Basic streetcar carbureted 4age 16v build

Nothing new or groundbreaking here but figured i would write this up as i do get a lot of questions on my engine setup and there is a lot of misinformation or lack of information on a 4age stuff online as they become older and less common. Unfortunately no teardown photos and missing a few build photos as well but you should know how to take it apart if you want to put it back together😁 to save us both some time (aka i dont remember all the specs off the top of my head as i write this) and to keep track of a super helpful resource here is the factory 4a toyota rebuild manual, everything here (torque specs, clearances, etc.) has been done according to this EXCEPT different torque specs for aftermarket parts (rod bolts, adjustable cam gears etc) and the main and rod bearing clearances have been opened up to TRD spec to compensate for the higher volume/pressure 20v oil pump and offer more protection 4A-GEManual.pdf (aeu86.org) so lets get started, there are 2 basic 4age blocks, 3 rib and 7 rib, 3 rib are earlier and not as strong, 7 rib are later motors and slightly stronger and better suited for higher rpm although either are fine at this power/rpm level. cleaned, degreased, threaded holes chased, oil galleys cleaned and flushed and machined surfaces masked off, ready for paint before paint you also need to check the bores and deck for any damage or distortion, this block checked out fine at standard bore and i only had to hone the cylinders and the deck passed the straight edge and feeler gauge test after removing all of the old head gasket material very carefully

i just went with Satin black high heat duplicolor for a factory-ish look

much easier to just have it hot tanked at a machine shop but if you live somewhere with minimal access to one like me, some degreaser, cleaners and lots of elbow grease can yield the same result

Up next is crankshaft prep, there are 2 crankshafts for a 4age, earlier ones with 40mm rod journals and later ones with 42mm rod journals, 40mm journal cranks use a factory connecting rod that uses a interference fit wristpin for the piston, 42mm cranks use a factory connecting rod that uses a floating wristpin for the piston, most aftermarket rods are for the 42mm crankshaft so if youre going with forged internals you want the 42mm crank. If youre planning on a stock or mild rebuild the 40mm is fine but youre more than likely stuck with factory rods. Youll also have to know for ordering the correct bearings (obviously lol) the crankshaft in my motor is a 42mm.

This motor still had good oil pressure when it was torn down and clearance checked okay but had gotten some contamination into the motor at some point causing light scratches on some of the journals, once again having minimal machine shop access (aka super long wait times, questionable work) and being familiar with building engines I elected to polish the crankshaft myself at home. (Do not do this if you dont feel comfortable with it or have a good "feel" for things or if you have scratches deep enough that the crank has to be actually cut down and turned)

im not going to go super into detail on this process as there are tons of writeups online and tutorials on youtube, but basically youre using very fine sandpaper strips (i used 800-2000 in steps) cut as wide as the journal and a string wrapped around at least twice for even pressure on the whole strip and light oil to wetsand the high spots out of the journals and metal polish after for a smooth finish, it is super important that you go slow and check as you go and clean every part of the crank (oil galleys too!) before you put it back in the motor to check for clearance or final assembly

Here is the final product before going back into the motor

Here is the #3 journal which was the worst of them before polishing after being installed and clearance checked with new King std size main and thrust bearings A lot of people like to talk down on using plasti-gage but it is actually more accurate than micrometers unless you have them regularly calibrated, you can also check out of roundness with it by checking clearances at multiple points around the journals, i did these in 4 spots per journal every 90 degrees with no difference in any of the readings.

