[chevydragster83]

I have a GM 350 crate engine its stock other than a edelbrock air gap intake and a edelbrock 750 carb part number 1407. headers and a 350 turbo trans with 410 rearend gears. I want to get new heads, and cam kit from compcams but I dont want to change the pistons or crank. I am going to get the pro-filer 195cc racing heads with 64cc combustion chambers. Not sure on the cam yet. I want to make atleast 400 hp this engine is only going to be used on the weekends and on the drag strip. Do you think I can reach my goal with out changing the stock crank, pistons, and rods? And will I brake them?

[automotive breath]

The pistons, are they dished or flat top?

[my87Z]

Originally Posted by automotive breath

The pistons, are they dished or flat top?

X2 we need to know more about the motor, what crate motor is it, where did you get it from, what are the specs on it

[chevydragster83]

the part number on this engine is 100067353. Its the 260hp-350 ft of tq crate. I got it from a GM dealer. the compression is rated at 8.5:1 but I've heard they dont really have that much. I think the pistons are dish. the heads are cast iron with 194in intake valves and 1.50 exhaust, 76cc combustion chambers. with a 383intake lift and 401 exaust lift hd flat tappet cam. I am going to get the pro-filer 195cc 202.0in 165.0ex 64cc combustion chamber racing heads, and a cam kit from compcams.

[matt167]

there rated 260 HP with headders and it's pretty accurate.. the cam is tiny and that's partly due to the low compression.. they are 8.5:1..

heads to bump the compression will help, but without changing the pistions ( I think there 10cc dish ) it might be a stretch to 400 HP

[chevydragster83]

would the 195cc heads and a better cam be ok to use untill I could replace the pistons?

[ap72]

put a blower on it. One of the new smaller blowers would be a perfect fit. Its 3G's though....

[automotive breath]

The important thing to focus on when doing something like this is
combination. Everything has to work together to meet your goals.
First off the compression ratio must match the camshaft. Assuming you will
be running pump fuel I calculated a reasonable compression ratio that
will work well with a decent size cam. Because I don't know the actual
numbers for your engine, I guessed for some of the numbers, this needs
to be accurate so recalculate with actual measurements.

Cylinder Head Volume (cc) 60
Piston Head Volume (cc) 10
Gasket Thickness (in.) 0.018
Gasket Bore (in.) 4.100
Cylinder Bore Diameter (in.) 4.0
Deck Clearance (in.) 0.025
Stroke (in.) 3.48
STATIC COMPRESSION RATIO 10.07:1

Because of the dished piston you will need a combustion chamber volume
of ~ 60cc, if you decide to bolt on a set of heads with a 64 cc chamber the
compression ratio drops to about 9.6:1, use a 0.040" gasket and it drops
again to 9.1:1 (along with losing you squish distance). It's these little
details that will make the difference wether or not you meet our goals.

Another thing to think about is the 195cc intake volume on the heads you
want to buy. I would not go this large for what you want to do, personally
I would chose something with about a 180cc intake port.

Are you with me so far?

[oldbogie]

Originally Posted by chevydragster83

I have a GM 350 crate engine its stock other than a edelbrock air gap intake and a edelbrock 750 carb part number 1407. headers and a 350 turbo trans with 410 rearend gears. I want to get new heads, and cam kit from compcams but I dont want to change the pistons or crank. I am going to get the pro-filer 195cc racing heads with 64cc combustion chambers. Not sure on the cam yet. I want to make atleast 400 hp this engine is only going to be used on the weekends and on the drag strip. Do you think I can reach my goal with out changing the stock crank, pistons, and rods? And will I brake them?

No brainer, stick a Comp XE268 in there put a 750 Holley on it, due a tune up and stand back.

For niceties replacing the pistons would make the engine a lot more tolerant of the compression on 92 octane and would pump up the bottom end power without so much ignition advance. This improves power output and fuel mileage, and makes the engine more resistant to detonation. What you'd want is something like Keith Black hyper-eutectic with a D shape instead of circular dish. This puts all the volume to trim the compression ratio under the valve pocket. The close closing of the opposite side of the chamber makes the piston act like a flat top for squish and quench. This stirs the mixture really good and shoves it toward the spark plug (squish) getting this dimension to .040 inch to may be .060 inch is big time effective. With circular dish the compression distance over much of the piston crown is .1 or more which looses much of the effect of squish and quench forcing you to up the octane, richen the mixture, back off the ignition lead, and cool the operating temperature all of which are things that cost power and reduce efficiency. The next thing the tight squish/quench does is really important for part throttle operation but nobody gives it a name, that is with most of the mixture shoved in front of the sparkplug, the density standing in front of the plug is increased; this makes it easier to light off and it burns faster. This reduces miss and late fires and increases cylinder pressure faster without the need for excessive spark advance i.e, anything over 32 degrees total. The last function which is named quench is provided by the high area to volume ratio on the far side of the chamber. This heat sink function reduces the tendency of the unburnt mixture on the far side of the chamber to blow-up before the flame front gets there, this is detonation. Since the detonation limit is now higher, the engine can be pushed to higher RPMs under higher loading before ping is encountered.

