is 11.2:1 compression too much for 91 Octane

[moper]

Ok, keep on keeping on then fools. I have spent the last 20 years taking out the junk 268 comp on 110 LSA and using ANYTHING close with less LSA and they are easier to tune, have LESS cranking pressure.LOL.. so you've sofened up all those combinations. Good for you...lol.

Do some study and see what big HP engines are now using for LSA's (hint hint I've used them as tight as 98 and I know for FACT some have gone to 95).
The best builders I know and have talked to and learned from do what's required on a specific build to reach a specific goal. They don't fixate on one narrow window of choices and limit themselves and they certainly don't "hate Comp Cams".

And most of the people I know STILL use comp junk but the order the SAME lobe without the comp junk catalog standard 110 LSA.
(meant as sarchastic as possible)So they run "Chevy lobes" ??!! lol.

 

[roccodart440]

Look at the EMC in December's Hot Rod Magazine.

#1 HP King a Ford 572 with a mild duration, high lift hydraulic roller cut by COMP CAMS.

 

[AndyF]

Hi I'm wondering if 11.2:1 compression is too much for 91 Octane (highest we have available here) to run properly without engine knock (pinging).

Engine is a stoked 440 (500 CUI) with edelbrock aluminum heads, roller rockers, RPM Intake custom ground hydraulic cam (540 lift), TTI headers and a 3" exhaust. Car has a 727 with 3800 stall and 3.73 gears, engine is currently in a dart.

That's pretty much all the info I have on 'r. I've read somewhere that Aluminum heads will take about a point more compression than steel heads, so just wondering if it would be fine or if it might be borderline running on 91 octane

Can't tell you unless you know which pistons are in the engine and what the deck height was set at. If you don't know that information then you'll have to pull a cylinder head off to see how the engine was built. If the engine has flat top or dished pistons and the pistons are set at close to zero deck, then you have a fighting chance of running that engine on pump gas. But if the pistons are down in the hole and/or you a have thick head gasket on there then no, you're not going to have much luck running it on pump gas.

Renegade Fuels sells an unleaded gas called Hot Rod 102 and even with the 102 octane rating they recommend 11:1 compression or less. They might be a tad conservative, but if anyone is going to know what works it would be the engineers at a fuel company.

 

[j par]

Can't tell you unless you know which pistons are in the engine and what the deck height was set at. If you don't know that information then you'll have to pull a cylinder head off to see how the engine was built. If the engine has flat top or dished pistons and the pistons are set at close to zero deck, then you have a fighting chance of running that engine on pump gas. But if the pistons are down in the hole and/or you a have thick head gasket on there then no, you're not going to have much luck running it on pump gas.

Renegade Fuels sells an unleaded gas called Hot Rod 102 and even with the 102 octane rating they recommend 11:1 compression or less. They might be a tad conservative, but if anyone is going to know what works it would be the engineers at a fuel company.

I imagine he figured it out 5 months ago ! !?? LOL

 

[rumblefish360]

Still worthy information to add.

 

[j par]

Still worthy information to add.

Wait a minute? Let's read that again, was he saying down in the hole i.e. less compression and could not run pump gas, and zero deck i.e. high compression he can run pump gas?

 

[AndyF]

Yes. Quench is important.