Next we'll move onto the rods and pistons, i decided to go with MRP forged H beam rods with ARP 2000 bolts and OEM smallport pistons with Mahle rings, these would make 10.3:1 compression with my smallport head with a factory headgasket and they make 10.7:1 compression with the TRD MLS .8mm headgasket that i used with my undecked smallport head the rods are unnecessary at this power level but the tolerance in weight difference of the MRP is much higher than OEM ones, much lighter overall weight and not much more cost to just buy these by the time you fit ARP bolts to factory rods and have them resized by the machine shop for the additional clamping force (YOU CAN NOT JUST PUT ARP BOLTS IN STOCK RODS AND RUN THEM, i dont care whos uncles brothers cousin told you it works, they will be distorted out of round and spin a bearing) pistons and wristpins are OEM toyota smallport standard bore out of a newer 4age with new Mahle rings gapped to factory spec, when ordering rings double check your pistons compression rings thickness because some have 1.5/1.5mm compression rings and some have 1.2/1.5mm compression rings like these ones do

rods and pistons installed after checking clearances with new King race rod bearings, the new oem Aisin 20v oil pump and pickup for the MRP fabricated baffled oil pan is also pictured here

MRP oil pan installed and TRD MLS .8mm headgasket pictured here before the head goes on Next we'll move onto the cylinder head, there are two different cylinder heads for 4age 16v, Bigport which are earlier heads with larger intake ports and Smallport which are later heads with smaller intake ports. Although it sounds like bigport would be better at first its really not on a milder motor up to 190-200ish HP because the intake ports are a little too large for a smaller motor to have good velocity at lower rpm's. So a smallport will usually make a broader power curve with more midrange power until the 190-200hp zone where the bigport starts to outflow it and the motor has enough cam/compression and rpm to take advantage of the bigger port.

Not to get too much into engine building theory as thats a whole other book to write but a factory bigport motor also has lower compression than a smallport which is why combined with the weak port velocity on a mild motor you will see a lot of bigport builds with cams and not enough compression to support them make very low power numbers. Not trying to knock anyone and theres nothing wrong with just using what you have as this stuff is getting harder to find and these cars arent meant to be fast anyway 🤣 just trying to help people select the right parts for their goals without a bunch of trial and error.

sorry for the lack of pictures of most of this but here is my smallport head, it was in pretty good shape other than the valves being out of adjustment and a couple small knicks here and there, you can see one under the cap on that front journal in the picture, no big deal and at this point most of these heads are around 40 years old so they wont be perfect but you do want to knock those down flush with the cap surface using a fine file or sandpaper, I also took the valves out and although they passed a leak test and the seats looked okay I lapped them by hand with some lapping compound while i had everything apart. Now onto the valve adjustment, there actually arent any adjustable parts on these so instead you change the shims that ride in the lifter buckets to tighten or loosen the clearance, this is a shim over bucket design which is good for 8-8.5mm lift depending on who you ask, anything over that you want to move to a shim under bucket or solid shimless design, my motor has bigport cams in it which are a little larger than smallport (7.56mm lift compared to 7.1 and 240 degree duration compared to 232) so i had no issue staying with the stock design

The clearances youre shooting for are 0.006-0.008 in. on the intake side and 0.008-0.012 in. on the exhaust side, to achieve this youre basically going to check your current clearance to know if youre in spec or have to loosen or tighten, they will all be different more than likely so you have to do them all individually. This should be obvious but while measuring, the cam lobe cant be touching the shim, you have to measure the clearance between the shim and the base circle of the cam. Once you know where your clearances are pull your shims out and measure their thickness with a micrometer and document what they all are (do not lose track of where they were in the motor doing this whole process, i used a large piece of cardboard marked with everything to help keep track of mine) once you have them all documented see if you can swap any around to get your clearances within spec, IIRC i got 6 or 7 of mine within spec from swapping shims around and with the few that were good to begin with i only had to order 8 or so new ones, to know what shims you will need to replace your out of spec old ones without just ordering a bunch and swapping them in and out use this formula. T = thickness of old shim A = valve clearance measured N = thickness of new shim required Intake valves: N = T + (A - (0.008in.)) Exhaust valves: N = T + (A - (0.010in.)) Then find the shims closest to your calculated values, if youre lucky and live somewhere more populated you can probably find some used around you you can measure and use, if not dont worry that theyre discontinued from toyota and not readily available from anyone in the aftermarket because they are just 25mm shims that were also used in tons of old motorcycles so theyre still available from some motorcycle supply stores, i think i paid $6-7 each for the handful that i needed.

