Claudius
Well-Known Member
After going through the details of the "My potential compression ratio" thread started by Octanejunkie and making use of the Keith Black web site noted therein, I am back to considering domed KB399 pistons again for my 0.040" oversize 318. Thanks to the contributors to that thread because I learned a lot!
This new thread is coming into existence because I was not smart enough to check just how far down in the well my pistons were before pulling them out. (Eager greenhorn mistake...#-o) However, more investigation seems to indicate that the pistons can typically sit from 0.025" to 0.080" down in a 318.
While the prevailing wisdom likely says that one should simply zero deck the block and use the KB167s, the cost differential from the 167 (5cc) up to the domed 399 (-6.2cc) is only about $26 and that is much cheaper than the costs of machining the deck a few mils. This puts me 'on the horns of a dilemma' and what a pain in the backside that can be. (Ouch!) I already had the block in the hot tank with the requisite frost plug and camshaft bearing swaps done in addition to a slight hone of the cylinder walls; I do not want to take it back. The block and crankshaft were in excellent condition from the engine remanufacturing in 1983 (have tag) with 0.040"/0.010"/0.010" machining.
Using the KB calculator and putting in all of the relevant data as applicable to the Fel-Pro head gasket from the kit I will use, an estimation of 61cc for my 340 heads (again, based upon more research), and the specs for the Lunati Voodoo 60400-60405 camshafts, I have a spreadsheet of data for SCR and effective DCR for 0-deck, 0.030" and 0.060" well depths (picked arbitrarily for calculation purposes).
Several questions after all this ranting:
1) As applicable to the 0.030" and 0.060" well depths, the effective DCR for the KB167s varies from 8.44:1 down to 6.83:1. The effective DCR for the KB399s varies from 9.17:1 down to 7.69:1. Since we can only get 91 octane around here at the pump, does anyone have any advice/experience regarding octane booster products?
2) If I were to follow my machinist's method of checking well depth (one piston installed and measured in the four corner cylinders) using an original piston before ordering new ones, would that be enough to gauge how another piston would sit or is each piston manufacturer/type a little bit different? (I could make the measurement while using some Plastigauge to check my new main bearing tolerances.)
The deeper the well, the easier it becomes to choose the 399s while avoiding the deadly detonation point of ~9.1:1 (effective DCR). This car will not be driven much (no racing) but there is a lot of pride involved with reassembling an engine for the first time and seeing what one can accomplish. Sometimes, we want to do things "just because we can" for the "fun factor" involved.
Any and all advice would be greatly appreciated.:cheers:
This new thread is coming into existence because I was not smart enough to check just how far down in the well my pistons were before pulling them out. (Eager greenhorn mistake...#-o) However, more investigation seems to indicate that the pistons can typically sit from 0.025" to 0.080" down in a 318.
While the prevailing wisdom likely says that one should simply zero deck the block and use the KB167s, the cost differential from the 167 (5cc) up to the domed 399 (-6.2cc) is only about $26 and that is much cheaper than the costs of machining the deck a few mils. This puts me 'on the horns of a dilemma' and what a pain in the backside that can be. (Ouch!) I already had the block in the hot tank with the requisite frost plug and camshaft bearing swaps done in addition to a slight hone of the cylinder walls; I do not want to take it back. The block and crankshaft were in excellent condition from the engine remanufacturing in 1983 (have tag) with 0.040"/0.010"/0.010" machining.
Using the KB calculator and putting in all of the relevant data as applicable to the Fel-Pro head gasket from the kit I will use, an estimation of 61cc for my 340 heads (again, based upon more research), and the specs for the Lunati Voodoo 60400-60405 camshafts, I have a spreadsheet of data for SCR and effective DCR for 0-deck, 0.030" and 0.060" well depths (picked arbitrarily for calculation purposes).
Several questions after all this ranting:
1) As applicable to the 0.030" and 0.060" well depths, the effective DCR for the KB167s varies from 8.44:1 down to 6.83:1. The effective DCR for the KB399s varies from 9.17:1 down to 7.69:1. Since we can only get 91 octane around here at the pump, does anyone have any advice/experience regarding octane booster products?
2) If I were to follow my machinist's method of checking well depth (one piston installed and measured in the four corner cylinders) using an original piston before ordering new ones, would that be enough to gauge how another piston would sit or is each piston manufacturer/type a little bit different? (I could make the measurement while using some Plastigauge to check my new main bearing tolerances.)
The deeper the well, the easier it becomes to choose the 399s while avoiding the deadly detonation point of ~9.1:1 (effective DCR). This car will not be driven much (no racing) but there is a lot of pride involved with reassembling an engine for the first time and seeing what one can accomplish. Sometimes, we want to do things "just because we can" for the "fun factor" involved.
Any and all advice would be greatly appreciated.:cheers:
