In a post about gaskets another memeber mentioned he thought that going from 12.5 to 15 would only be about 12 hp. I disagree and figure lot more.

I figure lets see what other have found, just to give both opinions a chance.

So if you have increased compression in a engine with little to no other mods .What was gain, what was increase and if other mods what do you feel was main contribution of compression increase.

While we are at it lets here from anyone on bore size increase. Reason I will be going up .125 bore and 2.5:1 on compression. Well maybe few other things that will better increase coming first. Some for power, some consistency and some because I damn well want them.

Yes I know it is bracket engine and power not issue. That is why half of guys here are running 600 plus cubic inch stuff.Me I am just trying to get as much as possible with cheap as Hemi stuff and yes its all made in America.

This message has been edited. Last edited by: wideopen231,

Interested in seeing what comes up in this thread. From what I understand higher compression helps substantially, but also has diminishing marginal returns.

So a jump from 10-12 would offer more of an increase than 14-16.

I did the opposite on my 434. I cut the CR from 15.6 to 14.2, and only lost about .02-.03 in the 1/8 mile, in my Nova. Saving $5per gallon on lower octane fuel. My checkbook is much happier.

At what point (ratio) is more compression a diminishing return??

quote:

Originally posted by wideopen231:
In a post about gaskets another memeber mentioned he thought that going from 12.5 to 15 would only be about 12 hp. I disagree and figure lot more.

I figure lets see what other have found, just to give both opinions a chance.

So if you have increased compression in a engine with little to no other mods .What was gain, what was increase and if other mods what do you feel was main contribution of compression increase.

While we are at it lets here from anyone on bore size increase. Reason I will be going up .125 bore and 2.5:1 on compression. Well maybe few other things that will better increase coming first. Some for power, some consistency and some because I damn well want them.

Yes I know it is bracket engine and power not issue. That is why half of guys here are running 600 plus cubic inch stuff.Me I am just trying to get as much as possible with cheap as Hemi stuff and yes its all made in America.

Do you understand what your asking vs basically no specific information given???

The answer is , it depends on what your starting with and I am not just talking about C.R. The entire combo matters and will impact the results.

Such as, if your cam is too big for your combo now, an increase in compression would show a much larger increase vs if you had the right cam to start with...

Sometimes more compression from a larger dome can hurt performance

the list goes on and on!

So it depends on your specific combo to start with...…...

quote:

Originally posted by TOP38:

quote:

Originally posted by wideopen231:
In a post about gaskets another memeber mentioned he thought that going from 12.5 to 15 would only be about 12 hp. I disagree and figure lot more.

I figure lets see what other have found, just to give both opinions a chance.

So if you have increased compression in a engine with little to no other mods .What was gain, what was increase and if other mods what do you feel was main contribution of compression increase.

While we are at it lets here from anyone on bore size increase. Reason I will be going up .125 bore and 2.5:1 on compression. Well maybe few other things that will better increase coming first. Some for power, some consistency and some because I damn well want them.

Yes I know it is bracket engine and power not issue. That is why half of guys here are running 600 plus cubic inch stuff.Me I am just trying to get as much as possible with cheap as Hemi stuff and yes its all made in America.

Do you understand what your asking vs basically no specific information given???

The answer is , it depends on what your starting with and I am not just talking about C.R. The entire combo matters and will impact the results.

Such as, if your cam is too big for your combo now, an increase in compression would show a much larger increase vs if you had the right cam to start with...

Sometimes more compression from a larger dome can hurt performance

the list goes on and on!

So it depends on your specific combo to start with...…...

Well said.

I’m pretty sure you’re an alcohol guy, and I was told by multiple sources when building my injected 632 that there was nothing to be gained by going above 14:1.

Maybe that’s specific to a conventional-head BBC.

quote:

Originally posted by TOP38:

quote:

Originally posted by wideopen231:
In a post about gaskets another memeber mentioned he thought that going from 12.5 to 15 would only be about 12 hp. I disagree and figure lot more.

I figure lets see what other have found, just to give both opinions a chance.

So if you have increased compression in a engine with little to no other mods .What was gain, what was increase and if other mods what do you feel was main contribution of compression increase.

While we are at it lets here from anyone on bore size increase. Reason I will be going up .125 bore and 2.5:1 on compression. Well maybe few other things that will better increase coming first. Some for power, some consistency and some because I damn well want them.

Yes I know it is bracket engine and power not issue. That is why half of guys here are running 600 plus cubic inch stuff.Me I am just trying to get as much as possible with cheap as Hemi stuff and yes its all made in America.

Do you understand what your asking vs basically no specific information given???

