8445 Heads- Combustion Chamber Volume??

[Maxxod73]

Hi everyone.....Does anyone know what the combustion chamber volume is on the 8445 cyl heads? Im trying to decide what pistons to use and this info would be very helpful. Im currently looking at KB performance pistons PN# KB220 which should give me 9.4 compression with 48CC combust chambers. Im also thinking about just getting the Buick 350 10:1 pistons and having them machined, as suggested to me before.
Thanks again for any help

 

[Chuck Leeper]

350 pistons?

I would not cut the tops on a piston for your engine. The reason being that the top is machined to a particular thickness to handle a N/A compression ratio. Cutting the top off severely weakens the piston and, while it lowers compression, it moves the top ring too close to the top, exposing it to too much heat. It also makes the top ring land too thin for a hi PSI TURBO application.
Compression ratio when under boost can come close to 20:1. A thin topped piston will soon cave in at those pressures. Furthermore, a ring land tht's too close to the combustion chamber will distort and pinch the rings, causing massive blow by, even if it doesn't break.

Do some research and I think you will find most turbo, blower, nitrous pistons have the top ring at least .100 below the top of the piston.

The cast iron heads are about the 47-49 CC area.

Is the KB a hyper piston or forged?? If it's hyper and you are planning to "lean on" the motor, I'd go ahead and spend the bucks for a forged set. Hypers have to be run too tie in the bore and will get too tite w/ the heat from alot of boost.

My $.02 worth.

 

[unboostedV6]

I believe he wants to run N/A....I think Freddie is using KB10:1's...48cc nominal GB

 

[REDS HOT AIR]

K.B.'s are like glas they break very easy ...if you want hypo pistons better check with speed pro and get theirs which are called sterling

they have
# h521np for turbo motors with 7.5-7.7 comp. depending on over bore

# h522p for non turbo motors which are 9.5-9.8 to 1 comp depending on over bore.

these are both for 3.8 motors

and yes i have used K.B pistons before they are very fragile

 

[Maxxod73]

Thanks for the help guys.....I'm gonna get the Speed Pro # h522p instead. I did not Know the KB's were so weak! Do you think I might have any detonation issues with these pistons? I normally run premium gas....I know 9:8 isnt very high....but I figured better to ask now then find out later.

 

[REDS HOT AIR]

what cam you put in it will have alot to do with cylinder pressure so bigger cam the more compression you can get away with but i dont think you will have problems with that as long as you got a desent cam and dont go nuts with the timing.

 

[b4black]

I believe that an '86 NA motor will have a knock sensor. If you are running the ECM, it will retard the timing when it detonates. Even is you git rid of the ECM, you can leave the sensor and controller in place and still use a knock gauge to see what's happening (although the timing retard will be gone).

 

[b4black]

#H522P.030

http://cgi.ebay.com/ebaymotors/ws/ebayISAPI.dll?ViewItem&item=1828968232&r=0&t=0

 

[Freddie's Buick]

Someone is nutz! KB's Hypers are Speed-Pros! Hypers are not glass! This only happens on turbos and is due to detonation issues.

Guys he owns an N/A engine! Forged by Sterling are super expensive.....and I guess if one only wants a race car then go forged. Let's put an end to this fear and confusion about Hyper pistons once and for all.

 

[unboostedV6]

I used to run 34 deg total timing at 10.4:1 on pump gas...car ran 13.60's at the time...drove it 80 miles to and from the track GB

 

[Turbo-Rich]

Originally posted by unboostedV6
I used to run 34 deg total timing at 10.4:1 on pump gas...car ran 13.60's at the time...drove it 80 miles to and from the track GB

SWEET!