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best compression options??

69greenleaf

69greenleaf

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hello guys im looking to build a street/strip capable motor out of my rb440. its a .030 over block with a set of untouched 452's 89cc from what I have gathered online. I was running a .040 head gasket and my flat tops are .092 still in the hole at tdc. so that puts me around 8.4:1 cr...…. I am wanting to get somewhere close to 10.5 to one. I have the motor apart and ready to do some milling. I am planning on going back with a .020 shim head gasket. so that puts me somewhere around taking 5cc out of the heads and .070 out of the top of the block with a shim head gasket. is that too extreme? im not trying to spend a ton of money. just trying to make a fun budget build. so I would like to hear some thoughs on how to get me closer to where I want to be without drobbing 2500 dollars on pistons and heads. thanks
 
Different piston ... my speed pro flat tops were .019" below deck. On my 383 ... Left deck height alone, felpro .040" head gasket, 440 source heads, ended up with 9.44:1 comp .....
 
I'm not sure on all the measurements, but if you take to much off the block and heads, you will also have to take some off the intake to make everything fit. IMO it takes close to 5K to properly build a big block Chrysler engine properly. Machine work is costly. New pistons is what I would do so that I haven't messed up a block and a set of heads.
 
If you deck the block .070 with a thin gasket watch your valve clearances.
If their is not much cylinder wear buy a good hone like a lyslie and square it up and spend 400-500 bucks for better forged pistons with valve releifs or go .040. No need to spend thousands, but it does depend on your shop as to final cost, or what you can handle yourself.
Port the heads as well if you haven't already. Those aren't bad heads to learn on.
Taking a bunch off the deck is generally not the best plan..Can you do it...Yes...should you..??? IMO, Less strength, cylinders likely will need to be bored with a torque plate to true things back up. Worst of all you can't put it back when its done... and most future upgrades are custom.
 
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haha somewhere deep down I knew just buying pistons would be the correct answer. I will just stars saving the pennys and get a set from 440 source with a .018 deck clearance. and go with the shim gasket. maybe eventually save for a set of 80cc aluminum heads for it. I appreciate the input!
 
I'd call 440 Source. Their Stealth heads are only a grand. No machine work, no engine tear down. Maybe your current pistons with the smaller cc heads would yield the C.R. you're looking for. And they're aluminum and can handle higher C.R. better.
 
You'll be happier with new pistons and heads. Do it right the first time and don't look back.
For years I played around with the 452 heads, poured wasted $ into them, larger valves, springs, ect. Last year I ditched them and bought new alum pistons and Edelbrock heads, cost me $1400 from Summit. Ended up at 10.5:1. So much better!
 
69greenleaf said:
haha somewhere deep down I knew just buying pistons would be the correct answer. I will just stars saving the pennys and get a set from 440 source with a .018 deck clearance. and go with the shim gasket. maybe eventually save for a set of 80cc aluminum heads for it. I appreciate the input!
Click to expand...
Be aware, all of 440 source forged pistons are .990 big block Chevy pins, you won't be able to use your stock con rods. Try uem/icon pistons . The have cast,hyper, two different forged alloys. I think 440 source are icons, but they don't offer icons whole catalog.
New pistons are DEFINITELY the right solution, but IQ52 has some amazing low compression builds on a-bodys only. Worth a look.
 
There are a TON of good ideas on this post. I think a lot of it will come down to 2 questions. #1 How much money do you have to put into this motor? #2 How much compression do you really need?

a. "el cheapo"..... run the heads you have with shim gaskets
b. "mid-level..... I'm leaning towards the aftermarket, aluminum heads with smaller combustion chambers & shim gaskets like diesel_lv says. It's MUCH easier than putting in pistons & you'll get some extra HP from the flow.....but I would expect you to spend a little extra money on the heads to "get them right" at a machine shop.
c. "top-level".....pistons for sure. "top-top" level would be pistons & heads..... all of this is much harder & more expensive.

I don't recommend ANY milling of block or heads to gain compression, just "square deck" the block & clean up the heads. Ask me how I know? I've had a ton of intake manifold alignment issues caused by milling blocks/heads... PIA. Also, if you target "about" 9.5 compression ratio, you can run on 91 octane. If you target "about" 10.5+ compression ratio, you'll probably need 93 octane all the time...….."approximately" on all this, so keep that in mind too.
 
Greenleaf, If you could purchase a new set of Edde 75cc heads and a good sharp cam that would accentuate your compression problem and that has a power band up to 5600/5800 I believe you would be surprised at the power increase. I'm assuming you have appropriate size headers and dual plane alum. intake with a vac. secondary 750 cfm quality carb, ign. I would lastly consider good p/rods and solid f/tappet lifters. good luck and these old engines will run like a raped ape AND hold together if you pretty much stay under these perameters.
 
