Choosing a new cam

Discussion in 'General IH Tech' started by Darrell Tuxworth, Nov 19, 2020.


  1. jordandoc

    jordandoc Binder Driver

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    As my friend used to say, "We agree that we can disagree!" I don't put much faith in Comp's specs. Look at the valve lift...they computed this with a Chevy rocker ratio of 1.5:1 rather than IH's 1.6:1. Comp lists 800 rpm as low operating range...that's basically idle. I have a Scout with a 392, 3.54 gears, 10.50X31 tires and a 4-speed and I can start off from an idle in 4th. Can't get any better than that! What they consider their "power band" is arbitrary. I have not seen any standardization of these numbers or how they are calculated. How do they arrive at these numbers? If you compare duration of these cams, the Comp has higher degree duration at .050 which usually means it is a higher RPM cam. LSA is the same at 110 degrees so overlap, in theory should be the same but may be longer in the Comp because of the longer duration. I have used Comp 252's in the past and haven't seen much difference compared to Isky. I've also used the Comp 260 and power was good but mileage was in the toilet! Years ago, Isky told me that they build in 4 degree advance to compensate for the emission timing gear (R1 vs R2) on flat top piston IH's. I tow a 5000 pound trailer in Montana with no issues. Also, all my motors run between 8.7:1 and 9:1 compression. Maybe that makes a difference as does the gearing and transmission. All three of my 1210's have 5 speed-OD's which are lousy towing transmissions but my Scouts are divided auto and 4 speeds and do well. I have one Isky 258 (not in their catalog as Ron ground it for me special) that I really like but I can't recall the lift or duration. I guess choice boils down to a number of factors and personal experience.
     
  2. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    Elgin doesn't list a 345ci application on their site, but they do show the 304 and 392. And this camshaft is shown as the part for both those engines. Would it be the same for the 345 as well?
     
  3. jeff campbell

    jeff campbell Lives in an IH Dealership

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    Should be, all SV cams are the same !
     
  4. kevingweq

    kevingweq Y-Block King

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    They have a 345 listing , Try putting in "1973" and "International" Same cam and lifters as 266, 304, 392,
     
  5. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    That's what I would have thought. I did a different search on their site just now and found the 345ci engine camp. Same PN.

    They are already sold out on ebay. You b@stards beat me to it! Elgin lists the part on their site but doesn't seem to show stock on hand or provide a way to buy direct. I'll be needing one of those some day; no desire to use a different grind than stock.
     
    Last edited: Nov 21, 2020
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  6. Challengeexcepted

    Challengeexcepted Farmall Cub

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  7. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    Anyway. Interesting discussion. I've thought about it a lot over the years. The idea of putting in a "better" cam has always inspired the gearhead in me. But what I have learned is that any change in camshaft on this engines will move the torque peak up the RPM range by some amount. It seems like the stock grind is really the way to go.

    Another thing to play with is cam timing. Advancing the cam will improve low-end torque, it's said; retarding the cam will improve power at higher RPM. A time-honored modification. A friend of mine tried this with his 345 back in the mid 1990s. He decided to rebuild his engine. He didn't need to care about smog checks (whereas I do) so he was pretty much free do what he wanted. He used one of Schneider's cams, I don't recall which one. One of the 'mild' grinds. And he installed it advanced. I don't recall by how much exactly. He did "degree" his cam in the engine to learn when valves started opening etc. To have a starting point. Long story short, he just advanced the cam by one tooth. Nothing fancier than that. Then he finished up the engine. He made a bunch of other changes to the engine so it's impossible to say what the effect of the cam actually was though. Like, he put on a 4-barrel manifold (going from a 2) and put on an Edelbrock 600-something CFM carb, and he monkeyed with this distributor advance springs. Lots of little things he read "might help" with low-end power. So we'll never know how all that effected everything. He never had it dynoed or did any other scientific analysis on the outcomes. Its idle vacuum was never the same though. Could never get it above about 15-16 inches (at sea-level elevation, FYI), as I remember. He was concerned about it at the time. All I could say was, "Well, you have a non standard carb on an engine with a non standard cam with non standard timing."

    However, the engine actually ran fine after that and is still running today. I wouldn't say it was that much better than my stock 345's power with Holley 7448 carb.
     
  8. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    Thanks! I think that first company popped up in my search. I saw "Overnight parts from Japan" and moved on. LOL But I might call them. Maybe they have the lifters. And I'll call Elgin direct on Monday as well.
     
  9. jeff campbell

    jeff campbell Lives in an IH Dealership

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    Id stick with good ole seal power / johnson lifters.
     
