For the Torque Master 267...do you know what the published Intake closing event ABDC is?

 

On my example cam that I've had ground for a customer doing a build of a 351C 2V using the Reed Torque Master lobes, Demos' Cams HL19-8/0 installed on a 106 intake centerline the intake closing event is 63.3 ABDC @ .006 28.6 ABDC @ .050.

If you take the plot of the XE 254 lobe which is on a 110 intake centerline it's intake closing events are 34.4 ABDC @ .006 and 58.8 ABDC @ .050. Move it ahead to a 106 and it's within a couple of degrees of the Torque Master.

 

According to Comps site information (and as most people already know) for this 351C/M XE256h cam that I’m referring to, it IS on a 106 centerline but with a 110 LSA (ground in advance) and of course gives a closing event of 54 at .006.
No ground in advance on the Reed??

 

When I had the cam ground I didn't put in advance but when I plotted it I did it on a 106 intake centerline and when I built the engine he also put it on on 106. It could have been ground on a 106 intake centerline just as well.

 

Here's another lobe for you; a Competition Cams 252H on a 106 int centerline. With 206 @ .050 duration, 267.5 advertised duration @ .006. The intake closes 65 ABDC @ .006, 29 ABDC @ .050

 

Not sure if I’m reading your post wrong but I know the 252h cam well. It’s advertised duration at .006 is in fact 252, not 267.5. With a 106 centerline and 110 LSA it yields a closing event of 52 ABDC at .006. with its 4 degrees ground in advance.

 

i have a spare 10320709 somewhere but it might be a but much without the compression to run it.

 

That data was generated by making a plot from an actual cam not from a cam card. Maybe I'm wrong. I'll have to look at it again when I'm at the shop.

 

With respect My final comments on the matter is this....

If someone has their own way of accurately selecting a cam based on manufacturer specs, plotting, technical data, prior usage, heresay, etc. then that’s great and I certainly won’t knock it.
For me personally, I’ll stick with the tried and true Harvey Crane way of giving relevance to advertised duration to help determine aspects such as, among others, dynamic compression and lobe aggressiveness/laziness (which he called Hydraulic Intensity by comparing duration at .050 to advertised duration). With a good understanding of different manufacturers timing event measurement methods and lobe profiles, I’ve done this for years on hot rods and restorations and it always works for me whether I’m trying to build more cylinder pressure in a lower compression engine or build a pump gas friendly high compression engine.
While it may not be technical enough to paint a perfect picture of every cams details, Ive found it very reliable when selecting from the majority of off the shelf grinds and even some custom cams I have had spec’d.
I also trust most popular cam manufacturers cam cards and assume they’re competent enough to provide at least fairly accurate specs. I have had no reason not to. I have also never received a bent camshaft that I’m aware of, but I guess like anything else it could happen. Maybe I’ve just got lucky over the years with assuming if the cam will slide in the bearings nice and run as expected it was straight.
And, any cam spec information that I post on this forum is taken directly from the manufacturer, not a number that I calculated, theorized, measured, etc. Afterall, the last thing me or any other FTE member needs/wants to see in the forums is inaccurate specs.
With that said, I don’t build max performance competition race engines, which I’m sure may go beyond my methods and realm of knowledge for that matter. I build engines for restorations and hot rods like nearly all the members on this forum who are building engines.
This has been an interesting discussion to say the least and that is my last word on the matter. I hope it works out well for the OP.
And to DaveMcLain...I see that you’re a fairly new user and in case no one has already told you, Welcome to FTE!

