my two cents worth. Would do a cam close to your l46 camshaft 222.. 050 oval track cam with 108 lsa to further crutch your compression problem or I should say lack of air problem.

 

Mike Jones. Www.jonescams.com. this guy has done cams for indy cars, nascar, every form of drag racing, boat racing, truck pulling and he does flat tappet cams. That said iskys 270 mega oval track cam .. 270/270 adv. 221/221.050 lift 465/465 lsa 108. do a 1.6 rocker on the intake side.

 

re post #15

 

this cam is the best recommendation thus far. I run from 4000 to 8500 and run a 270/270 on a 108 LSA .549 lift at the valve, that’s 219/219@.050. It’s a roller vs flat tappet so the ramp is probably a bit faster.

run some 1.6 rr for as much lift as you can get. Also important is intake velocity, so maybe a 4 hole gasket below the carb vs the open plenum, and a dual plane intake.

I would get the heads shaved to bump the CR at or above 11:1. As pointed out GM’s 11:1 was more like 10 something.

you’ll still need a higher stall if it’s automatic so as to by pass low rpm poor performance, say anything below 2500 rpm.i run a 3000 stall and it works great for this high altitude scenario.

 

Really are you all that deceived? 221 is less duration and the they just altered the valve timing events and 108 to give the car a race car sound. That is just as dumb as the Comp Cams Thumper Series of cams. All Show and no real go! So the question is do you want actual performance and reasonal MPG or even improved MPG or do you just want the sound. Like the gear driven cam drive that is made to make noise like you have a blower under the hood. The Mega cam will have a higher than stock TQ peak and then fall off fast compared to the other quality modern cams which will have a higher overall average in HP and TQ.

Your best MPG is up around 114 Or you can delay the opening event like powermax cams to limit intake reversion. Crane cams are ground 4 degrees retarded compared to say a Comp cams Extreme series cam of the same duration.

 

https://www.jeepstrokers.com/forum/calculator/

so I used this calculator when building my L-48.

I put in your numbers with flat top pistons and your 64 cc heads and it comes up with 10.9 :1 CR with the 270 cam on a 108 that is 9.06:1 dynamic CR. However calculate in altitude (which this calculator does) and you get a 7.66:1 DCR.

Use something like the xe268 and that further drops to 7.60. The overlap on both cams is at 54*. I would say the xe268 would work good if you bump the CR up a bit more. I'm not a big fan of the XE series based on what guys have experienced in wiping lobes, but that's just reading, not my experience.
I'm running 7.95 DCR with my aluminum heads. So a 7.6 ish DCR with cast iron heads may not be too bad, detonation wise that is, lack of power wise, you're going to feel it. I'm confident that I could run a much higher DCR since I can run 87 octane now with no detonation. You could run more in the range of 8.0:1 DCR with good quench (.040") and get away with that just fine as long as the cooling is also in good order.

Anyhow I would play with the numbers see what you can get with what you have.

 

all companies when they do an oval track cam use 106 to 108 lsa and it's not done for any sound. The mega cam is single pattern there is no comparison to it an the thumper cam that uses extreme amount of exhaust duration. If you look at say comp cams the majority of there cams are 110 lsa not 114 only time they do that there listed for computer fuel injection or boosted stuff that has all kinds of compression. Not trying to deceive anyone, but making a comparison to a single pattern cam and the thumper is decieving. The OP has what is today considered a small engine 350 not a 434 with a true measured 11.7 compression as you have gkull he needs the tighter lsa in the 7000ft he is at. If I wanted him to have a nasty idle well high duration cams do that far more then any tight separation. But I never suggested any form of high duration now did I. Many people try to tell people to overcam a small engine in a heavy street car with street gearing when they need nothing more then best midrange they can get out of the small engine they have.

 

You missed the calculation somewhere on you input numbers. Your typical 4.030 and 3.48 stroke .025 deck height, 64 cc heads, .021 thin gasket 4.060 dia. -7 cc valve reliefs comes out to C/R of10.015920601889151 It is hard to make compression in 350's much over 10 without domed pistons.

I like what you are figuring out on the DCR. But to everyone you have to use the cam card valve event numbers.

http://www.csgnetwork.com/compcalc.html

 

opps, forgot the valve relief volume of 7 cc’s. I used .015 shim head gasket volume vs .021. And your right it comes out to 10.03 CR with a 4.00 bore and the .015 gasket.

