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351 c Compression question
#1
Anybody know what the compression ratio would be on a 1973 dished pistons Cleveland with 4 bbl open chambered heads?too low to make decent power?thanks
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#2
about 8-1

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#3
(02-27-2017, 05:11 PM)Jeff73Mach1 Wrote: about 8-1

How about t using closed chambered?at least 9:1?
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#4
I put closed chamber heads and a cam in my 73 and got 300 at the rear wheels before I dropped a valve. Depends upon the condition of the bottom end and your goals

If you are willing to rebuild, pop up pistons can make the stock block and heads capable of significantly more power.

My opinion is that 10:1 compression is really about the baseline for building respectable power but then again, I tend to overbuild

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
  Reply
#5
(02-27-2017, 05:33 PM)Jeff73Mach1 Wrote: I put closed chamber heads and a cam in my 73 and got 300 at the rear wheels before I dropped a valve.  Depends upon the condition of the bottom end and your goals

If you are willing to rebuild, pop up pistons can make the stock block and heads capable of significantly more power.

My opinion is that 10:1 compression is really about the baseline for building respectable power but then again, I tend to overbuild
Ok,this motor was rebuilt not too long ago and was punched .030 over but stock style dished so I'm looking for the easiest way to make a eecent motor
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#6
If you are not looking at doing popups or at least flat tops, then CC heads would get the compression ratio up to where you need to be. Once you determine your course of action on this front you will need to decide on a different cam. When I was starting mine I called comp cams and discussed in detail what I was doing and what I was shooting for and we came up with a custom grind. I also went full roller valve train as the cam they spec'd would destroy a flat tappet in no time. I believe the stock dished pistons have are 8 cc's. Hope this helps.

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
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#7
(02-27-2017, 05:47 PM)73pony Wrote: If you are not looking at doing popups or at least flat tops, then CC heads would get the compression ratio up to where you need to be. Once you determine your course of action on this front you will need to decide on a different cam. When I was starting mine I called comp cams and discussed in detail what I was doing and what I was shooting for and we came up with a custom grind. I also went full roller valve train as the cam they spec'd would destroy a flat tappet in no time. I believe the stock dished pistons have are 8 cc's. Hope this helps.

Ok,thanks for the help.
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#8
Hi

You can use flat pistons and shave the heads down to 67-68 cc. It should give you about 9.5.1 of course heads should be shave in both directions.

Regards Rob

For knowing your limit you have to pass it thumb
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#9
(02-28-2017, 01:42 AM)Robsweden Wrote: Hi

You can use flat pistons and shave the heads down to 67-68 cc. It should give you about 9.5.1 of course heads should be shave in both directions.

Regards Rob

Thanks,the biggest issue is that I don't know enough about motors to feel confident changing pistons,is it difficult?spany special tools involved?thanks.
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#10
Hi

It all depends, but changing pistons is not that difficult.  Tools depends, Pistonring compressor, torque wrench, the machineshop  can replace  the piston to the rod.

Regards Rob

For knowing your limit you have to pass it thumb
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