351C LSA selection and Vizards "magic" number

[falcongeorge]

I am building a cleveland for my '67 Falcon, primarily for street use and a bit of track time. I am looking at one of Howards .875 specific solid cams, 236/240 .621/.638 on a 108 LSA, 104 ICL. The motor is a '71 4v with flat tops and will be right around 11/1 with a cold air setup. My EA is indicating an 8.18 dynamic compression ratio with 211 psi cranking. The car is fairly light, and will have either 3.89's or 4.10s, 26" tall tires with a 3600 stall converter, so it will flash past peak torque fairly quickly and wont be lugged at all,  I have Chevron 94, and am fairly comfortable that this will be ok on my fuel, but its probably on the edge. I am currently running a 355 chevy at 11/1 on this fuel with 8 degrees more intake duration, a 110 LSA and underhood air, and it is fine on this fuel, has never rattled.
Heres the thing, I have been reading the thread on Speedtalk on Vizards "magic" 128 method of LSA selection, using that formula, it indicates that the optimum LSA for this combo should be 110. But virtually every solid cam I have looked at over the years for a cleveland is on 108 (except for Comp, and they just automatically default to 110 for every street/strip cam in their catalog ) I cant help but feel a little sceptical, especially considering that 98% of what Vizard does is small block chevies.
Assuming I install the 110 cam 4 degrees ahead like the 108 version, spreading the LSA 2 degrees would back the cranking compression down a bit, and it would idle like a real pussycat, which is attractive to me. The cam is probably a hair on the small side for the combo, and delaying the intake closing point may make it hang on a little longer on top, but I do not want to do that if its going to give up torque in the 4000-5000 range.
Anyone have any thoughts on this? Any engine builders on here have dyno time comparing 108 and 110 LSA's in Clevelands?

[garyv]

I sent Brent Lykins a message and I'm sure he will chime in when he gets time.
He builds a lot of Cleveland Engines and he will be able to give you some information based on years
of experience with them.
garyv

[falcongeorge]

Thanks Gary, I was kind of hoping he would chime in here. FWIW, I just tried this in Engine Pro, not that I use that a lot, it wanted a 102 LSA on a 100 ICL! talk about opposite end of the spectrum! Funny thing is, that kind of jives with what I have seen on Kasses cleveland based EMC entries, but those motors are 40+ci bigger than mine, which I would think would tend to want a narrower LSA relative to a 357 inch motor.

Should also mention, I am looking to make peak power in the 6300-6500 range (6800-7000ish shift point), and the heads will have the pockets done and the guide bosses cleaned up. I have built 4v clevelands in the past, but the last one was like 3 decades ago, theres a lot of water under the bridge.

[Falcon67]

I don't see any problem with those numbers.  108 is a good number for a 351C.  Most of Vizards work is with SBC and a 351C is not an SBC.  When his magic stuff says 110, you can bet -2 is better for a 351C (108). 

[blykins]

A 235°-ish duration @ .050" will get you roughly a 5800-6000 rpm horsepower peak. 

With the gear ratios and the torque converter, I'd rather see something around the mid 240's at .050" for a solid flat tappet. 

You will not find any good off-the-shelf Cleveland cams because the 4V head needs a good 10-12 degree split between intake and exhaust and you need a tight LSA. 

Honestly, if you really wanted to make it hit a good lick, I'd be somewhere around 242/252 @ .050", with .600-.620" lift, with a 106 LSA on a 102 ICL. 

A Cleveland has a big fat intake port....kinda the same deal as a Tunnel Port FE head.  They have lots of port volume and a smaller engine will need help to get things going.  The overlap will help the exhaust scavenge the intake. 

If you need vacuum for brakes, etc., then I would prefer to leave the duration split and widen the LSA, but keep the advanced ICL.

Vizard is a salesman and that's about it.  If you emailed him for a cam recommendation, you'd send him $100 before you got an answer.

[falcongeorge]

No power accessories. Trying to put as much area under the curve between shift recovery and shift point, just pulling some numbers out of my ass, I figure thats going to be 4500-6800ish. Dont care one way or the other how it sounds. Thanks guys.

[blykins]

A tight LSA will do that...mucho torque like that.

[garyv]

Glad to see Brent got back to you. 
If you really want that thing to hit a lick I'd call him up and have him get you a custom ground
cam for that thing. 
Good luck
garyv

[falcongeorge]

most can probably tell by the tone of my first post that I was looking at that 110-111 LSA recommendation with a great deal of scepticism myself. It just doesnt sound right and his formulas recommendation flies in the face of pretty much every cam grinder out there.
FWIW, I have dyno tested a 108 LSA against a 110 LSA in a 427 chevy (Vizard says add 2 degrees of LSA for canted valves) and the 108 was better everywhere that mattered, but that combo had a MUCH bigger cam with more static compression (278 intake @050 12.3/1).
Another thing I will mention, EA also suggests a big duration split for my cleveland, my experience with EA is, that as a general rule, the gross numbers are a little happy, but its pretty accurate in terms of trends.

[falcongeorge]

I think I am going to go with a pair of .875 Ultradyne lobes, I have had very good experiences with Harolds stuff in the past. I tried a 244/252 .617/.638 on a 108 LSA in EA, on a 104 ICL, it had a dip in the torque curve at around 4200 compared to the Howard, based on what Brent had said, I advanced it a couple degrees, which brought the dip up a bit, then I went to a 256/.643 exhaust lobe, which seemed to flatten the dip out. This final set-up was better everywhere from 3500 up than the Howard, I think I will go with this. I doubt I will ever dyno this engine, its kind of a low-buck deal, so I think thats about as good as its going to get. FWIW, EA is saying Pk hp of 454 @ 6500, pk torque 414@4900. Based on my past experience with EA on engines I have dynoed, the rpm is probably about right, but the gross numbers are probably about 4% happy.