I thought Summit sold it on their brand but it appears not......but Comp does not make this cam......they don't make any of their flat tappet cams. It is probably in the Elgin catalog.....if I have time...I will see if I can find it.

The rest of the parts look ok. Inspect your lifters with a straight edge on the heel.....it should be slightly convex.....if not, send them back.

Jebby

 

Another cam similar to the 268 HE cam is the Isky 264 Mega cam with 214-214 .450-.450 lift and a 108 LSA. Had one in my 76 L82 with T400 and 3.36 gear. Had much better low and mid range than the L82 cam.

 

The bolded part is NOT true. The Summit/Elgin 1065 cam does not list at what lift their advertised duration numbers are taken from in their catalog or on the cam card. You can compare them with their lift @ .050" numbers, which are both 218. Using the .050" numbers, both cams will have an identical overlap amount of -2*, since they also share the same LSA of 110*. The lobes on the Elgin 1065 may be more aggressive than the Comp 268H, but they aren't so aggressive as to cause break in problems or driveability/vacuum issues. I have the 1065 in my stockish L48 (with Headers and duals!) and it runs and drives perfectly fine. It pulls 14" of vacuum at my chosen idle setting and will pull more if I up my idle some. Summit/Elgin even have a 218/218 cut with a 106 LSA (Summit/Elgin 1785) that will drive fine in a stock car. Vacuum for the headlights may be questionable with the 1785, but it isn't with the 1065.

The biggest difference between the 268H and the 1065 (other than the lobe intensity question) would be the ground-in advance. The 1065 has 5* of advance whereas the 268H has 4*, which would shift the power curve down the rev range slightly.

I had no issues breaking in my 1065 with the same Melling lifters and Summit springs that OP listed in his shopping list and using the Jebby Method.

 

Your list looks fine, but a cam swap is next to worthless if you are still using the factory 2" exit ram's horn exhaust manifolds and factory 2-1-2 exhaust.

 

Jebby,

The Summit/Elgin cam can be found on the Elgin .pdf catalog on page 9. E-1065-P

https://www.elginind.com/wp-content/...ck-Catalog.pdf

 

Thanks for all the input!

I ended up going with the Comp unit suggested by Z0Tex.

Found at least 1 leak, snout of balancer is grooved. I have a repair sleeve so assuming the zero line is still correct, no problem.

 

No wonder my car is coated with oil underneath.

 

If you do not care about a numbers matching vette I would consider a crate motor with a warranty. Find out how much an engine rebuild would cost (?) compared with a new crate motor (4 to 5k).

 

If you don't mind road-tested parts, you can do an LS swap for $2K or so. Less if you are very thrifty.

 

I am glad you like the Elgin cam.
But the fact is that although the two cams have the same .050" duration, the Elgin cam has 66 degrees overlap, and the Comp 268H has 48* overlap, and the Comp will make more cylinder pressure and TQ than the Elgin cam. The Elgin cam is the one with the milder lobe ramps, giving it more overlap, the Comp cam is the one that has the steeper ramps, and shorter adv duration, and less overlap, but still not enough to cause lifter longevity issues.
Because of the adv duration differences, the Comp 268H will kick in harder at a lower rpm, by a hundred or two. The Elgin, because of the extra overlap, should carry it's HP better past it's peak, say after 5500 or so.
I am glad you like the Elgin cam, but the Comp will idle better. At a lower rpm, with more vacuum. It will work fine with a tight stock convertor. Have driven a dozen of them.

There is a lot more to cams than just .050 duration numbers.

 

As inexpensive as balancers I would not press a sleeve on it......if it is old enough to have grooves in it then the rubber damper ring is probably petrified, and ready to spin.

Jebby

 

A lot of times the old single pattern design 268h cams get mixed up with the newer dual pattern 268xe cams so be aware they are different. the XE has more aggressive lobe angles to give more of the advantages of a roller in design but at the same time it makes breaking them in correctly more important. The 268h cam is as old of a design as the cam in your l48 now.. Not that it wont perform but it is an older design.

I ran the lunati version of the xe cam (262/268) in my car for about 10 years before going to the comp 270hr retro roller. I chose not to run the 268h cam because it did not perform as well with the desktop dyno software when I simulated it with my combo even those a 268h cam with less than 700 miles on it came with the block I purchased to go through and rebuild if needed. (I still have the 268h btw with the matching lifters for sale)
I noticed quite a bit of change between the 2 (lunati voodoo 262 and comp 270) in how the engine behaves. For one I really need to get the new trans and higher stall converter in the car because its very finicky with idling in gear especially before fully warmed up. its very cold tempered and like to stall at lights until its warmed up. The lunati cam was more stable as far as starting the cold engine and pulling out of the garage less than a minute later. I did not feel more torque with the smaller cam like folks said I would but my engine more equivalent to an l82 the an l48 (which is collecting dust on an engine stand in the corner) The 270 cam gave me a noticable power boost once I get the rpms above 3500 IMO over the smaller cam.

