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Compression ratio & 1.5 vs 1.6 rockers

1967coronet440

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Evening gents, 2 questions for you guys. At what compression ratio is it necessary to start using race gas, also what is the difference between 1.5 & 1.6 rockers? Go easy on me I'm a rookie! Trying to figure out which pistons to get with the stroker kit so I can stay on pump gas, and what rockers to get with my cam. a little background on my current build - 440 block, scat 505 stroker, trick flow power port 240 heads, leaning towards comp xtreme energy 286 solid roller cam.

As always Thanks for your help
 
Rocker ratio's are simple, multiplication by lever. For every distance of 1x that the pushrod moves, the rocker moves the valve 1.5x (or 1.6x as the case may be).
 
As far as fuel Requirements go, it comes down to the dynamic compression ratio.

IF you can surply the static ratio and the actual cam you intend to use, it would be of great help. Some of us can calculate the dynamic with the info I mentioned and some know via experience with the info I asked for.

Generally speaking, a pump gas car can live easy with a 10-1 iron head or at 11-1 aluminum head with the cam you mentioned above.

Also realize you need not grab every last bit of compression to make excellent power. There is more power in the engine with great flowing heads and other great flowing parts. Intake, headers, the exhaust system.

You will grab more power with that than a tiny 3% more with an extra single point of compression.
 
The compression ratios are not really a limit on their own. So the question doesn't really have a definitive answer.
In terms of your build - I build pump gas street engines for the most part. I use the dished pistons and place the deck height above deck because I'm a firm believer in using quench. The static ratio usually lands just over 10:1 and with the cams I like to run I land the dynamic arouns 8.25:1 which is good for the pump swill we have. You should be working with your builder or machinist to determine the package because it all works together.
 
If the cam is close to stock, a true 10-1 big block Mopar will not run on pump gas at full timing with iron heads on 93 octane. Pick you cam and compression as a package. Larger cam , more compression.
Doug
 
Evening gents, 2 questions for you guys. At what compression ratio is it necessary to start using race gas, also what is the difference between 1.5 & 1.6 rockers? Go easy on me I'm a rookie! Trying to figure out which pistons to get with the stroker kit so I can stay on pump gas, and what rockers to get with my cam. a little background on my current build - 440 block, scat 505 stroker, trick flow power port 240 heads, leaning towards comp xtreme energy 286 solid roller cam.

As always Thanks for your help
I run the same stroker set up. a little bigger solid roller (292 extreme) w/ 1/6 rockers, about .620-.628 lift, 10.3 comp., icon dished pistons , .039 cometic gaskets. w/ a better flowing raised port head. "that`s still not much cam compared to the chevy boys." 91 octane REAL gas only. wish I`d went w/ a 3000 convertor, mine is a 3500-3800, and it sure seems mushy on the street, I would like for it to lock up(?) a little sooner. that big a motor doesn`t need much help down low. good luck !
 
Thanks all, perhaps I'm jumping the gun a bit I just dropped off my block at the machine shop I am trying to plan ahead.
 
I run the same stroker set up. a little bigger solid roller (292 extreme) w/ 1/6 rockers, about .620-.628 lift, 10.3 comp., icon dished pistons , .039 cometic gaskets. w/ a better flowing raised port head. "that`s still not much cam compared to the chevy boys." 91 octane REAL gas only. wish I`d went w/ a 3000 convertor, mine is a 3500-3800, and it sure seems mushy on the street, I would like for it to lock up(?) a little sooner. that big a motor doesn`t need much help down low. good luck !
Thanks, maybe I will go with the bigger 292 grind cam.
 
Nothing wrong with that, you are above average. Most don't plan enough, then wonder what went wrong.

Curious, what machine shop are you using?
The motor is being built through Chicago connection, first time going through them but they did a hell of a job on a few of my buddies motors, including a 1000hp lsx. Same guy owns the local drag strip.
 
Nothing wrong with that, you are above average. Most don't plan enough, then wonder what went wrong.

Curious, what machine shop are you using?
Just seen you're from northern Indiana, the guy owns US 41 drag strip. How is the idle on that 292 cam, comp has it listed as radical.
 