All of that stuff is a good thing and really optimizes power output. To make the change to a better piston design at this point is just going to cost you a an overhaul gasket set, the pistons and rings, and installation onto the rods for a much improved engine. This change will push the motor well toward 450-470 horsepower around 6200-6400 RPM.

Bogie

[my87Z]

i agree with one of the statements before about using a 195cc head, i would stick closer to a set with 170-180cc. i recomend the RHS pro tokers or the pro action heads. or just a set of vortec heads that have been bowl blended, and had the usual rebuild with guide work, then you would benifit from shaving them about .030" to get something closer to 60cc out of the combustion chamber, so you could raise the compression

[chevydragster83]

ok well I am a 19 year old college student, so I'm on a budet. I only have about $1,400 to spend on it right now. I want to get a good set of heads and then work up from that. I want heads that will make decent power with the set up I have now plus a good cam kit. but that will be capable of makeing better power as I can upgrade.

[ap72]

Originally Posted by chevydragster83

ok well I am a 19 year old college student, so I'm on a budet. I only have about $1,400 to spend on it right now. I want to get a good set of heads and then work up from that. I want heads that will make decent power with the set up I have now plus a good cam kit. but that will be capable of makeing better power as I can upgrade.

RHS 200cc runner with a 50cc chamber

http://www.competitionproducts.com/R...info/RHS12333/

That with a good flat tappet mechanical cam will put you at the edge of what that short block can handle- maybe a little beyond that.

[automotive breath]

You could run a 200CC runner, thats larger than what you need, and 50cc
chambers would work also, if you are willing to buy high octane fuel.

Cylinder Head Volume (cc) 50
Piston Head Volume (cc) 10
Gasket Thickness (in.) 0.018
Gasket Bore (in.) 4.100
Cylinder Bore Diameter (in.) 4.0
Deck Clearance (in.) 0.025
Stroke (in.) 3.48
STATIC COMPRESSION RATIO 11.4:1


I use something like this, you will need to mill them down to ~60cc to get
the compression you will need.

http://www.competitionproducts.com/E...uctinfo/60899/

[oldbogie]

Originally Posted by chevydragster83

ok well I am a 19 year old college student, so I'm on a budet. I only have about $1,400 to spend on it right now. I want to get a good set of heads and then work up from that. I want heads that will make decent power with the set up I have now plus a good cam kit. but that will be capable of making better power as I can upgrade.

Then I'd go back and just use the cam I suggested. You don't need a big huge port to get 400 hp out of a 350. In fact that hurts bottom end with a big cam as the mixture velocity in the ports slow as the volume gets bigger. With a long duration late intake closing cam the slow mixture speed allows the rising piston to reverse pump mixture backwards thru the carb, this is called reversion. This would force you when on the street to run the trans in lower gears to keep the revs up to where reversion and its attentive loss of bottom end power is prevented by high RPM operation even when driving slowly.

I also would suggest more compression with the stock pistons. These have a dished crown the bottom of which is a long way from the squish/quench deck. This encourages detonation and that will limit compression ratio before anything else. With a cast iron head and OEM pistons 9 to maybe 9.5 is the limit GM uses several different pistons, it isn't uncommon to find 20 ccs in the crown which is a deep dish that just wipes out the squish/quench function. On unleaded fuels where the best you can do is 92-93 octane, without carefully managing flame propagation it is real easy to get into detonation. Detonation sets the engine's power limit. No-mater what else you've bolted on, when you hit that limit you cannot stay at that power setting with out regard to any super sized ports or gigantic camshaft timing. You're there, going any further will be costing really expensive pieces.

Bogie

[ap72]

I don't believe the dish is 10cc's, but I could be wrong. Nonetheless it will put him at the edge of pumpgas, that is for sure. 60cc heads aren't a bad option and would be easier to deal with on the street.

I think the dish volume is between 12 and 15cc's, I'm not sure of which, either way it should be measured.