Most painless way to get more compression?

[bb71challenger]

I have a 400 out of a 72 station wagon. About 10k miles before I bought it the engine was rebuilt by a friend of mine. He got the guy to pop for forged pistons but they were low compression like the originals. How likely is it that I can buy a set of pistons and pop in there to get me by until I can afford to build my stroker? I know its all speculation without pulling the heads and showing pics but when I did put a set of slightly worked 906 heads on it there was not a lip in any of the cylinders. I did not measure it so I dont know what size bore its at but my guess would be 30 or 40 over. Naturally I would change things like bearings and rod bolts but in you guys opinion can I do something like that on the cheap and have it last 10-20k miles? Oh the engine has a K-56 engle cam in 3 hole, Crane gold race rockers in 1.6 ratio, smith bros. pushrods and a nice 2 row billet timing chain set. Thanks for any optimistic replies and I will even take the pessimistic ones lol.

[73Chally]

If it was me I would not touch it until I was ready to build the stroker.  I'm no expert but wouldn't you have to basically tear the motor apart to put in the new pistons no matter what?  It's just a few hundred more to buy the whole stroker kit.  As far as trying to build compression, you could mill the heads or use a thinner gasket (if possible).

[bb71challenger]

If it was me I would not touch it until I was ready to build the stroker.  I'm no expert but wouldn't you have to basically tear the motor apart to put in the new pistons no matter what?  It's just a few hundred more to buy the whole stroker kit.  As far as trying to build compression, you could mill the heads or use a thinner gasket (if possible).

Yeah I had the 906 heads milled .050 and am using .020 stock style head gaskets. From what I factored it should be like 8.5 or so. It started out at a whopping 7.6 if you can believe that    Was rebuilt with the stock 452's or whatever they were and the blue .040 felpro head gaskets. I guess I could just clean it up and paint it and just be happy to cruise with it until I can build. I just wish it had more oomph. Heck I guess I could scour the want ads and try to find a procharger for a good price. With the compression the way it is and having forged pistons it would make a nice blown engine. Probably wasted money to try and just put pistons in there and make it work like that.

[firefighter3931]

Brett, the only way to increase the static compression would be to install taller pistons or use cylinder heads with much smaller combustion chambers. One thing you could do to help would be to advance the cam which would move the powerband down a few hundred rpm. I've done this in the past to "cover up" a weak (low compression) engine combination. 

Then tune the timing curve to come in early with lots of base (idle) spark lead. 


Ron

[71chally416]

Deck the block 

[bb71challenger]

Thanks Ron, you have always been there for me when I ask about engine mods 
The reason I really dont want to deck the block is because it is the stout thick web casting block. I know a 400 is still just a 400 but with the main webs so much thicker than other big blocks I dont want to do anything to alter it permanently. I can see a cleanup cut to true the deck but nothing more than that. Looks like the cheapest solution is to be patient.

[73Chally]

I would hold off on doing anything until you can afford the stroker kit.  You can make a really killer stroked 400 that can kick major a$$.  If nothing else, get new pistons and drop a stock 440 crank into it.  I forget the resulting cubes, but it will be a doozy.

[71chally416]

A standard B or RB motor doesn't have any inherent weakness in the block in the crank area. I would never plow a ton of $$ in a block just because of extra metal there. The important thing is the cylinder wall thickness. Only a sonic check will tell you what you really have.   

[firefighter3931]

Thanks Ron, you have always been there for me when I ask about engine mods 
The reason I really dont want to deck the block is because it is the stout thick web casting block. I know a 400 is still just a 400 but with the main webs so much thicker than other big blocks I dont want to do anything to alter it permanently. I can see a cleanup cut to true the deck but nothing more than that. Looks like the cheapest solution is to be patient.

Brett, i wouldn't be decking that block to raise compression....that will only create manifold alignment issues. The best thing to do at this point is to simply advance the cam timing and tune it as best you can. It should still run pretty strong and smoke some tires. 

A lowdeck 470 rotating assembly and a set of Indy EZ-1 heads will make more power than you can possibly hook up on a street tire. That's the direction you should be looking when the time comes. 



Ron

[moper]

I agree with "for now" simply living with it, or advancing the cam to cover it. As far as decking... I'm assuming you mean to take the entire thing down to a bare block. Anyone who decks an assembled block is flat out stupid hack. It is typical to have to deck them, but if this is a future bigger package, it is not wise to cut it now. 400s and 383s always ned to have more than a "skim cut" to get them to blueprint height. The "inherant weakness" is in the RB main saddles and webbing. And honestly, it aint that weak..lol. They do eventually fail, but they take a lot of abuse first. Wait until you sonic test it and see what a farse the "230 cold weather blocks" deal is.

[bb71challenger]

Thanks for the feedback guys! I am going to do the best I can with it and just live with it until I can do a quality build. I have the steel crank to do a 451 but I dont know if I want to do that or build a stock 440 for my 70 and leave the low deck engine for a stroker. Thing is I dont trust anyone around here to cut down the crank without messing it up. Patience is a virtue I guess.

[71chally416]

I've never had the main webbng break on ANY Chrysler block. It's always a cylinder wall. On the 400's it eventually breaks right above where you fill it too on race motors using the hose. The last one I built I filled completely, and it didn't break. Of course you can't do that with a street motor.

[Chryco Psycho]

My solution has been careful cam choice . 112* LSA high lift short duration , it will fill & capture the pressure in the cylinders better & can surprise you will the available power

[bb71challenger]

I was wrong. I was on Engle's website looking at my cams profile. I thought I had a K-56 but its a K-54. Ron(firefighter3931) recommended it to me for my low compression 400. I think I might have to advance it a bit more like he suggests. It would lay a patch pretty easily with a 2.94 sure grip so I think I can live with it for a while.

[challeng61]

Have you considered locating an older set of Closed chamber heads? This will quickly boost comp.