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Keeping everything the same, what can I expect on a compression ratio increase on a 9:1 BBC, switching from an open chamber 119 cc to a closed chamber OEM head?
 

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What CC is the closed chamber head??

there are several often considered closed, or semi-closed conv=fused for closed...96cc, 99cc, 101cc, 106cc

What size engine makes a difference too.....change will be a little less on a 454 than a 396.

On a 454 for 119cc down to 99cc, you'll pick up 1.6 points....providing the engine was really 9:1 to start with....if it doesn't have somewhere near a 18-20cc dome in it now, it wasn't anywhere close to 9:1 to begin with.....if this is a flat top piston truck 454, you'll be lucky to have 7.8:1 with the 119cc head, and 9.4:1 with the 99cc closed.
 

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Discussion Starter #3
What CC is the closed chamber head??

there are several often considered closed, or semi-closed conv=fused for closed...96cc, 99cc, 101cc, 106cc

What size engine makes a difference too.....change will be a little less on a 454 than a 396.

On a 454 for 119cc down to 99cc, you'll pick up 1.6 points....providing the engine was really 9:1 to start with....if it doesn't have somewhere near a 18-20cc dome in it now, it wasn't anywhere close to 9:1 to begin with.....if this is a flat top piston truck 454, you'll be lucky to have 7.8:1 with the 119cc head, and 9.4:1 with the 99cc closed.
Thanks Eric, it is a 4.310" bore x 4" stroke 468 and did have a probe flat top piston (1.645 compression height) with a single valve relief in it. The block was decked .030" once when I was working on raising the compression ratio at the machine shop. The piston was very, very close to the top of the cylinder.

I really don't want another race fuel engine, so I'm trying to keep the compression down around 10.5:1.
 

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Discussion Starter #4
Eric, I don't have the heads yet. Still looking.
 

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Discussion Starter #7
Thanks guys!
 
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8.5 to 1 the way the engine is now if it has a 119cc CC, with a 96cc chamber it will be right under 10 to 1.
Yeah, I came up with about the same, the .030" deck cut should put the piston .010" up out of the hole @ TDC, would need an .045" minimum head gasket thickness to be safe....8.2:1 w/119cc now and 9.8:1 with a 99cc head, 10:1 with a 96cc head
 

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Discussion Starter #9
Thanks again!
That helped me narrow down my search. Looks like its closed chamber to get he the compression goal.
 

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Thanks again!
That helped me narrow down my search. Looks like its closed chamber to get he the compression goal.
Thanks again!
That helped me narrow down my search. Looks like its closed chamber to get he the compression goal.
Mark,

Wouldn't it be a lot simpler and possibly cheaper to put a set of pistons in?
Get the compression you really want rather than settling on what a closed chamber ends up at.

Jim
 

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I would agree with the last post. It may be worth looking into changing the pistons to get where you want to be. I think there is more power in airflow differences in an open chamber 2.19 valve head over a closed chamber 2.06 valve head then there is in 1-1.5 numbers of compression. Do the piston, get compression AND air flow.
 
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Discussion Starter #12
Mark,

Wouldn't it be a lot simpler and possibly cheaper to put a set of pistons in?
Get the compression you really want rather than settling on what a closed chamber ends up at.

Jim
Hi Jim,
One of the reasons for this build is to use up some of the many "left overs" from the race car improvements over the years. That being said, I did find some open chamber heads that should put my compression at about 9.5:1. I really don't want to build another "race fuel"engine.
 

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Hi Jim,
One of the reasons for this build is to use up some of the many "left overs" from the race car improvements over the years. That being said, I did find some open chamber heads that should put my compression at about 9.5:1. I really don't want to build another "race fuel"engine.
Edelbrock makes a head with around 100 cc chamber
 

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Hi Jim,
One of the reasons for this build is to use up some of the many "left overs" from the race car improvements over the years. That being said, I did find some open chamber heads that should put my compression at about 9.5:1. I really don't want to build another "race fuel"engine.
Mark,

the problem is, the heads you are pulling off are now also "left overs"......

You are a wheeler, dealer.
Sell off all the 30-40 year old out dated stuff.
A friend of mine educated me years ago on what he calls dead money.

Put in a set of pistons around 12/5-14to1 flying toilet or similar on methanol.

Methanol is SOOOO easy to run and, cheap.

Jim
 

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You can get a Race Rite oval with a 100 cc chamber.... all about the Benjamans
 

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Discussion Starter #16
Mark,

the problem is, the heads you are pulling off are now also "left overs"......

You are a wheeler, dealer.
Sell off all the 30-40 year old out dated stuff.
A friend of mine educated me years ago on what he calls dead money.

Put in a set of pistons around 12/5-14to1 flying toilet or similar on methanol.

Methanol is SOOOO easy to run and, cheap.

Jim

I may be making the change to Methanol in the Vette. I got an email to Weldon to make sure my 2025 fuel pump can handle the volume.

Its too easy to end up with a big money/power engine.
 

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Discussion Starter #17
I may be making the change to Methanol in the Vette. I got an email to Weldon to make sure my 2025 fuel pump can handle the volume.

Its too easy to end up with a big money/power engine.
PS: I don't have the heads for this engine I'm trying to build.
 

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Mark, what's the purpose of this engine? HONESTLY Look at the Flotek 290 head. There 112cc out of the box. BUT can be milled to 102. All new and in the $1000-1500 range ready to bolt on. Those with a thin gasket to help with compression.

FYI I had a 409/425Hp W motor. It was stroked to 474 with GM 454 4" stroke crank. 9.1 compression, 1964 409/425Hp heads with some work, typical GM SR streetcam and Edelbrock 2X4 intake with 2 750 Edelbrock cars, headers. Motor made 575 and pushed a 1961 Pontiac (3800 lbs) to low 10's in the 1/4. Also years ago, we did a 478 BBC (4.500 bore 3.75 stroke) 9.0 to 1 motor, BMF heads, nice solid roller. Don't know the Hp, but did push a 3200lbs big tire street '69 Nova to 9.0's on motor and 8.40 in nitrous.

So you can make some power with low compression.
 

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Discussion Starter #19
Mark, what's the purpose of this engine? HONESTLY Look at the Flotek 290 head. There 112cc out of the box. BUT can be milled to 102. All new and in the $1000-1500 range ready to bolt on. Those with a thin gasket to help with compression.

FYI I had a 409/425Hp W motor. It was stroked to 474 with GM 454 4" stroke crank. 9.1 compression, 1964 409/425Hp heads with some work, typical GM SR streetcam and Edelbrock 2X4 intake with 2 750 Edelbrock cars, headers. Motor made 575 and pushed a 1961 Pontiac (3800 lbs) to low 10's in the 1/4. Also years ago, we did a 478 BBC (4.500 bore 3.75 stroke) 9.0 to 1 motor, BMF heads, nice solid roller. Don't know the Hp, but did push a 3200lbs big tire street '69 Nova to 9.0's on motor and 8.40 in nitrous.

So you can make some power with low compression.
Thanks for your post!

I have a 1995 S-10 Blazer pro street car that I stripped all the good parts off to build the Corvette in my avatar. I'm just using up a bunch of left over parts to build an engine and will stick it back in that.

I just got back from picking up a set of 049 casting steel heads. They look nice. I'm heading to the shop to pull them apart and inspect.
 

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I believe 049s are 73 open chamber heads. 119 cc.
I have a 454 + .030 under the bench w them.
Easy fit for 219/188 valves if not ready done.
But by time you add up costs, there are alternatives mentioned here for a low buck street motor.
Good luck w your engine.
 
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