[JLMounce]

How does the car behave now? Does it run hot, does it audibly ping? Just because the static compression ratio may be higher than 9.5:1 with iron heads, doesn't automatically mean you're going to have issues.

The problem here, is there's a ton of different scenarios and a lot of assumptions being made. I like you was in a pretty similar place when I purchased my bird in 98. The engine was built previous to my ownership and all I really had to go on was what I could visibly inspect. No clue what cam was in it, no clue what the rotating assembly was except for a part number I was able to pull from a piston top with a bore-scope.

Lots of unknowns makes it hard to really make any real progress towards a goal. I had decided on doing a top-end swap because I knew I couldn't run my engine on anything less than 100 octane without it pinging noticeably. That process uncovered everything that was in the engine for me. I'm now no longer in the dark so to speak and can make better educated decisions surrounding tuning, upgrade parts etc. Especially since I've now installed new equipment in the original engine.

It's a couple weekends worth of work, but my suggestion would be to get the heads, intake and valley pan off the engine. You'll be able to see what kind of rotating assembly is in there and more importantly you can measure your piston to deck height. If you wanted to go further you could also cc the combustion chambers on the heads.

You can't really ID the cam without taking the timing cover and water pump off, but that's really not that much extra work if you've already got the top-end off. Then you can ID the cam and also inspect it and the lifters. Based on what you find, you can make some decisions. If you decide to make no changes, all you're out is a bit of time and the cost of some new gaskets. At least in my opinion that is well worth piece of mind.

Then, you can come back here and give enough detail that experts can really help put together a package that's going to best work for you and whatever your budget may be.

[72projectbird]

Slap on a plate and a .073 jet in it and let it eat!

[footjoy]

Originally Posted by JLMounce

How does the car behave now? Does it run hot, does it audibly ping? Just because the static compression ratio may be higher than 9.5:1 with iron heads, doesn't automatically mean you're going to have issues.

The problem here, is there's a ton of different scenarios and a lot of assumptions being made. I like you was in a pretty similar place when I purchased my bird in 98. The engine was built previous to my ownership and all I really had to go on was what I could visibly inspect. No clue what cam was in it, no clue what the rotating assembly was except for a part number I was able to pull from a piston top with a bore-scope.

Lots of unknowns makes it hard to really make any real progress towards a goal. I had decided on doing a top-end swap because I knew I couldn't run my engine on anything less than 100 octane without it pinging noticeably. That process uncovered everything that was in the engine for me. I'm now no longer in the dark so to speak and can make better educated decisions surrounding tuning, upgrade parts etc. Especially since I've now installed new equipment in the original engine.

It's a couple weekends worth of work, but my suggestion would be to get the heads, intake and valley pan off the engine. You'll be able to see what kind of rotating assembly is in there and more importantly you can measure your piston to deck height. If you wanted to go further you could also cc the combustion chambers on the heads.

You can't really ID the cam without taking the timing cover and water pump off, but that's really not that much extra work if you've already got the top-end off. Then you can ID the cam and also inspect it and the lifters. Based on what you find, you can make some decisions. If you decide to make no changes, all you're out is a bit of time and the cost of some new gaskets. At least in my opinion that is well worth piece of mind.

Then, you can come back here and give enough detail that experts can really help put together a package that's going to best work for you and whatever your budget may be.

I understand what you are saying and I will take it apart. The only two things I don't know are where the cam is degree wise and what is my true deck height.
Cam is a Crower 60240
Pistons are Speed pro 400 .040 with four reliefs + 6.7 cc

Greg

[pastry_chef]

Originally Posted by footjoy

I don't know are where the cam is degree wise and what is my true deck height.
Cam is a Crower 60240
Pistons are Speed pro 400 .040 with four reliefs + 6.7 cc

It would be interesting to see what type of cranking PSI you have now.

[JLMounce]

Originally Posted by footjoy

I understand what you are saying and I will take it apart. The only two things I don't know are where the cam is degree wise and what is my true deck height.
Cam is a Crower 60240
Pistons are Speed pro 400 .040 with four reliefs + 6.7 cc

Greg

Agree with pasty_chef here. Would be interested to see what it pumps with a compression test.

Even if the block had never been decked, you’d have to have a fairly anomalous engine for those pistons to be any more than .010 in the hole. I have the same basic piston in my 455 with factory rods and crank. They range from .007 at the front of the block to .005 in the back.

I don’t like assumptions but some of these parts are quite repeatable.

