2003 Edge with SLP 903 Motor

i have a few rides on a sled that i made my own thicker cylinder base gaskets for to lower comppresion to help me get away from race gas.
some will say gasket paper will fail on you... i coated mine with red sealant let it set then instaled them. also consider that cometic gaskets will custom make any material any thicknes gaskets for you.
start by doing a compresion test and a solder squish test.
i figured on an 85mm boar .010 thicker gasket made 1.4cc more chamber volume.
port timing is not changed much try it out big difference in compresion over only 5 thousandths change.

I would think you could use the same base gaskets as the crankshop 910? They have a few different thickness' to choose from.

http://thecrankshopvt.com/product_info.php?cPath=21_23&products_id=404

here is my experience - its hard to tell what the thicknes of any given paper will be once its torqued down to specs.
know your squish gap and know your compresion readings before any modifications
squish specs can vary motor to motor set up to set up, generaly smaller bore motors have smaller gap.
indy specialtys recomends 65 thou on an 800 liberty motor others have segested as little as 50 thou.
i think you need not concern your self with minimum as you aim to decrease compresion.
to date i have not got my hands on a set of stock gaskets to check compresed # i can tell you 3/32 paper crushed to .035 , i hear rumors stock thicknes is .030
consider cylinder dome volume- cc and usaly pistons are domed and that dome pushes into the compresion chamber.
on my 800 i determined .010 cylinder lift would add 1.4cc volume to the total- i think i went with 5 thou more and i get around at sea level on a slp 3/6 thousand foot head on 94 octane no issues.
50.5 cc volume changed to 51.2 in my mind lol,
if you presently need 110 octane fuel what head do you have are the domes changable?

your a tuff customer.

first off clearly i have stated i mess with an 800-85 mill bore, you run an 87 mill bore?
if you remove the base gaskets they will no longer be compressed when you measure them? ya?
do the squish and compression tests to get a baseline
you might want to establish cylinder deck height with your present gaskets while the cylinders are still torqued down .
it would be nice if one try got it right, on base gasket remakes but who the hell knows the compressed height of any gasket paper from an industrial supply store.
i can remove both cylinders and the head as a unit and change the gaskets out in less than an hr. {just do it} as its easy then you will know.

Do you know how to do a solder squish test ? Pull spark plugs curve then put solder in the cyl in alignment with the piston pin, do 2 testes each side of each cylinder. Solder should be at cylinder wall on tests. I usually do a test snip off the peace repeat tests -post it
also post your compression readings each cylinder ,throttle held open plulling until numbers quit climbing post the numbers here.
It don't matter much about readings numbers just to confirm they are dropping after the new gaskets go in.
On my sled I have a cheater head from slp, it looks so stock with the stock head cover on it at first look but it is not so be aware that if you have one you can get the numbers off the domes then simply step up in to domes that work on the fuel you want to run at the elevations you play, it's about 80 bucks each for an 800
Their you got it step by step ,

Motor build

If you want it perfect the first time you need to blueprint the cylinders / head config. The engine only knows what you throw at it and you don't know what you have until you measure everything! Or, you can just keep throwing parts/pistons re-nick cylinders at it until you give up or run out of money.
It's not easy to figure this all out, but then nothing worth a s>>> usually is!!!!!!!
Take the time & do it right. That motor had some good results in the day if I remember correctly. Bore & stroke looks good.

First, have a goal what you want out of it.

oh good an expert, take it away lance i always like to learn...

he wants to have no detonation at lower elevations.
he wants it to turn over and start easyer
he wants it more user friendly and he stated its now using 110 octain
- i think less compression is a big key ?

Time to go to work

peaceofwork said:

oh good an expert, take it away lance i always like to learn...

Click to expand...

First you need CCV which is combustion chamber volume

You'll need a 50cc glass burrette preferably with stand
Dial indicator
good set of accurate calipers
piece of clear plastic 1/4" X your dome od + 1/2". Drill 1/4" to 3/8" hole in the middle and debur.

Take head off,
roll engine to TDC,
lightly seal around edge of piston with grease. Try to gently push down @ edges to get good seal. Clean up any excess grease. Check your TDC again,
Re-install head
pour gas & oil mix that you run and fill to top of spark plug hole.
Record cc volume.
Pull head,
Screw spark plug in hole,
Put plug in vice and set a level across both ways, then lightly apply a very thin bead of Vaseline around on dome to seal against plastic. Press down firmly and or add weight to hold down.
pour through hole until full. You'll have to play with a little to get it level, just watch the bubble when it comes up against the plastic. When it comes up against bottom of hole in middle STOP!
Record cc volume. This is your head "flat plate volume". This is to reference to this dome only . Deduct plug hole volume from CCV, which is usually around 1.8 to 2cc. (You can measure this with your burrette) to be certain.
Now it's just math, divide cylinder volume, (stroke times bore) by CCV and you have your compression ratio pretty precise if you measured good.

You will do a squish to piston clearance with solder when you have head off also.

Now, the biggest things that is going to dictate what you can run for compression are head combustion chamber design which includes a whole lot of variables, of course fuel, altitude and all the rest pipes, pipes etc.>>>>>>>>!!! Your combustion chamber is going to dictate where your timing will be. We can get into that later.

Biggest thing I've noticed with people buying mod motors that don't have any idea what they bought, who can't find good info on the particular build, they end up with a disaster.

This will get just get you started. If this is too much bother for you to get a nice mod motor to run perfect, don't bother any more because it's just the beginning. I can steer you the right direction when I have time.

Good luck!

But wouldn't SLP have done all the working calculations already? Don't they put a ID# on their motors for future reference?
If the original poster is lazy couldn't he assume slp' work is good?
If he's complaining of tough turning over the 110 Oct race gas motor why not just assume it's got a race gas head on it then confirm and go find a pump gas head?
How the solder going to squish with no head on the motor ?

903

Jim is a sharp guy. He should be able to get you in the running. Let me know if you need some more help. I'd like to see you get this dialed in. Should really rip!!!!!!!!!!!

One more thing,
Make sure the pipes you have are set up for your elevation also. Jim should know stinger id dimensions for your altitude hopefully. If not, you'll need to come up with a good pressure gauge to check pipe pressure. Trouble is, they're very expensive. If you have high altitude pipes they're going to be too tight for lower elevation = bad things = checkbook!!!!!!!!!!!!!!!

post back with what measures you take with this sled to get it how you want it,
is flathead lake froze over now