Team Chevelle banner
  • Hey everyone! Enter your ride HERE to be a part JULY's Ride of the Month Challenge!
1 - 20 of 31 Posts

·
Registered
Joined
·
820 Posts
Discussion Starter · #1 ·
hi all , wanting to know witch is better 108 or110 lobe seperation , iv always ran on a 110 thanks:thumbsup:
 

·
Premium Member
Joined
·
7,230 Posts
107
 

·
Registered
Joined
·
820 Posts
Discussion Starter · #8 ·
There is more to it then that what size intake valve and engine?
427 bbc 40 over ,10.25.1 , 1966 closed chamber heads, 2.19 intake 1.88 exh , cam is 520 lift ,dur is 280 , on a 110 ls hyd baby cam, edelbrock victor jr , 750 holly dp :thumbsup:
 

·
Registered
Joined
·
5,422 Posts
I built the same deal for a buddy Used the 280H in his 396 it is .030 over and strip dominator with 800 carb and 3" exhaust through borla's. The engine has 2.19-1.88 valves open chamber Ported oval GM heads from 1969.

It pulls hard to 6700 then valve float.. recently in the cold it would pull lickity split to 7000 rpm.. which is closer to about right. The springs on this one are comp set at 121 psi seat.. I feel I need to up that a little to keep it out of valve float. Those large valves are heavy.

We have 11:1 compression on that one and 210 PSI cranking pressure. Runs excellent on 91 octane and 38 total timing.
It is in a 4200 lb 1966 chevy truck with 3500 stall and 308 gears currently.
Yea 308 It did run 13.7 in the 1/4 in that deal.

I like tight lobe centers if you need the early closing intake. But going to 108 from your 110 you may not notice much at all really.


But crank it to 105 or 106 LSA you will notice.
I have a solid flat tappet on a 105 LSA for my 433" One day it will go together.
Will not be MPG friendly though The wider LSA does improve MPG.
 

·
Registered
Joined
·
820 Posts
Discussion Starter · #10 ·
I built the same deal for a buddy Used the 280H in his 396 it is .030 over and strip dominator with 800 carb and 3" exhaust through borla's. The engine has 2.19-1.88 valves open chamber Ported oval GM heads from 1969.

It pulls hard to 6700 then valve float.. recently in the cold it would pull lickity split to 7000 rpm.. which is closer to about right. The springs on this one are comp set at 121 psi seat.. I feel I need to up that a little to keep it out of valve float. Those large valves are heavy.

We have 11:1 compression on that one and 210 PSI cranking pressure. Runs excellent on 91 octane and 38 total timing.
It is in a 4200 lb 1966 chevy truck with 3500 stall and 308 gears currently.
Yea 308 It did run 13.7 in the 1/4 in that deal.

I like tight lobe centers if you need the early closing intake. But going to 108 from your 110 you may not notice much at all really.


But crank it to 105 or 106 LSA you will notice.
I have a solid flat tappet on a 105 LSA for my 433" One day it will go together.
Will not be MPG friendly though The wider LSA does improve MPG.
thanks jeff can always count on you my friend:beers::
 

·
Registered
Joined
·
161 Posts
there is more to it then just LSA,pick the lobes based on what the heads need. The LSA is what it is.
Thats how it was explained to me. I never understood how lsa was arrived at or the difference from one to another.
 

·
Registered
Joined
·
276 Posts
were can i find this vizards rule .
Look up lsa selection chart on google or google "be the camshaft expert" there is a good article on cam selection.
 

·
Banned
Joined
·
11 Posts
Let’s take a look at which method makes the most sense for selecting a cam, LSA (lobe separation angle) or Overlap and Duration. Many cam designers and engine builders will tell racers, hot rodders and gear heads to start with some particular LSA for choosing a cam. And of course you hear guys say, that they are going to be picking a new cam, and that they will be using "such and such LSA", but that they haven't yet decided on the lift and duration. And they don’t even consider the specific overlap value at all.

The whole idea of starting with some given LSA as a starting point, simply makes no sense at all. Here's why: LSA has no value at all, in and of itself, because of the fact that it is "overlap" that defines an engine's operational characteristics. And LSA is merely a “by-product” of that overlap. In fact, Comp Cams guru Billy Godbold and I share the same philosophy about that. And he said this:

"LSA doesn't mean anything except for how it affects the camshaft centerlines. You determine the centerlines, which determines OVERLAP, and THAT has performance effects."