I quantify this by saying I’m not an expert, but that’s a mighty small cam for what likely is a near 10:1 400. Even the generic catalog info on that cam has it all done around 4800 rpm. I think it needs a bigger stick.

[footjoy]

Originally Posted by JLMounce

Agree with pasty_chef here. Would be interested to see what it pumps with a compression test.

Even if the block had never been decked, you’d have to have a fairly anomalous engine for those pistons to be any more than .010 in the hole. I have the same basic piston in my 455 with factory rods and crank. They range from .007 at the front of the block to .005 in the back.

I don’t like assumptions but some of these parts are quite repeatable.

I quantify this by saying I’m not an expert, but that’s a mighty small cam for what likely is a near 10:1 400. Even the generic catalog info on that cam has it all done around 4800 rpm. I think it needs a bigger stick.

First off this engine was built by a novice, me. And also it currently has #15 heads with 85-87cc heads.

The compression test was 160-165 psi

[footjoy]

I appreciate all of the help I might have confused some people.
The engine as it is.

400 .040
#15 Heads 87cc stock except for screw in studs
Crower 60240 not degreed put in dot to dot(big mistake)
Speed pro 400 .040 pistons with 6.7cc relief
deck Height don't know.

Alternative
I have a set of #16 heads that ccd at 75cc but not on the engine

I just wanted restate what was in it now.

Thanks
Greg

[steve25]

Lets get down in dirt here and really see where your at and where you can go head wise!

When I run the numbers on your current number 15 head then assuming it is at 87 CCs and your deck clearance is the stock average of .023" and then using the CC amount from a Fel Pro 1016 head gasket of of 9.4 CCs I come up with a compression of 9.32 to 1 for your .040" over 400.

If we substitute in a 75 CC chamber into the formula then the compression come out to 9.54 to one.
If you want want to I will post up the formula with all the numbers.

In short I fully think you would be better off running the 15 heads you are now, but installing the bigger valves along with a mill of .020" , this is assuming that the number 15 heads are rebuilt already and are in better shape the the number 16 heads?

If the valves in the 16 heads are not worn more then .001" on there stems then you can use those in the 15 heads and save that cost and put it towards the needed valve job to get those big valves in.

[footjoy]

Originally Posted by steve25

Lets get down in dirt here and really see where your at and where you can go head wise!

When I run the numbers on your current number 15 head then assuming it is at 87 CCs and your deck clearance is the stock average of .023" and then using the CC amount from a Fel Pro 1016 head gasket of of 9.4 CCs I come up with a compression of 9.32 to 1 for your .040" over 400.

If we substitute in a 75 CC chamber into the formula then the compression come out to 9.54 to one.
If you want want to I will post up the formula with all the numbers.

In short I fully think you would be better off running the 15 heads you are now, but installing the bigger valves along with a mill of .020" , this is assuming that the number 15 heads are rebuilt already and are in better shape the the number 16 heads?

If the valves in the 16 heads are not worn more then .001" on there stems then you can use those in the 15 heads and save that cost and put it towards the needed valve job to get those big valves in.

Both sets of heads have less than 2000 miles on them. I am curious to see your formula because all I know is the Wallace calculator. And it comes up with 8.73 on the 15s. And the 16s come up 9.74

And I have to ask as a Dummy both heads being relatively fresh is the 16s with 9.54 to much in your thinking?

Thank you very much for your time and thought into this.

Greg

[steve25]

Sorry, my math had errors in it yesterday!

I use this formula and I add in a RLV ( ring land volume) factor of 1.5 CCs.

This takes into account the ring land back clearance of the top two 5/64" rings that your likley running in the motor and the volume of the piston to wall clearance from the top of the piston down to the top compression ring.

A Fel pro 1016 head gasket has a volume of 9.4 CCs when compressed.

You already know your VNV ( valve notch volume ) of 6.7 CCs.

With these compression ratio's stated I am assuming you have a piston deck clearance of .023", if you had a zero deck clearance any of these compression ratio numbers would change / go up by .6, which is a big change!

Here's my new numbers for you and your 4.160 Bore 400.

87 CC head= 8.6 to 1

82 CC chamber = 8.97 to 1

78 CC = 9.29 to 1

75 CC = 9.4 to 1

72 CC = 9.8 to 1

A 75 CC chamber with zero deck would be right at 10 to 1 compression.

[footjoy]

Originally Posted by steve25

Sorry, my math had errors in it yesterday!

