what do you guys think

[69hemibeep]

I'm running a std bore AMC 401 std stroke with KB 392 pistons witch are rated 10.9-11.8 depending on chamber volume. My iron heads are the big 58cc with cleaning and porting but I never cc'ed them so that's a mystery. I run 10 degrees on the crank with a total 34, I just did a dry compression test witch averaged 160 with a high 163 using a std felpro blue head gasket. The cam is a Lunati solid 249@.050 duration or 306 advertised,552 lift 1.6 rocker with a 104 center line. This is in a 2600 lb sand jeep 2wd used for cruising the dunes and a 1st 2nd shift on long wide open hill climbs with a torque flight and 4.56 gears in the butt. My question is do I need to blend fuel as I have in the past for more octane or am I ok with pump gas?

 

[george68hemirr]

i am running 11.5 to 1 compression with 93 octane pump gas......keep in mind i have a aluminum block and heads which gives me an extra point in compression for pump gas....iron would be 10.....10.5 to 1 .....my 2 cents

 

[69hemibeep]

i am running 11.5 to 1 compression with 93 octane pump gas......keep in mind i have a aluminum block and heads which gives me an extra point in compression for pump gas....iron would be 10.....10.5 to 1 .....my 2 cents

All we have is 91 octane with 10% alcohol, so I better keep blending to boost the octane.

 

[69hemibeep]

Well I used an online calculator and mixed 13 gal of 110 to 37 gal of 91 for 50 gallons of about 96 octane. I headed out Saturday till Thanksgiving to tear up the dunes :drive: :drive: P.S. what do you guys pay for race fuel, this is 110 Sunoco pumped out of the ground for $7.25 per gal.

 

[Jim S.]

$6.99 for 110 race gas at the Citgo station up here.

 

[george68hemirr]

Well I used an online calculator and mixed 13 gal of 110 to 37 gal of 91 for 50 gallons of about 96 octane. I headed out Saturday till Thanksgiving to tear up the dunes :drive: :drive: P.S. what do you guys pay for race fuel, this is 110 Sunoco pumped out of the ground for $7.25 per gal.

same price....$7.25 unless it went up since a month ago ......114 for only 412.00 a gallon.....at the air port up the street they have 120 octane.....have to see how much for that.....that should burn some holes in your pistons :drive:

 

[abodybill]

I mix sunoco 94 with 110 race fuel for my Dart.

Race fuel is $6.00 at the citgo and $6.50 at the track.

 

[moparchris]

160 with that cam on that LSA is pump gas territory. I am not familiar with AMCs chamber design but I run 180psi on pump gas with no problem (small block with X head) and as high as 200psi on pump gas with a very good chamber (gm fast burn/vortec). Also you are only 34 degrees of timing so unless you run it at 200 degrees with 100 degree air temp, then I would say you are safe.

 

[69hemibeep]

160 with that cam on that LSA is pump gas territory. I am not familiar with AMCs chamber design but I run 180psi on pump gas with no problem (small block with X head) and as high as 200psi on pump gas with a very good chamber (gm fast burn/vortec). Also you are only 34 degrees of timing so unless you run it at 200 degrees with 100 degree air temp, then I would say you are safe.

Chris, I think I'm on the lower end of the compression scale for these pistons. The heads have never been milled and the heads have a big wedge chamber. The pistons have a 3/8 inch raised portion the covers about a third of the top with valve relieves. I'll try and get a pic of another head thats in the ole jeep barn.