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420 rwhp / 390 rwtq
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Discussion Starter · #1 ·
This may be my setup, but I have some concerns about my dynamic compression ratio. 93 octane is very available in my neck of the woods. I will for sure be using Patriot stage 2 LS6 style heads with 59cc combustion chambers. I cc'd them tonight and it looks like the real number in 59.5cc per chamber. I would like to go with the TR224/224 .563 112 LSA cam. This setup nets an 8.83:1 dynamic compression ratio and an 11.29:1 static compression ratio. To get these numbers I have to run the stock gasket at .055", so unfortunately, assuming I will be .007" out of the hole... I will have a quench of .048". Not terribly desireable, but seemingly it is necessary.

The ultimate question is, can I run this DCR SAFELY? All I have seen is 8.5 is safe, but is 8.83 on the ragged edge, or am I still okay.
 

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Didn't you just make a thead on this?

8.83, the math checks. Sounds like a good DCR.
The cam your running is by no means "very aggressive"
 

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420 rwhp / 390 rwtq
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Discussion Starter · #3 ·
I hadn't gotten it calculated yet. It was a question on the actual calculation. Now that I have real numbers, I am asking the question. Like I said, everything I read says to stay around 8.5,and clearly I'm not around 8.5. The cam doesn't need to be very aggressive to create a high DCR. People attribute aggressive cams to high lift and duration, and not when the intake valve closes.
 

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I would go with a cam with more duration or install the 224 straight up to close the intake a little later. Since your an M6 I would go with the bigger cam with a later IVC to get your DCR closer to 8.5 with a thinner gasket to lower your Quench. Don't forget to check piston to valve.
 

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I've probably pissed off a few people on other boards but don't get too hung up on picking the ideal DCR. It's only ONE of many factors when building a combination. Yes it does play a role in overall power but there are a lot more important items you must consider. After all, the DCR number can be skewed very easily with some creative typing.

It still boils down to a proper "balance" of components is a hell of a lot more important than that one little DCR number....

Ed
 

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420 rwhp / 390 rwtq
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Discussion Starter · #6 ·
The ICL of this particular cam is about 108-109. Those degrees of advance are ground into the cam design itself correct? If the cam is installed straight up, it should theoretically put the ICL at 108-109 correct?
 

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420 rwhp / 390 rwtq
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Discussion Starter · #7 ·
Straight out of the horses mouth... I just talked to someone at TR and if the cam is installed straight up (dot-to-dot) the 4 degrees of advance are ground in. No need to advance the cam for the 108 deg ICL. Now, it looks like I will need to degree the cam only to make sure it is ground correct.

Installing the cam straight up as said by 1bdindn will NOT retard the cam 4 degrees. It will close the intake valve at 66.7 degrees ABDC just as the cam card says. To retard the cam I would need to degree it back 4 degrees and not install it straight up.
 

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juice12ufo said:
Straight out of the horses mouth... I just talked to someone at TR and if the cam is installed straight up (dot-to-dot) the 4 degrees of advance are ground in. No need to advance the cam for the 108 deg ICL. Now, it looks like I will need to degree the cam only to make sure it is ground correct.

Installing the cam straight up as said by 1bdindn will NOT retard the cam 4 degrees. It will close the intake valve at 66.7 degrees ABDC just as the cam card says. To retard the cam I would need to degree it back 4 degrees and not install it straight up.
I guess I used the wrong terminology, I meant to install the cam retarded 4* to negate the 4* adv. ground in. This in my mind is "straight up", but my mind works in strange ways some times.:confused:
 

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420 rwhp / 390 rwtq
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