Here’s an example of what we are talking about.
Let's say some old time cam designer or engine builder tells a young kid that he should use a 110* LSA for an old 327 ci flat tappet SBC that he wants to do his first modification on. So, the kid pulls out a Comp Cams catalog and looks up solid flat tappet cams for it. And since he was told to go with a 110* LSA as a starting point, he comes across these two cams that have the 110* LSA as was recommended, as well as the following “advertised duration” and “.050 duration”:

CAM..………….ADV DUR…………….. .050 DUR
#1……………….256*/262*……………….218*/224*
#2……………….306*/306*……………….260*/260*

Now, anyone at all familiar with cams would see a very significant difference between these two cams. Old Pro's know what they are seeing, but the kid can't tell much about them. And yet they both have the SAME EXACT recommended 110* LSA. So, targeting that particular LSA didn't tell the kid anything at all in terms of how the cams will operate/perform in his engine. But if he'd calculated "advertised overlap", using the procedure below, he'd get advertised overlap values of:

Cam #1 = 39*
Cam #2 = 86*

There is obviously a HUGE difference between these advertised overlap values, but again, these two cams have the SAME EXACT 110* LSA. Now if he looks at the adv overlap reference chart below, he'd see that cam #1 falls between the “ordinary street” and “street performance” categories. So, that cam isn’t much more than Granny’s grocery getter cam. But, cam #2 falls fully into the “race” category, making it a wicked cam by any measure. Now the kid can see that they are radically different cams, even though they have the SAME EXACT 110* LSA. So, it took the "overlap" to finally show him that he is dealing with two entirely different cams that have COMPLETELY DIFFERENT operational characteristics.

This clearly shows how LSA, all by itself, does NOT make a distinction between operational characteristics, and is virtually useless in defining a cam. But on the other hand, ADVERTISED OVERLAP absolutely DOES define a cam's operational characteristics, every time. So, it makes much more sense to go in knowing how much overlap you want, then select a cam based on that, which will best meet your needs. Now the kid can make a much more informed buying decision.

As shown above, cams can be wildly different with the SAME EXACT LSA, but ADVERTISED OVERLAP will always show you what’s going on. and here are some reference examples of how various overlaps compare :


“APPROXIMATE” SOLID LIFTER ADVERTISED OVERLAP PERFORMANCE REFERENCE CHART

300ci………………………….400ci………………………...500+ci………Typical usage
10*………………………………25*………………. ………...40*…………. towing
30*………………………………45*……………….. ………..60*…………..ordinary street
50*………………………………62.5*…………….. ………..75*…………..street performance
70*………………………………80*…………………………..90*…………...street/strip
85*………………………………92.5*……………………….100*…………...race
95*………………………………105*………………………..115*…………...Pro race


Here's the CORRECT way to calculate your cam's ADVERTISED OVERLAP which is needed for the chart above:

• Add your intake and exhaust advertised duration (typically shown as duration at .015 tappet lift. NOTE: duration at .050 tappet lift will NOT give you the correct advertised duration value)

• Divide that answer by 4

• Subtract the lobe separation angle (LSA) from that answer

• Multiply that answer by 2, and you have the CORRECT advertised overlap to use in the chart above

NOTE: Because of the differences resulting from not having any lash, and the way hydraulic cam advertised duration is rated, if you want to figure the “advertised overlap” for a HYDRAULIC LIFTER cam, so that you can use the chart above, REDUCE the Hydraulic cam’s listed ADVERTISED DURATION (typically shown as duration at .006 tappet lift) by 8*, for both intake and exhaust, then follow the calculation procedure as shown above.

If you consider OVERLAP rather than LSA, you can make a much better decision about the cam you select for your next build.

540 RAT

For the truth about motor oil wear protection, that is not just opinion or theory, see my "TECH FACTS, NOT MYTHS" Blog, which now has over 250,000 views worldwide. You can see the Blog and my entire 195 motor oil “Wear Protection Ranking List”, which is "proven" by the Physics and Chemistry involved, and EXACTLY matches real world severe over-heating experience, real world Track experience, real world flat tappet break-in experience, and real world High Performance Street experience (test data validation doesn’t get any better than this), along with additional motor oil tech FACTS, by going to the Blog link below. Credentials, methodology, proof, facts, data, Industry endorsements, real world validation, etc, are all included in the Blog. See for yourself, the engine you save may be your own.

http://540ratblog.wordpress.com/
 

·
Registered
Joined
·
5,422 Posts
Vizard's secret '128' cam spec # revealed ? Speed Talk

This talks about the 128 rule.

The OP never said he was going to pick a cam based on LSA.

I have ran the same cam lobes but on different LSA in same engine. One was the 280H comp flat tappet used it on 110 and 106. The other was the 268H one on a 110 and one on a 106 and then an odd ball left the very early closing intake intake lobe of the 106 LSA and moved the exhaust lobe only .. to make 112 LSA.
Currently running it in my 57 and it is 40HP down past the peak HP vs the 106LSA. This is where more exhaust duration and or lift on the ex lobe would help things.

