Getting my 516 heads done.

[33 IMP]

It doesn't matter what it WAS, it only matters what the pistons and heads are now! And you won't know anything for sure till you get a final deck height and a cc. of the heads.

 

[BeepBeepRR]

I agree but just wanted to know “about” where the starting point is or should have been. If it were the 9:2-1 2bbl engine to start with it makes it a tad easier to get it in the 10:1 range. It’s just my curiosity that has me going in circles. Plus I like doing the research lol I’m bored.

 

[33 IMP]

Also, there is a WORLD of difference between 65cc heads on a 030 in the hole flattop, and a 70 cc.head on a .060 in the hole flattop.
Did your machinist say what your deck height is now?
Remember, the specs you provided for your piston have them almost .090 in the hole!

Edit: just for giggles , i calculated the two examples above .
70cc heads, flat tops with no reliefs, 060 in the hole with a .041 felpro.....9.3
65cc heads, flattops with no reliefs, 030 in the hole, with a .022 shim hg.....11.1 (and still with what some would consider not a tight enough quench.)

 

[origcharger]

Hopefully it won't be quite that high, but it will be the machine work that puts it there. It also tells me that it was originally a 10:1 engine. I just didn't realize that the pistons on the 66-67 383's were down in the hole. Originally when I saw that they were in the hole, I thought 9:1 2bbl. engine.

Not that it matters but the lower compression 2 bbl engine used a dished piston, the deck height around the edge was probably no different than the 4 bbl 383

 

[BeepBeepRR]

I used 2 feeler gauges one .019 and .021 together and had very little resistance between the piston and straight edge. With those two I get 0.04 deck height....

.020 and .021 wouldn't fit between the piston and straight edge. He did not mention deck height at the time due to the fact I forgot to ask.

 

[Cranky]

I knew I should have kept my kids PLay DOh....

My kids played with my dough.....thought it was theirs!

Still going to 1.74?

Hope no one in their right mind would keep the 1.60's lol

Ok by using a straight edge I can get a .021 and a .019 together under the straight edge with a little drag at TDC So the measurement is 0.04 piston height at the deck. Does that sound correct? I also went back with the straight edge and checked the block sag and Im not so sure its sagging now but its hard to tell because of the aluminum level is not rigid enough to swear by the measurements.

When you use a straight edge like that, flip it and check again. If there's say a .010 difference, the straight edge had a .005 bend in it.

Well the block needs to be decked.. So I have to take it apart so I can get it fixed. Also needs to be honed but hopefully I wont have to buy new pistons.. I watched him use his straight edge and feelers got some sag spots that were 7 thousandths low. So its decking time. Also Hes saying with the combo Im going to be running I'll be close to 11 to 1 with 039 gaskets. Assuming the heads are at about 65 to 70 cc. He said he will check the CC's after he gets the valves in the heads.

I've checked a few heads in my years and have never come across a stock 65cc big block head. Closed chambered are usually 80 and if they've been 'fixed' a time or two, they might end up being 75. Open chambered are usually around 90cc. The Mopar 'Bible' isn't even right. They were going on what they were 'supposed' to be...

Edit: Meant to say open chambered heads are usually 90.....

 

[BeepBeepRR]

Not that it matters but the lower compression 2 bbl engine used a dished piston, the deck height around the edge was probably no different than the 4 bbl 383

I did notice that information somewhere but forget where... The pistons that are in the engine are flat top no dish.

 

[BeepBeepRR]

My kids played with my dough.....thought it was theirs!

Hope no one in their right mind would keep the 1.60's lol

When you use a straight edge like that, flip it and check again. If there's say a .010 difference, the straight edge had a .005 bend in it.

I've checked a few heads in my years and have never come across a stock 65cc big block head. Closed chambered are usually 80 and if they've been 'fixed' a time or two, they might end up being 75. Closed chambered are usually around 90cc. The Mopar 'Bible' isn't even right. They were going on what they were 'supposed' to be....

His 65 to 70 cc was an estimate after he took off the 20. So he was guessing at that point until he gets the valves installed I guess there is no way of knowing until he checks the CC's..

