Compression Ratio Help

[My427stang]

Easy then, once you have the deck height measurement, you subtract 10.139 from that and that is your clearance for compression calculation and add that to the compressed thickness of the gasket to get quench.

Now a set of rebuilt connecting rods could be ever so slightly shorter, but we'd be getting a little overboard for your needs.

Be sure to report back! I will be out of town for a few days, if I can sign on I will, if not I'll be right back at you, or email me

[sparky72]

Easy then, once you have the deck height measurement, you subtract 10.139 from that and that is your clearance for compression calculation and add that to the compressed thickness of the gasket to get quench.

Now a set of rebuilt connecting rods could be ever so slightly shorter, but we'd be getting a little overboard for your needs.

Be sure to report back! I will be out of town for a few days, if I can sign on I will, if not I'll be right back at you, or email me

I will! I dropped the heads off today and confirmed that he did square deck the block. He seemed pretty remiss to measure the main to deck distance rather than just have me put the crank, a rod, and a piston in and measure that. I guess it’s something of a production to measure the main to deck distance? I could have pushed it but I figure that, since the decks are square, I’ll just measure it myself with the piston and a deck bridge. I’ll still end up using the same rod and piston to measure at all four corners I suppose; don’t really have anything to lose by doing that. I’ll have that done within a few days, pending the arrival of a deck bridge! Heads should be cc’d tomorrow, I am told.

Hopefully this will move along fairly quickly after this is all done!

[My427stang]

12 inch caliper on all 4 corners, measure to main bore and add 1/2 of main bore size to number. Not tough to be close enough to where you need to be

However, who knows....standing by

[sparky72]

Measured the piston to deck clearance to be about 6 or 7 thousandths. I took a video and uploaded it to my youtube channel to make sure I'm not measuring it incorrectly. I thought I read somewhere on here that videos are only allowed in a particular forum...so I suppose I'll just link to my channel?

https://youtu.be/fpMhadVWeWE[/video]

https://www.youtube.com/channel/UCG05JS ... 3ljdHlfofA

Hopefully the heads will be ready for pickup with cc measurements tomorrow.

[DuckRyder]

Remember on the camshaft that it is all about the Intake valve close @ advertised for dynamic compression ratio, so it isn’t necessarily the radcalness In and of itself. This is one of those times when an older camshaft design might be preferable ... as has been said solid numbers to work with are needed...

Edit, Tried to insert the video...

[sparky72]

Well, the heads cc'd at about 68cc. Crap. He said he would see if he has any other heads, possibly later heads (?) that would be bigger, and just trade me those for the ones he rebuilt for me (i.e. the 68cc ones). Though now I'm starting to wonder if I should have just heeded everyone's advice and bought Edels in the first place...

By my calculations, 68cc and 7 in the hole puts me at about 10.5 with a 41 thou gasket. That's assuming about 7cc piston valve relief volume.

Nuts

Edit: He just called back and said he has a set of C6-something-something heads that should be about 74cc. He'll cc them and let me know the volume and the casting number soon. Then'd we'd just do a switcheroo and I should be okay...hopefully

Edit 2: They are C6AE, 75cc.

[DuckRyder]

All that is starting to sound familiar...

Make sure to check the exhaust ports against your headers/manifolds if you swap...

[sparky72]

I’m planning on buying headers, but haven’t bought them yet. Are headers that fit C6AE heads readily available? If not, that may be a good reason to bite the bullet and order Edelbrocks...

[sparky72]

Here’s a picture of the new heads. C6AE 6090 R. Seems to be a pretty standard head. I confirmed with him that they did in fact measure at 75cc.

[DuckRyder]

So:

I’m no expert, but:

Those heads appear to be drilled for Thermactor (Air Injection) so that will have to be plugged.

“Truck” heads are generally "low port" and some “truck headers” (Hooker for sure) are designed with this in mind and won’t work with standard port heads. I’m not sure which the c6ae-r are.

Trucks use 8 exhaust bolts per head, one top and one bottom, make sure these 8 bolts holes match up, I believe there are 12 and 16 bolt heads in addition to 8.

Maybe this will get you started researching until My427stang or one of the other FE experts can get by...

EDIT: Oh and that nick in the valve cover rail brothers me a little unless it looks a lot worse than it actually is...