[377MONTE]

Hello, I am new to the site, so.. Its nice to meet you guys and I look forward to hearing from you all.

I am in the process of building a 377 stroker motor for my 85 Monte SS. (350 block, stock bore, 3.75 stroke) Ive been looking at a few of the different rotating assemblies available, and now I have some questions about piston and ring selection.

My first concern has to do with compression ratio. (It will be a street/ occasional strip car) My block is decked to 9.010, and I will be using a set of Dart Iron Eagle heads with 64cc combustion chambers. With this combo, wouldn't a flat top piston put me out of pump gas range? Is there any reason why running a dished piston would be a bad idea? What is the max compression ratio I could run safely?

Second, I have heard good things about the reliability and temp resistance of moly faced rings, but I also just read that the cylinders need to have a special finish to seal properly with moly rings. I just got the block from the machine shop, and dont really plan on sending it back. Is it a bad idea to run iron rings in a mild performance engine? (I am hoping for 450+ hp and tq)

Thanks for the help.

PS I know dynamic compression ratio is what really determines pump gas driveability, but I don't have a specific cam picked out yet.

[vinniekq2]

what end results are you looking for? how much power,or whats the performance you want for that car

[hcompton]

So the machine shop looked at the block and said the stock bore was fine?

64cc heads is what you need to make the power you want but will be out of pump has range for small cam. But you will be going with a large cam anyway to hit 450+

Alum. heads would be the best way to go. 64 cc with flat tops and normal to thick gasket to get it safe on pump gas. But you need to measure it up to be sure. Just go with a large enough cam to keep the dcr low enough for pump gas.

[377MONTE]

Vinnie, I would really like to push 450+ horsepower and torque. Reasonable goal. But I want to be sure it is streetable. Am I basically forced to run dish pistons since I cant run a large enough cam to keep my dcr in pump gas range, BC I do plan to drive it on the street?

[377MONTE]

Hcompton,

would a cam large enough to keep my dcr in pump gas range w flat top pistons even be streetable? Im looking at somewhere around 11:1 with flat tops and a comfortable quench. If it were your build, would you choose flat tops and a large cam, or just go with the dish style piston?

[techinspector1]

Using a Keith Black #102 standard bore piston with 18cc dish, the static compression ratio would be 9.5:1. Using a cam with the intake closing point at ~35 degrees ABDC would yield a DCR of 8.4:1. Look, for instance, at the 119671 on this page.
http://www.cranecams.com/68-71.pdf
Second set of numbers from the right tell the cam timing @0.050". Notice that this cam opens the intake at 1 degree BTDC and closes the intake at 35 degrees ABDC. I'm not saying to use this cam. I'm just trying to show everyone on this board how to arrive at a cam that will work with a given static compression ratio. You can always PM me if you like the way I do things but don't want to ask on a forum.

[cobalt327]

Originally Posted by 377MONTE

Hcompton,

would a cam large enough to keep my dcr in pump gas range w flat top pistons even be streetable? Im looking at somewhere around 11:1 with flat tops and a comfortable quench. If it were your build, would you choose flat tops and a large cam, or just go with the dish style piston?

"Streetable" covers a lot of ground I'm sure you know. But to use that much compression (64cc heads and FT w/good quench) will mean a lot of cam and that means a lot of stall rpm and rear gear. It might be drivable on the street but I wouldn't call it streetable, at least not on a daily basis. Maybe when I was 18....

Much better to build it w/12-18 cc dished pistons, IMHO. I'd suggest a reverse dome or D-cup piston to maximize the quench effect.

[1Gary]

These are I-Con's which are a pretty good deal given the offset pins to help cold piston slap and are .030 5.7 rod stroker pistons.Reverse dome 18cc's with a .010 down deck and a 67cc head ends up to be 9.3ish SCR.







I'm kind of confused why when your replacing the pistons anyway you didn't take the option of boring it .030??.I don't think you would find .030 pistons costing more.You do know that bore sizing should be fitted to the pistons you going to use.So the bore/hone should not be done until the machine shop has the pistons in hand.I would seriously question the machine shop that measured your bores on a block that old why they didn't find some of the bores oval.Not a bad thing in SBC's,just pretty common wear factor.How round on center the bores are with a very good hone is very important.

[377MONTE]

Gary,

I purchased the block directly from the machine shop. I didnt tell them how to prep it, it was already done. I kind of like the idea of doing something a little different, and everybody builds a 383, so i like the sound of a 377 stroker a little better LOL. They did give me a sheet w all the things that were done to the block. Clean, degrease, magnaflux, hone, and decked. I guess i may end up having to go with a 383 after all though, I didnt really know the bores needed to be matched to the piston in hand. Good thing I havent ordered the rotating assy yet.

[vinniekq2]

there is also a 377 that has the larger bore and shorter stroke.
measure the block and look around to see if you can find pistons to fit,or better yet,get the machine shop to find the pistons to fit there machine work? If the cannot,then they can bore the block for free or take back their block. different pistons require different piston to block clearances

[377MONTE]

cobalt,

why am i under the impression that dish pistons are second best? maybe I am mistaken, but i figure lower compression by a whole ratio, maybe even more, would equal less power? Are my 450+ hp/tq goals still realistic with dish pistons?

[377MONTE]

ahh, thanks vinnie. makes sense now. bores need to be finished to the pistons clearance requirements.

[1Gary]

Not sure I would want to deck a block either if I didn't have the pistons in hand.Do you know if it was decked to 0??.

[377MONTE]

gary,
it was decked to 9.010.

[hcompton]

so here is where i am at. i got more question than answers. I run the numbers i get 10.3:1. with 6cc flat top 4 valve relief, .043 gasket with gasket bore of 4.063, 4 inch bore and 3.75 stroke. Even with a smaller XE262H it will be around 8.8:1 dcr. with a magnum 270H its 8.5:1 dcr. I would recommend alum. heads.

That being said what type of pistons do you have and how far down in the block are they. You say your deck hieght is 9.010 but has it been cut that or is that measured at the pistons highest point.

so what type of pistons aka what cc are they

and how far down are they installed in the cylinder

Is this a new block? Your build sheet says 4.00" bore? Has the stock bore been meausred to make sure its correct? Seems to me its going to need to be bored out to atleast the first std. over bore of 4.030 if not already at 4.060.

If you havent purchased the rotating assembly yet you can just buy pistons that are .015 or more in the hole and lower compression that way. Or use a thicker gasket.

Best thing to do is measure everything and check the cr and dcr with this link.
United Engine & Machine Co. Incorporated