 

[Jerry Hall]

I did notice that information somewhere but forget where... The pistons that are in the engine are flat top no dish.

Yes, 2bbl or 4bbl was already out the door with the previous rebuild and 30 over flat tops.

 

[BeepBeepRR]

Yes, 2-bbl or 4-bbl was already out the door with the previous rebuild and 30 over flat tops.

I agree with this.. So at this point its no longer considered the lower compression 2-bbl engine that it originally was. But without real measurements its all guess work at this point.. Just working on my brain muscle... lol

Just found this chart talking about CC's of all BB heads.. If you can believe this 73.5 cc's on the 516 heads...

http://www.hotrodreference.com/758/big-block-mopar-cylinder-head-casting-numbers/

 

[Cranky]

Just found this chart talking about CC's of all BB heads.. If you can believe this 73.5 cc's on the 516 heads...

http://www.hotrodreference.com/758/big-block-mopar-cylinder-head-casting-numbers/

Nope....they are going by the book too and still say the 741 case rear end is weak lol

 

[33 IMP]

Nope....they are going by the book too and still say the 741 case rear end is weak lol

I agree with Cranky, that's just a regurgitation of mopars' fantasyland numbers
906s at 79.5, really more like 89.5, a full point less compression than mopar claimed.

 

[1 Wild R/T]

I typed up a nice long response but decided to delete it...

I suggest if you want to really know your compression ratio you should buy some tools & invest some time doing research..

Don't believe what printed in manuals or magazines... It's rarely 100% correct..

 

[BeepBeepRR]

I typed up a nice long response but decided to delete it...

I suggest if you want to really know your compression ratio you should buy some tools & invest some time doing research..

Don't believe what printed in manuals or magazines... It's rarely 100% correct..

This is good advice. Thanks. Any reply's here is food for thought. I do understand that hell, even the HP ratings were skewed to up-ease the government. Yes I do need better tools for measuring. I do appreciate your help.

 

[BeepBeepRR]

Got the heads back today 3 new intake valves, all new guides the springs are good to 500 lift and all of the exhaust valves are 1.74. I will cc the chambers when I get my wife’s food injector that has cc’s on it I know to use a piece of plexiglass and put it over the chamber and fill it till full but not pouring out of the fill hole. Is that correct?

 

[33 IMP]

I use white grease to seal the plexy, put the fill hole at the top edge of the chamber, with the head tilted so the chamber is at an angle. I then use some food colored alcohol and a veterinary syringe, 0-50 cc (got it for free from my vet) , put in 50cc, refill, and add till its just about to run out. I would have rather had a 100cc syringe, but free is free, and it works for me.

 

[1 Wild R/T]

I use a bead of Vaseline to seal the plexiglass to the head, I prefer to position the hole in the plexiglass at the very top edge of the chamber, I tilt the head so one end is an inch or two lower than the other... In a recent thread it was discussed that some like to use alcohol since it has lower surface tension than water & that makes it easier to get an accurate number.... I've always just used colored water but in the future I plan to try the alcohol..

 

[1 Wild R/T]

I use white grease to seal the plexy, put the fill hole at the top edge of the chamber, with the head tilted so the chamber is at an angle. I then use some food colored alcohol and a veterinary syringe, 0-50 cc (got it for free from my vet) , put in 50cc, refill, and add till its just about to run out. I would have rather had a 100cc syringe, but free is free, and it works for me.

Could have saved some typing if I'd just waited... LOL..

 

[33 IMP]

You mean i actually out-typed somebody? Wooo hooo!!

 

[BeepBeepRR]

Also i just made some mopar money.. today.. When I do odd jobs on cars I use that money to fund my mopar fun.. I changed 2 struts and rotors, brake pads and new rubber lines on a ford escape.. Made enough to get my block machined. So For a little work on someone elses **** I don't have to come out of pocket to get stuff done. I mean in the grand scheme of things I work on others cars then have to work on the 383... So its absolutely all work on my end.