The motor is being built through Chicago connection, first time going through them but they did a hell of a job on a few of my buddies motors, including a 1000hp lsx. Same guy owns the local drag strip.
Sounds like maybe you found someone that knows what he's doing but the LSX engines are a different animal than our older Mopars. Yeah, it's still an engine but not all engines are created equal. Is the LSX carbed or EFI? The X engine was designed with racing in mind while ours really wasn't. Anyways, one thing I like to look at is how much cranking PSI will the cam produce with a given static compression ratio. Once you get up around the very high 100's range, you need to be careful with pump gas. If the build is right, you can go with the higher PSI's but you can also make a low compression engine ping it's *** off just as easy as making a 11 to 1 engine run right on pump gas if you know what you're doing. Quench is also something I like to consider in the build and having good flowing heads and the list goes on.
 
Sounds like maybe you found someone that knows what he's doing but the LSX engines are a different animal than our older Mopars. Yeah, it's still an engine but not all engines are created equal. Is the LSX carbed or EFI? The X engine was designed with racing in mind while ours really wasn't. Anyways, one thing I like to look at is how much cranking PSI will the cam produce with a given static compression ratio. Once you get up around the very high 100's range, you need to be careful with pump gas. If the build is right, you can go with the higher PSI's but you can also make a low compression engine ping it's *** off just as easy as making a 11 to 1 engine run right on pump gas if you know what you're doing. Quench is also something I like to consider in the build and having good flowing heads and the list goes on.
The lsx is fuel injected, damn thing knocked the cobwebs off the rafters when he fired it up. The guy is actually a mopar junkie his store front is nothing but mopar parts, but he will build any motor. I've seen quite a few of his builds run in the track and they are strong. I'm going to give him my parts list that I've come up with and take his recommendations if he advises any changes.
 
The lsx is fuel injected, damn thing knocked the cobwebs off the rafters when he fired it up. The guy is actually a mopar junkie his store front is nothing but mopar parts, but he will build any motor. I've seen quite a few of his builds run in the track and they are strong. I'm going to give him my parts list that I've come up with and take his recommendations if he advises any changes.
I'm looking forward to the build! I want to do one more....for me this time....and have some ideas floating around in my skull that I want to try. I already have the block, crank, rods and several sets of pistons to choose from sitting on the shelf. The heads are nothing exotic....Eddy RPM's. I'm going to basically run them out of the box but do a bit of exhaust port cleanup and see how they do. I have an old .660 lift Isky roller that needs to be reground due to a failed valve spring letting a lifter exit it's bore and leaving it's sister lifter to just sit and spin :D Still not sure of the final numbers for it yet...
 
I'm looking forward to the build! I want to do one more....for me this time....and have some ideas floating around in my skull that I want to try. I already have the block, crank, rods and several sets of pistons to choose from sitting on the shelf. The heads are nothing exotic....Eddy RPM's. I'm going to basically run them out of the box but do a bit of exhaust port cleanup and see how they do. I have an old .660 lift Isky roller that needs to be reground due to a failed valve spring letting a lifter exit it's bore and leaving it's sister lifter to just sit and spin :D Still not sure of the final numbers for it yet...[/QUOT

I can't wait to get the motor back. This is the first one I'm doing by myself. Me and my father did the current motor in my coronet just a stock bottom end 440 with 906 heads and a 484 purple shaft. He didn't want me getting too crazy. Now I'm building what I want. Next winter I'm ripping the hemi out of my SRT and building a 440 stroker. Hope all goes well with what you planning on building and I'll be sure to update as mine makes progress. And I'm sure I'll have many more questions!
 
Just seen you're from northern Indiana, the guy owns US 41 drag strip. How is the idle on that 292 cam, comp has it listed as radical.

Yeah, I know where the drag strip is but I don't know him. As for the 292 cam, I think you want to talk to "not so famous Bob" about that.
 
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Sounds like the place is reputable. Tell them what you want, and let them deliver. If you are not sure why he's going in one direction or another with it, ask and listen. Builders are like cooks. One good one makes a great dish. Too many ruins it.
 
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