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I have a 400 bored over to a 406 was curious if these are stock .30 over pistons, and what kind of compression I'll be getting with some 291 camel humps.
The engine is complete and running right now just looking back on some pictures and got a bit curious on compression. It's a 1973/4 block made 245hp originally with 400 ft torque.
Last edited by thelargechic; Jan 17, 2016 at 12:51 PM.
I have a 400 bored over to a 406 was curious if these are stock .30 over pistons, and what kind of compression I'll be getting with some 291 camel humps.
The engine is complete and running right now just looking back on some pictures and got a bit curious on compression. It's a 1973/4 block made 245hp originally with 400 ft torque.
You can cc the pistons in the block to find out how big of a dish you got. How far up the bore the piston comes a TDC is a factor as well. The dish looks pretty deep and large on those pistons.
Look here to see how to check those two items. Post #31 2nd page.
I have a 400 bored over to a 406 was curious if these are stock .30 over pistons, and what kind of compression I'll be getting with some 291 camel humps.
The engine is complete and running right now just looking back on some pictures and got a bit curious on compression. It's a 1973/4 block made 245hp originally with 400 ft torque.
Ok.....according to NHRA....the 73' 400 made 150 horsepower.....pathetic I know but that is no matter.....
They show a 19.5 cc dish and a 74cc chamber .390/.410 cam.
Assuming .010 in the hole and a .041 gasket....you should get about 9.65 to 1.
Yes the pistons do look stock.....have you measured the bore?
Put a nice cam in it....a pair of real cylinder heads...and a RPM intake with a 750 carb and this will make you smile. Lots of torque and power.
Ok.....according to NHRA....the 73' 400 made 150 horsepower.....pathetic I know but that is no matter.....
They show a 19.5 cc dish and a 74cc chamber .390/.410 cam.
Assuming .010 in the hole and a .041 gasket....you should get about 9.65 to 1.
Yes the pistons do look stock.....have you measured the bore?
Put a nice cam in it....a pair of real cylinder heads...and a RPM intake with a 750 carb and this will make you smile. Lots of torque and power.
Jebby
Hi,
9.65:1 sounds a bit to high, are your sure it is 9.65:1?
From: Las Vegas - Just stop perpetuating myths please.
Those pistons dont look like OEM. Stock piston will ususally have vlv reliefs cast into the crown/dish.
Now that u have the heads off is would be a great missed opportunity not to measure the volumes for compression calcs now. It would be easier to guess someones weight than to guess your compression w/o measuring volumes. And REEL'R is our forum expert for this so u should follow his advice/instructions for this.
Looks like some L2352F (or equivalent) pistons. If you could measure the dish, as close as possible with a small ruler, you may get a better estimate. The dish should be around 3.400" x .082" deep??
Many of the aftermarket pistons had a 12/13cc dish with the above numbers. This looks like what you have?? Tough to tell from the photo though.
Thanks, Gary in N.Y.
P.S. Assuming it is the 12/13cc dish, with the OEM factory 400" heads you would be near 9:1, substituting the 64 cc chambers would place you at 10:1.
I have removed heads from original lo-po engines and some had no valve reliefs. My fave was a 69' 350 truck engine that was stock bore and the pistons were .020 in the hole...dished...no reliefs.
400 rebuilder cheapo pistons have no valve reliefs.....sealed power replacement 400ap30 pistons have no valve reliefs.....
I believe the NHRA chart I posted as it was the letter for many years and after cross checking I have found it to be right as far as cam, pistons, etc....the power numbers are their own factored in deal. Close.
You are not going to see 10 to 1 with those pistons....
And just to clarify....I am just pointing out facts.
Anyhoo....9.64 to 1 is great on the street.
Why don't you bolt some Vortec heads on this? Have the steam holes drilled and get a nice intake.....that would run very well. It has a 64cc chamber.
Anyway here are the number I plugged in....
Jebby
Last edited by Jebbysan; Jan 17, 2016 at 04:38 PM.
Well the whole engine is assembled already these are some older pics. I plan on saving for some dart iron eagle 215's this summer and I have a XE294H cam ready to be put in, currently It has a L79 350/350hp cam with 1.6 rockers, edelbrock performer intake(edelbrock scorpion waiting to be put on) and a 750 vacuum secondary on it right now (750 DP waiting to be put on)
And the compression would be slightly higher as the bore is 4.155 not 4.125 however I have no idea on how dished these pistons are as I'm having a hard time finding pistons like them. I can't find stock 400 pistons for the life of me.
Those pistons dont look like OEM. Stock piston will ususally have vlv reliefs cast into the crown/dish.
Now that u have the heads off is would be a great missed opportunity not to measure the volumes for compression calcs now. It would be easier to guess someones weight than to guess your compression w/o measuring volumes. And REEL'R is our forum expert for this so u should follow his advice/instructions for this.
Well the whole engine is assembled already these are some older pics. I plan on saving for some dart iron eagle 215's this summer and I have a XE294H cam ready to be put in, currently It has a L79 350/350hp cam with 1.6 rockers, edelbrock performer intake(edelbrock scorpion waiting to be put on) and a 750 vacuum secondary on it right now (750 DP waiting to be put on)
And the compression would be slightly higher as the bore is 4.155 not 4.125 however I have no idea on how dished these pistons are as I'm having a hard time finding pistons like them. I can't find stock 400 pistons for the life of me.
Will be kind of mild but should run great....
The L79 cam loves 1.6 rockers...
You will have a lot of fun with your "mutt" LOL!
Report back and let us know how it is.....
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Are these stock pistons?