 

I know that there is more than the .050" numbers, but I was making a comparison with numbers from both cams that were published. I learned something today. Thank you for the bolded explanation!

FWIW, the 1065 in my L48 seems to peak at about 5100-5200 and then levels off or falls off after that, using the butt dyno as a guide. I shift at 5400 when I want to "get on it".

 

A lot of cams have been mentioned in this thread.
And they are all very good choices, depending....
I thought it might be useful to compare them all, as they cover the full gamut from a stock L48 up to L82/L46 HR street performance.
Very likely everyone will have a different favorite, due to their different preferences.

This is the absolute minimum amount of information that I would want to know if I were going to pick a cam.
Or even if he is going to talk to an expert and have a basic understanding of some of the trade-offs involved.
This is the way we did it in my engine builder & best friends speed shop for 40 years.



Here is the same chart but resorted by gentleness of cam lobe (H.I.)


Terms:
Overlap calculated from adv duration and LC: http://www.wallaceracing.com/overlap-calc.php
Hydraulic Intensity; Difference in Advertised vs .050” duration
Advertised Duration: typically at .004” lift, but not for old GM specs, L48 & L46 Specs from Crane “equivalents” cams
Method of determining basic engine range is to use .050” duration numbers: Advertised duration numbers have more effect on overlap and scavenging effects than breathing
Overlap either increases or limits breathing by the scavenging effect. More overlap increases scavenging, typically works better at high rpm, can increase volumetric efficiency, lowers vacuum and TQ at low rpm by increasing low speed reversion
Hydraulic Intensity is Lobe Steepness or Aggressiveness, or Cam Profile Intensity. At any Given .050” duration, less advertised duration increases both TQ and HP by decreasing the advertised duration. Sounds backwards, but it traps more gases in the cylinder. It increases V.E. and reduces overlap, and increases idle vac. And low rpm behavior. But these shorter H.I cams have steeper ramps or cam lobes, and the steeper they are, the more break-in and longevity problems they have, unless rollers are used. The old school long lived flat tappets from GM approach 70* H.I. and have very gentle and long living cam lobes, and get by with softer springs. Most solid rollers are 40* H.I. and that is how they gain extra power, by throwing the valve open/shut quickly. Short H.I. cam profiles also need much stiffer valve springs.
Suggested RPM Range is as suggested by Mfg.

Cam selection Recommendations:
Step 1- Duration Chart
This chart from Grumpy Jenkins Performance makes it easy to select a cam’s .050” duration based on what your rpm boundaries you prefer, and also considers your engine size. The lower end is where the reversion is great and the engine begins it’s power curve. The upper end is peak HP rpm. And this varies significantly by engine size. This will typically match mfgrs recommendations, but they almost always assume a 350cu in engine size for a SBC. With the proliferation of stroker motors these days I find this chart very handy to check.


Step 2 - Overlap chart
This chart helps you rough recommendations for overlap based on intended use.
Once you pick the rpm range (duration) you want, you can vary the overlap to balance your desired high rpm scavenging and low rpm reversion preferences. Both adv duration and lobe center effect this one.


Step 3 - Hydraulic Intensity:
Now is the time to consider your lobe intensity, and how much PITA you want to put up with.
H.I.
60-70 Old GM cam flat tappet cam specs, very gentle, light valve springs, long life, easy break in
50-60 Typical 1980-1990 flat tappet cam specs, slightly more aggressive lobe, boost TQ & vac, 1 step up spring, still has long life, more careful break-in
50-60 Some older Hydraulic Rollers in this range, very gentle lobes, long life, light springs. Current GM rollers possibly fall here, but no good specs avail.
40-50 Two of the above flat tappet cams have H.I. in this range. Requires more spring, break-in very critical, longevity typically compromised. I am not fond of flat tappet cams in this range.
40-50 Typical current Hydraulic Roller Cam Specs, more spring, long life with rollers, more TQ & vac than older rollers. Some failures reported. Must use enough spring.
40 Typical Solid Roller Cam Spec, still more spring, more maint required. More TQ & vac than Hyd Rollers at same .050 dur.
30s Race only, very high spring requirements & maint.

Beyond this all the other specs are just minor "tweaking" and should not really change any of the above very much.

I changed my Roller Cam in my BBC, after going thru a lot of research, and speaking to a lot of experts, just to change my 40* H.I. to a 58* H.I. . And cut my valve spring pressures from 230/580# to 190/440# ... with a milder lobe profile, just for improved reliability and longevity. The prior solid roller profile would have been very maintenance intense. The new one is a milder H.R profile. I kept the .050" duration exactly the same. The downside was the overlap went up some, and I will lose some of that 550# TQ peak that we had on the dyno at a very low 3500 rpm. Those were my trade-offs. The extra TQ was not worth the extra maint., not to me.

