Hemi Compression Ratio You've Used

[Nxcoupe]

Looking to see what compression ratio some of you have used in your hemi builds. I've ran 12.5 to 1, but that was on Sunoco 96 back in the day.
Just curious what some of you are using in your builds and what fuel you are running.

Thanks in advance. I'm looking for input from guys that are driving their cars and have a hemi.

 

[6PKRTSE]

I have 10.5:1 with the Hemi in my Challenger and run on 93 octane pump gas on the street and run VP NO2 on spray at the track.

 

[Darter6]

I sold my Hemi car in April. 472 Indy 426-1 aluminum heads.
We wanted pump gas friendly because car was built for street only. (91 octane here in southern Nevada)
9.8 to 1 Very street friendly.

 

[snakeoil24]

Really need to know what cam your going to use before you go further and what you going to do with it. Also remember to be conservative with total timing and get a set of stage 5 aluminum heads.

 

[INTMD8]

Mine is 438ci, iron block and heads. 12.4-1 262/262 @.050

E85 mainly though has EFI with a composition sensor so if necessary to run on gasoline auto adjusts fueling and removes timing.

 

[69 hemibee]

Mine is a 10.5:1, nothing too radical with the internals. Run 93 octane and she never misses a beat.

 

[Hemirunner]

Looking to see what compression ratio some of you have used in your hemi builds. I've ran 12.5 to 1, but that was on Sunoco 96 back in the day.
Just curious what some of you are using in your builds and what fuel you are running.

Thanks in advance. I'm looking for input from guys that are driving their cars and have a hemi.

I ran 12:1 on 93 octane for a decade on various drag weeks. Cam was 276/[email protected]. I sprayed it with a splash of 110 octane on top of that. Current 9.5:1 combo did Midwest Drags on 87 octane adding VP C16 once I arrived at each track.

 

[Paul_B]

I’m at 10.5:1 in my 528 hemi with MP iron heads. It runs on pump 93. I did back the timing off to just 30 degrees total. It likes more timing when on race gas when it was dyno’d.

 

[64 Sportfury]

10.5 to 1, 250ish solid flat tappet cam by Porter Racing Heads, MP ported iron heads, MP cross ram w/worked holleys and a 5 speed. Timing -18deg initial, 34 total. Vehicle weight is 4250lbs. Plugs read very good for timing and AFR meter readings good.

 

[gtx6970]

Im told mine is about 11.5. Give or take a 10th

it would like base timing up near 18 or 19

But to get it to run on pump gas . Ive got it backed down to about 13 -14 base range.

Otherwise it requires race gas / high test mix.
And 110 octane near me is $10 per gallon

 

[w.Hudson]

I put plenty of miles on a Hemi with 10.3 to 1 compression. Iron MP heads with a Barton solid flat tappet cam. Duration @ .050 was 252 degrees and
.543 lift.
Ran it on 93 octane pump gas with no problems. Base timing was 18 degrees with a total of 34 degrees.

 

[Nxcoupe]

Really need to know what cam your going to use before you go further and what you going to do with it. Also remember to be conservative with total timing and get a set of stage 5 aluminum heads.

Thanks, but I'm not asking people for opinions on what compression ratio I should use, I'm asking what people with hemis are running in their current combos.

 

[snakeoil24]

We understand that it’s dictated by what your looking to do I run 10:1

 

[diesel_lv]

Thanks, but I'm not asking people for opinions on what compression ratio I should use, I'm asking what people with hemis are running in their current combos.

I've found quite often there are some who just like to post, without reading or comprehending what they've read.

 

[snakeoil24]

I've found quite often there are some who just like to post, without reading or comprehending what they've read.

Diesel are you confused?

 

[diesel_lv]

All the time just doesn’t get it!

I'm referring to you.

 

[snakeoil24]

I'm referring to you.

Then you also don’t get it

 

[66 Sat]

I think Snakeoil is asking a reasonable question. Yes, get the conpression ratios of what other folk are running, but also state your intended use (mild, hot street, street/strip, drag only etc) as it will help with the advice given. Luckily most who post their compression ratio are also giving their use and fuel they run, but if all they did was answer the OP's question you'd have a bunch of compression ratios with no context of how well they run, what usage etc.

 

[Nxcoupe]

Again, thanks, but I am not looking for opinions. I want real world experience from hemi owners who drive their cars and know what's in their engines.

 

[Bold & Old]

9.5-1 but not on the road yet........ @ 5800 hydraulic lifters.... dynoed

A fun car with worrying about doing any higher end issues.

still yielded 580 and 555. plenty for me

A good mid-range... cam.

39 degrees total revised 12/28/22 (01247)