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Discussion Starter #1
With a d15b7 block how much compression can I get away with running with 110 leaded? It must have a good idle, but will not see street, only track.
 

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no need for race fuel if your not gonna use a bigger cam, and no need for lots of compression if your not gonna use a bigger cam, what are you doing with this thing and what are your goals and track rules.
 

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I agree with Bone.

OK to expand on Bones comment.

Depending on intake valve closing point, exhaust scavenging, ignition timing, detailed combustion chamber work, quench pads, piston to head clearance, a:f, intake air temperature and coolant temperature, 14:1 should be fine.

Power increases can be had all the way up to about 17:1 if you have the fuel to support it, but after about 12:1 the laws of diminishing returns are really starting to kick in and the problem of getting more compression and still being able to light the mixture, and not shroud the valves and not have piston to valve clearance issues and not have the dome kill flame propagation all become more difficult while the gains become less.

Look for at least 12:1 and take any extra you can easily get, but don't lose to much sleep about if you get 13 but not 13.5:1
 

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I agree with Bone.

Depending on intake valve closing point, exhaust scavenging, ignition timing, detailed combustion chamber work, quench pads, piston to head clearance, a:f, intake air temperature and coolant temperature, 14:1 should be fine.

Power increases can be had all the way up to about 17:1 if you have the fuel to support it, but after about 12:1 the laws of diminishing returns are really starting to kick in and the problem of getting more compression and still being able to light the mixture, and not shroud the valves and not have piston to valve clearance issues and not have the dome kill flame propagation all become more difficult while the gains become less.

Look for at least 12:1 and take any extra you can easily get, but don't lose to much sleep about if you get 13 but not 13.5:1
Bone, you said all that? Damn... I must have blinked.

LOL! (I know you added to it!!)

You will have to worry about O2 sensors. Lead will ruin them. That is if you are even going to put one in.
 

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OK OK

It's fixed.
 

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OK OK

It's fixed.
I was kidding. I get so busy reading. I read yours, and I thought maybe I didn't see it all. I was crakin myself up. I thought maybe Bone had some powers of persuasion on you.
 

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I knew you where kidding, but I fixed it anyway
 

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I've nothing to add, Pat nailed my thoughts.

Pat can make better posts, I'm sorta Stephen Hawking at times trying to get my thoughts across.
 

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Discussion Starter #12
Yea I was looking in or around low 13's to still hopefully get a decent idle. The idle is the hardest thing for me. I mean I am dealing with some dumbass rednecks that can't even tell a z6 on a b7 block, but Forrest Gump could tell when it lopes at a idle and screams on the track that it's probably not stock. And to elaborate I am probably going to mill my b7 head and block and run the lightest pistons I can find.


Anyone know how much you can take out of a crank. My last one had 11 pounds out and 4 put back in to balance with some heavy metal. I am wondering if any of you have more imput on this. Need more imput.
 

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I see no point in taking that much off an inline 4 cylinder crank then adding some of it again.

Obviously the best place to remove rotating weight is from the flywheel and clutch. An aluminium flywheel then a small dia twin plate clutch will yield a lot more performance than a few pounds off the crank as the weight is being taken off at larger diameter.

If you wish to reduce weight from the crank, weight can be trimmed off each couterweight equally, but you will introduce some extra crank flexing unless you take an equal weight of the big end journal ends. To take weight off the big end journal area you need some skill and knowledge to retain strength. Best way is to hollow out the big end journals and thin the crank arm once well outside the journal overlap area. On an inline 4 you don't need heavy metal unless it is to correct a mistake. On high speed engines, heavy metal has been known to tear out and do considerable damage.

Eleven pounds seems a very large amount of weight to remove from a crank as small as a Honda D series
 

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^^^ X2
Compression hardly affects idle. Cam, port and manifold sizes and flywheel weight all have a much larger impact.
 
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