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Old 10-14-2005, 03:15 AM   #11
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From a strictly metallurgical standpoint, grinding a hardened part to different depths (like you would with a cam lobe) and then re-hardening is NOT a good idea. At least not preferable compared to a part made correctly to begin with. I don't suggest going that direction.
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Old 10-14-2005, 05:55 AM   #12
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What if they only have to grind minimal material off and leave hardend surface intact?
Like the seats on a head, you can port them, but only so far before you have to use a lead additive.
People regrind cams all the time. What do they do?
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Old 10-14-2005, 12:48 PM   #13
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Quote:
Originally Posted by willwren
From a strictly metallurgical standpoint, grinding a hardened part to different depths (like you would with a cam lobe) and then re-hardening is NOT a good idea. At least not preferable compared to a part made correctly to begin with. I don't suggest going that direction.
I've gotten the impression that cam regrinds are somewhat common, so I'm guessing there'* a proven method for rehardening that achieves reliability. I'll have to do more searching and have a longer conversation with Comp in the near future.

As far as the exhaust manifolds are concerned, the plan is to do the tried and true porting method of welding the outsides and opening up the insides. You don't think ported manifolds will be able to handle higher compression? I didn't think it would make that big of a difference. Have you read anything or had experience that leads you to believe we'll run into difficulties?

Also, keep in mind that the heads might not get milled the full .060". If the cam regrind dictates a lesser amount we can take off the heads while still using the stock valvetrain, we'll go a little less. A lot of the plan hinges on the cam regrind (unless Bill is correct and it'* a bad idea). We'll make sure to keep everyone posted with our findings as this project creeps along.
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Old 10-14-2005, 11:12 PM   #14
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Many times when you take the cheap route, you get what you pay for. Have seen amny go through this same scenario. Regrinding a camshaft, no matter what they tell you, never performs the same as the original ground core. I have many people on the past, copy camshafts I have developed and take them to a regrinder to copy the cam. then come back and 'fess up that they had my cam copied, but the car did not go faster and many times it even slowed down.

When a camshaft is reground, many times they reduce the base, therefore changing the ramp angle. There is a big difference when a cam is repaired and regorund; during this process, the lobe is welded and additional material is added and then ground. the camshaft maintains its ramp design, which affects acceleration rates.

Also, there are lots of metallurgical processes that are done to the cam after is ground for hardness and lubrication. many shops that regring camshafts do not have the equipmemnt to do such. Yes, reground camshafts are used on daily, non-high performance rebuilds. I have used them in the past for a cheap rebuild to help someone that does not have a lot of cash.

Also, to add some more info on the subject, there are many that put high lift rocker ratios on their engines. Although you see an increase in peroformance, if you woild have a camshaft developed for the specific rocker ratio, you would see even more power increases.

Anytime you mill the cylinder heads and use a reground camshaft, I recommend that you check you pushrod length; you would not want to bottom the lifter plunger.
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Old 10-15-2005, 02:12 PM   #15
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Quote:
Originally Posted by ssei1995
Anytime you mill the cylinder heads and use a reground camshaft, I recommend that you check you pushrod length; you would not want to bottom the lifter plunger.
Which is exactly why we need to figure out just how much they take off of the cam after it'* ground. Mill the heads the same amount within .015" and we're golden. The cam hardness etc has brought some concern to my mind as well.... We'll have to see. Thanks for the info guys.
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Old 10-15-2005, 05:38 PM   #16
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Quote:
Which is exactly why we need to figure out just how much they take off of the cam after it'* ground. Mill the heads the same amount within .015" and we're golden.
You got to be kidding me???

You cannot grind material off the cam to compensate for the pushrod difference.

Did you carefully read my comments regarding the camshaft ramp base and the ramp angle.

If you grind the camshaft to compensate for milling the heads, you as well can take the camshaft and instead of putting it on the engine, put it in the trash can.

I understand many of you do not have the $$$$ to purchase many of the parts to make our cars go fast, nevertheless, there are no shortcuts for same items such as camshafts. Our parts cost more because there is not a big demand for them. We do not have a Chevy or Ford small block which you can find all kinds of mass produced high performance parts. There are even more USA Made race and high performance parts in the market for foreing cars such as Hondas and Toyotas than for our own US made cars.

