scottyp99

Hi, guys, I'm getting ready to take advantage of the sale Summit Racing is having on their store-brand camshafts, and I would like some opinions on which cam to purchase. Here are the 3 cams I have narrowed it down to:

http://www.summitracing.com/parts/SUM-K1103/

http://www.summitracing.com/parts/SUM-K00052/

http://www.summitracing.com/parts/SUM-K00042/

The cam will eventually end up in the following combo: 1980 'vette, L48 engine with 70,000 miles (compression between 150 and 160 on all cylinders) Edelbrock Performer 2101 intake manifold, Holley 1850 600 cfm carb with 1" 4-hole spacer, Corvette Central 2 1/2" dual exhaust with block-hugger headers and Magnaflow mufflers, Dart SHP heads with 64cc combustion chambers and 180cc intake ports, using a Felpro 1094 gasket to achieve a 9.5:1 static compression ratio, according to my calculator. (This is an estimate, I haven't actually torn down the engine and made any measurements, I'm assuming a 64cc combustion chamber, .015" thick head gasket, 12cc dish, and .025" deck height) This will be in front of a 700r4 transmission with a 2000 rpm stall converter, and a 3.07 differential ratio.

I am leaning toward the smaller of the three cams, the 266/210 .440 cam, because I am really looking for low-end grunt and a reasonably nice idle (I would like to keep manifold vacuum at idle at at least 16", more if possible, the 1850 carb has a reputation for being set up for a mild engine with plenty of idle vacuum), and would like to keep my shift point at 5000-5200 rpm.

Using this online calculator,

http://www.jeepstrokers.com/calculator/

the K1103 cam gives me a Dynamic compression ratio of 7.7, the K00052 cam gives me a DCR of 7.81, and the K00042 cam gives me a DCR of 7.97, all of which should run well on 93 octane fuel. I would appreciate any and all opinions before I make my final decision and actually purchase the cam sometime next week. Thanks,


Keep the shiny side up!
Scott

resdoggie

I would go with a retro roller cam and not outdated FT designs. If you're on a budget, I would wait and save the money for a HR. That said, I would go with this one based on your setup:

http://www.summitracing.com/parts/SUM-K00052/

scottyp99

Thanks for the recommendation, and I also appreciate the unsolicited advice on the roller cam. Any and all advice will be cheerfully accepted! Any idea what level of manifold vacuum at idle I can expect to see with this cam?


Keep the shiny side up!
Scott

63mako

With everything in the above post. I would guess you will be @ around 16 vacuum.

resdoggie

I'm running a Comp Cams Magnum 280H FT. With my old stock 2.02 76cc heads I was getting about 14" vacuum but the heads were worn. I'm now running new AFR 195's 65cc and getting about 16" with the same cam but higher compression of 10.7:1.

Matt Gruber

of the 3 choices i'd use the 216/216/110.
Idle vacuum depends on idle SPEED. For example, my XE262 218/224/110 idles at 550 in drive, 12.5". PBrakes work fine.
Sounds like a great combo! The low 1st gear will let you fry the tires at take off anytime u want. No need for a smaller cam imo.

BKbroiler

I think you should use either of the two hotter choices. Vacuum won't be a problem.

63mako

Looks unanimous.

scottyp99

Looks like there is a consensus on the K00052 cam. I'm a little apprehensive about overcamming the engine, I guess the 2000 rpm stall converter and the steep first gear on the 700r4 transmission will allow a little more cam than I figured. I'm a little surprised there are no fans for the K1103 with it's 112 LSA and split-pattern grind. Plus, it's 30 bucks less than the other 2 cams. Anyway, I feel good about the K00052 cam, it is basically the old Crane Energizer 272H cam. I'll give it a few days, look at a few more responses, and then pull the trigger. Thanks for taking the time to help me make my decision.


Keep the shiny side up!
Scott

garygnu

maybe look into the comp extreme energy cams xe262 or the xe268.you have good heads that need a more modern cam design to maximize their flow potential..the summit 224/234 cam should make the most torque.

billla

The Summit cams are an "old skool" lobe (relabeled Elgin) that I wouldn't use - and I wouldn't use a single-pattern cam on a GEN I SBC, period.

There are a number of good CompCams XE choices in that same lift range that would be a far better fit for the heads.

johnt365

Scotty, how committed to a Summit cam and lifter kit are you? I know the price is appealing. I have nowhere near the experience as billla has shown. However, I can tell you from my limited experience that a cam change is a pretty major deal. When I installed my comp XE268H I gained 60 hp at the rear wheels from just the cam. If you could spend an extra $150 or so and gain an extra 20-30 hp over the Summit cam would it be worth it? (just a question)

Billla, I would be very interested in your experience or anybodys experience with the Lunati Voodoo 268. http://www.summitracing.com/parts/LUN-10120703/ The cam kit with lifters is $200

Or, how would that cam do with Scottys combo and a set of Rhodes lifters?

REELAV8R

I find this thread very interesting since I am looking at going the same route with the stock engine on mine.
I was looking at slightly more agressive durations like 226/226 @.050. this would put the power a little higher, like 1800 rpm and up.
I'm in no position to give advice on cams that's
for sure but given your 2000 rpm stall with the 700r4 trans seems you could go a little bigger than k00052 which has a duration of 216/216@ .050. at least judging from what I've read.
Given that I have no real experience with cam changes and effects
I can't speak from anything other than the reading I've done.

Seems like 63mako and billa have the most real world knowledge here.

I wonder if billa could expand on why he would not use a single pattern cam on a gen I SBC. There seems to be two different schools on single or split duration, just haven't seen why.

