Here's my dilemma,
I have a GMPP 454 mark VI crate engine. A while back, I followed an Chevy High Performance article on the same engine where they did a cam swap and some minor head work, trying to reach 500hp.
I did the same to mine but added MPFI.
Now I'm in the process of doing some detail work with the engine out. Not real happy with my chassis dyno numbers, I was thinking of changing cams again. But in doing research, I found out why my dyno numbers are not what I expected.
Seems the 8.75:1 compression my engine has is not high enough for the Crane cam I'm using (#168731).
I talked to Crane, they suggested going to a smaller cam.
I like an aggressive idle so I'm not really interested in going smaller.
I don't have a lot of money to spend, so I was trying to figure out, Do I bite the bullet and raise the compression? Or do I use a different cam.
So now here are a couple of more questions.
How high of compression can I go and still use 92-93 octane fuel? 10:1 -10.5:1?
The heads are 118cc's.
Also GM recommends 93 octane for my engine. Why so high of octane if the CR is only 8.75:1?
I hate to spend money on new pistons when I need money to address some other issues with the car, but I also want it to be right.
The car doesn't run bad now the way it is, I just expected more.
So I either leave it alone, change pistons, go to a smaller cam. Or possibly have a custom grind done with a LSA of 108* instead of 112*. What I learned from that is I'll lose top end and vacuum, so I guess that wouldn't be a good idea.
Any thoughts on my issue?
Thanks guys.
I have a GMPP 454 mark VI crate engine. A while back, I followed an Chevy High Performance article on the same engine where they did a cam swap and some minor head work, trying to reach 500hp.
I did the same to mine but added MPFI.
Now I'm in the process of doing some detail work with the engine out. Not real happy with my chassis dyno numbers, I was thinking of changing cams again. But in doing research, I found out why my dyno numbers are not what I expected.
Seems the 8.75:1 compression my engine has is not high enough for the Crane cam I'm using (#168731).
I talked to Crane, they suggested going to a smaller cam.
I like an aggressive idle so I'm not really interested in going smaller.
I don't have a lot of money to spend, so I was trying to figure out, Do I bite the bullet and raise the compression? Or do I use a different cam.
So now here are a couple of more questions.
How high of compression can I go and still use 92-93 octane fuel? 10:1 -10.5:1?
The heads are 118cc's.
Also GM recommends 93 octane for my engine. Why so high of octane if the CR is only 8.75:1?
I hate to spend money on new pistons when I need money to address some other issues with the car, but I also want it to be right.
The car doesn't run bad now the way it is, I just expected more.
So I either leave it alone, change pistons, go to a smaller cam. Or possibly have a custom grind done with a LSA of 108* instead of 112*. What I learned from that is I'll lose top end and vacuum, so I guess that wouldn't be a good idea.
Any thoughts on my issue?
Thanks guys.
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