Just be sure the top ring is steel of some sort. If its a stock bore, ford navigators came stainless top ring. Just a thought.
Ultimate Budget 2v Motor
- Thread starter 98snakehorse
- Start date
Nighttrain
Well-Known Member
Second this
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98snakehorse
Well-Known Member
Alright I've been doing further research into building my spare NPI block. Whats your thoughts on me doing a .030 over bore. Using my factory PI heads and cams (maybe upgrade the two at a later time). 13 coyote rods. Now for compression ratios.... I have no idea what type of piston to use? Im thinkning of keeping it around 9.0:1.
Do they make a master engine bolt set? I cant seem to find the bolts for the side of the main caps? Im assuming those will need to be replaced.
Do they make a master engine bolt set? I cant seem to find the bolts for the side of the main caps? Im assuming those will need to be replaced.
Why not keep it at pi swap compression? Somewhere in the 10:1 range. Boss rods are a good idea. Im not sure about the full bolt set, I got mine individually wherever I could get it the cheapest.
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98snakehorse
Well-Known Member
10:1 range would be good too. I just dont know how that works to come out to certain compression ratios. Like would I just by a factory headgasket do pistons effect the ratio in any way? I really am a newb to this? Also did you replace your side main cap bolts? I cant find those for the life of me....
Basically piston dish, squish distance (distance from top of piston to head surface while the piston is at tdc), and head chamber cc all make up the compression ratio. The less all those numbers are, the higher the compression. Youll use stock thickness gaskets. Im going to copy a link to our 2v section, the thread is awesome and explains a lot of what you would want to know. There are compression calculators on line that will tell you what selection of parts will get you certain compression ratios. I will try to get some info together for you. Also, I did not replace the side bolts. I was pretty sure ARP has a set though.
http://www.sn95forums.com/showthread.php?66316-Squish!
On a compression calculator;
bore: 3.582
stroke: 3.543
Head gasket thickness: .036"
Compression height: .00
piston volume: 17cc
combustion chamber: 42cc
Static compression 10:1
That means if you order a .030" piston with 1.23" compression height and 17cc dish, with a stock head gasket and combustion chamber, you will be at 10:1 compression
bore: 3.582
stroke: 3.543
Head gasket thickness: .036"
Compression height: .00
piston volume: 17cc
combustion chamber: 42cc
Static compression 10:1
That means if you order a .030" piston with 1.23" compression height and 17cc dish, with a stock head gasket and combustion chamber, you will be at 10:1 compression
On a compression calculator;
bore: 3.572
stroke: 3.543
Head gasket thickness: .036"
Compression height: .00
piston volume: 16cc
combustion chamber: 42cc
Static compression 10.1:1
Now if you order a .020" piston with 1.23" compression height and 16cc dish, with a stock head gasket and combustion chamber, you will be at 10.1:1 compression
bore: 3.572
stroke: 3.543
Head gasket thickness: .036"
Compression height: .00
piston volume: 16cc
combustion chamber: 42cc
Static compression 10.1:1
Now if you order a .020" piston with 1.23" compression height and 16cc dish, with a stock head gasket and combustion chamber, you will be at 10.1:1 compression
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98snakehorse
Well-Known Member
You are the man thanks for doing that. Did you bore your cylinder walls over at all or did you find an aftermarket piston for the stock bore?
Mine is .020" over bore. I got my pistons at a really good price so I got my block done to accommodate them. You can order pistons in any variation. If you are wanting to order a custom forged piston, you could call diamond and give them the specs and they will build them for you. Be prepared to pay for it though.
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98snakehorse
Well-Known Member
Thanks reason I ask is there is a guy on another forum who has a set of manley 18cc platinum series pistons that are .030 over. Now after we talked a bit I think the 18cc will drop my compression ratio a bit too much. They are listed for a good price though.
Those are probably 18cc with a 1.2" compression height. That would put around 9.6:1. So you would be pretty much stock, just with a forged piston. I think you should bring the compression up a little bit, honestly.
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98snakehorse
Well-Known Member
I agree, I think i'm going to go ahead and start ordering my bolts / bearings and gaskets. I will probably wait to bore the cylinders until after I make a piston selection. Probably a stupid question but I assume if I bore the cylinder .020 or .030 over I will need a specialty head gaskets to match the new bore diameter?
No sir, the head gasket is already larger than the bore size. I think the gasket is like 3.7" on the bore but I could be wrong. I know it fits though.
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98snakehorse
Well-Known Member
Awesome thanks. Well I added up as many of the parts I think I need to get this accomplished down to the assembly lube I think this budget build is going to run me around $1600 not including the engine machine work. I cant complain about that.
Am I aloud to say look in the classified section?
Thomas_W
Well-Known Member
your piston should be based on the engine block bore requirements, not the other way around.
4.6's have a pretty thin cylinder wal and overboring just thins them out where they can deflect more at high Hp and Rpm's, less over bore is better. If your block doesnt Need to be overbored and can be honed to use a factory bore piston, that is what i would do.
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98snakehorse
Well-Known Member
Normally I would agree with this but I am trying to keep it budget so If I can find a good deal on pistons that are 20 or 30 over I will probably go that route. If I had the funds to buy everything brand new I would for sure opt to keep the standard bore as the spare block I will be using has very good conditioned bores.
Thomas_W
Well-Known Member
If you can keep a stock bore, you can use terminator Pistons, ive seen those go for under $300
not go mention, depending on what your machine work bill costs and the deal on the pistons, you could potentially come out at the same price with new pistons, assuming you only need to hone/cross hatch the cylinder walls.
