Does intake need machining after zero decking block.

[dan juhasz]

This all pertains to a 69 440 hp. I pulled the 906 cylinder heads to install 440 source aluminum cnc ported heads. This engine ( six pack engine ) always pinged unless I ran 100LL and still with that my all in timing couldn’t exceed 30/32 degrees.
I know from receipts from the po the block had .020 removed and .010 from the heads.
I saw some oil on the intake tray gasket valley. Looking closer at the gasket crush the top of the gasket down to the midpoint the raised embossed ring was flat, the bottom of the gasket ports were not flattened and the embossed area were still raised.
Does this factory Edelbrock manifold need some machining because of the block being decked ??
If you look closely at the gasket photos you can see what I mean.
Another thing I saw was the inside of the exhaust ports in the exhaust manifolds. Some look very white. From the intake not sealing ??
Was this the root cause of the pinging?? The combustion chambers all look pretty normal to me.
Love some input, thanks

 

[69Bee]

No, do not touch the manifold. If all you did was remove enough to clean up the block, it will be fine. It is best to take material off of the intake side of the heads. If you remove material off of the intake, it is married to that engine. I would do a mock-up to test fit the heads to and manifold. Don't forget to use a valley pan. Maybe use 4 bolts in the four corners (only hand snug them) and look at bolt hole alignment. If the other 8 bolt holes register with bolt holes in the heads, you will be okay as it. If a lot was taken off of the block and the intake sits too high, mill the head intake surfaces.

I will add that the 0.010" on the heads is moot as you want to go to Edelbrock heads. Also, the new heads will have a thicker deck, so you could gain some back from the 0.020" taken from the block. Are you using the original manifold and if so, was it milled?

 

[33 IMP]

If I were you....
I'd use the fattest head gasket (within reason) I could find (no quench to lose with a 906 head), a new bathtub, and use both gaskets that come with it.
The fat head gasket will take the place of the material removed, and lower the compression ratio a bit, so you can maybe use pump gas.
I'd also look at the intake face of the head, to see if it has been milled too.
It sounds like some of the angles of the head/intake interface aren't quite right.
Bolt the heads on (temporarily, with the old hg), bolt the intake on, without the bathtub, and to only one head, and see what it looks like on the other side

 

[dan juhasz]

If I were you....
I'd use the fattest head gasket (within reason) I could find (no quench to lose with a 906 head), a new bathtub, and use both gaskets that come with it.
The fat head gasket will take the place of the material removed, and lower the compression ratio a bit, so you can maybe use pump gas.
I'd also look at the intake face of the head, to see if it has been milled too.
It sounds like some of the angles of the head/intake interface aren't quite right.
Bolt the heads on (temporarily, with the old hg), bolt the intake on, without the bathtub, and to only one head, and see what it looks like on the other side

I like that idea

 

[dan juhasz]

If I were you....
I'd use the fattest head gasket (within reason) I could find (no quench to lose with a 906 head), a new bathtub, and use both gaskets that come with it.
The fat head gasket will take the place of the material removed, and lower the compression ratio a bit, so you can maybe use pump gas.
I'd also look at the intake face of the head, to see if it has been milled too.
It sounds like some of the angles of the head/intake interface aren't quite right.
Bolt the heads on (temporarily, with the old hg), bolt the intake on, without the bathtub, and to only one head, and see what it looks like on the other side

It had fel pro permatex torque blue head gaskets and I measured their compressed thickness at ,050. If I use cometic I can easily get a fatter head gasket. Bore measured .030 over but the fel pro gaskets measured 4.5 bore. Shouldn’t I use a smaller diameter gasket?

 

[dan juhasz]

No, do not touch the manifold. If all you did was remove enough to clean up the block, it will be fine. It is best to take material off of the intake side of the heads. If you remove material off of the intake, it is married to that engine. I would do a mock-up to test fit the heads to and manifold. Don't forget to use a valley pan. Maybe use 4 bolts in the four corners (only hand snug them) and look at bolt hole alignment. If the other 8 bolt holes register with bolt holes in the heads, you will be okay as it. If a lot was taken off of the block and the intake sits too high, mill the head intake surfaces.

