17 to 1 if you never close the intake valve, there are 27 million threads on this they all say the same thing

 

11:1 is very doable, 12:1 is pushing the limit with the timing, cam, engine load being very very critical

 

11:1 is very doable,12:1 is pushing the limit with the timing, cam, engine load being very very critical

That's funny right there.......My 414 sbc Is 12.36:1
It only Pumps 180 psi................

Think I can run pump gas????????

 

Going from 14:0 to 1 to a lower compression since racing is out of the question for a couple of years.Wondering what is the max compression with 91 octane I can safely get away with on the street.

1965 Mustang
SBF 408w,naturally-aspirated,4.30bore x 4.00 stroke
AFR 225 CNC cyl heads
Dougherty Racing Cams,266/272 @.050,310/310 duration,.694/.672 lift
Edelbrock Super Victor 4150 portered,Pro-Systems 4150 1000CFM carb
Peterson Wide-Vac wet sump pump
C4 trans 10" converter for now

Why is racing out of the ??

Don't see your local in your info there but, is there any access to e85 around you ? Leave the cr where it's at if you can make the switch

 

that would work

 

Right now with two kids in pre school and dumping money into the house,racing is not on the top of the list.Northern Ca,E85 I can get.

 

Right now with two kids in pre school and dumping money into the house,racing is not on the top of the list.Northern Ca,E85 I can get.

not a bad choice in your situation

 

really depends more on the Cam.....
keep your dynamic compression down around 8.5:1 and you can have a very high static compression


I was at 12.5:1 on 93 octane pump gas here in TN....but I also had a large cam that got my dynamic compression down around 8.3:1
and I was exactly the same timing as I had on my motor when it was 10:1 with a stockish cam

 

Set it up for 12 to 1 use 93 pump bring your total timing back a bit, if you want to race it run VP-109 or even better still leave the engine as is and buy a good E85 carb from Sullens you might even make more power.

 

I was thinking, dont touch the engine just get a E85 carby of Mark and you will be very happy.
http://www.marksullense85carburetors.com/

 

not to thread jack, but how do you calculate dynamic compression?

 

It's the same as calculating static compression, except the you shorten the stroke in your calculation by the distance that the piston travels upwards from BDC to your intake valve closing point. The compression stroke doesn't "actually" start (as the engine sees it) until the intake valve closes. The trick is in knowing exactly when your intake valve closes. Not as easy as it sounds. Moot point though, as the biggest factor is actually the dynamic CYLINDER PRESSURE. You can idle around all day at 14:1 compression on 87 octane gas.......but the first time you run an efficient engine up towards it's high VE area, it's going to detonate. Same with a hot street type engine. It may run just fine at 11:1 on 93, but the cylinder pressure changes as it gets more efficient in the upper rpm's.

 

There is one on Wallace. BUT it also will depend on the way the whole car is set up for loading the engine.

 

I have an engine sim that calculates dynamic compression.....not sure as to how accurate it is for that part...but my last engine matched the guestimate on the dyno pretty closely...so I assumed it was somewhat correct.

 

easier question, how many miles are you planning on putting on it?

500 or less a year? dont even worry about it, just order a 55 gl drum of the good stuff and drive with a smile..

 

Peak TQ is not your friend on pump gas. Jeff S, Move along nothing here to see.......................

 

LOL, you catch me lurking?

 

Whats the smallest fuel pump you can get away with E85

 

I would say a A1000