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Lowering compression for turbo build crf450

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Ok guys well I'm going to Turbo charge my crf450 and I would like to lower the compression. The motor is in my shifter kart that I'm going to be drag racing once that the nhra makes rules for gokarts. The motor is a 511cc right now with stage 3 cam and a bunch of other things.i would like to bring down the compression from 12to1 to 10to1. They don't make low compression  piston so I was thinking about 1. Stacking some head gaskets together or 2. Machine 1mm to 1.5mm  dome on the piston. But this will weaken it just a bit. Boost will be about 6 to 8 psi. I also am running a microsquirt and a liquid to air intercooler and q16 co race gas. If I ran the 12to1 I might get away with 6psi but would like to run more. What are the pros and cons of running 2 or 3 head gaskets. W.e do this to cars all the time.

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You can also remove cc's from the volume of the head.  Interesting build.

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I would agree with taking a little material out of the chamber in the head to lower comp instead of the piston top. And I'm not an expert but I would think you would get a little more reliability from double base gaskets since they don't see cylinder pressure like head gaskets do. 

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I wouldn't stack gaskets because it will alter your cam timing. If you have an adjustable camshaft then you can correct it. Best bet is to remove material like suggested above

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22 hours ago, EnglertRacing said:

you will blow a stack of head gaskets.

have a piston made

Call CP, talk to TJ see if they can do a reverse dome piston

it will be $$$

I called do it's 530 for 1 piston 1350 for 4 piston. I used to stack head gaskets to lower compression before cosmetic started to make thicker head gaskets. I've made over 700rwhp on a few cars and not once have a head gasket ever blown. We ran rap head studs torque them down good and that's all. So I think that's a false statement about blowing head gaskets. I'm looking for some rap head studs and going to order an adjustablecam sprocket. I'm also not going to run the big bore for turbo but a 2002 jug and piston since that piston is the lowest compression one and I want the cylinder wall as think as I can have it. Waiting for my tig welder to come in this week I'll post pics up soon

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I'm going to keep the striker crank in it when I run turbo I'll put the stock bore in and when I want to go parking lot bashing I'll put the 100mm jug in. I have a 13.5 to 1 piston it it and according to hotrod the crank adds half a point so I'm at 14 to 1 compression. I only run q16 go race gas at all times.  Goal is to make 100rwhp. I'll start to post up pics soon of the build. I been turbocharing cars and building turbomanifolds for about 10 years now. Sold my last welder but I get my new one this week

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3 hours ago, Tito Mercado said:

I called do it's 530 for 1 piston 1350 for 4 piston. I used to stack head gaskets to lower compression before cosmetic started to make thicker head gaskets. I've made over 700rwhp on a few cars and not once have a head gasket ever blown. We ran rap head studs torque them down good and that's all. So I think that's a false statement about blowing head gaskets. I'm looking for some rap head studs and going to order an adjustablecam sprocket. I'm also not going to run the big bore for turbo but a 2002 jug and piston since that piston is the lowest compression one and I want the cylinder wall as think as I can have it. Waiting for my tig welder to come in this week I'll post pics up soon

Hmm, were those stacked head gaskets mls?

when you stacked them did you make them from 2 sets drilling the rivets and rearranging them, or did you literally just throw one atop another?

another option is a custom copper head gasket, probably can do that for 100$

another possibility is racetec pistons, they can do it much cheaper IF they have a suitable forging.

and another option is to make a base gasket spacer or use a stack of base gaskets instead of messing with a stack of head gaskets. you could quite easily scan a base gasket, import it into cad, trace it, and have it water jetted from aluminum for like 50$ run a base gasket on either side..... 

a second reason i threw out custom pistons is because i don't like to see quench thrown away, people say it doesn't matter with a turbo. But it does off boost.... which may be quite often as this is a single cylinder, and i suspect turbo sizing may end up less than ideal, and if this is not a drag bike........ then........ it wont be the best ride...

another option,

run methanol instead of q16, leave the compression where it is and :ride: .  You get to enjoy full power off boost and hold on, when the boost comes up.

what are you going to use this for?

are you going to use the FCR? blow through or suck through?

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3 hours ago, Tito Mercado said:

I called do it's 530 for 1 piston 1350 for 4 piston. I used to stack head gaskets to lower compression before cosmetic started to make thicker head gaskets. I've made over 700rwhp on a few cars and not once have a head gasket ever blown. We ran rap head studs torque them down good and that's all. So I think that's a false statement about blowing head gaskets. I'm looking for some rap head studs and going to order an adjustablecam sprocket. I'm also not going to run the big bore for turbo but a 2002 jug and piston since that piston is the lowest compression one and I want the cylinder wall as think as I can have it. Waiting for my tig welder to come in this week I'll post pics up soon

Hmm, were those stacked head gaskets mls?

when you stacked them did you make them from 2 sets drilling the rivets and rearranging them, or did you literally just throw one atop another?

another option is a custom copper head gasket, probably can do that for 100$

another possibility is racetec pistons, they can do it much cheaper IF they have a suitable forging.

and another option is to make a base gasket spacer or use a stack of base gaskets instead of messing with a stack of head gaskets. you could quite easily scan a base gasket, import it into cad, trace it, and have it water jetted from aluminum for like 50$ run a base gasket on either side..... 

a second reason i threw out custom pistons is because i don't like to see quench thrown away, people say it doesn't matter with a turbo. But it does off boost.... which may be quite often as this is a single cylinder, and i suspect turbo sizing may end up less than ideal, and if this is not a drag bike........ then........ it wont be the best ride...

another option,

run methanol instead of q16, leave the compression where it is and :ride: .  You get to enjoy full power off boost and hold on, when the boost comes up.

what are you going to use this for?

are you going to use the FCR? blow through or suck through?

 

another thing,

weld the crank.

or your going to weld it the second time you build the motor.....

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I'm going be running fuel injection and a microsquirt. It's going to be a drag gokart. I working with nhra div1 to get rules so we can race them. I would run meth but I'm going to be running a liquid to air intercooler. And q16 also lowers exhaust temps and makes more power.

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Also with meth you need to run more fuel then q16 q16 is about 20% more fuel because the fuel is oxygenated but meth you need to run about double if it was gase. Have to keep in mind about injector duty cycle.  

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I just rebuild it so I will weld around the crank main bearings for more strength  next time around boost will be set low for now

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Stroker crank has a shorter rod than stock = BOOM in a high cylinder pressure motor. Bad rod-to-stroke ratio. You need a crank with a rod that is longer than stock, not shorter. Then add a spacer plate and longer timing chain.

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APE has adjustable cam gear in stock. And Im going to go with eddie on this one. If your going to go with a stroker crank at least go with a stock length rod. I have a gen1/gen2 stock stroke crank in stock with a Carrillo rod installed. Tough to make a turbo make big gains out of a 1 lunger. Good luck. If there is anything we can do to help message me at Jeff@aperaceparts.com, or call (661)256-7309.

 

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9 hours ago, Jeff@bigborethumpers said:

APE has adjustable cam gear in stock. And Im going to go with eddie on this one. If your going to go with a stroker crank at least go with a stock length rod. I have a gen1/gen2 stock stroke crank in stock with a Carrillo rod installed. Tough to make a turbo make big gains out of a 1 lunger. Good luck. If there is anything we can do to help message me at Jeff@aperaceparts.com, or call (661)256-7309.

 

I started to buy parts for another motor I want to use stock bore for thicker walls. I also have a new hotrod crank. Going to buy another head and bottom end with trans. Going to keep the 511cc all motor and put it in my other gokart. Thx for the info man. Let's see what she can make under boost.

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