The answer is , it depends on what your starting with and I am not just talking about C.R. The entire combo matters and will impact the results.

Such as, if your cam is too big for your combo now, an increase in compression would show a much larger increase vs if you had the right cam to start with...

Sometimes more compression from a larger dome can hurt performance

the list goes on and on!

So it depends on your specific combo to start with...…...

No. I am asking what others have found when they changed compression. I never asked how much t would make difference on my combo or anyones specific combo. Just what they had seen.

quote:

Originally posted by Lenny5160:
I’m pretty sure you’re an alcohol guy, and I was told by multiple sources when building my injected 632 that there was nothing to be gained by going above 14:1.

Maybe that’s specific to a conventional-head BBC.

I agree there is less power increase when going for 14 to 15 than there is when going 13 to 14.Gains do drop.

In my case it just gives me more flexablity/ If I t 15 with .040 gasket I can step up gasket and drop compression to what I want.well to a point. Every .010 gasket if worth 2.45 cc's.

Now on topic of dome. I agree with comment that big dome can hurt performance. This iver true on Chevy head design. Mine is in Hemi motor and its going to have a dome if you have any compression. Again not looking to compare results from Chevy to Hemi. Just a question as to what other have seen.

My biggest gains will be in valve pockets. Pistons I have have a ton of piston to valve. Like .050 to .080 more than needed.

On two of my engines that were both for the sake of argument were nitrous engines we lowered the compression . Both after lowering the compression 1 whole point from 15.0-1 to 14.0-1 lost 50hp on the dyno and both slowed just over a tenth in the 1/4 on engine only as well as on the nitrous. In the long run i ended up having to spray more to run where i was at before so it wasn't worth dropping it. It was only lowered to allow me to be able to put a bigger tune up it to it which i never did.

50 is more than I would have thought. Thanks for straight out reply.

Me too but both the dyno and time slips showed it. It affected my engine combo for sure. Both of mine are spread port head deals at 600+ cu in.

quote:

Originally posted by wideopen231:

quote:

Originally posted by TOP38:

quote:

Originally posted by wideopen231:
In a post about gaskets another memeber mentioned he thought that going from 12.5 to 15 would only be about 12 hp. I disagree and figure lot more.

I figure lets see what other have found, just to give both opinions a chance.

So if you have increased compression in a engine with little to no other mods .What was gain, what was increase and if other mods what do you feel was main contribution of compression increase.

While we are at it lets here from anyone on bore size increase. Reason I will be going up .125 bore and 2.5:1 on compression. Well maybe few other things that will better increase coming first. Some for power, some consistency and some because I damn well want them.

Yes I know it is bracket engine and power not issue. That is why half of guys here are running 600 plus cubic inch stuff.Me I am just trying to get as much as possible with cheap as Hemi stuff and yes its all made in America.

Do you understand what your asking vs basically no specific information given???

The answer is , it depends on what your starting with and I am not just talking about C.R. The entire combo matters and will impact the results.

Such as, if your cam is too big for your combo now, an increase in compression would show a much larger increase vs if you had the right cam to start with...

Sometimes more compression from a larger dome can hurt performance

the list goes on and on!

So it depends on your specific combo to start with...…...

No. I am asking what others have found when they changed compression. I never asked how much t would make difference on my combo or anyones specific combo. Just what they had seen.

So you don't know what your asking but expect to receive worth while responses??

quote:

Originally posted by TOP38:

quote:

Originally posted by wideopen231:

quote:

Originally posted by TOP38:

quote:

Originally posted by wideopen231:
In a post about gaskets another memeber mentioned he thought that going from 12.5 to 15 would only be about 12 hp. I disagree and figure lot more.

I figure lets see what other have found, just to give both opinions a chance.

So if you have increased compression in a engine with little to no other mods .What was gain, what was increase and if other mods what do you feel was main contribution of compression increase.

While we are at it lets here from anyone on bore size increase. Reason I will be going up .125 bore and 2.5:1 on compression. Well maybe few other things that will better increase coming first. Some for power, some consistency and some because I damn well want them.

Yes I know it is bracket engine and power not issue. That is why half of guys here are running 600 plus cubic inch stuff.Me I am just trying to get as much as possible with cheap as Hemi stuff and yes its all made in America.

Do you understand what your asking vs basically no specific information given???

The answer is , it depends on what your starting with and I am not just talking about C.R. The entire combo matters and will impact the results.

Such as, if your cam is too big for your combo now, an increase in compression would show a much larger increase vs if you had the right cam to start with...

Sometimes more compression from a larger dome can hurt performance

the list goes on and on!