The best bet of course is tear the eng down and build it with new pistons for zero or close to zero deck height with a flattop piston that has nice valve reliefs in them. Then run an aluminum head with the .040 head gasket to have good quench which helps stop pinging/detonation and with the right cam you can easily run 10.5 comp on that build. I run a setup like that with good quench and 10.6 comp and I run and race on 92 pump with no detonation ever. If not and you fool with your combo I would not go over 9.5 comp with iron heads and no quench. Good luck whatever you decide. Ron
 
A pair of Eddy heads 484 purple shaft, performer rpm, 600 Eddy, headers, .100" in the hole reringed short block. , 3.91, stock converter, 255 Radial T/A . This combo put us in the 12.90s in a stock 65 Belvedere. From my experience; 9.7-1 906 heads with KB pistons, measured .035" quench (each chamber adjusted to equal depth). [email protected]" cam, 3.23 gear 70 Coronet. This combo will not run at 36 degree timing on 93 pump without ping. Unless you're going to run aluminum head dont run over
9.3-1/9.5-1. Plus milling to get zero deck will require an intake cut to fit. And the head cc are probably larger than you think. Look, you can find a pair of used Eddy heads for 1k, we did. No machine work. Bolt them on.
Doug
 
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Took .070 off this block, L2266 pistons (had them notched). I run a .020 steel gasket and my quench comes in at a perfect .040 with closed chambered heads. You just have to play with the intake to get it right. Either mill the head face or manifold.
IMG_1503.JPG
 
Honestly, you can do any of the offered solutions. Some are preferred over others, but usually at a cost.

IMO, the answer will present itself when you get clear on your goal for the car, your budget, and when you want it. What you have on hand, what you can do yourself, and what level of "less than perfect" you can live with plays a big role it this decision too.

Generally, in cases like this, I'm an advocate of not touching the short block. Usually the cost of tearing into a motor solely for the purpose of a some additional compression related horsepower is a poor bang for the buck. Take that money and put it in the heads and a good cam and you'll get better HP/$.

The only possible lower $ piston change option would be if the motor has 2266 pistons, and the cylinders measures pretty round and straight with little ridge, then you might be able to put a hone on it and put in some 2355s. If it is this, or 75cc Eddy heads, heads all the way.
 
with those heads I helped design the kb quench dome specifically for that build
ft are totally wrong for those heads unless class racing where you have to use them
now closed chamber different answer
 
wyrmrider said:
with those heads I helped design the kb quench dome specifically for that build
ft are totally wrong for those heads unless class racing where you have to use them
now closed chamber different answer
Click to expand...
Please explain this a little more. I am currently restoring a 67 Satellite 383 4-speed. I was planning on using a set of 915's and 67 HP manifolds in the build, and just retaining the 516 heads and log manifolds. I do want more than the stock 325 HP, but really want it to be stock appearing. I'm all for at least bigger exhaust valves with the 516's, but would not be opposed to going with 214/181 valves and some port work. I know it will diminish some HP gains with the stock exhaust manifolds. My plans for this car would be show for a year or so then drive and enjoy with performance in mind. My questions are pistons, cam, and what is the different approach in porting. Also no more than 10.25 compression.
 
I can't answer all your questions Jerry, but one I can handle. If you are gonna use either 516 or 915 heads, you can't use the quench dome kb pistons, because you would have closed chamber heads.
In 68 Chrysler changed from closed chamber to open, which killed the quench, because of the new open area on the intake side of the head. The kb
reverse dome piston was designed to get the quench back, along with some more compression . Instead of the normal dome location in the combustion chamber, that area on a kb is flat, and there is a little dome on the opposite side, to fill the area opened up to make the open chamber. That piston therefore would collide with a closed chamber head.
Also, a good cam grinder can get you a cam especially for exhaust manifolds. There is a way to crutch the timing, I just don't recall what it is. Maybe wider lobe centers, like those ground for fuel injection setups. I would talk to Dwayne Porter.
 
Jerry Hall said:
Please explain this a little more. I am currently restoring a 67 Satellite 383 4-speed. I was planning on using a set of 915's and 67 HP manifolds in the build, and just retaining the 516 heads and log manifolds. I do want more than the stock 325 HP, but really want it to be stock appearing. I'm all for at least bigger exhaust valves with the 516's, but would not be opposed to going with 214/181 valves and some port work. I know it will diminish some HP gains with the stock exhaust manifolds. My plans for this car would be show for a year or so then drive and enjoy with performance in mind. My questions are pistons, cam, and what is the different approach in porting. Also no more than 10.25 compression.
Click to expand...


Jerry, I'd be happy to give a response. Life has gotten a little better for 383 owners that don't want to stroke with some new piston offerings out there. But maybe start another thread, as the 383 is a different story than the OP's 440 situation.
 
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