 

Today I looked back at my data on the 252H cam and what's interesting is that it has 252 duration when checked at .008 not .006 so as you said, knowing exactly what lift the advertised duration comes from is really important. This is especially true when looking at durations at very low lifts where the lifter is moving very very slowly per degree. Much like finding the centerline of the lobe by dropping down .050 or .100 off of each side and splitting the difference is much more repeatable than trying to find it using a dial indicator.

most of the time cams are pretty close to what's on the cam card but they do vary especially if they are roller cams that are produced using masters. Usually but not always the masters are designed to produce a lobe for a standard size small block Chevy. When the cam is ground for a small Ford the duration will grow 3-4 degrees at .050 while the lift remains the same. If ground for a big Ford this is about 6 degrees. So the question is which data do they use? The theoretical design data or what the cam actually checks? Who knows.

I plot every camshaft that comes through our shop using the Performance Trends Cam Analyzer stand and software. This has been a great learning tool and it has allowed me to gather a lot of information which has improved the engines that I build without question.

It's always fun to discuss this sort of thing and I've been enjoying FTE. Thanks.

 

I have just started a build on a 400 and have asked this question in another thread that hasnt gotten much response. The machinist will do what he can to up the compression some (he is a Ford guy and is familiar with the 400). My rig is a 80 F350 DRW, C6, 4.10 gear. WIll be used for hauling and some towing. It will not be a daily driver and I do like some rumble at idle (who doesnt) .4 brl edlelbrock intake, headers (have questions on those), machinist recommended a Quick Fuel 680 HR vac sec carb. I was looking at a Lunati cam, 10320701K (I called Lunati and that was their recommendation) Advertised Duration (Int/Exh): 256/262 ; Duration @ .050 (Int/Exh): 213/219 ; Gross Valve Lift (Int/Exh): .524/.540 ; LSA/ICL: 112/108 ; Valve Lash (Int/Exh): Hyd/Hyd ; RPM Range: 1200-5500. Machinist thinks this may be too much lift without a different torque converter and possible valve length issues.
I have always been under the impression that split pattern cams were better as the intake and exhaust are not really doing the same thing. And of course I thought more lift was better. It appears I am off base?

 

For what you're doing that is too much duration and too wide of a lobe sep to really run effectively at low speeds with a stock torque converter, towing etc. The lift isn't really any problem as long as you can get the spring rate low enough so that your open loads are not too high. More than about 270lbs open is too much.

The reason to run a single pattern cam in this sort of application is because of a few things. First off, single pattern cams make the most peak torque. 2nd, adding more exhaust duration will tend to give the engine more torque above the torque peak and less below which can be helpful to horsepower especially with a very free flowing exhaust but very bad for low speed torque when running a street exhaust system. 3rd and possibly the most important, it tends to raise the EGT greatly on a low or moderate compression engine. This will make the headers glow red hot all the way down to the collector during a dyno pull.

 

What would you recommend for an off-the-shelf camshaft (something that is available from a retailer such a Summit)? I plan on buying a kit with springs, retainers, etc.

 

I think the only reason for single pattern cams is it's easier to manufacture.

 

You might think that but that's not the case. Single pattern cams make more torque than a dual pattern profile particularly one with more exhaust duration. If you look at the torque curve as it rises, peaks and then falls first with a single pattern cam and then one that's dual pattern what you would see is that the single pattern cam produces a higher peak torque value, while the dual pattern will produce a lower amount of peak torque AND less torque below that peak while producing more above the peak. This is good for horsepower numbers but that comes at the expense of a lot of low speed torque which is generally more usable in a street type application. The extra exhaust duration also tends to(by a lot) increase the EGT.

Thinking about the 460 that's in my '79 F-350 as an example: I built the engine about 20 years ago using a Reed Cam flat tappet hydraulic 205/210 degrees at .050 on a 112 sep in on 108. KB pistons giving 8.4:1 compression with D3VE heads, Performer intake, Hedman headers, and a Holley carburetor. This engine made 330 horsepower at about 5000rpm and 500lbs/ft torque at around 3000 or so. It would make the header glow to the collector during a dyno pull. Knowing what I know now about camming a low compression application I would have done 205/205 on a 108 in on 106. This would really help now since I've changed from a C6 to an E4OD in the truck and dropped from 3000rpm to 2200 cruising on the highway.