4A-GE bluetop pistons & rods into a 4A-FE = kaboom? - Toyota Nation Forum : Toyota Car and Truck Forums
6th Generation (1988-1992) Specific discussion of the AE92

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#1 Old 04-15-2012, 03:10 AM
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Question 4A-GE bluetop pistons & rods into a 4A-FE = kaboom?

Couldn't find a topic from searching, here or elsewhere. Just wondering if it's feasible to run a 4A-FE on the stock computer with the 9.4:1 4A-GE pistons & rods on the 4A-FE crank? FE crank is supposed to have 40mm rod journals, just like the early GE crank.

I'm guessing there might be problems with interference? I know that the GE piston dome & the FE combustion chamber don't have the same shape. I'm curious about this because sometime soon I will need to pull my motor & tranny/transfer case to change out the clutch / pp / resurface the flywheel. (I have a 4A-GE build slowly going at the moment, but I want to break in its clutch before the engine swap.) I have a set of bluetop pistons & rods sitting in a box. I could clean them up, get some new rings & bearings, and do a minor rebuild of the FE while it's out.

Crazy idea I know... it is 3am right now and I need to get some sleep.

Other thought is, I have a set of pistons (and bad/bent rods) from a 1997 4A-FE sitting in my garage. Could I throw those pistons onto the bluetop rods (same 18mm press-fit pin, I believe) into my 1988 4A-FE and see an increase in compression? I can't remember the reason for Toyota's redesign of the FE pistons for the '93-'97 years.

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#2 Old 04-17-2012, 07:17 PM
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4age pistons in 4afe will not net you 9.4:1 c/r . The 4afe combustion chamber a lot smaller than the 4ag so the compression ratio will be higher than 9.4:1. Didn't do the calculations but my guess would be mid 10s c/r.

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#3 Old 04-18-2012, 04:01 PM
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it would be more around 12-13.... the combustion chamber volume in a 4afe is significantly smaller than a 4age and is why the 4afe pistons are dished.

I my guess would be that there's high possibility of valve clearance issues using the 4age pistons with the 4afe head.

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#4 Old 04-18-2012, 06:27 PM
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Thanks guys. Someone else told me he thought it would be more like 10.5:1. He's gone through the process of rebuilding a 4A-FE for more output, though he used 4A-GZE pistons to bump up the compression a little.

Quote:
bluetop pistons in a 4af application would raise the static CR to about 10.5 to 1. The std camshaft for the early F head is very short duration... 10.5 CR and a short duration camshaft might be too high a DCR... and so it could cause ping. A bit more duration(10 degrees maximum) might be useful.
DCR = dynamic compression ratio, something I need to read up on when I have the time (for my main build)...
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#5 Old 04-21-2012, 08:07 AM
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With my rough calculations I calculated a 10.7:1 STATIC c/r with the bigport pistons. I havnt done it myself so I have no idea if it would ping on pump gas. My curiousity would still tell me to go ahead and do it.

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#6 Old 04-21-2012, 11:05 AM
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I'm very tempted to try... mostly I wonder how the ECU will handle it.

As for pump gas, the highest we have in my area 93 octane. I'm going to have to switch to that anyway once my 4A-GE build is done.
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#7 Old 04-21-2012, 02:03 PM
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I have done many things that a lot of the "experts" said couldn't be done . I say f@ck it ! Go ahead and do it. I did a 10.8:1 c/r 4agze with stock ecu on 4ag pistons on 91 octane, zero problems. If you have any pinging issues on 93 octane ( I highly doubt you will) just retard the ignition timing a degree or 2 at the distributor.

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#8 Old 04-21-2012, 10:10 PM
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Thanks for the input... now I'm just wondering what the 1 point bump in compression will do. Increase torque & HP a little bit? Not too worried about MPG since I already get semi-crummy mileage from pushing the FE motor to "go faster" limits (though not redlining). If this works, it would be great for others to copy & get a little more out of the 4A-FE.

I'll definitely get new bearings, but do you think I should get new rings & wrist pins?


Edit: I suppose this idea would work best with "supporting mods" like 2" exhaust, custom or aftermarket header, etc.

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#9 Old 04-22-2012, 06:24 AM
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While you at it a new set of rings would be a good idea, they only $30. If the wrist pins are in good shape, no need to change them.

With the increase in compression you will get a slight increase in torque and hp . How much ? I cannot tell you. I can just say my 4agze pulled like nothing I have ever seen.

Exhaust is not really needed with just a compression bump but if you got the $ then go ahead and do it .

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#10 Old 04-24-2012, 08:33 PM
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Quote:
Originally Posted by RogueMoog View Post
Couldn't find a topic from searching, here or elsewhere. Just wondering if it's feasible to run a 4A-FE on the stock computer with the 9.4:1 4A-GE pistons & rods on the 4A-FE crank? FE crank is supposed to have 40mm rod journals, just like the early GE crank.

I'm guessing there might be problems with interference? I know that the GE piston dome & the FE combustion chamber don't have the same shape. I'm curious about this because sometime soon I will need to pull my motor & tranny/transfer case to change out the clutch / pp / resurface the flywheel. (I have a 4A-GE build slowly going at the moment, but I want to break in its clutch before the engine swap.) I have a set of bluetop pistons & rods sitting in a box. I could clean them up, get some new rings & bearings, and do a minor rebuild of the FE while it's out.

Crazy idea I know... it is 3am right now and I need to get some sleep.

Other thought is, I have a set of pistons (and bad/bent rods) from a 1997 4A-FE sitting in my garage. Could I throw those pistons onto the bluetop rods (same 18mm press-fit pin, I believe) into my 1988 4A-FE and see an increase in compression? I can't remember the reason for Toyota's redesign of the FE pistons for the '93-'97 years.
Which gen 4afe are you going to put the bluetop piston on?
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#11 Old 04-25-2012, 05:09 AM
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1st gen, 1988. 4A-FE, not a 4A-F...
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#12 Old 04-25-2012, 05:15 PM
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oh thats cool to see someone still experimenting with the 1st gens, but if your putting bluetop pistons on a 1st gen 4AFE and it runs well it should work for the 4A-F as well right? Since there both the samething just one is EFI.

When you can I would like to see some pic's of your build.
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#13 Old 04-26-2012, 06:40 PM
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I'll definitely document the process if I go ahead with it. But before I get too crazy with this, can anyone confirm the rod journal size (the 'big end') for the '88-'92 4A-FE? Is it 40mm or 42mm?
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#14 Old 04-26-2012, 09:51 PM
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I can confirm that ae101 4afe rods have 40mm journals not sure about ae92 1st gen . I am guessing 40mm as well.

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#15 Old 04-28-2012, 05:26 PM
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OK, thanks. Whenever I have my 4A-FE pulled out, I will verify so everyone can know.

I think the '97 FE rods I have use a press-fit 20mm wrist pin, but have 40mm big ends. I will have to double check & edit this post.

Another thing I'm wondering about... stupid question time. Are the F/FE and GE cams interchangeable? I'm wondering why Web Cams shows the same grinds (like the 294 grind) for both engines. I thought they were different, mostly because the intake cam is slaved to the exhaust cam in an F/FE. Curious because I'm planning to get a set of #294 for my GE build.
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