Hi everyone,

I am in the process of rebuilding the 351m in my 79 f150 4wd. It has 3.50 gears and a 4spd manual. Bored .030 over, heads shaved .010 and block decked .020. I have ordered and recieved 3 Lunati Voodoo 10320700 cams that were all bent from summit. My machinist chucked them up and verified it. Anyways nobody has any more of that grind that I can find and am looking at other options. I want the most bottom and midrange torque I can get. I would like a little choppy idle but thats not a deal breaker also. I am going to be running a edelbrock 4bbl manifold and a 600 cfm summit m2008 carb. I already have upgraded springs on the heads that will handle lift to .600". Stock exhaust for now but will eventually get headers when money permits. Which of these cams would be my best bet for what I'm looking for? Or should I just wait until I can get Lunati to send me a straight one?

Comp XE256
Comp XE262
Oregon Cam Grinding 1333 or 640 Hydraulic Camshaft Specifications
Enginepro MC1733 or MC24204
Crane 5203901
Summit K5200

Thank you all so much in advanced.
Kyle

 

Don't know the specs on all those but back in the later 1980s I put a Crane Fireball hydraulic cam in my '77 F-150 with 351M, auto, 3.50 gearing too. Already had a Edelbrock Performer 400 intake on it. I put the cam "straight up" with new chain & sprocket set, I used a Holley 600 then ... but a few years ago switched to an Edelbrock 600 (and needed a FPR as stock pump will pump 7 psi but Edelbrock carbs copied from the old Carter AFB will flood over 6 psi ... because the float arms are set up different) , and I already had put in a quick advance kit. I set my timing to 35 degrees BTC after all mechanical advance is in, with the vacuum canister disconnected, then I reconnect the vacuum line to ported vacuum on the carb. I used stock springs, rocker arms ... & new stock lifters too. I did not know you could get a bent cam as all I've seen were cast iron and I have seen them dropped ... and they busted.
Don't kniow if they make it now or the part number, but specs are:

Basic Operating RPM Range: Idle-5,500
Duration at 050 inch Lift: 204 int./214 exh.
Advertised Duration: 282 int./292 exh.
Valve Lift with Factory Rocker Arm Ratio: 0.484 int./0.510 exh.
Lobe Separation (degrees): 112

I like it.

 

That Lunati grind - 207/213 @ 0.050", .503/.524" lift looks like a good grind for your purpose. I'd further investigate the "bent" problem. Lunati and/or Summit should make it right and the cam is still listed as available from Lunati. There may be some counterfeit cams floating around. Who knows? There is a serious "problem" here and both manufacturer and vendor should help you figure it out. Have you taken the cams to another machinist just to double check? I suppose your machinist could even have a problem with his equipment.

If you can - it's best to post all the specs for the various grinds yourself, save everyone viewing the thread an hour chasing part numbers.

Looking through various camshaft catalogs, there are probably only two "torque grinds" per manufacturer. You're not going to notice 3-5 degrees duration or 0.015" difference in lift (at the valve), that said - I'd opt for a cam with more lift and less duration.

 

It is VERY common to find a bent cam after shipping and they can be straightened easily. In fact straightening the core before grinding is a big part of producing a quality camshaft with minimal base circle runout. If it is straight when ground then everything will move together when it gets bent again so the base circle runout won't get worse if it is made straight again.

If it were me and I wanted the best low end torque I would use a single pattern cam with a tight lobe sep and short duration. In a low compression 400 Ford I've used HL19-7/A1 from Demos Cams. These are the Reed Torque Master lobes and this one has 205 degrees at .050 is ground on a 107 lobe sep and gives .493 lift with a 1.73 rocker arm. This will make more torque than any of these grinds that are in this thread.

The problem you'll have right now is getting a cam because nobody has any cores.

 

It's far more likely a flat tappet cam will be broken in shipment rather than bent. They are brittle.

 

While it is true that being a casting does allow a flat tappet cam to get broken they can and do get bent too in shipping. A month or so ago Demos ground a flat tappet hydraulic for one of my customers who was building a 250 Chevy. The cam got bent about .010 in shipping and had to be straightened so that it would fit into the engine.

