I am in the process of a 390 buildup. Engine specs are : .030 over block with oil mods, Ertel flat top pistons and pins, Edlebrock streetmaster intake manifold(ported), C7AE-B rods with ARP rod bolts, C8AE-H heads in progress(ported, going to install hardened exhaust valve seats), high flow oil pump with ARP oil pump driveshaft, double roller timing chain, felpro gaskets. Engine is going in a heavy 67 f-250 with 4:10's and 34"tires. The two cams that I am choosing between are crane 343901 and 343941. I want to run the 343941 but Crane Tech told me that I need 10:1 compression ratio to run it. Is the tech guy on crack? Maybe I should try Comp 262H.

 

Bigger cams tend to bleed off compression. So to compensate you need higher compression. Hope this helps.

 

I dont think the tech guy was on crack, I think he was smokin' some wild weed. If you check here, you will see that it says 8.75 - 10.75 compression ratio for the 343941, while the 343901 says 8.0 - 9.5. So you'd probably be OK with either one.

 

What is your compression with the flat tops?

Both of those cams are really pretty small. In fact, I would be afraid that the 901 would actually build so much compression it would be hard to keep from detonating on pump gas.

 

I have the 343941 in my 410. I originally built it with 10:1 CR, and had major problems with detonation under the typical heavy loading that I do, even with Edelbrock heads. I have since dropped the CR to 9:1, and no sign of detonation on regular 89 octane. The 343941 has a very slight "lump", but seems to pull well at low RPMs, and I can really feel when the engine starts to get up "on cam". Steve

 

Thanks Steve. The 343941 seems more versatile and is hotter than the 343901, so why does the 343901 seem more popular? Is it because people are worried to over cam?

 

What's your comp ratio? If it's 9 to 1 then try a Comp Cams 268H or the 270H. If your comp's around 10-10.5 to 1 then the Crane 272 degree Energizer works good in a heavy vehicle. I'm running one in a 68 Monterey ( 10.5 to 1) with a C-6 and 2.75 ratio rear, it runs fine on 87 octane mixed with CD2 lead substitute, timings at 12 degrees initial. Ran it on straight 93 the other day, still doesn't ping.

 

I believe my compression ratio is 9.5:1. The engine had a 2V intake. Ratsmoker can you see any reason why I shouldn't run the Crane 343941.

 

I'm not Ratsmoker, but I sure don't see any reason not to run the 941.

You seem to be right in Crane's compression range:

I'd stay with a dual pattern unless you have really good head work and exhaust. (IE: not a comp cam)

 

I know you are not Ratsmoker, but he knows cams and I want his input. I am doing head work now but still think that the fe would benefit from a dual pattern. If I run Crane 343941 with the single plane Streetmaster intake and I lose all my low end I will scream. I am into 4x4ing and need to have some bottom end.

 

Little miscommunication there....

Just a couple things here:

When you guys say dual pattern, I think of same I/E duration/lift, but that isn't the case. What is meant by dual pattern?

I'm running the 801 with flat tops and reworked heads, and it works great, I think. What exactly do you look for if the cam isn't a good match?

Redneck hillbilly, I think I've talk to you before about the streetmaster. Your going to lose some of your low-end by going with the single plane. A dual is much preferred.

 

Pics of the streetmaster in my gallery.

 

The FE series engines don't get the benefit from dual pattern cams that other Ford engines do. The others suffer from restricted exhaust passages, which is something the FE's aren't cursed with.

 

I tend to disagree with Baddad. Stock-size exhaust valves and manifolds can definitely use a dual-pattern cam (more timing and lift on the exhaust side than on the intake) to help them breath better. If you up-size the exhaust valve, maybe do some porting, and use good headers, then a single-pattern cam can fill the bill. You just need to do your homework to assure that everything matches up to optimize your breathing potential.
Most will agree that a dual-plane intake is better suited to low(er) end performance at the sacrifice of some top end horsepower. Just got to decide what's most important.
Steve

 

I've run single pattern cams in all my FE's ( 390's and 427) and all performed flawlessly. About the only way you could tell the difference between a single and dual pattern is to rent some dyno time and compare them. I don't run stock exhaust manifolds on an FE motor, the only exception to this rule was the CJ manifolds on my 427 in a 67 Stang ( headers are a pain in big block Stangs) or if you popped for a set of 427 cast iron headers. As restricted as the common flat log manifolds that the 353-360-390's came with, even a dual pattern cam ain't gonna help much. The only port work really needed is to clean up the undervavle area ( the bowls) on FE's