how much should i shave??

JWMotorsports · Post by **JWMotorsports** » February 12th, 2005, 1:11 pm

That is a very good suggestion...ARP head bolts are cheap insurance at $110 w/ a 200,000 psi tensil strength per bolt! You could reuse your stock bolts, but you'ld be taking a definate risk. You'ld have to over torque them a couple pounds w/ some Red Thread Locker (high strength) to accomodate for the stretch. Like previously stated...it is HIGHLY advised to use new head bolts to avoid future problems.

Joey's mx · Post by **Joey's mx** » February 12th, 2005, 1:21 pm

thanks for the good advice guys.....so .030-.040 would be a good amount to take off to see some gains??

Tunes67 · Post by **Tunes67** » February 12th, 2005, 1:51 pm

Honestly.. I dont know if I would shave the head at all.. stock the DOHC 1.6L is running a 9.4:1 compression ratio already.. which is pretty decent to begin with. Plus if you do shave the head and run into a overheating issue where you warp the head slightly, you wont have that extra bit of tolerance to true the head up if you have to rebuild it. IMO... I would leave the head the way it is.. get a couple of good high lift (or even longer duration) cams and if neccessary different pistons to accomodate the additional valve travel. I think you would see more gains from improving the efficiency of the valve train than you would from increasing the compression ratio. Like porting and polishing the head & intake, and the header mod you have underway..Just my two cents.

Tunes67

Tunes67 · Post by **Tunes67** » February 12th, 2005, 1:55 pm

One additional thought.. if you ever plan to run NOS.. with a high compression ratio.. you will blow that engine apart very quickly.. Heh.. guess this makes it my 4 cents now eh?

Tunes67

Joey's mx · Post by **Joey's mx** » February 12th, 2005, 2:35 pm

never running NOS...

JWMotorsports · Post by **JWMotorsports** » February 13th, 2005, 11:59 am

You'ld have to run a INSANE amount of nitrous to blow it up. As long as you give it enough fuel and timing retard it will run fine w/ a 150 shot and 11.5:1 compression when using forged internals. Nitrous has soooo many bad raps...they are myths! Nitrous itself isn't even flamable, it's an inert gas (actually an oxidizer). The nitrous is injected and be comes a gas, it boils off as gas at around -126*F, it gives off tons of Oxygen molecules. The Oxygen it gives of is where you get your HP & Torque gains. It's just adding more air, same purpose of a turbo or SC only Nitrous does it instantly with no lag, unless you add a progressive controller. People blow up their motors because they don't through enough fuel to the fire to control combustion temps (the lean out) and or don't retard the timing enough and it detonates (actually sparks before the piston even reaches TDC because of the increase in cylinder pressure). Adding cams would give you larger power gains than shaving the head. You can shave the head .06 and still have room to shave more befor hitting the combution chamber's dome. That's how much was taken off my race head and I'll be running around 9:1 compression w/ 30psi and 150 shot on top of it, as long as the valves clear. They should clear but it they don't I'll have to use thicker head gasket.

JWMotorsports · Post by **JWMotorsports** » February 13th, 2005, 12:33 pm

PS

Shaveing the head will only net a fraction of a compression point. We are estimating mine will go from the 8.7:1 (Wiesco .20 over pistons) to 9:1 just by shaving the head, we shaved a lot. If you don't have to remove the head, then don't unless you have a lot of pocket change you want to spend on it. As forementioned, your better off getting a good set of cams. However if you have it off then shave it .020"-.030" and use a stock size Cometic Head Gasket, unless your building a purpose built race car then go .040" w/ a stock size Cometic High Pressure Head Gasket. You still need to check the valve to piston clearance first because you never know if the previous owner rebuilt it before hand or not! Don't forget to replace your stock head studs w/ ARP's. Your looking at around $280 if you take the head off and put it back together. And while you have it off you should go ahead and have a 3 angle valve job done which tacks on around another $135. When I did my brothers Talon TSi's head I didn't charge him any labor for my 28 hours of port and polishing. We put 1mm over sized and back cut Ferrea Super Flow Competition Valves in, my port n polish (free bee), with a 3 angle valve job. He has $575 in the head another $110 for the Cometic High Pressure Head Gasket, and another $110 in the ARP Head Studs. Thats $795 with me taking the head off and puting it back on for free. Any where else it would have cost him $1500 for the head instead of the $575. I'm telling you this because if your taking the head off and your wanting big power gains you need to do as much as possible now while it's off. It's a lot cheaper to do it now than later and if you have the tools to port n poslish you'll save a TON. If your interested in porting and poslishing your self you'll need at least a dremel with sanding flap wheels (60, 120 grit) and finishing abrasive buffs at a minimum. I use air tools w/ carbide burs to rough the port work, then with sanding drums to smooth out every little detail (don't hit the valve seats with anything), then poslish using the dremel w/ finishing abrasive buffs. There is an art to it and if you don't know what to look for you need to have someone else do it. You don't want to just make the port larger as it will kill your port velocities. You want to shap the port like a velocity stack and knock of and sharp or high spots. You want to avoid making anything sharp ( it shears the air, not good), you want to round things off.

Joey's mx · Post by **Joey's mx** » February 13th, 2005, 1:01 pm

thanks again for the advice..i am also getting the 3 angle valve job and pot and polish!!