 

FWIW my '71 L48 (pretty much same as yours is described) original '929' cam was changed to a Crane HMV-260-2 many many years ago. I think it was 204/216 dur for comparison. A little more aggressive than the OE 929 but not as aggressive as most of what has been mentioned. It's not going to set the world on fire but for a 50 year old car I have no complaints about the cam over the years. I would imagine there are similar kits to this one still around.

As a point of reference I think the OE 962 cam in L46 and L82 engines had 218/218 dur. (someone correct me if that's not so). Something in that neighborhood might be at the upper end of aggressiveness for me on an otherwise mostly stock L48.

 

SWDuke actually profilled several OEM Chevy cams on a cam doctor machine and documented them here. He measured them at .050" lift, unlike GM.

The 151 L79 cam and the 962 L82 cam are pretty similar at .050" duration, 221* & 224* . However the L82 is on a much wider 114 LC, so it probably had 4* less overlap.
Unfortunately he did not measure them at .006" lift for advertised duration, per the SAE std, as is typical these days for Hydraulic cams.
He also had a very interesting way of measuring the solid lift cams. at .050" lift after the recommended lash was taken up.
Look at the 229* intake duration he measured on the LT-1 cam using this method. vs the often quoted but never measured 242*. He called this effective duration.
It lets one compare hydraulic and solid cams directly since the meaningless valve lash ramps on an unopened valve are not included in the duration spec.

Looking at it this way the L79 had 224/224 dur @ .050"
The LT-1 was just slightly bigger at 229/237*
And the 302 DZ / 63 Fuelie cam was 237/237*

 

GM only made two basic cams in this range:

• The 300HP L48 / 929 cam at 195 dur
• And the pair of 221/224 dur L46/L82 cams, the 151 and the 962. Pretty close to being the same cam. The 350HP cam. So 50+ HP stronger.

I would never run anything on a stock L48 short block as big as the L46/L82 cams.
They need a little more CR ratio to work well, those cams would bleed off some cyl pressure from the already low 71+ L48s, and would be "soggy" down low.
That is where the aftermarket came up with their in-between 218 cam, the original 268H, and manipulated the rest of the valve events to help trap cylinder pressure and increase TQ/power on the low 8.2 CR ratio engines. It works so well it is like adding a point of CR.
It works better on an L48 than the L82 cam. Like Jebby worded it: "It just works"

The mentioned 270HR cam has very similar specs, just in a HR format.
These are two extremely good choices for an L48 upgrade.

Do not run one of these two cams on an 11:1 CR engine. It's too much. We tried it, ....once. It only stayed in 4 days.

 

I went with the xe270hr because it was one of the few cams in my list that actually helped me keep a healthy DCR if I remember right without detonation risk. Maybe I had something wrong?
Since I had 10 to 1 compression already (and iron heads at the time) and want to be able to stick with 91.. I have 1.6RR which is why the numbers are effected below. I know its very hard to see the white text fields. Sorry. Anyway I found this free desktop dyno tool to be good for comparison regardless of how optimistic the numbers are since they are still based off the math. My buddy is running my old lunati cam in his 64 impalas 327 now... It had only about 1800 miles on it but still looked new as far as the lobes. YMMV I always used zinc back then as well as the springs lunati recommended.

 

Leigh - You never cease to amaze me with the way you compile and present data on numerous complex subjects. Keep up the good work.

 

Thanks guys; That means a lot!
Making sense out of a pile of "random" data is just what us science guys do...

But also, I was over at my buddy's speed shop all the time, like almost every day til late, for many many years.
And then Fri nights was semi-official "hang-out" night.
As long as you brought a six-pack, you had full access to the six bay garage to work on your own car. And Jeff and Tommy and I lent assistance.
I learned so much about musclecars helping troubleshoot a hundred different issues. We usually had a full house!
It was like hanging out at your buddies house, helping him on his car, but on a much larger scale, with a full stocked speed shop and engine machine shop right there. Everyone took turns helping everyone else out.
And Jeff was the reigning troubleshooting guru in the tri-state area. I never saw a problem he couldn't fix.
Guys drove in from 1-2 hours away, some on trailers, every type of musclecar you could imagine.
You have no idea how quick you can even pop an engine in with that many guys around.
Fun times!

How I miss that shop, and Jeff, and all that camaraderie we had back then.
It is much lonelier doing one of these cars all alone, like you and I are now.
But this forum helps a lot!
I just wish I could have my head under the hood with you, with each and every one of you!

This forum feels a little bit like a "virtual" night at your buddies house.