technical debate

Mr. Rustypwnz

Mr. Rustypwnz

Advanced Member
Jun 1, 2005
1,761
63
69
indianapolis/ valdosta ga
#1
ok i have recently killed my stock 2v motor, because a valve spring broke and wiped out the piston. Now im debating on doing this..

mark shortblock
pi heads with work
custom cams (have already)
eddy intake
all other associated crap..

ok i know that this will put me at 12.1 with a .030 hg. so pretty much what im asking is will this thing run well (street friendly) and how long will the bottom end last, or at what rate from a stocker will it depreciate? it is getting re-ringed and all that good stuff.. heads will be ported by me, but i have heard that taking the dam out of the combustion chamber will only make it detonate more easily, which would lower the comp ratio to around 11.1

im not going for a world record, just something mildly fast, so imput is key..
 

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#4
Depends on the cams really, you need a good bit of overlap to bleed off some of the cylinder pressure. I would want to see a minimum of 15 and prefer 20 degrees of overlap at 050 lift to run this combo on pump gas. I have done a few of them now and this range is ideal for the stock plastic intake on a street car.

Don't touch the swirl dam unless you know what you are doing, and by all means do not gasket match the heads unless you want to go slower.
 
#6
read the first post.. im going with a teksid to drop weight, AND im forging this motor..

nick: the guy was using these cams with 13:1 comp so i should be fine on that aspect.. heads will be ported not hogged..

keith: stock springs are good to bout .540-.550 newb... it aint gonna have stock springs either..
 
#10
Mr. Rustypwnz said:
well come to find out the cams are around an 11-12 overlap not like i thought, might have to drop the cr a little..
Click to expand...


You can squeeze the quench height (means you need to deck the block and/or higher comp ht pistons) to get the piston at least zero decked and preferably sticking out 10 thousandths (what we do on the race motors) This will help with detonation on pump gas.

It sounds like you have either a smallish cam or a wide centerline medium sized cam to be honest. Probably not the best for high comp NA with the Eddy intake but if you already have them I can understand using them. Cams I do for the Eddy intake NA usually have 20 minimum and go up as high as 50 degrees overlap at 050 to give an idea.
 
#11
ok, decking would up the compression further right? could it be possible to take some material out of the chamber to resolve this? or maybe run like some meth injection to suppress (which I don't want to do) I could run e85 but, I make a lot of long distance trips so finding it would be a pain in the ass.
 
#12
Decking will raise the compression, but the amount it raises it does not affect the detonation as the tighter the quench the higher the compression you can run on pump gas.

There is nothing you can do to the chamber to make it bigger that helps really. You can remove the swirl dam for ~2cc but then its a slow swirl chamber and that doesn't work good NA unless you are over 6000 RPM.
 
#14
Mr. Rustypwnz said:
ok the cam spec is what I pm'd you about the other day I mean if these won't really be the best I would rather sell em and put it towards a better cam.
Click to expand...


I calculated 19 degrees of overlap on the specs in that PM?

You would make more power with a tighter LSA cam especially with the Eddy intake, but if cost is an issue I would just run those. IMHO they would be a good nitrous cam with 4 degrees of advance.
 
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