Best way to lower compression on 12.5:1 440

[moper]

You can;t build a 440 for $1500. So you did fine. But - it's not usable as is. I doubt that the Ross pistons can be milled. They are usually light and don;t have the extra meat. But - they shobe floating so the rods can be removed easilly. Take it all apart and have the bores measured with a dial bore gage. That wil show the actual bore size - because chances are it's not exactly ".030" over or whatever. You can use those measurements to determine which pistons will work best. Buy those, and then have it rebalanced. Then put it back together, maybe with a cam and valve springs more suited to street duty. When you're one you should have a great pump gas 440, fresh and ready to go, for under $3K.

In fact the Ross pistons can probably be sold to get back some of that money...

 

[76maverick]

While I`m picking your brains. I have a set of 2.19 intake 1.81 exhaust valves that came with my charger. Will my heads along with some port work support these valves ? Good idea for a healthy street engine ?

 

[moper]

I'd be surprised if a12:1 engine didn't have big valves already in it...
But I always install oversized valves. It's cheaper than new intake seats and generally will help with low lift flow.

 

[Garys1969RR]

Yes, larger valves can be installed in 452 heads. That can make a big difference in flow, if it's done right. The proper porting helps too. My 440 had larger valves and some port work done on the 906 heads, and it ran really good!

 

[76maverick]

I pulled the engine apart and did the math on it all. My 12.5:1 engine is in fact a 11.16:1 engine. From what I have read 7.5 cc is worth a point of compression so if I have the dome milled off the pistons that should put me pretty close to 9.5 (correct?) so that makes me happy. Back to my heads, with having a 510 lift cam will I see a benefit from using the larger valves or is there a chance that it will make my engine lazy at lower rpms ?

 

[Cornpatch MO]

I pulled the engine apart and did the math on it all. My 12.5:1 engine is in fact a 11.16:1 engine. From what I have read 7.5 cc is worth a point of compression so if I have the dome milled off the pistons that should put me pretty close to 9.5 (correct?) so that makes me happy. Back to my heads, with having a 510 lift cam will I see a benefit from using the larger valves or is there a chance that it will make my engine lazy at lower rpms ?

I have never personaly examined a domed piston. Might they be domed up on the inside of the piston, making them to thin to mill any of the dome off? .....MO

 

[76maverick]

I have never personaly examined a domed piston. Might they be domed up on the inside of the piston, making them to thin to mill any of the dome off? .....MO

They are solid on the back side so the thinnest point is at the valve reliefs and will still be at the valve reliefs once the pistons are milled

 

[Garys1969RR]

Larger valves (if done correctly) will improve the flow of your heads. Should not hurt the torque at lower RPMs. It should improve low RPM torque, due to better cylinder filling of incoming charge. Too much cam will hurt lower RPM torque, but but I think your .510 lift cam should work well.

 

[76maverick]

Excellent ! Didn`t want to waste the money on having the larger valves installed if this set up wasn`t going to benefit from it.

 

[Garys1969RR]

You can get lots of advice here, but every engine is an experiment of 1, as has been said. Get the info, do your research, plan your build, matching all the components with the C/Ratio you want, fuel used, and end use of the motor. I.E. Street, Street strip, or Drag Race only. There are a lot of things to consider. It can be mind boggling.

 

[Garys1969RR]

I'm building a 440 six pack motor with a top end that will have Perf RPM heads, 035" of quench, and 11 to 1 C/Ratio. It also has a solid lifter cam at .525 lift, and Crane Gold Rocker arms. How will it run? I won't know for sure until I get in it and drive it.