I use this formula and I add in a RLV ( ring land volume) factor of 1.5 CCs.

This takes into account the ring land back clearance of the top two 5/64" rings that your likley running in the motor and the volume of the piston to wall clearance from the top of the piston down to the top compression ring.

A Fel pro 1016 head gasket has a volume of 9.4 CCs when compressed.

You already know your VNV ( valve notch volume ) of 6.7 CCs.

With these compression ratio's stated I am assuming you have a piston deck clearance of .023", if you had a zero deck clearance any of these compression ratio numbers would change / go up by .6, which is a big change!

Here's my new numbers for you and your 4.160 Bore 400.

87 CC head= 8.6 to 1

82 CC chamber = 8.97 to 1

78 CC = 9.29 to 1

75 CC = 9.4 to 1

72 CC = 9.8 to 1

A 75 CC chamber with zero deck would be right at 10 to 1 compression.

Thanks Steve

It looks like the #16s with 75cc are a doable option .

Thanks again
Greg

[JLMounce]

Originally Posted by steve25

Sorry, my math had errors in it yesterday!

I use this formula and I add in a RLV ( ring land volume) factor of 1.5 CCs.

This takes into account the ring land back clearance of the top two 5/64" rings that your likley running in the motor and the volume of the piston to wall clearance from the top of the piston down to the top compression ring.

A Fel pro 1016 head gasket has a volume of 9.4 CCs when compressed.

You already know your VNV ( valve notch volume ) of 6.7 CCs.

With these compression ratio's stated I am assuming you have a piston deck clearance of .023", if you had a zero deck clearance any of these compression ratio numbers would change / go up by .6, which is a big change!

Here's my new numbers for you and your 4.160 Bore 400.

87 CC head= 8.6 to 1

82 CC chamber = 8.97 to 1

78 CC = 9.29 to 1

75 CC = 9.4 to 1

72 CC = 9.8 to 1

A 75 CC chamber with zero deck would be right at 10 to 1 compression.

I still don't really believe it's possible for his piston to be that far in the hole. Not unless his block is anomalously tall to begin with and has never even had a surface done on it.

Compression height on his pistons is 1.714" So that math suggests

1/2 stroke = 1.875"
Rod length = 6.625"
Compression height = 1.714

total assembly height = 10.214

Most literature I've seen puts the factory deck height around 10.25-10.5, with most factory blocks coming in around 10.3". If that's not correct, my apologies, but given that information, if after decking, the height is somewhere around 10.28" or so, his pistons are only in the hole .005 to .008".

[steve25]

He will have to confirm his deck height when he yanks his heads to zero in on what he has , or will have for compression.

Sorry that my attachment is upside down, but this is factory info on a 1970 400 that clearly states a .023" deck height.

It's very interesting to note that it takes a .060" over Bore on the 400 and zero deck clearance with a 75 CC chamber to get to 10.1 to 1 compression!

[amcmike]

Originally Posted by footjoy

I have a 400 bored .040 fresh(2000 mile)
Deck helght .021
The block is built and not going to change

The heads are # 15 small valves 87cc right now about 8.6:1 SCR

He stated his desk height was .021, but I don't know if that was an assumption, or measured.

[steve25]

Well basically for every .010" of deck height either way ( up or down) on his 4.160 Bore equals close to 2 CCs.

[footjoy]

My deck height is assumed by the following information.

The machinist did not deck the block.

Federal Mogul/Speed Pro Piston Part
Number

Application Power Range Special requirements Compression information Ring groove size Pin diameter Rod length Stroke Deck clearance Skirt clearance
L2262F+40- Pontiac 400 - 4.160" bore (at +.040") Flat head w/4-valve reliefs. DurOshield skirt coated piston. 1967 Car (USA); w/4-Bbl. carburetor 1968-74 Car (USA); All 10.75:1 CR idle to 6500+rpm Compression distance: 1.714" Head volume -6.70cc Approx. Compression (w/.030" bore): w/69cc heads 10.24:1 w/87cc 8.70:1 w/111cc 7.30:1 5/64" 5/64" 3/16" ring grooves Pin diameter; .980"; pins included For stock length rods Press-fit only Stock 3.750" stroke .021" deck clr .0020" skirt clr

Looking at the last line it says Deck clearence .021 Skirt clearence .0020

I am sorry if I mislead anybody I am pulling the heads off to get an accurate measurement.

Thanks
Greg