383 to 496

[moper]

Moper if I heard and understood you correctly you're say that even with brand new pistons, rings and all the goodies if i rebuild stock, I'll still be sitting at a low cylinder compression and low overall low compression. Now changing from flat top pistons to a different style and cam upgrade with heads would increase my overall compression correct?

The issue is the block. not rods, pistons, cranks, gaskets, etc. Factory 383 blocks are all tall. Some very tall. Factory chambers (big open and closed versions) are as-originally-assembled normally larger than the published specs. Add a valve job or two in the eons since it was first bought and the chamber sizes get even larger. To get a real "10.5:1" or even a true 9.5:1 with any factory head takes blueprinting the block and the heads to remove the extra height and the extra volume respectively. Even with domed "shelf part number" pistons. No flat top will be anywhere near 10:1. If your engine has a stock 2bbl piston, a composite head gasket, and the least and lowest budget machine work done during the rebuild, I would be shocked if it's over 8.2:1 when measured and calculated. Most guys didn't do this in years past because the milling was heavy requiring multiple passes, cost more money, Mopar decks are usually pretty flat with the 17 head bolts used, and the operation when done on the old-school equipment removes all stamped numbers from the ID pad on a B wedge. Modern machining centers can do the blueprinting and retain the numbers.

PS - all the issues will effect any stroker combo based on the B wedge block too. So if you want the correct compression ratio the block has to be blueprinted.

 

[twostick]

Or you can measure your current deck height and choose a piston with a compression height that will put it flush with the deck.

Kevin

 

[twostick]

When I built my 440 based 493, it only took .007" to square and zero deck the block.

Kevin

 

[FuryDan66]

Yeah they're flat top 2bb piston for sure. The bottom end is being done but looking for a 440 block possibly

 

[moper]

Or you can measure your current deck height and choose a piston with a compression height that will put it flush with the deck.

Kevin

First - RB blocks are slightly better - although I'd wager if you only needed the cleanup the black was not square decked. Your machinist cleaned up the gasket surfaces. So you can pretty much do what you said.
In terms of a B wedge (read that as 383 and 400 - I have never touched a 361 or 350) no, you really can't. The block is taller, so no matter what you try to look up, the only pistons that will be truly zero deck on the vast majority of these engines will be a custom piston. In most cases the block has to be addressed to put any shelf piston at true zero deck... And that will do nothing to help the larger-than-spec chamber.

 

[FuryDan66]

So I'm buying a full 440 1977 motor small-ish refreshed bottom end never bored with new rings. Has freshed heads (will find put more tomorrow about those ). Has a Edelbrock performer 440 intake. So my question is would the edelbrock performer be equivalent the air gap one?

 

[moper]

Equivalent, no. Enough of a difference to provide some value by replacing it with an RPM? No. Run it as is. Performance-wise its head-and-shoulders over the 383 already.

 

[twostick]

First - RB blocks are slightly better - although I'd wager if you only needed the cleanup the black was not square decked. Your machinist cleaned up the gasket surfaces. So you can pretty much do what you said.
In terms of a B wedge (read that as 383 and 400 - I have never touched a 361 or 350) no, you really can't. The block is taller, so no matter what you try to look up, the only pistons that will be truly zero deck on the vast majority of these engines will be a custom piston. In most cases the block has to be addressed to put any shelf piston at true zero deck... And that will do nothing to help the larger-than-spec chamber.

Mine was square decked and zeroed.

Any decent 383 piston I think is going to be custom.

Stroking it to 496 will solve the low compression lol.

Kevin

 

[FuryDan66]

Well tbis is a standard bored just been re-honed with new rings. Heads redone 516. I need a distributor and carburetor and exhaust but while I have it out of the car I was kicking around replacing a camshaft to something a little bit more fun. I will post a pic of the camshaft that is in the car right now you guys tell me what you think and I paid 1200.00