Does anyone have Aussie heads with a stock bottom end? I built a 400 a few years ago this way, and just recently found the time to install it, fire it up and drive it. I've been running 100LL avgas through it, since I had a few barrels of it from work. It loves that stuff. After doing some research here I see aussie heads with stock bottom end are not detonation friendly. Anyone have this setup and know if its possible to run 92 non-ethonal fuel or anything? Or will I be filling up at airports from now on? I think the cam is a lunati with .508 lift or something like that FWIW.

 

The problem that I've ran into with these heads is that the static compression is really high running 133052 (single pattern 228@0.050 & 0.550" lift) CraneCams. My pistons are 4.030" w/ 4cc intake valve relief flat tops w/ 0.055" deck clearance. My measured cold cranking dry cranking pressure is over 220psi. If you want to run these heads some consideration needs to go into your static and dynamic compression, and suitable cam selection that will be less forgiving on detonation.

Link to very user friendly static/dynamic compression ratio calculator:
United Engine & Machine Co. Incorporated

Theoretically ideal DynamicCR is 8.0:1 & should be able to run on pump gas, I'm 800ft above sea level, have 9.5:1 StaticCR, and have had no trouble with detonation using 93 octane Shell, the only fuel trouble that I have had has been stock fuel pump supply(and suspected lifter pump up) above 5500, and am seriously considering running a slightly larger solid for my drag race only app.

 

You really need to get the pistons deck height down. Having them that far down in the holes is not a good idea especially with a quench chamber head.

 

Yeah that is one of the disadvantages of using the stock rods, and stock bottom end. I know it's losing torque since the piston is so far away from the combustion chamber, but it's not noticeable in the seat. Additionally, I've learned to use a quality head gasket.

 

Do you have this setup?

 

Yes, and I strongly emphasize attention to your cam selection, and static/dynamic compression ratio for your intended application.

 

What cam would you recommend? I have a lunati with high lift, low duration, that's all I remember.

 

It's been said that making a camshaft recommendation is like seeing a dentist by mail. I'd need to know your vehicle weight, final gear ratio, tire size, piston design & deck height, intake, and favorite color - j/k on the color I'll guess blue. I can tell you that these heads with 4cc valve relief flat tops with the 133052 CraneCams http://www.cranecams.com/product/car...detail&p=23840 shaft is entirely too conservative.

 

Ok figured out which cam I have. Lunati truck avenger with .508 lift, 260 advertised duration, duration at 050 lift 210, lobe seperation 110. Intake and exhaust appear to have the same grind. Ad says 1,200-5,000 rpm power range, but I find the engine loses power around 4,000.

 

Cams rpm range usually typical of a 351cid engine. 400's have a tendency to perform at 400-500 rpm less than advertised on cams, especially when directly compared to a 351cid engine. Next issue is cam timing. It does seem like your cam could use an advance in timing relative to the crank to keep the power in the advertised powerband of that cam. Of course, this will sacrafice a bit of low-end grunt, but that cam should rev, with plenty of power, to 53-5400 in a 400, even with a stock intake and pistons.

 

I've got a performer intake, and a Holley truck avenger 770 carb, for what it's worth. 2 1/4" true dual exhaust, with Hedman headers. You think advancing the can a bit would help the top end?

 

It would be wise to measure the timing of your cam, and then evaluate the next modification, pun intended. Before tearing the engine down the than chain, use a paperclip or close pin to make certain your secondaries are opening http://www.holleytv.com/video/11341, then evaluate your ignition, and ignition timing curve.