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Mike Kojima posted on November 20, 2009 19:05 
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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.
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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!
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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.
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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.
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| The bearings are ACL tri metal heavy duty Formula Atlantic bearings. The Tri Metal construction give 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 embedabilty 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. |
Thursday, October 29, 2009 6:57 PM
Nice write-up. All this work is done for a n/a motor?
Thursday, October 29, 2009 7:17 PM
Well a 4AG makes about 85-90 whp in stock trim and we are more than doubling it. We are also raising the redline from 7500 to 10,000 rpm. The engine and its architecture was not designed for anywhere near this amount of stress. NA motors often put more load on the internal components than forced induction because to increased horsepower greatly, the revs must be raised. Centrifugal loads from high RPM are harder to deal with than compressive loads generated by forced induction from an engineering standpoint.
Saturday, October 31, 2009 2:45 PM
Thanks for sharing Mike. I'm reallly interested. I'm building a high comp. 2RZ engine myself, and I've been taking all these steps so far (and more)....the crankshaft got sent to Castillo for magnaflux, straightness, knife-edge, v-shape, blue print, micropolished..... Ti rods from Cunningham, 12.5:1 Arias piston with Swain coating, lots of porting and polishing in the head/ combustion chamber, along with swain coating as well. Pretty much all the details you can think of. I hope it pays of in term of reliability and power. I can't wait for the next feature.
Tuesday, January 12, 2010 7:55 PM
Mr. Kojima, Excellent write-up. I'm currently building a 4AGE motor for my own project, so this was a very interesting read. One quick question about the oil restrictor for the head: Did they mention what diameter the hole is? And is it threaded or pressed into the block? Is it something as simple as a grub screw with a hole drilled through it? Thanks.
Tuesday, January 12, 2010 9:06 PM
It is exactly that. I bleive the hole is 2mm but let me check that and get back with you.
Thursday, January 14, 2010 6:16 PM
Great. Thanks for the help.
Thursday, December 30, 2010 7:22 PM
Really enjoy this series Mike, great walkthrough blow by blow. Since I grew up with two March's and a Lola hanging around (Dad raced FB SCCA, then Atlantic in the 70's) I used to think it was just normal that a I-4 had DOHC 16V and 10k revs. Those were Cosworth-Fords (and only 8V in the earlier motors) but man did they rev with the dual Webers. Before you had to buy a spec motor (had to late 70's) Dad usually had 2-3 motors in various states of build/completion. Some of the most elegant profanity I've ever heard came when things like a cam pulley sheared off or other tragedy struck a BDD/BDA motor, a LOT of $$$ was paid out for the work he didn't do himself, losing a motor was very infrequent (3 times in 6+ years?) but it seemed to strike only when he was doing very well...Murphy's Law.
Thursday, December 30, 2010 7:27 PM
Stupid double comments. Best way I've heard this stated, people assume FI is always always harder on a motor, I have to write this down somewhere: "NA motors often put more load on the internal components than forced induction because to increased horsepower greatly, the revs must be raised. Centrifugal loads from high RPM are harder to deal with than compressive loads generated by forced induction from an engineering standpoint. " I try to communicate that when people talk about pushing an NA 10:1 SR20 above 8k rpm on a regular basis even with some upper end replacements like the Ti springs, retainers, cams, etc. Same motor will literally spin itself to pieces at 10k-11k when it can run all day at 6k-8k.
Thursday, December 30, 2010 7:35 PM
Only have 2-3 pics of the first March's left, great cars in their day: 722 in FB trim at Portland: http://www.facebook.com/photo.php?pid=274053&l=a2738529e3&id=1746021421 74B in FB/FA trim at Westwood with cheesy handmade lettering/numbers, he had just bough the car I think from Don Briedenbach in SF, towed it up to BC and slapped Player's series stickers over old sponsor logos: http://www.facebook.com/photo.php?pid=274463&l=a4d7527b56&id=1746021421
 
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