"What was the CR of your stock headed 383 engine with flat top pistons running on pump gas. I'm sure you were using a camshaft with alot of overlap to bleed off cylinder pressure to be able to run on pump gas. I mean your dynamic compression should be within the limits of pump gas use"

If you do a search on DCR I think you'll find out I know a little bit about that. This setup was faily low DCR 8.4:1 range on the last motor I had on the pump, normally 8.8:1 on more aggressive LT stuff like you are asking.

Let me say this part once for you.... OVERLAP DOES NOT BLEED OFF COMPRESSION and has nothing to do with DCR.

When I do a SR setup, it's not cheap. I don't know if you are going to drive this alot, but I don't think adjusting valves is a whole lotta fun.

Basically your 450rwhp is not easy and needs to be done right or you have no shot at it. The heads, cam, compression everything needs to be perfect.

Bret

 

I should have said valve events, then.

 

One valve event IVC is the only one that matters for cylinder pressure, and that's normally connected to DCR.

Bret

 

you will have a very hard time getting the results you want with a -16cc piston. Anyway you look at it your gonna kill your compression.

You can run anything you want, but at Bret said you need to have alot of things right on target to get 450rwhp. You cant just slap a custom cam and tiny heads just to make up for the wrong choice of piston and expect 450rwhp... not gonna happen

You would be better off making some changes.

I'm building a 355 now and hoping to hit that 450rwhp mark. I'm also running 13cc domed pistons and a 63cc chamber on a 220cc TFS head. DCR is up at almost 9.0.... with a custom SR from cammotion, and I am only hoping to hit that 450rwhp mark.

 

Good luck in your project and thanks for the heads up. Who did your 63cc chamber on 220cc TFS heads.

So, you are saying I should change to flat top pistons in place of those -16cc pistons then build it from there with Heads/Cam.

I want to confirm that since I read someone is running stock LT1 heads milled to 48cc for more compression. Anybody confirm that for me.

How about if I keep my -16cc pistons unchanged and go with a max effort LT1 Head/Cam package, what should be my reasonable target.

I would prefer to swap head/cam only over changing pistons since the engine has low miles since the stroker build and is still doing good. I will change pistons only if I decide to go for fully ported aftermarket heads like AFR or Trickflow.

 

Yes, Flat tops are the way to do this. You are going to beat the hell out of that head trying to get it too 48cc.

Bret

 

my heads were done by TEA, but there are several people on this board who can put a set together for you including Lloyd.

It sounds to me like your whole problem here is your piston. You can do a max effort head and cam but with a -16c dish you will never get the compression up. Heck even with a 48cc chamber your compression will be low.

If you want it to run right you will have to change pistons. The -16cc piston is the killer of this whole situation. Rund a flat top with a stock size chamber, or run a dome with a large chamber aftermarket head.

You can have all the head and cam in the world but if your compression is at 9.0 static you wont make 450rwhp...

 

I still think flat top pistons will not run on pump gas with 54cc LT1 heads. I searched for the flat top pistons for 3.75 stroke, 6.0 rods and here is the CR with each head cc:

Cubic Inch:385
Bore Size:4.040
Stroke: 3.750
Rod Length: 6.0
Comp H/t: 1.125
58cc: 11.9
64cc:11.1
70cc: 10.4
Dome Volume: -5cc

So, with 54cc heads, it will be more than 12:1 CR which is very high for pump gas. Tell me that cam selection will dectate.

I have a friend who ran flat top pistons with stock LT1 heads and cc306 camshaft in his 383 engine and it was knocking all day with pump gas. Had to switch to 64cc Trick Flow heads to run on pump gas cause it was his daily driver car.

 

Well as I stated above, compression of my 385 engine with -16cc pistons should be around 10.8:1 not 9.0. Are you refering to 355 engine when you mentioned 9.0 CR.

Here, I am refering to these pistons, it is this stroker kit that I have, 10.4 CR w/58cc. My heads are 54cc.

http://www.cnc-motorsports.com/produ...ID=9090&CtgID=