Bored and stroked 440 to 499 compression question.

[1969CoronetR/T]

I had my 1969 Coronet R/T 440 engine bored .040 and stroked to a 499 cid using an Eagle rotating assembly, .040 Wiseco pistons, roller camshaft (do not know brand, maybe Comp Cams) Harland Sharp roller hydraulic lifters, high volume Melling oil pump, Moroso Perm-Align valve cover gaskets, 3000 stall converter with ported Indy EZ-1 heads and port matched Indy intake. The cam is 545 lift with a 235/241 duration and 110 lobe separator / 106 centerline. The compression is 9.6 to 1 and this seems too low for a stoker. It has not been dyno tuned yet as I need to break the engine in first. So, a few questions:

Is the compression too low?
Would a higher compression produce more horsepower and torque?
Are the Moroso Perm-Align head gaskets to blame for the lower compression as I thought a 440 cid is 10.1 to 1 compression from the factory.

Thanks again,
Mark

 

[happyjackdaddy54]

Flat top pistons? How far down in the cylinder is the piston? Boring the block will increase CR also. How thick are the head gaskets? You can break the engine in on a dyno.

 

[1969CoronetR/T]

The gaskets are .172 thick I will have to ask the engine builder about the flat or dome pistons and their position in the cylinder. It runs great, but I think the compression ratio is low...

 

[66Satellite47]

In order to know REAL compression ratio you need to measure chamber CC's (actual, not advertised), distance piston is below deck, dish/dome including valve reliefs ( if any), head gasket thickness, actual head gasket bore (it's not the same as the cylinder bore, probably 4.400). Then covert units (CC's to cubic inches", calculate volume at BDC divided by volume at TDC & you have static compression ratio. Factory ratings are approximations. I've never seen a stock 440 head anywhere near the "blueprint" CC's.
The 9.6 CR seems low to me, the aluminum heads want more CR for max power. Heat disipation is so much greater with aluminum compared to iron. My 500" with 10.5 actual runs fine on 92 octane. Good luck.

 

[happyjackdaddy54]

Why are head gaskets so thick?

 

[Hemirunner]

That's a record thickness for a head gasket. What dictated that? Pistons out of the hole?

 

[terzmo]

9.6 is fine...I'm running 10 to 1 on my 472 hemi with aluminum heads....had 9.5 on an earlier 499 stroker with iron heads....ran great

 

[1969CoronetR/T]

Please disregard the part about Moroso gaskets as they are valve cover gaskets and not cylinder head gaskets (brain fart). I am running aluminum heads. So, ported aluminum heads can use a higher compression ratio for more power? I feel like Tim Taylor.

 

[MOPOWER871]

pump gas today is not the same pump gas 10 years ago. i'm building a 493 aluminum head pump gas motor and my engine guru decided to go with a icon piston ,with a final compression ratio of 9.7 with a 84cc camber i can run today,s pump gas all day long and not worry about hammering my bearings to death. street car is the key word.$3 and change is better then $ 13 bucks a gallon i'm not chasing 10th's anymore. all them cubes should make up for a 1/2 a point in compression anyway good luck p.s. thanks for the converter

 

[383man]

There is nothing wrong with your comp as it all depends on the build. If its a street car like yours and will run on this crappy pump gas we have then it will depend on alot like if the eng has quench and the cam that is used as that has alot of effect on cyl pressure. On my 493 I use Indy EZ heads wih the Indy dual plane intake myself and my heads are 75cc's. I am using these 440Source D-dished pistons you see here to keep my comp at 10.6 and still have good quench. I run a good size solid flat tappet cam that keeps my cyl pressure low enough that I run on 92 pump with no problem. If your cam does not have the intake valve closing timing and the other specs in check with cyl pressure then that may be why your eng builder decided to go with 9.6 on your eng. Actually with a smalller cam it wont always knock the cyl pressure down enough as you cant run as much comp with a smaller cam since it wont have an intake valve closing to keep cyl pressure in check for pump along with all the other parts and specs on your eng. I would say if it runs strong and has no ping I would not worry about it as even if you changed it to 10.5 or about that it wont make the car that much faster. You may be talking about 20 hp or so and may be a tenth or so in the 1/4. And you could also talk to your eng builder and ask him why he went with that comp but I do see many street strokers with comp in the mid 9's. Ron

 

[hunt2elk]

I think 9.6:1 would be just about right. I have 10:1 with aluminum heads on both my cars and had to retard the timing a couple degrees from optimal because of pinging on the 91 octane gas sold here. If it would be an easy fix, I would drop mine down to 9.6 in a heartbeat.

 

[1969CoronetR/T]

I run 115 octane although 93 octane would probably not cause detonation. I would run 93 octane all the time instead of the $9.50 a gallon race fuel, but I am trying to stay away from ethanol as it sits in my garage more than it is driven. Pittsburgh weather sucks lately. 43 degrees coming into work this morning and yesterday barely cracked 50 degrees as a high.

 

[Hemirunner]

It should actually make more power with the quicker burning 93 octane. We have a couple big HP cars (1500) that don't even need 115 octane.