SHOtimer
#2910
My first thought is if they ran in another car previously, they have to be good. Just a matter of getting the timing right.
Doug
Problems with SHOshop cams. Mismatched cams How do I time these?.
- Thread starter zach44102
- Start date
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My first thought is if they ran in another car previously, they have to be good. Just a matter of getting the timing right.
Doug
SinisterSHO
Rust free
maybe thats how it had all that power to lift the front wheels..
You have an ATX cam there and it is on backwards. The hole needs to be on the other side.
See here in the picture:
Do you have a picture of the cam bearing surfaces?
Would you like me to take pictures of the cam bearing or the bearing surface in the head?
Mr Anonymous
Tire Wall
He wants to see the cam surfaces, they are ground down on stage 2 cams to clear the edges of the buckets.
SHOtime2511
CGP
Chris had those in a running SHO for awhile.
Eaxctly the side shot looked odd, but it may of just been the view.
jayro
SHO Member
Then couldn't Zach contact him to ask about the way he correctly installed them? Or atleast that is what I would do.
I did contact him.
Yes the bearing surfaces have been ground down on the edges.
You would install these just like normal, no issues.
The timing belt side is the same, atx or mtx. Sure, the hole in the chain side of the cam may be in a different spot, but just install the chain drive gear as you would on any atx cam and you are good to go.
The timing belt side is the same, atx or mtx. Sure, the hole in the chain side of the cam may be in a different spot, but just install the chain drive gear as you would on any atx cam and you are good to go.
Zach and I spoke at length (mainly I talked, loud mouth that I am), and all should be fine. If there were any advance built into ATX cams (where is the info confirmed?), it would represent a barely 1% difference, which I bet is within the average tolerance of a reground SHO SHOP cam anyway. Regardless, they were installed an running in a SHO previously, one with stock cam gears, so all is well. I removed them from a set of heads, and it never occurred to me to inspect them to see if they were ATX or MTX cores. Next time I remove a set of aftermarket cams, I will be mindful of this, but only so that I can alert the new owner, not because it affects the performance of the cam any.
jayro
SHO Member
Glad to hear it is figured out.
I bought the cams installed in heads years ago. All I did was time it properly with timing belt on a 3.2. You can hear in the videos the car running with the cams in them. When Tim bought everything he got the cams just as they came out of the car- still installed properly in the heads.
I don't know who removed the cams from the heads or why you cannot time them properly.
I don't know who removed the cams from the heads or why you cannot time them properly.
Mr Anonymous
Tire Wall
Some Canadian guy who seems to be an expert on such things.
I don't doubt that a motor will run with the cams as-is, but to have two exhaust cams in the same motor with different advance and overlap is not going to be optimal. A motor will also run with .020" gaps between the lobes and shims; but again it doesn't mean it's optimal.
Given SHO Shop's history of no two sets of anything being the same, there are probably quite a few motors out there are not optimal but otherwise run ok and are reliable. Hopefully if anything is learned from this it's that paying top-dollar for old SHO Shop parts probably isn't a good investment.
A fool and his money are soon parted...
We will see what the dyno says. If it runs and I see improvement right now i will be happy. Tim seems to be very knowledgeable and I would trust his word.
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While Josh (I assume) has a great deal of knowledge, I would still love to see the technical info relating to the ATX vs MTX cams. This is the first I have heard of ATX cams having 4degrees of advancement in comparison to the MTX. Either way, take an ATX intake cam and swap it into an MTX and I would bet money you be hard pressed to measure any difference on a dyno. And that difference becomes even smaller after a reground.
A fool and his money are soon parted...[/QUOTE]
I do not know what Zach payed for the cams, but the dollar per hp value I am sure was better than a new set of cams from any current SHO vendor.
This is from Josh's web site on camshafts.
As a primer, here are the measured specs of the stock cams:
MTX Intake 0.348” Lift, 205° Duration @ 0.050”
MTX Exhaust 0.328” Lift, 201° Duration @ 0.050”
ATX Intake 0.328” Lift, 201° Duration @ 0.050”
ATX Exhaust 0.328” Lift, 201° Duration @ 0.050”
The ATX Intake chain ****** is also advanced 4 crankshaft degrees relative to the MTX cam. As the Intake chain ****** is what drives the Exhaust cam, this effectively advances the Exhaust cam in an engine with ATX cams by 4 crankshaft degrees, which also reduces the overlap by 4 crankshaft degrees. Compounded with less duration on the ATX intake lobe, there is substantially less overlap with the stock ATX cams. In total, there is 6 crankshaft degrees less overlap, 4° due to the advanced exhaust cam, and 2° due to 4° less intake duration (1/2 of the total duration difference). Note that if you are regrinding cams, it is critical that both intake cams be either MTX or ATX, or you will have mis-matched exhaust lobe centerlines between banks due to the 4° difference between MTX and ATX exhaust cam timing, as driven by the intake cam flanges. We carefully check each set of camshafts to verify that we have matching intake cams for each set of cams made.
Thanks Mr. Joshua!!!:wave:
As a primer, here are the measured specs of the stock cams:
MTX Intake 0.348” Lift, 205° Duration @ 0.050”
MTX Exhaust 0.328” Lift, 201° Duration @ 0.050”
ATX Intake 0.328” Lift, 201° Duration @ 0.050”
ATX Exhaust 0.328” Lift, 201° Duration @ 0.050”
The ATX Intake chain ****** is also advanced 4 crankshaft degrees relative to the MTX cam. As the Intake chain ****** is what drives the Exhaust cam, this effectively advances the Exhaust cam in an engine with ATX cams by 4 crankshaft degrees, which also reduces the overlap by 4 crankshaft degrees. Compounded with less duration on the ATX intake lobe, there is substantially less overlap with the stock ATX cams. In total, there is 6 crankshaft degrees less overlap, 4° due to the advanced exhaust cam, and 2° due to 4° less intake duration (1/2 of the total duration difference). Note that if you are regrinding cams, it is critical that both intake cams be either MTX or ATX, or you will have mis-matched exhaust lobe centerlines between banks due to the 4° difference between MTX and ATX exhaust cam timing, as driven by the intake cam flanges. We carefully check each set of camshafts to verify that we have matching intake cams for each set of cams made.
Thanks Mr. Joshua!!!:wave:
jayro
SHO Member
I wonder how much one tooth on the cam sprocket would change the timing? To figure it out, would it be as simple as counting the number of teeth on the sprocket and dividing 360 by that #?
# of teeth=x
360/x=the change in degee per tooth.
Then 90 teeth would equal 4 degrees.
Probably not 90 teeth on the sprocket though.
Is my thought process correct, or am I totally clueless?
# of teeth=x
360/x=the change in degee per tooth.
Then 90 teeth would equal 4 degrees.
Probably not 90 teeth on the sprocket though.
Is my thought process correct, or am I totally clueless?
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. So what are we saying here guys? 4 crankshaft degrees is quite substantual. So the advancement is not ground into the cam but in the way the chain ****** bolts to the cam? If i ran one bank advanced 4 degrees how would it effect the car? Hp wise i think we are talking less to really care about like 2-3 hp. But any other ill effects?
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Crankshaft degrees and cam degrees are two different things.
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