  10. Challengeexcepted

    Challengeexcepted Farmall Cub

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    I did a little digging on them and apparently “overnight parts from Japan” is something of a joke name. It’s a quote from a really bad early 2000s car movie(I’ll let imagination fill in the blanks) they are actually US based. looks like the cam kit includes lifters
     
  11. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    Hah. Good to know. Suspect though. You can add the cam to a cart, but it says "Inventory at Kalamazoo MI Store : (Drop Ship / Special Order Part)". Meaning their store? Someone else's? I should call them to verify their source actually has one. Hopefully they'll answer honestly. :clown:
     
    Last edited: Nov 21, 2020
  12. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    Wise disclaimer on this one. I was wondering about this kdnoorse company so I went looking for reviews. Not just an auto parts site, which is very suspicious. Didn't find too much other than this rather poorly written web page where the author(s) rip kdnoorse to shreds. I don't know who's full of poop here, but this is enough to scare me off LOL:
    https://de-reviews.com/kdnoorse/

    Overnight Parts from Japan (ONPFJ) on the other hand, at least there's a page with no complaints on BBB web site. Been in business for five years and lists the owner of record:
    https://www.bbb.org/us/mi/kalamazoo.../overnight-parts-from-japan-llc-0372-38196809

    ONPFJ is in Kalamazoo, so that is obviously their store. But it says "special order" which likely means they don't have one and wouldn't even know for sure if anyone else has one until a customer pays for it in advance.
     
  13. Robert Kenney

    Robert Kenney Binder Driver

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  14. jtorre4272

    jtorre4272 High Wheeler

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    I agree. The comp specs are suspect and I just don’t trust the numbers. My 392 fuel economy is in the toilet as well. A really stinky one at that. So I basically messed up my idle vacuum, was too stupid to install high compression pistons (9.5ish:1), created an engine that has terrible combustion quality at idle and light load, shifts the power band to a region I don’t use, and allows me to watch the fuel gauge move as quickly as the speedometer. I have to run 93 octane to allow aggressive idle advance but prevent over advanced centrifugal timing (and resulting knock).
    I’m a dummy. The IH engineers were not.
     
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  15. RinTX

    RinTX High Wheeler

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    Am I reading this correctly - the same stock camshaft will fit 304, 345 and 392?
     
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  16. jeff campbell

    jeff campbell Lives in an IH Dealership

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    20201122_091029.jpg 20201122_091011.jpg Yes they will
     
    Last edited: Nov 22, 2020
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  17. wjajr

    wjajr Binder Driver

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    I have messed around with camshaft profiles with my slant six. Rule of thumb is as the separation or overlap of valve events increases the compression ratio has to increase. You have to have higher compression to over come the effects of poor cylinder fill and purging at low rpm which will cause rich condition, poor fuel mileage, stinking exhaust, and a gutless engine off idle; and idle rpm much higher than stock just to keep it running. At idle a portion of the incoming charge is dumped un-burnt out the exhaust. As rpm increases the gasses enter and exit combustion chamber more efficiently. In other words the emptying of combustion gasses tends to suck the fresh charge of A/F mixture in. That is why cams have an rpm range listed for an example say 1800 to 5200 rpm. This means that a slow turning IH engine won't begin to pull or develop torque until it goes past 1800 rpm. On the other side of the equation it will never come close to 5200 rpm unless a lot of changes are made in its breathing ability over stock carburetor & intake, exhaust, head modifications, and a lot of internal work blueprinting and balancing the rotating mass so it can spin up to 5200 rpm without vibrating apart.

    Your best bet would be to stick with the stock profile, increase the compression ratio a bit. But before you pull a ratio out of your hat, run the engine's dimensions through a compression calculator, and pay attention to the calculated "Dynamic Compression ratio". DCR takes into account the overlap between intake and exhaust valve events found in stock and high performance cams, and is different than the static compression ratio which is most often given on a spec sheet. The DCR is what predicts engines octane requirements. Get that DCR much over 8:1 and tendency to knock increases beyond what pump gas can handle. Stock cams have less over lap, and small changes can quickly move DCR over 8:1 turning that engine into a knocking mess.

    One needs to contact a cam grinder with tire size, rear gear, transmission type & gearing, carburetor size, compression ratio, any head & intake modifications, rocker ratio, and exhaust modifications. Then tell them what your goal is, be it low end torque to tow or handle heavy loads, high rpm power, or something in between.

    If you decide to regrind a stock cam, what happens is they take some material off the base circle (opposite from lobe crown) which in turn makes the lobe become taller (this is a simple explanation). Now to make up for the difference in valve train dynamics, generally when the head is shaved to restore a true surface, and milled some more to make up for thicker compression robbing aftermarket head gaskets & calculated compression increases over stock, most often the stock push rods can be reused.

    I have worked with Oregon Cam Grinders, as have many of the guys over on slantsix dot org that build stock to all kinds of crazy race engines. I went from a full out loping race cam profile that only started to pull hard at 4500 rpm up to 6200 rpm to something a bit tamer with nice idle with 15" of vacuum, low stink exhaust, and a power band one can use on the open road & in town.

    If you take a look on OCR linked above look for "Camshaft Basics" where there is a nice explanation.
     
  18. Patrick Morris

    Patrick Morris Lives in an IH Dealership

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    I ordered one from that company. We'll see out it goes. Should arrive around 12/4.
     
