hi

I am building a stroker motor (383).
but going with a supercharger from vortech on this build.
I have a stroker kit on this engine at the moment and Probe P3831F pistons.
this is pistons used with 5.7 in rods compression hight: 1.425.
now to get compression down i plan to use pistons made for 6.0 rods Compression height: 1.260
this bring the compression down from 10.6 to 8,00 I use thick head gasket now and change to a thin gasket with the supercharger.
but this is all theoretical....
is this a way to do this?
can I use the piston made for 6 in rod on a 5.7 in rod?
are the 1.260 inch piston too fragile in the top, to use with a supercharger?

hope this can be done, cause then I have pistons and don't need to by new one.

 

Ask the piston manufacturer.

 

If stroker kit is 3.75" stroke and setup for 5.7 rods and 1.425" pistons, you can not use a 1.26" piston on that crank and 5.7" rod. Piston will be below the deck .165"!

You need a 5.85 rod to run a 1.26" piston with a 3.75" crank. But it be below deck .015 if 0 deck 9" block

6" rod 383 3.75" stroke uses a 1.125" piston height


Its simple to calculate. Half the stroke length, + the rod length + piston height = rotating height which you want to be the deck height either 9.025" or 9.0" or somewhere in between

 

yea it is down .165
but this give me static compression close to 8:1 that is my goal.
if my calculations are correct
deck height: 9.025
bore: 4.03
stroke: 3.75
rod: 5.7
camber: 64
gasket: 0.02
piston volume: -4
pin hight: 1.26

I use this calculator:
http://www.eaglerod.com/index.php?op...d=40&Itemid=25

or am I missing something?

 

Missing the idea that quench height is important and that motor may not run well.

Some say over .100" piston to head deck, motor becomes less detonation prone. Hard to say i never tried it. Between .060-.100" its very detonation prone and usually ideal is .035-.045".

Your build i would rather see new pistons for a 5.7 rod 3.75" crank with a dish that will give you ideal compression. Rather than open up the piston to deck clearance.

 

with your twin turbo build Orr89RocZ, you should know a little about this. so I guess you are right!
i hope to reuse some parts from the shelf here. but I probably have to think a different way to use my supercharger.

 

Try to search for some more info on quench height/piston to deck height for boosted applications, and see if people are getting away with large clearances.

How much boost and power you shooting for?

It could be possible to do as you wish, keeping .165 in the hole. It may work. You could try and see what happens just be careful with the tune up, slowly work up the timing and keep it fueled well

 

look like a theme with different opinions.
http://www.hotrodders.com/forum/squi...ne-135973.html

I would agree about the fact about blower mixing the air alot better than N/A engine and maybe better with a carb than a injection.
I did tryed the blower on a 350 and had serious problems to keep pressure down. 30 psi would be no problem. for the horsepower aim, I hope to see 800-900.

 

Yeah theres been alot said that in a typical sbc chamber, .060-.100 is a danger zone. Over .100" is somewhat ok. Not sure why this is.


You'll need a fairly big blower to make 800 plus. 383 tpi will need a well ported manifold base, ideally one thats been welded up and portedto 1205 min gasket and large tube runners. More rpm you can pull the better.

Tpi is relatively lower rpm. Blower will feed boost linear rate and extend power curve however you'll need a small pulley to make the type of boost to get 800 hp

Procharged 385 i tuned made 520's whp tko 500 trans i think at lower boost 8 psi ish. I think 550-575 was doable if it wasnt throwing belt off above 5800 rpm. 12-14 psi by 6000. Pretty stout 383. 800 crank would be more like 650-700 whp depending on trans
Likely need 20 psi through tpi since its so restrictive

 

the TPI is "long gone"
alu heads with 210 runners and intake matched to this.
only drag race this engine.

 

Oh my apologies i thought i read tpi somewhere in there. Thinkin of something else i believe

Then you'll be good to go. Wont need more than 14-16 psi i would guess if cam and heads make peak power up in the 6500 range.

Just comes down to do you want to believe in the .100+ quench distance can live and not detonate.

Ideally i'd shoot for 9-9.5:1 comp if intercooled well

 

Way back in the day the Buick Grand Nationals ran with their pistons sitting way down in the hole at TDC (from the factory). Part of how they got their sub-8 compression ratio. They seemed to run strong for what they were back then.

 

I wish I could easily do a power adder. My alcohol engine is around 14:1 so adding boost is very limited. Wouldn't be any fun if I spent all the money for blower, turbo etc and could only put in a few pounds of boost. It would be easier to just build a new engine.

If I was going to build a new engine, I'd start from scratch and build it to use SR20 heads. Head design means pistons designed for the heads. Conventional BBC pistons won't work unless they were flat tops. My current pistons have huge domes to boost the ratio up. BBC chamber/valve design allows for dome pistons much better than a SBC.

In your situation, it would be better to use flat top pistons set to zero deck height then adjust the chamber size to drop the ratio down providing the heads have enough metal around the chambers for heavy porting. The larger chamber will also unshroud the valves for better air flow. Small combustion chambers will increase the ratio but also restrict valve sizes.

Playing with stroke length, rod length and piston height can affect a lot of factors. My BBC is technically a stroker but it's also bored out almost to the maximum allowed for the block. I use a 4-3/8" stroke crank and use 0.250" longer rods. The pistons I use has the wrist pin up in the oil control ring when normally the wrist pin is below it in a more stock type piston. My 588 pistons are lighter than the ones I was using in the 540. Larger diameter piston but a lot less metal below the wrist pin and on the inside. I also went with thicker walled wrist pins. My Howards I-beam billet rods are lighter than the Eagle H-beam rods I was using plus they're a lot stronger. I can't remember what the total bob weight is but my engine balancer got the crank down to 0.0 grams which wasn't easy for the big internally balanced crank. The extra counterweight was in the way where he needed to drill to add heavy weight.

 

Thanks AlkyIROC good input. giving me new ideas...
I guess if I put the blower on the engine like it is at the moment. around 11:1 comp with the 64 heads. I would go alcohol, witch could be a way to go. this is a race engine anyway, so why not.
I just have to put a new fuel pump, or a dual fuel pump set up. I actually have metering blocks for the 750 blower-carb, and with a little boost I would flow "ok" with air.