63mako

I do agree there are much better choices. XE 262 or XE 268. I like this cam if your going flat tappet and are looking for under 220 intake duration @ .050.
http://www.lunatipower.com/Product.aspx?id=1983&gid=287

billla

The GEN I SBC suffers generally from weak exhaust ports, with I/E ratios that are often well below 75%. A bit more lift or a bit more duration really helps - this is why folks used to use 1.6 rockers on the exhaust side.

Top-notch heads like AFR often meet or exceed that 75% I/E ratio...meaning that a dual-pattern cam isn't as critical...and a single-pattern may make more power.

Matt Gruber

Are Dart SHP heads all that weak on exhaust? I have not checked. But it doesn't matter. A weak exhaust doesn't limit power until higher rpm.
The OP says 5000-5200 max!
That is why i'm not suggesting the XE262, the xe262 is good to 6000 easy. More exhaust duration is well known to extend the rpm range, and it simply isn't needed in this case.
If he is willing to recalibrate the governor for a higher shift, say 5700-6000, then i'd use XE262.

76strokervette

As another option check out howards cam and lifter set pn 112571-12.
Should work with the shp heads very well.Probably towards the high side of
your rpm range but should still idle decent with 112 lsa.Howards cams have
a 5 year warranty on their matched sets.You may want to factor that into the equation with the abundance of flat tappet cam failure threads even on
this site.And summit also sells these.I agree with the previous posts about
the hydraulic roller but only you know your budget.
Have fun and good luck,
Dave

billla

Virtually ALL GEN I heads have a weak exhaust port - it's an aspect of the fundamental design. Dart's numbers for the 180cc heads show good flow (about the same as Vortecs) and excellent I/E - but still need help on the exhaust side.

.200/139/114/82%
.300/190/145/76%
.400/218/164/75%
.500/222/172/77%

Compensating for the weak port is more important at low- and mid-range RPM; high-RPM cams typically have less of a dual-pattern split or none. Compensation for valve events at higher RPM is handled by both the advance ground into the cam and the overlap of cam events...essentially providing more lead time to compensate for how fast valve events are happening to compensate for flow dynamics. Even the stock L-48 cam was dual-pattern.

Look at "RV"-type (low RPM) cams for the GEN I - dual-pattern but with less overlap/more advance, and with racing cams (high RPM) - sometimes dual-pattern (less split) but with more overlap/less advance.

There are a lot of factors and cam design is always interesting discussion, but often the best learning comes from just looking at the cam catalogs and applications.

I would tend towards one of the XE "4x4" cams for this application - either the X4254H or the X4262H.

Matt Gruber

bill
of the 3 choices, what is your pick? sounds like the 214/224/114
Right? it is cheaper.

scottyp99

As usual, Billla has to chime in just as I'm about to make up my mind, and muddy up the water with facts!

While I will admit that cost was a factor, it wasn't the overriding factor in my decision making process. The fast ramps of cams like the XE and Voodoo series cams scare me. I don't want to deal with a wiped lobe, or worse, an entire wiped out camshaft, and the ensuing expense and hassle involved in recovering from such a disaster, so I began looking at cams that didn't have so much "hydraulic intensity", I think the technical term is. Now I have been reminded that we had this discussion at length several months ago, and I made a decision based on that discussion, and I think I'm going to stick to that plan. Thanks for reeling me in, Billla.

One thing I have noticed, with the XE series of cams from Comp Cams, is that when people complain of wiping a cam, it's almost always an XE268H or larger cam, so that gives me some courage to go ahead and use the XE256H, which is what I decided on months ago. I am going to use the Crower Camsaver lifters to try to mitigate the risk of wiping the cam somewhat. From studying up on the subject, I have come to the conclusion that one of the most important factors in avoiding a wiped cam during initial break-in is making sure the lifters are able to turn freely in their bores, and I can verify this by marking the lifters and observing them while checking for pushrod length. One thing I am concerned with is reports of these cams making a "sewing machine" noise from the valvetrain, can anybody tell me if the smaller XE cams do this? If it's not too loud, I guess I could live with it. Anyway, here are the cam and lifters, and I think I'm just going to plunk down the money and buy the cam, so I won't be temped to change my mind again!

http://www.summitracing.com/parts/CCA-12-234-2/

http://www.summitracing.com/parts/CRO-66000X3-16/

Thanks for everybody's input, I really appreciate it. Man, asking for cam advice is like asking how much of a certain hot sauce you should use! Some say "Only use a little, it's strong!", and some say, "Use a lot, it's pretty mild.", and in the end, all you can do is splash some on and see for yourself. I'm sure there are people who will recommend a larger cam, like the XE262H, or XE268H, but I want to keep the rpms low, and I can't see the point of using a cam which has a power range above what I'm going to be using. Something that runs out of steam at around 5500 will be more than enough to suit my present needs. Although, I am aware of the "100 more horsepower" phenomenon. My brother is literally experiencing it right now. He souped up his '97 'vette last spring, it's putting out about 392 horsepower at the rear wheels, and, man, it's a pretty fast machine, but he is already saying "I want another 100 horsepower.". So, he's going to install a blower this winter. It's a sickness, I tell ya! right now, I'll be happy with 250-275 rear-wheel horsepower, but I know it will only be a matter of time before the "100 more horsepower" bug bites me. Oh, well, I'll burn that bridge when I come to it!

Edit--I see Billla has edited his post and recommended a 4x4 cam. It uses a 111 LSA, as opposed to the 110 LSA of the XE cams, and has slightly less intake timing and lift. The calculator I am using shows the X4254H as having the exact same dynamic compression ratio as the XE256H, (8.17:1) I assume because the wider LSA compensates somewhat for the shorter duration. It also has the same power range (1000-5200 rpm). What advantage will the X4254H have over the XE256H, Billla?


Keep the shiny side up!
Scott