So it depends on your specific combo to start with...…...

No. I am asking what others have found when they changed compression. I never asked how much t would make difference on my combo or anyones specific combo. Just what they had seen.

So you don't know what your asking but expect to receive worth while responses??

\
I know exactly what I asked. I asked what folks had seen with their stuff when changing compression. It has nothing to do with what My stuff will do. What is so hard to get?

I seriously doubt anyone here is running a tfx-92 Hemi with 296 at .050 cam with 825 lift with 116 lobe centerline,12.5:1 with ss dyke top and gapless second and std tension 3/16 oil, BAE billet heads(175 cc chamber),stage 5 rockers, topped with sheet metal intake with two blade injector running 16 nozzles and using a dsr pump pumping 6.9 gpm at 8000 rpm all of which is fired off MSD mag 12.
Which is why I did not give my info it had nothing to do with question.

Any Hp to gain from 11/1 to 12/1 406 sbs? Wide open on your motor I would not go thinner then 40 thou head gasket.Play it safe for what your doing. Are you gonna go back bracket racing one day

Footloose,
Only reason for gasket question in other thread was I have gotten a set of rods. Well two sets at a great price that are .020 shorter than mine. Just getting compression back where is now there. All clearances will be same as now. About only thing that can happen is push gasket out.

As for this thread I am simply seeing what others found when they changed compression. Thru various engine programs and cpl dyno guys and cpl pulls I know what mine will should do power wise. I just like gather info on anything engine related for the knowledge for future reference if need,
As for bracket racing .While I built car for mostly bracket racing. After years of heads up and now working with a TA/D team on A/fuel its hard to get real amped up on running car w/o tuning on it between runs.Sorry I just love the hell out of tuning the car.Driving is second place for me.I know I pissed lots off here with that comment and its not down playing the work it takes to win at bracket racing. Heck in lots of ways its harder.
Maybe once I get few consistent laps in and run cpl weekend deals I will get more amped up for it. Still will ne hard as hell to control the crew chief inside that wants to tweak this and try that.

[QUOTE]Originally posted by wideopen231:
"116 lobe centerline,12.5:1"

That stood out….I don’t know for sure if you’re speaking LSA or ICL, but either way, I believe you will be disappointed with a N/A induction system, that compression ratio and cam grind. I get the tuning thing you enjoy, but I would spent the 4 bills for another grind so your tuning efforts show some dividends.

Typically you will always find power with an increase in compression unless some of the other factors are in play such as combustion damming or the combo is already at peak efficiency with the present ratio. I follow what Top38 is eluding too as there is no one answer fits all, but interesting topic….

I would also choose another top ring for N/A as I don't believe you will have the cylinder temperature or pressure to use that efficiently.....or even getting it to seat properly.

I spent zero on the cam grind in fact I have another on shelf along with 10 or 12 others of different grinds. Have another cam ordered for car but like everything in covid world it takes for freaking ever to get now days. New c am is 284/286 112 with .800 lift.

As for ring package they have always worked fine with NA motor.We ran them in one lil brother ran for while. We switched to different piston and rings at same time with only .025 gain and I figure the extra .030 piston with extra compression 11.6 to 12.5 was to blame for gain.I am not saying they are perefect for na motor. I do have to allow for times when I want to play and drop big load of nitro in tank and bolt on bigger pump.At whcih time I will probably need new converter or a bolt together that can be changed. That deal is whole different story but does figure into rings part of short block. Can't even order pistons till new cam is here. I want to run piston to valve,send current piston with numbers to manufacture and have them leave extra material in pockets and I will fly cut to fit ninimum clearance. 15:1 in Hemi is a push.

I never disagereed with top38 on what others see with theirs will probably have little to do with my result.Again totaly different than about anyone here car and owner.LOL Now total seal did recommend gapless top wset with 1/16,1/16,3/16 ring package if I order new pistons. That is still up in air. Even with .125 extra bore and 2.5 increase in compression they are not biggest bang for buck and actually around 3 or 4th on list. Heck Nitro is biggest bang for buck or bucks at 40 per gallon.

Right now with cam and pistons in motor I have 215 cranking compression.I figure for a cam that is 12 to 15 degrees too big that is not terrible. The few shot I have gotten show same 4.90's shaking and peddling is not that crappy for 482 ci.

This message has been edited. Last edited by: wideopen231,

When I dropped my compression down from 15.9 to 14.7 I noticed ZERO ET change. None. Your mileage may vary.

I do think when you get too high compression it limits your tuning window and options. You obviously do everything different than the rest of us maybe it will work for you.