When was the last time you saw Dart build an aftermarket block or cylinder heads for a Series I or II engine??? They have them for Hondas. When was the last time you saw an aftermarket Moroso oil pan for a Series I or II??? Moroso has them for Hondas, Mazda and Toyotas!!! They make all these parts because of demad and market.

Saying this, I noticed people complaining about Intense and ZZP cam prices; they do not make their cams. They have to buy them, put them on the shelf and wait for someone to buy them. In the mean time, their money is gathering dust, not interest, on their shelves. Kudos to them for taking the risk of making these parts available to the public; they could be making a lot more money with ricer parts!!!

Well...let me get off the soap box and enough venting on the subject.
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Old 10-16-2005, 01:39 AM   #17
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Quote:
Originally Posted by ssei1995
You got to be kidding me???

You cannot grind material off the cam to compensate for the pushrod difference.
Whoa whoa whoa, hold on just a second. I think we've had a misunderstanding here. Let me write it out and see if it makes any more sense.

When a cam is reground, the base circle of the cam lobes is reduced. Regardless of the resulting cam profile after the regrind, you must compensate for the new, smaller radius of the cam base circle. The answer could be one of two things: either lengthen the components of the valvetrain (longer pushrods) or use adjustable rocker arms. Since a new set of rockers would be over $400, we feel the logical 'budget' choice is longer pushrods for only $100.

However, we're combining a reground cam with milled heads. When you mill the heads you must install shorter pushrods to compensate for the material that is removed. So our plan is to get the cam reground and find out how much longer the pushrods would need to be, then have that exact amount removed from the heads in the milling process. The end result should be a decent cam with higher compression that maintains the stock valvetrain geometry with the stock components.

If I'm making an error in logic, please let me know. We think this should work out, but we're always open to critcism and suggestions. Like I said before, this project is still far from becoming reality, so this is just the research phase. Thanks.
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Old 10-16-2005, 02:32 AM   #18
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Adjustable rocker arms will not compensate for a smaller base; a mistake that many make. If you use adjustable rocker arms to compensate, then you will damage the tip of the valves and put additional loading to the valve guide. The reason is because the pattern on the tip of the valve will either be over or under extended. That is why on every high performance or racing application, you must check the pattern on the valve tip with either Dykem blueing fluid or even with a felt pen marker. When you have the proper pushrod length, the tip of the rocker will stay on the center of the valve tip during the full rotation/cycle of the camshaft.

Also, whom are you paying $100.00 for pushrods??
There are many ways to save money on the proper length push rods:
Determine the proper length of the pushrod you need.
Go to a local engine machine shop and let them look in their engine parts catalog for a replacement OEM pushrod with the proper ends, length and diameter.

You will be amazed that you can get a set of great pushrods for about $36.00; and you might even get a set of hardened pieces too. Any OEM engine that had guide plates from the factory, had hardened/heat treated pushrods. The engine parts catalogs show thousands of part numbers for pushrods.

You need to either buy or make an adjustable pushrod to get the proper length; you cannot guess by the amount you milled the heads. Also, you have to take into consideration the hydraulic lifter plunger travel too. You should have 0.020" to 0.060" preload on the lifter plunger; my preference is 0.030"/0.040" preload.

The way to do it is to turn the engine until the engine is at top dead center firing on the cylinder you are adjusting. At this time, both lifters will be on the base circle of the cam lobe and both valves will be closed. Put the rocker arms and the adjustable pushrod. Torque the rocker arms to the factory setting. Turn the adjsutable end of the pushrod
until it makes contact with the fulcrum of the rocker arm with no airspace between the rocker arm and the pushrod and no preload in the lifter. Measure the length of the pushrod, then look for a pushrod with an additional length of 0.020" to 0.040". Also make sure that all the valve stems are all the same height or within the range.
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Old 10-16-2005, 02:55 AM   #19
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Sorry to hyjack...If I were to get longer pushrods and shaved my heads down like .030-.040 this would give me a different rocker duration larger than stock right? what if you just put in longer pushrods without the head work?
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Old 10-16-2005, 03:12 AM   #20
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If you alter the length of the pushrod to try to change the duration; you will mechanically put undue constraints on the valve tip just like I explained earlier. When you have the proper length, the rocker arm tip will stay in the middle of the valve stem tip duration the whole camshaft cycle or rotation.
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