Now that thats done we can get the head back on the motor (it can be done with the head installed but is a lot easier with it off) I just used new OEM headbolts, this motor will always be naturally aspirated in my ownership so there was no need to use ARP studs or anything like that.

Now install the camshafts according to Pg. 231 in the link to the 4A manual at the top of the page

Then install the cam seals, gears, belt tensioner and timing belt according to Pg. 232 and 233 in the 4A manual, the dot on the crank pulley also has to be aligned with the dot on the lower timing cover when installing the timing belt. The T3 cam gears are kind of confusing as the holes for the cam pins in them are drilled 180 degrees out from each other for some reason but to install the cams correctly in the head the pins are only 160 or so degrees apart (reference diagram on pg.231) so the faces of the gears dont line up although this is the correct "straight up" installation on both sides. Although they seem decent quality for this reason alone I would get different cam gears but these came with this motor and I decided it was easier just to reuse them.

Heres the motor with all of the valvetrain installed along with a new OEM tensioner, new OEM water pump and dipstick and water neck cleaned up and reinstalled

Now onto the quickie valve cover resto, aircraft stripper applied to get the 3 previous coats of painted over grease paint off and since the new aircraft stripper isnt as good as the old poisonous kind put a plastic bag over the parts while theyre marinating for quicker results

Here they are after chemical stripper, i also used a wire brush in a drill to get the rest of the stubborn spots pictured off

Masked and primed along with the grass

Satin Aluminum high heat paint applied

And then bust out the Tamiya model paint and handbrush the letters for an OEMish look

Heres the finished look with the polished plug cover and TRD oil cap, id really like to go to two right side valve covers for two oil breather ports as the single one isnt quite enough for a higher strung motor.

Now onto the carb refresh and rejet, these had been opened up and cleaned not too long before i got the car and didnt have much mileage on them since the previous owner couldnt get it to run anywhere close to right so I didnt have any Ethanol green crud to dig out from them sitting. If you have an unknown set going on your motor take them apart and clean them as good as you can because the smallest chunk of anything can clog these tiny jets and passage ways, but be very careful what youre cleaning with as some cleaners are too harsh on the plastic and rubber parts and can make them brittle and crack. Most of the motorcycle carbs are pretty similar in how theyre set up and are much simpler than a car oriented carburetor, so most of this stuff will apply to other bike carbs as well they will just take their own designated parts and adjustment techniques. These are Keihin 37mm off an early 00's Yamaha YZF-600R, on motors up to 175-180hp range the smaller openings of the 600cc carbs will give you better throttle response and port velocity than the larger openings of 1000cc carbs and over that power level you would want the larger carbs to not be restrictive but either can be made to work on any motor. The motorcycle carbs also run at a lower pressure (2-4psi) than car ones or EFI so make sure you are running a carb specific fuel pump and pressure regulator, i run a Holley Mightymite fuel pump and Aeromotive low pressure regulator in my car set at 3psi. As far as jetting and setup goes this will be different on each motor so you cant really take what i have here and apply directly to your setup and the ways of making these adjustments might be different on your carbs as well but this should give you an idea on what you need to do to get yours dialed in. You can read plugs to get your fueling right but its a lot easier with a wideband as the only way plug reading is accurate is shutting the motor off at a certain rpm/load level and that gives you a reading for that rpm/load level, so shutting off at wide open shows whats happening at wide open, shutting off at idle shows whats happening at idle etc etc. I run an AEM UEGO wideband with Bosch 4.9 sensor in my car with no datalogging ability and just watched it while driving.

