[mkpontiac]

If two cams have the same 0.050 duration lift and LSA but very different duration at 0.006 lift(advertised) and therefore different overlap what are the affects on idle, vacuum, and mpg? I am looking at about 215° @ 0.050
Cam 1 has 288 @0.006"
Cam 2 has 272° at 0.006"
Assume that the compression ratio is the same.

Thanks for your insights.
MKPontiac

[pastry_chef]

If the advertised duration is rated the same, then less advertised will benefit idle, vacuum, and mpg.

On cams for improved mpg.

by CamKing » Tue Mar 08, 2011 7:07 pm
You need to measure the cam at .006"
Most production cams are too long at seat for the amount of area they have.
You could go to a better design that has more area on the intake, without increasing the seat duration.
Reduce the exhaust duration to increase the pull on the Intake at lower RPM's, and advance the intake
centerline
Mike Jones
Jones Cam Designs

[Jay S]

Before you get to deep in to making a decision make sure your not looking at the same cam with a different rating. A summit 2801 for example is 214@.050, has a 288 rating, and a 280 rating, and a 272 rating. 288 is ASAE SAE measurement of .006 at the valve, rocker arm ratio effects that rating. 280 is closer to the actual .006 tappet rating. 272 is a number picked in a board room by advertising as an acts like number.

I have ran into some cams that have a LOT of seat timing. To a point the cam can run more seat timing and not see much difference in overall performance. But eventually the engine needs more or less compression to help the engine manage the seat timing. It will effect hp, tq, milage and vacuum. The lowest points of lift are were the highest pressure differentials are. The effects can be substantial at low idle, some OEMs used seat timing to drop the combustion temp for emissions. Some OEM cams use a lot of extra seat timing for the exhaust.

I have ran a couple cams that had huge differences in the seat timing but the same .050” number and lsa. The widest spread I can remember were these two cams:

308/310 SAE, 292/295 @ .006, 218/218 @.050”

Versus

274/274 SAE, 268/268 @.006, 218/218, .050”

[Cliff R]

The big problem with all of that deal is that many of the cams being offered by different manufacturers with similar specs are the SAME cam. They "juggle" the numbers as far as advertised and even change the LSA on occasion to make it look like their own cam. They have been doing this for decades.

If you don't think it's true do some research on the very popular "RV" camshaft sold for SBC engines. It's rated at 204/214/112 LSA and sold under at least a dozen labels and I've even seen it listed on a 110LSA a few times but will bet anyone reading this it's the SAME cam as all the others.

WAY back when I started building engines and buying aftermarket cams I noticed that on each end of the cam they were painted. Never paid it much mind but one day I asked my main parts supplier why the cams were painted on each end. He said that the company grinding them did that so the workers could get them into the right box. He told me that CMC was the MAIN supplier for most camshafts and his business wasn't too far from their plant and he even did a plant visit once.

This was over 30 years ago and I doubt if much has changed as far as companies buying those cams in bulk and changing the numbers slightly to make it look like something they grind in house.

With this in mind it becomes difficult to make an educated purchase as more times than not you are comparing the same cam when the specs are close and it's being offered from two different vendors.

When you get time check out this link:

http://www.pontiacpower.org/PontiacCams.htm

Take a look at the 204/214, 214/224, and 224/234 offerings and you'll quickly see what I'm talking about above. Summit, Edelbrock, Speed Pro, Crane, Crower, etc all have offerings in those ranges and every single one of them is the SAME cam just slightly different advertised specs and once in a while they change the .050" numbers slightly as well........Cliff

[mkpontiac]

That all makes sense, thank you. Without consistent seat timing specifications it makes it difficult to determine seat to seat duration and correct dynamic compression which makes it difficult to decide on the right compression ratio. Does it just come down to experience?
Taking 2 Crower cams:
60918 - 288/298 advertised, 214/228 @ 0.050 & 0.440/0.464 lift on 112 LSA
60241 - 276/281 advertised, 215/221 @ 0.050 & 0.460/0.464 lift on 112 LSA
Would the Crowers advertised durations be taken at the same lift as each other?
Taking those numbers on a 9.5:1 compression ratio would result in dynamic compression ratios of roughly:
60918 - 7.1:1
60241 - 7.5:1
The 60918 could run 10:1 static compression to result in the same dynamic compression as the 60241.
Is this all correct? If so which cam would idle the smoothest and get the best MPG or would it be a wash? Would performance be similar?
Thanks again for your input.

[pastry_chef]

Originally Posted by mkpontiac

Would the Crowers advertised durations be taken at the same lift as each other?.

No, Crower is very confused about advertised rating.
Once Steve C got a callback from one of their deign engineers and the data conflicted with their cam card as well as what members here have measured.

For optimal performance both the area and the shape of the valve lift curve matter.

[Jay S]

The Crower 60918 is the same grind as a Summit 2801 or the generic white box cams 204/214/224, same cams Cliff referred too. Crower techs claim they grind all their own cams, so they may have the master and grind it themselves. The 288/298 rating is the SAE rating. The .006” tappet lift rating is 280 or slightly under 280 for that cam. I think I usually use 276* as it’s .006” duration. Which happens to be the same as the 276/281 Crower. The DCR’s are going to be basically the same between those cams. The 276/281 has slightly more intensity, but the 60918 has a earlier exh opening and large exh profile. I think the 60918 could run a bit more compression.

If your after MPG I would use the 276/281 cam. The extra exhaust duration on the 60918 will negatively effect the economy. Vacuum would be nearly the same. These cams seem run the best on pump gas with the dcr close to 6.8-7.0 in most engines.

