Static Compression to Octane

-

josekh7

Well-Known Member
Joined
Apr 26, 2013
Messages
95
Reaction score
2
Location
los angeles
Hi Guys i just finished my BB440 and i am about to break it in. I used edelbrock 84cc heads flat piston with 2 valve reliefs which brought me up to 10.23 compression. Can i use 91 octane or whats the safety area on octane gas i can use?
 
Not enough info. You'll need to list cam specs. Duration @.050, lobe separation and installed centerline.

Otherwise start with high octane and work down until it grenades - then build the next one and always use more than what kills this one ;)
 
Aluminum heads should let you get by with 91. A short duration cam or low overlap profile could make it a little dicey.
 
RPM-Range: 2500-6800 Value Lift Int/Ext: .485/.485 Value Lash Hot Int/Ext: .000/.000 ADV Duration Int/Ext: 280/280 .050 Duration Int/Ext: 232/232 Lobe Center: 108

Isky 280 mega hydrolic
 
My build 440 lunatti solid roller 237/243@.050 .566/.577 lift. Eddy 84cc static 9.9-1. MRL recoommended 89 and up. I would contact your builder and ask them what they recommend. Safest way to go in my opinion.
 
Ask your builder for the measured specs he used ( combustion chamber volume, volume of the area from the top of the piston, If the deck is above the piston top, Gasket volume and the formula to calculate his answer. It will be good info in the future for any other project you may want to build and will help you in your parts choices.
Here is a posting by Krazycuda a few years back.
http://www.forabodiesonly.com/mopar/showthread.php?t=278215
 
Another note here is don't forget altitude and timing. They have an affect on what compression you can run.
 
how would you listen to pinging or detonation?

Sounds like marbles in a glass jar - nasty.

Keep the timing low, start with 93. Check spark plugs as you go. Detonation/pinging will leave little specs of aluminum (piston) on things. Sometimes.

Based on your questions and concerns I'd contact your engine builder and have some conversations regarding what you should do and how he can help.

Early tuning on a new engine can be tough and inexperience can lead to costly mistakes in a hurry. Higher compression tends to be less forgiving of timing mistakes and the like.
 
I would run 93 and I don't think you'll have a problem but a lot of no detonation is about your tuneup. So - listen for pining, and check the plugs with a lit magnifier for signs of aluminum transfer.
 
........I always build the engine to my fuel choice, not the other way around, as many ppl don't want to buy the more expensive fuels...........kim........
 
That thing will probably run on 87.
 
Way to muddy things with irrelevant specs. Cam, chamber design, quench, it all matters. 11.25:1 on 93 isn't even half the conversation.

Ok here you go, cam is 520/540 lift on 110lsa, 244/252 @.050. Chamber is a "J" head, heat crossover blocked, no quench, no sharp spots on Pistons/heads, polished exhaust port, VERY cold plugs, 14 initial 30 total all MSD, 10w30 oil flowing faster to pull heat out, I'll even add a bit more, thermo coated headers, J54 hood which allows a little cold air under the hood, elec fuel pump, 4 row radiator without trans cooler, sealed and air dams to direct airflow to radiator, 4,400 stall with stand alone cooler, 3,450lbs demon with driver, runs and sounds great !! Oh 195psi cranking.
 
Ok here you go, cam is 520/540 lift on 110lsa, 244/252 @.050. Chamber is a "J" head, heat crossover blocked, no quench, no sharp spots on Pistons/heads, polished exhaust port, VERY cold plugs, 14 initial 30 total all MSD, 10w30 oil flowing faster to pull heat out, I'll even add a bit more, thermo coated headers, J54 hood which allows a little cold air under the hood, elec fuel pump, 4 row radiator without trans cooler, sealed and air dams to direct airflow to radiator, 4,400 stall with stand alone cooler, 3,450lbs demon with driver, runs and sounds great !! Oh 195psi cranking.

Perfect! Now we can see how you get away with it ;)
 
Perfect! Now we can see how you get away with it ;)

It's not like it's ever been a secret. He's shared his build a hundred times I bet. Probably the best pump gas build on here, IMO.
 
Hi Guys i just finished my BB440 and i am about to break it in. I used edelbrock 84cc heads flat piston with 2 valve reliefs which brought me up to 10.23 compression. Can i use 91 octane or whats the safety area on octane gas i can use?
Like Rusty said, it'll probly run on the crappiest gas you can find, unless you put in a cement truck with hiway gears, with a rotten tune.
Well he didn't actually use those words, I'm paraphrasing.
 
11.78cr Lunati 292/512H, eddy heads, 36* total, 93 octane, 340 .040 over w/360 truck crank, 3yrs no problems. Like MRL said, it all depends on the combo!
 
-
Back
Top