.

Only if something is badly amiss would I let the rpms fall, and then only because I felt that I had to shut it off. There'll be time to set timing and idle later. My timing is really close thanks to my first step. I have been known to use even weak stock springs and swap in the cam kit ones the next week. I won't say the 335 series of engines are great engines & I won't say flat tappets are better than roller lifters either, but I will say that both have done OK for me. My truck just needs to move under it's own power and haul my loads, it doesn't get used to do burnouts at Walmart or do hill climbs, mud bogs, or get raced.

 

Chip,

you realize the same company that machines the flats also is machining your rollers?

lol


Btw pls don’t make blanket statements about engine builders walking away from flats…last one I had done was an aggressive custom for a street strip 521 by an engine masters pro builder….I told him weekend warrior not professional and he said flat all day long if I am not doing consistent PM’s on the valvetrain…..too many issues with rollers coming unglued wrecking alot of parts.

 

The ramps don't have to be crazy to be more efficient. retrofit roller lifters are fine as long as they're made by Johnson.

Flat tappets are just like 335 series engines. those with them will do their best to convince you they're great, those without them are just thankful they have something else. I have 400's and I have flat tappet V8's, and I have good engines and rollers. you're not fooling me but hey someone might buy it .

 

What does every OEM do? They build more engines and pay more warranty claims than anyone.

As to rollers all I've seen, which isn't much, is the roller rockers coming apart in LS motors, spreading tiny needles throughout the engine.

Roller cam followers probably do come apart but I haven't seen a thread about that...

Lots of wiped out flat tappet cam threads though.......

 

Roller rockers have failed forever that why I don't use them. they offer no advantage unless you have super high lifts anyway.

Roller lifters are like anything else they can and will fail, the earlier 5.7 hemi engines are known to lose roller lifters around 150k miles . for any older V8 like we're talking about 150k is what you call a total success so go for it.