 

Single patterns are generally used on say open header type motors. As to 221/221 being a oval race cam, highly unlikely unless it is one of the 350 cfm two barrel sportsman or a highly restricted classes.

As to cams I don't buy the faulty austempered cam cores because of the high failure rate. for a few more bucks you can have any LSA you want in a billet steel core.

As to a few degrees tighter LSA actually increasing dynamic compression ratio...… run all the numbers and it is not that much difference. I have always questioned the DCR numbers because they don't bring into account the partial cylinder filling because of overlap reversion at lower rpm. The reason why you get a higher peak TQ with tighter LSA is the rise in compression up in the rpm when the intake valve is only open in the a few 1000th of a second and not causing reversion You can also very the valve events by where you install the cam advanced or retarded and see how the DCR number change

 

As I see it using the L-46 head is a negative in the first place. It won't flow like modern heads, nor burn as quickly, nor dissipate heat like aluminum heads will. A flat tappet cam vs a roller is also a performance loss. These are not just a loss to top end power but a loss to power and responsiveness everywhere in the RPM range.

So these things in themselves are detrimental to the performance and are going to limit it's potential. JUST a cam with better events will make things better, but IMO there is so much more to it than just the cam alone.
I get about 440HP out of my little roller cam due to several factors, not just the cam events.
Timing, jetting, intake velocity, cold intake charge, valve lift height and the speed of that lift,HEAD FLOW!! Big deal this one, roller cam vs flat tappet, 3000 stall torque converter, reducing intake reversion ( particularly at high altitudes since air is less dense and has less inertia), etc, etc. It all has an effect and matters to some degree.

I would still get the head milled down to get better CR vs a dome piston, if it can be done without sacrificing the integrity of the head to a degree that will not promote cracks.
My AFR heads were angle milled from 64 cc's to 55.5 cc's. This really made a difference in the performance over my previous heads @ 62 cc's.

Your L-46 heads may advertise a 64 cc but if they're GM original they are more likely in the 66-67 cc or higher range.

 

if he wants to he can do a bit more exhaust duration not single pattern but he will still be better off with the tight lsa and midrange type of cam that 221 is in a 350. I started out on this thread trying to say don't even think about a 248 .050 int. Lt1 cam ,the cam he has now is better then that where he is at.

 

Boy, this is a lot of information to take in. Mike Jones replied with a cam suggestion, and I think I'll take his advice and give it a shot.

I bought this car as a numbers matching, and right now I'm just looking to get it back to that. Eventually, I do plan to do it up a bit better. The heads I got were cheap, so those plus the cam is still less than I would have paid for just a set of modern heads. Then I've got them, and the car is back to its original engine configuration.

I'm not entirely helpless with engine stuff, but picking out a cam has never been something I've spent time working on. I've worked on enough to know that these heads may not be the best choice, but I'm okay with that for now.

 

I've heard nothing but good things about Mike Jones, so I'm confident anything he has to recommend will perform better than what a part time enthusiast suggests.

If you don't mind sharing with the forum, What cam spec is he recommending?

 

OP
Tell Mike Jones you're Not breaking-in on a Dyno or Track ... Ask him if he recommends flat-tappet break-in of his cam with lighter springs ... Follow his break-in advice to a Tee.

 

this is a smart move Jones will spec you cam that is as close to perfect any human can do as long as you give him correct info to work with. Chris straub could do it for you also
It may cost you a hair more but he will put you into things like quality lifters. No guessing game with him.

 

Thanks for the tip, just emailed him.

For those curious here is the cam he recommends:
Cam# SBCH, H70330-69310-110+4
224/220 @.050"
.330"/.310" Lobe Lift
.495"/.465" Valve Lift
110 LSA
106 ICL

 

Now that's interesting, less lift and duration on the exhaust than the intake. I wonder if that is because of less atmospheric pressure the exhaust has an easier time getting out? or to combat intake reversion? Curious.

Or maybe it would be more accurate to say exhaust reversion/ intake contamination.

 

I don't know, but let me ask him.

 

Ya, that would be real useful information. Thanks