[Cliff R]

Almost all major cam manufacturers claim to grind their own cams. They "juggle" or move the specs around on "box" cams from CMC otherwise every single potential customer would simply "google" the grind number to the brink of extinction to find the cheapest possible price with free shipping.

I learned that deal early on in the parts business and why I will NOT provide specifics on most parts when you are calling for "tech support" and wanting to place an order.

Every single time I give up details I get some BS excuse at the end of the 45 minute conversation when I've finished writing up the order and asking for credit card info that the dog ate the card or it's on the dash of the truck in their wallet and the wife is at Walmart and woln't be back for several hours, etc, etc.

Yes, due to Amazon, Ebay and a few others left standing at the moment the rules have changed for how folks spend their money, and it's NOT for the better. If you don't think I'm right take a look around at how many small businesses are gone or going under. Covid 19 will be the final blow to many of them, but Amazon and the others are making billions from it.......FWIW.......

[Jay S]

It is hard to believe Crower grinds the 60918 when CMC grinds it for everyone else.

When I increase compression but want to put an emphasis on fuel economy I like a bigger single pattern cam or a smaller exhaust to intake duration split. We haven’t seen much correlation with more vacuum adding fuel economy. I am sure it is there, just hasn’t shown up as a large trend, but I have seen a trend for better economy running a smaller exhaust profile on many engines.

[Steve C.]

Here is a "claim" they do.....

"Crower grinds all of its camshafts in-house much as it has done for decades. Each cam is closely inspected and checked before shipment to the customer.

https://www.hotrod.com/articles/unde...ImageId=933017

They ground a custom cam for me years ago.


.

[phil400]

Originally Posted by Steve C.

Here is a "claim" they do.....

"Crower grinds all of its camshafts in-house much as it has done for decades. Each cam is closely inspected and checked before shipment to the customer.

.

Maybe that explains why their Flat tap cams are So much more expensive then every one else's.

[Cliff R]

Crower's 60919 cam used to be exact specs of the SPC-8. Even though their website said 304/316, 231/240, 112, the cam card had it at 113LSA, and it came it right at 112-113ICL if you installed it "dot to dot". Makes me want to believe they just bought them from CMC and re-boxed them, but who's to say?

I also had a customer tell me that he bought their 214/224/112 cam and it was identical in specs when he measured it to the Summit 2801.

Of course things may have changed some and I haven't used a Crower 60919 cam in at least 5 years. Judging from other reported the specs are different than the older version it may now be an "in house" cam.......

[Steve C.]

And that was a magazine article. They might have been spoon fed that Crower does "ALL' in house with out any verification. Google for pictures inside the Crower facility, plenty shown for cranksgafts, roller lifters and other production. I didn't see banks of cam gringing machines.

Maybe a phone call to them


.

[Cliff R]

Financially it makes no sense at all these days to grind a cam "in house" when it's readily available from CMC and all you have to do is re-box it.

This is why I firmly believe that most of if not all the 204/214/112, 214/224/122, 224/234/114 and 231/240/112-114 cams are all from CMC and re-boxed no matter who is selling them.

Having to advance the 60919 4 degrees pretty much proves that Crower wasn't grinding them "in house" or someone forgot to grind the advance into them to get them to match up to the cam card they supplied with them....duh?

On the subject of camshafts I've been FLOODED with calls and emails since the Pandemic started.

The biggest complaints I used to get were from someone with a "fresh" engine rebuild who installed a Comp XE cam. The Thumper and Mutha Thumper series are very quickly becoming more popular with that crowd. The only thing users are liking about them is the sound at idle, and hating every other single attribute from them. The worst complaints are the wife refusing to ride in the car because it stinks here hair up!.....LOL......

[ta man]

Nothing worse than spending good money on a well built short block and good flowing heads and picking a turd cam for "the sound".

[STEELCITYFIREBIRD]

The cam sound at idle deal makes me flat laugh out loud.

You can literally listen to clips of the sound on some manufacturers websites.

Sorry...

[Tom Vaught]

Originally Posted by Cliff R

Financially it makes no sense at all these days to grind a cam "in house" when it's readily available from CMC and all you have to do is re-box it.

This is why I firmly believe that most of if not all the 204/214/112, 214/224/122, 224/234/114 and 231/240/112-114 cams are all from CMC and re-boxed no matter who is selling them.....LOL......

Isky Cams used to have a cartoon in his advertising (in the 60s) where a dump truck was dumping camshafts on the ground behind the "Camshaft Business" that claimed they were making their own camshafts.

Isky is a smart cookie and knew all about the re-box guys so I totally agree with you Cliff, on this one. I have a list somewhere (that Don Hubbard V.P. at CMC gave me) that gives all of the buyers of the Camshaft Machine Cams products. Don H was "The Man" at CMC. The only guy higher than him was Harvey Crane in Florida.

Tom V.

[Steve C.]

"So, what the heck happened to turn respectful camshaft competitors into the mudslingers responsible for waging the infamous Camgrinder Wars that entertained and enraged Hot Rod and Drag Newsreaders from roughly the late '50s until the mid '60s? All signs point to Ed Iskenderian, though Howard Johansen and Jack Engle both played critical parts in the conflict's early stages. Exactly when the first shot was fired is less clear."

Who Started The Camgrinder Wars?

https://www.hotrod.com/articles/who-...r-wars-part-1/



.

[mkpontiac]

If I aiming for 89 octane, which gives me some room if 91 is required, what compression ratio should I aim for with the 60918 and 60241 cams? Is 9.5:1 too high? Assume 0 deck and 400 ci.

[Half-Inch Stud]

May 2020 Reality Check; Where can/do we go for Custom-Grind FLAT Tappet Cams?