But I did it for a MPG test only. and it worked by getting 6 MPG more.

They all acted very different.
The 268H on a 106 had the most cranking pressure pulled the hardest out of the hole and out of all the 268H grinds pulled harder on the TOP because there was more overlap 56 degrees compared to the 112 LSA having 44 as per 540's math.

I do like my overlap.. But I do like early closing intake valves.

I like high compression and high cylinder pressures makes an engine snappy.
Overlap really helps the heads I use.. ported stock iron stuff. You can say it is almost like a crutch for crappy heads.

I have ran the crane F3 lobe in a 10.4 compression SBC 355" it was [email protected] .050 and .536" lift solid lashed at .026" and ground on a 106 LSA pulled 11.5" of vacuum and power brakes worked. This was in a 76 stepside.
Had small heads 601 castings ported.

Fun stuff juggling cam LSA.

Here is a fun fact. the 280H BBC cam has .520" lift.
I know for a fact you can use the small block chevy master and put it on the BBC cam and the .480" sbc lift becomes .544" lift on the BBC.
I had a friend get that .544" grind for his work van 454" engine. WOW! thing would scoot.
No Idea on his LSA though.
 

·
Registered
Joined
·
246 Posts
What's weird about all this is I have run 2 SBC 350s with hyd f.t. cams with ballpark similar cams and have very different acting engines:
350 #1 is bored .060
283 power pack heads, 59cc, stock size valves, no porting. Approx. 10.75:1 compression.
Flat tops with 4 v.r.'s
Edelbrock Performer 2101
600 v.s. Holley
Headman 1 5/8 long tubes, dual exhaust.
Erson TQ20H cam, 214/214 @ .050, 292 adv. duration. .449 lift. 111 LSA, 70 degrees overlap.
Super strong low and mid range power, from idle up, signed off at 4750 rpms, all done.
Perfect smooth idle. Idle at 550 rpms.
TH350 with Hughes 2500 stall and 3.08 12 bolt, if wondering....
Stealthy sleeper street cruiser that can street fight a little respectively.

350 #2 is bored .040
041 heads, 64cc, 2.02 and 1.60, bowl work done, quick cleanup on ports- very minimal, dish pistons with 2 v.r.'s, maybe 9.5 compression at best.
Edelbrock Performer RPM, non air gap.
Same exact 600 Holley from 350 #1.
Jeg's 1 5/8 long tube headers, dual exhaust.
Comp HE268H 218/218 @ .050, 268 adv. duration. .454 lift. 110 LSA, 48 degrees overlap.
Not quite as good power low down, but gets with the program real quick and pulls up to 5500 plus.
Choppy lopey cool sounding idle, smooths out at 1500 rpms. I idle it at 550 rpms.
TH350 with Hughes 2000 stall and 3.55 10 bolt.
An in your face sounding 350 street machine that can street fight a little also.

Now other than compression differences between the two, intakes being close, and the poorer flowing cylinder heads on 350 #1, it would seem they would act similar, cam wise. Nope. Not even close. Actually, the Comp cam at first glance looks only a hair bigger, more lift, and a hair more duration at .050, but it seems like I just went to almost the bottom of the cam catalog page just listening to the two.
Two relatively similar 350s, on paper, but act so totally different. I highly doubt the 1 degree of LSA made that huge of a difference between the Comp and the Erson. Overlap math shows the Erson has 22 degrees more, but its manners were much tamer than the Comp 268. I have a hard time in the idea of selecting a cam based solely on overlap. My results seem to contradict the overlap idea. What am I not getting?
 

·
Registered
Joined
·
1,865 Posts
Arch,
I do not believe using the adv duration #s for overlap is very accurate. As you have found out! The cam with 48* overlap makes HP to a higher rpm than the cam with 70* overlap? It should be the other way around...but isn't!
So I think this shows that using adv duration, especially from different brands, is unreliable for determining the expected performance range.
Plus, the can of worms that comes with hydraulic lobes.
Using your example, I see these variables that will affect the actual overlap that the valves will see:

[1] Comp uses 0.006" as the lift point for adv duration. Does Erson use the same? I have seen 0.004, 0.0045, & 0.008". Differences here skew the #s & make comparisons meaningless.
[2] The lifters bleed down, so that the for a Comp lobe the lifter clearance when the valve seats is likely to be more than 0.006".
[3] Lifter bleed down rate affects the final clearance as the valve seats.
[4] Spring tension affects this as well. More tension, more bleed down, more clearance as the valve seats.
[5] Oil viscosity also affects bleed down rate.
[6] Higher rocker ratios will also cause more bleed down, shorten overlap.

So I believe using seat duration for hyd cams to calculate o'lap is unreliable because of so many variables.
 
1 - 20 of 31 Posts
Top