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Mike Kojima posted on November 20, 2009 19:05 
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High strength ARP studs allow a higher torque and more clamping load for the cylinder head and main caps. Studs are also inherently stronger than bolts and unlike the stock torque to yield bolts, they can be reused. Special hardened washers and high strength nuts are used as well but are not shown.
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CBY, a Japanese 4AG tuner supplied this billet stroker crank. At 83mm of stroke, up 6mm from the stock 77mm, this crank punches out the 4AG to 1800cc when paired with 83mm big bore pistons. The stroker motor is good for 30 more hp over the standard 1600cc engine. The stock 4AG crank is also a weak point on the engine. The early AE86/AE82/AW11 version of the 4AG had smaller rod journals at 40mm and were very weak. The stock crank fails at the #3 rod journal when the revs are pushed beyond 8000 rpm and the power above 180 hp. The CBY crank is made of high strength 4340 high nickle alloy and uses the larger diameter 42mm late rod journal size. The CBY crank has generous fillets and chamfered oil passages and is post machining heat treated and shotpeened for extra durability. If you are building your own low buck 4AG, it is advisable to run the later 1988 and up supercharged MR2/AE92 crank, rods and bearings. This crank is much stronger.
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CBY rods are H beam and feature super strong rod bolts and floating pin bushings. They are machined from 4340 alloy billets. The piston pin uses the larger late post 1988 4AG 20mm diameter as the smaller 18mm early pins were prone to distort and wear the rod bushing at high RPM. The CBY rods are shotpeened for greater fatigue strength.
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Greddy cam drive belt is heavy duty and Kevlar reinforced for extra strength and durability at high rpm.
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| HKS supplied this MLS (Multi Layer Steel) head gasket, important to ensure sealing at high compression ratios. MLS gaskets require good block and cylinder deck preparation to obtain a good reliable seal. |
Stay tuned, in part two we will dig deeper into the guts of the ultimate naturally aspirated 4AG.
Sources
Technosquare
Pages: 3 of 3 Previous Page
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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