disregard the 190/55 numbers thats just what the jets started as when i took them apart the first time All of these adjustments will affect the others a little bit so its kind of a dance keeping everything happy as you change things. You also need to make sure everything is cleaned and assembled correctly with no leaks or blockages and the carbs are in spec, float heights set correctly(yellow), mixture screws set to default settings and all even etc etc. before tuning or you will just end up chasing your own tail. This will be different for every carb so you will have to look up specifics for your application. Even though youll be starting on a default bike setup this should get you a car that starts and is ready for tuning. The main jet (red) controls the majority of fueling as it controls overall fuel output so changing this will change the fueling everywhere so you will want to get this close first, usually a bigger number is a bigger orifice size a.k.a. more fuel but check for your application. If your carbs are fresh off the motorcycle these will likely be way too small to begin with. I ordered larger jets for "supposedly" a 4ag application and i was still lean under heavy throttle so ended up having to drill my jets out even larger. I shot for 12.8:1 A/F at WOT in my car. The secondary jet (green) controls your cruise and partial throttle fuel flow, youll want to do this next, every motor will be a little different on what it wants here and what you can get without affecting other areas too much, about as lean as i can get mine here without affecting other areas is in the low 14's A/F ratio. Needle spacing and vacuum slide spring tension (no pics of this, sorry but theyre under the black plastic covers on top of most carbs) will also affect fuel flow and enrichment rate so heres where the "dance" of keeping everything happy as you change things comes into play. More than likely after you have gone through all of the adjustments you will have to go back through and fine tune everything. On these carbs the needle height is adjusted with small shims, adding shims onto the base of the needle raises it and lets more fuel flow through and taking away shims lowers it and restricts fuel flow, this affects fueling everywhere except wide open throttle when the vacuum slides are all the way open. Adjusting the opening rate of the vacuum slides adjust the speed of "enrichment" in the carburetor, on my carbs it is set with springs, a stiffer or taller spring slows the enrichment rate and softer or shorter springs quickens it. Air/Fuel mixture screws (blue) are next, this controls the "signal" the carb sees from air passing through it and along with jet sizes controls how much fuel the carb pulls in, you want to make sure these are all even while adjusting and only adjust them a little at a time, youll want to adjust them with the car warmed up at idle and running and basically what youre shooting for is idle quality and idle A/F ratio, I have my car idling at around 14.7:1 warmed up Dont expect to get this perfect on the first, second or maybe even third try. It will probably never end up "perfectly" tuned like a standalone efi setup can be either, thats just the nature of carburetors and why fuel injection was invented 😅 but you can still get a great running (and sounding) car from it. After you have the fueling where you want it youll want to set your idle speed (mine is set with the knob that can be seen in the top picture of the carbs) they also usually dont like idling as low as car carbs do and mine is happiest around 11-1200rpm And lastly youll want to synchronize the throttle blades, this will improve the "drivability" and will solve any hanging idle issues, youll need to get some kind of synchronizer or vacuum gauge tool for this (i used the cheap $40ish dollar one from amazon pictured below) the adjustment technique is a little different on different kinds of carbs but youre basically trying to get each cylinder to pull the same vacuum at idle, on my carbs carb 1 & 2 are tied together and 3 &4 are tied together so you adjust those pairs first and then adjust the 2 pairs together.

After all of that you should have a car that runs almost like modern EFI and better than the OEM abysmal flappy door AFM efi setup that these cars came with in the US, even on cold (10-20 degree F) days my car will start in a few cranks with the choke on and once its anything warmer than "dead cold" the choke is never needed again to easily start it. On warmer summer days it starts without the choke easily even for the first time in the morning, it also drives smooth with no misfires, bucking, stalling or hanging/surging idle and makes much more power and sounds waaaay better than a factory common plenum efi manifold would. Im using a DanSTengineering intake manifold to mount these on the motor with silicone couplings and a modified USDM GTS throttle cable to run them, you will have to figure out a linkage/cable setup depending on what carbs youre running.

Here is what it all looked like dropped back in the car before wiring anything (I ended up dumping the UNI pod filters for a large Pipercross single filter i will show in later pictures ) ended up selling the car so kind of forgot about this lol, but wiring and igniton setup was very simple, a 6al msd box to fire the ignition and an 8981 msd box added on for ignition timing control, the wiring for both of these is super simple and easy to find online. However the 8981 box is now discontinued so instead of using those 2 youre much better off using the 6523 ultra 6al MSD just realized earlier this year.