Extreme Engine Tech, Technosquare’s Monster Naturally Aspirated Toyota 4AG


The 4AG’s oil pump gears become unreliable at around 8000 rpm.  TRD used to have special stronger gears but these have not been available for a long time.  The alternative is to dry sump the engine.  For a max effort 4AG, a dry sump is worth the expense in increasing reliability.  Here the main passage from the removed stock oil pump is blocked off.


This restrictor is placed in the block deck to limit the amount of oil pumped to the top end.  This reduces windage for increased power and lower oil temps and sends more oil to the main and rod bearings.  This mod can be done for engines running the stock oil pump as well and it is probably needed more in that case!


This beefy cast Formula Atlantic dry sump oil pan was important in a Formula Atlantic car because the engine was a stressed member and the 4AG is a wimpy flexy engine that would self destruct with chassis loads being fed through it.  The thick pan reinforces the block.  For sedans the heavy duty pan helps strengthen the block for durability reducing main cap walk and flex for longer bearing and crank life.  A Barnes 3 stage drysump pump is used with 2 scavenge and one pressure stage.  The dry sump ensures that the engine will always get a good supply of oil not matter what the G load or how high the rpm.


One of the weakest parts of the 4AG is the crank support system.  The main caps flex and distort under heavy loads causing the main bearings and even the crank to fail.  This happens above 9000 rpm and 220 hp.   Tomei makes these main cap reinforcements out of high strength steel.  The tops of the cast factory main caps are machined flat and the main bolts replaced with ARP studs.  The reinforcements are then bolted on top of the main caps.  This greatly reduces flex improving bottom end life, especially when combined with the Formula Atlantic oil pan.  This mod is also useful with turbo cars.

The bearings are ACL tri metal heavy duty Formula Atlantic bearings.  The Tri Metal construction gives superior load bearing capacity.  The bearings look ugly as the latest trend in racing bearings is to forgo the traditional zinc plating top overlay.  On a stock engine this zinc gives a bit of embeddability making the bearing less sensitive to dirt. The thinking is that this zinc layer reduces heat transfer and does nothing in a racing engines that is cleaned carefully during assembly.

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