I will add that the 0.010" on the heads is moot as you want to go to Edelbrock heads. Also, the new heads will have a thicker deck, so you could gain some back from the 0.020" taken from the block. Are you using the original manifold and if so, was it milled?

Yes factory Edelbrock six pack manifold and the broach markings seem original , pretty rough cut.

 

[Cranky]

I like that idea

Keep in mind that air/fuel falls off a step a whole lot better than having to go over a step....best not to have any steps especially when the step is up.

 

[33 IMP]

It had fel pro permatex torque blue head gaskets and I measured their compressed thickness at ,050. If I use cometic I can easily get a fatter head gasket. Bore measured .030 over but the fel pro gaskets measured 4.5 bore. Shouldn’t I use a smaller diameter gasket?

Yeah, I'd like to have the gasket diameter closer to the bore size, but I'd look first for the thickness I want.
Time to do some calculations to find how much available gaskets affect the comp ratio.
I've always used the Wallace calculators, and without actual measurements of the heads, I use 88-90 cc's.

 

[dan juhasz]

What also confused me is when I used a simple compression ratio calculator plugging in the values of existing setup it really shouldn’t have had a pinging problem.

 

[33 IMP]

Yes factory Edelbrock six pack manifold and the broach markings seem original , pretty rough cut.

I have a later build Eddie 440 Sixpack manifold, and the machining and core shift is gruesome. Wouldn't surprise me a bit if it needs some correction.
The trouble is finding a machinist that can do it, and KNOWS what he's doing.

 

[dan juhasz]

Yeah, I'd like to have the gasket diameter closer to the bore size, but I'd look first for the thickness I want.
Time to do some calculations to find how much available gaskets affect the comp ratio.
I've always used the Wallace calculators, and without actual measurements of the heads, I use 88-90 cc's.

I used 87cc guessing the .010 milled from the head would be around 87 but I could be off with that value

 

[33 IMP]

Just now re-read your first post. Are the source heads you're planning on using closed chamber?
What cc?

 

[dan juhasz]

Just now re-read your first post. Are the source heads you're planning on using closed chamber?
What cc?

80, I was hoping being aluminum might make enough of a difference. Even with the 80cc chamber the cr is 10.2, it really shouldn’t have had ping unless the intake issue was leaning things out causing hot spots

 

[69Bee]

That calculator is not taking into account the total head gasket volume as it doesn't incorporate the hole diameter. It also doesn't take into account the volume from the top of the piston to the top of the first ring let alone the piston chamfer. My estimation would be that you could be closer to 9.8:1 CR. If you got me a piston number, I could work something up with my calculator that I made up in MathCad14.

 

[dan juhasz]

That calculator is not taking into account the total head gasket volume as it doesn't incorporate the hole diameter. It also doesn't take into account the volume from the top of the piston to the top of the first ring let alone the piston chamfer. My estimation would be that you could be closer to 9.8:1 CR. If you got me a piston number, I could work something up with my calculator that I made up in MathCad14.

 

[Bird 426]

Your new heads are going to change everything. When you get the heads on, you'll have to sit the intake on without gaskets and see just where you are at with a feeler gauge. Then figure out how much to correct it, and where. I'm no engine builder, but I would rather trash an intake over altering the cyl head. The cyl heads alone have altered things, almost everytime you change one thing, you change something else. Just my opinion.

 

[69Bee]

View attachment 1951241

There is no part number to get piston specs. Can you provide a link?

 

[dan juhasz]

There is no part number to get piston specs. Can you provide a link?

My bad

There is no part number to get piston specs. Can you provide a link?

srp 213455

 

[dan juhasz]

There is no part number to get piston specs. Can you provide a link?

SRP 213455

 

[69Bee]

The calculation, not including the ring volume (I need to call JE tomorrow for those specs), the CR comes to 10.044. The piston deck height is actually 0.008" as the crank/rod/piston stack-up is 10.697" (1/2 Str 1.875"+Rod CC 6.760"+Piston CD 2.062"). The OE block height is 10.725", so the difference is 0.028" less the supposed deck mill of 0.020" results in a 0.008"deck height. The info I need is the diameter of the piston in the ring section of the piston and the top land thickness (top of piston to the top ring groove.). That info, to include the chamfer dimension, will get me a more accurate number for the CR. I will report back tomorrow after I call them.