 

Thanks Dave! I had no idea this was such a problem. Pretty crazy to happen in the modern day if you ask me! Anyway - yes, if his machinist has told him three cams were bent, why not just have the machinist bend one straight? Get the cam you want spend $20 or whatever to ensure its straight and be done.

 

I still don't understand how you can bend cast iron. Maybe I just don't get it.

 

The people doing the shipping can find a way.

 

I have a low mile 351M I put This cam in same specs as the summit 5200 (https://www.rockauto.com/en/moreinfo...05603&jsn=1604) 52.98 right now. Due to the low factory compression ratio it runs imo about equal to the stock cam but pushed up the mid range a bit more. I do also have the straight up timing set. I understand the stk timing set put more power to the low end. I built a 460 cause I wasn't impressed went with a Howard's Cam for that build, They are very helpful perhaps a call to them on the 351M might be a good idea.

 

The reasons that cam is somewhat a disappointment is because it has too much duration(about 10 degrees) and too wide of a lobe sep(about 2-3 degrees) to really work well in a low compression and low speed applicaiton. The stock timing set on some of those engines retards the cam 8 degrees and this is done along with EGR to reduce low speed cylinder pressures which also reduces nitrous oxide emissions.

 

With these low compression engines it is very important to pay attention to the ADVERTISED duration and LSA when selecting a cam. From this you can determine the cams intake valve timing events, which is extremely important to cam performance. Low compression needs low advertised duration and tight LSA. That’s why a cam with similar specs to the Comp 255deh or xe256 works very well in these stock engines. They have 255 and 256 advertised durations respectively along with a 110 LSA which produces a decent dynamic (running) compression resulting in good street power/torque.
Case in point the Summit K5200. Yes it is a upgrade with some people liking it, while others hate it. With an advertised intake duration of 282 (about 275 when measured like Comp cams) it’s valve timing effectively bleeds off what little compression you have then add to that a 112 LSA and it’s made worse producing a very low dynamic (real) compression. This cam really needs around 9 to 1 compression to perform best. This is usually what you find with the cheaper cams that use slow ramp “lazy” lobes.
IMHO, The original poster chose a good cam for his engine being a 260 advertised, 110 LSA, and decent lift/duration. Although I would install it advanced in his situation to pick up a tad more low rpm torque.

 

One thing you have to really watch out for with designs like those Comp XE flat tappets hydraulics which are quick off the seat is that they tend to be noisy. The positive acceleration as the lifter gets to the the ramp is higher than some other designs and this can make them sound like a solid lifter cam.

Some people like that they have a lot of lift for a given duration. This is achieved by having a section that dwells at or near max velocity; max velocity isn't higher it is just maintained for a period. Some cam companies use this type of a design in many of their flat tappet designs yet a lot don't.

A 110 or wider lobe separation is wider than you need for this duration. Get that tighter and the engine will make more torque and run better. The reason why Comp and other cam companies use such wide lobe separations on their catalog cams is simply because most people choose a cam that's too large and that makes the design more forgiving in that situation.

 

Yes, I agree totally. I just referenced that specific cam (xe256h) because it is so popular and shows a lower advertised duration to compare. Personally I won’t run the XE series cams because I feel the ramps are just to aggressive to get any longevity out of. To me all they’re really good for is to “crutch” low compression engines.
Not wanting to stray too far off topic, I also feel like these extremely aggressive lobes such as XE, Vodoo, Rattler, etc. is ONE reason (coupled with others) why we’ve seen so many cam failures in recent years. I prefer to compromise with a bit milder ramps. My philosophy that has never let me down is If you want a big duration cam then run adequate compression so you don’t need extreme ramp cams.

 

What can be deceiving about looking at seat timing is that it doesn't take into consideration where the duration is on the profile. In other words the design could have almost no ramp on the opening side yet have a really long slow ramp on the closing side yet still look the same as or even shorter than a cam that's either more symmetrical or has moderate length ramps on both sides. This is what's been done on the XE designs.

If you take an XE 254 lobe which in my plot has 253 duration at .006 and 208 at .050 with a tappet lift of .300 and lay it on top of a graph of a Reed Torque Master with 267 at .006 and 205 @.050 with a tappet lift of .285 you can really see how the closing side ramp is basically identical yet the opening side of the XE is shorter. That's where the main difference in seat timing really lies. The Torque Master is an excellent running flat tappet series that's quiet, revs well and is easy on parts.