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  19. BinderBookie

    BinderBookie High Wheeler

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    There is one aspect that hasn't been talked about too much here. In my experience, this topic transcends the actual camshaft specs. It's fine to discuss the relative specs of each cam but those specs are only useful relative to the configuration of the rest of the engine. And the vehicle itself. The global picture. As far as the engine goes, the compression ratio, induction system, head flow, exhaust, general engine condition. Maybe more important is gearing, transmission type, vehicle weight and intended use. If you build the engine for those seductive peak power numbers and not towards that global view, you are spending money and hours on being underwhelmed, disappointed or screwed when you go to drive the Scout around.

    In fact, I submit that many people are barking up the wrong tree when they start thinking about a camshaft as the magic bullet for mediocre performance. Often, they are driving a Scout that is grunting around with 31x10.50-15 tires and 3.07:1 axle ratios, with an automatic, tipping the scales at 6K pounds and wondering why garbage trucks are aceing them at stoplights. No torque multiplication via gearing. Moving your torque band higher in that case is contra-indicated and the stock cam is the perfect choice because that's the torque/rpm band you will be operating in. Want to improve? Add more displacement and torque (bigger engine no matter what type). Or change the axle ratio and multiply the torque more via gearing. Perfect formula: An overdrive trans (manual or automatic) with relatively low axle gearing (3.73-4.10:1 or as indicated by the engine). This will turn even a 304 into an acceptable stoplight commando and deliver good highway performance and economy. Plus good trail capability. Get your gearing house in order first. You'll get better results than throwing mismatched parts at the engine.

    As far as camshaft effects on the engine goes, the limiting factor that slaps you in the face right off is the low compression ratio. That was partly emissions and mostly due to the engine being designed for medium duty use. It's all about combustion temps and pressure. You put an old-school high compression engine into heavy duty use, being lugged at relatively low rpms and they will detonate, burn valves, melt pistons, blow head gaskets, crack heads and block... and worse... unless the camshaft overlap isn't increased to bleed off some of that high pressure but then you lose all that low end. Yeah, you could engineer past those things but if you wanted to sell trucks at a reasonable cost, you were stuck with components in a certain price range. The practical answer was low compression ratios and short duration cams, which moved the torque band down low and to a narrow range, but those trucks had gearing (read torque multiplication) out the wazoo and they didn't need to go fast. Because the engineers knew the engine wasn't going to operate outside those ranges, the induction, exhaust, timing, etc , wasn't any more whiz-bang than it needed to be... which also kept costs down. Since horsepower is work times RPM, the horsepower ratings showed low. Even with an engine like that, a little external tweaking in the form of external airflow improvements can extend the rpm range a fair bit and improve the midrange power. The starting point is to make the SV breathe better with a four barrel (or a larger 2-barrel) with a suitable air filter and free (-er) flowing exhaust. The stock cam isn't the sole limiter to a better midrange.

    Google static compression ratio and dynamic compression ratio. If the compression ratio isn't matched to the cam profile.. . mainly duration, overlap and lobe separation angle... the cam is going to loose all that low RPM combustion pressure.. the combustion pressure that does the work. The static is the calculated ratio based on the total cylinder volume at BDC vs cylinder volume at TDC. Dynamic is the combustion pressure, which is a combination of the static as influenced by the cam profile and how much of that static pressure is bled off by valve timing at low rpm. A high static combined with low overlap/duration will have a high dynamic. And vice versa. The stock 8-ish:1 ratios with the stock short duration cam delivered what IH determined was a good dynamic that worked in both LD and MD applications. Later, as the SVs were near the end of their production life, emissions became an issue and low-ish ratios were part of the low emissions formula of the time. For light duty use alone, my opinion is that the IH engineers could have gone a bit higher but they were using the same engine for both light and medium and they weren't about to built a LD-only engine that cost a lot more to build. They did what they did. Most of the changes they made were to save costs (the "A" engines) or with the emission control gun to their head.

    Bottom line is that if you are going to increase overlap and duration, the compression ratio had to go up a corresponding amount. That's a simple statement but it's not so easy to implement because there are so many other contributing facts to consider... pinging being only one. If you aren't going to change gearing, increase the displacement to multiply torque. A four barrel (sized to displacement, gearing and use) and dual exhaust will deliver moderate gains no matter what. Next gearing... overall gearing (axle ratios factored by tire size), trans type and an assessment of weight and intended use. THEN start thinking about a cam.

    SIDE STORY: I did "Project Blazer" for Four Wheeler magazine in the '90s. It was a 6.2L diesel K5 with a 700R4, 3.07 gears and 235/85R15 tires. It was a turd. Great fuel economy but a turd, even with stock tires. Before I did anything else, I put in 4.10:1 axle ratios and it transformed that truck. That 6.2L had similar power output to a 304 and a similar operating range (much better MPG, tho). Those 4.10s took the 0-60 times from the high teens (nearly 20 seconds) to about 10 seconds and it could climb hills on the freeway that would have dropped it into second before. Yeah, the higher rpms cost about 1-2 mpg (from about 24-25 to 22-23-ish in optimal conditions... 650 miles per tank!) but the performance gain was worth it.

    I may have oversimplified this but I did it inbetween other things and didn't spend much time.
     
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  20. Darrel

    Darrel Dreams of Cub Cadets

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    Vibration with that small of a cam and FI? How much are we talking about? 1/4 in/hg? 2 in/hg?
     

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