It seems to me that every ambitious 420A owner wants their engine to have a higher output. I did too, which is why this article exists. And that's an understandable desire, as the 420A was designed to be a fuel efficient daily use engine. And not a high performance engine, despite what Wikipedia says.
Now there are many ways to get more ouput from an engine. But due to the ONLY fuel efficient designing of the 420A cylinder head (undersized ports), it takes quite a bit of time & money for larger gains, and spending little money brings little or no gains. For a random example: if you were to put cheap long tube headers on a 5.0 Ford you could possibly gain 15hp just from the bolt on. But with a 420A I wouldn't expect more than a 4hp gain, if that. This is because, aside from having half as many cylinders, the cylinder head is a most restrictive factor. You could potentially gain more if the engine is properly tuned, but tuning a 420A with a cast iron manifold and tuning a 420A with an exhaust header doesn't look very different.
To kick things off I'm only going to name a few modifications that help with output (categorized as "cheap" or "best"). As I build more of these engines and come up with new ideas, I will update this article with more modifications and the specifications about them.
Mandatory:
- Obviously, start with maintenance and verifying engine health. Do not start modifying if you are due for engine repairs or maintenance. Focus on that first. Your engine will have zero output once it self destructs.
Cheap, output on a budget:
- As mentioned already, the exhaust header. $48 is the cheapest 4-1 that I've seen, but 4-2-1 can go upwards of $500. A 4-1 is your classic, cookie cutter, short exhaust header. The 4-2-1 is the closest thing to a long tube design you can get, are usually higher quality, and in theory would be a greater help to the mid RPM power range.
- Also to increase airflow, a cold air intake; or at least an intake that flows better than the stock airbox. $33 is the cheapest "CAI" that I've seen, but I do not recommend using an Ebay filter. I recommend assembling your own custom air intake. Get yourself a name brand filter, some quality aluminum piping, couplers and clamps. Route the filter as far away from the header/manifold as possible, but not low enough that it will inhale road puddles. If you car is not fog light equipped, placing the filter behind the fog light vent is optimal. You can also fiberglass wrap the pipes to prevent heatsoak from engine components.
- 60mm Jeep throttle body from the 4.0L models. $35 from my junkyard, or you can search for a used one online. This will require slight modification to the throttle body and the intake plenum. There is a 2gnt.com guide for this if the site hasn't died.
- Coils, ignition wires, spark plugs... See my posts below for more information on these. A stronger ignition system is key once you start adding fuel and adjusting ignition timing.
- One of the most popular starter upgrades: Cat-back exhaust system. The cheapest that I've seen is $115. Be careful with basic Ebay systems as they are low quality materials and may not last long. Quality systems can be pricy. 2024 update, options have dried up. The Yonaka is still a nice system that I use, but slightly undersized for very high boost applications.
- This will improve power to weight ratio, but not necessarily engine output!: Weight reductions. Remove emissions & accesories, EVAP system, vacuum lines, EGR, cruise control, A/C. If strictly a race car you may consider the power steering. This is free, you may even be able to sell parts for $.
BEST modifications, no more penny pinching:
- Let's get it tuned up - electronically. MegaSquirt MS3. $775 is the total bill for the components I installed, but a used MS2 can be sourced for cheap sometimes. This is required to tune the 420A, and is a bit time consuming to install & set up. If you want to fully delete the stock ECU you will basically need to make an engine wiring harness from scratch.
- Performance camshafts. Price depends largely on the grind and brand of the camshafts, but the cheapest that I've seen were $285 for the OBX camshafts, which are HORRIBLE quality and I do not recommend! They are produced from a soft scrap metal essentially and the lobes will round off as the journals become scored. High zinc engine oil may prolonged their failure but I would never install those in one of my engines. You want Brian Crower, Crane, or Crower which were quality brands for the 420A at one point but they have all stopped producing 420A grinds in 2024. You can still custom order any grind you want from Crower but expect a multiple week turnaround. I use the Crower Stage 2 camshafts and they perform exceptionally well. The Brian Crower Stage 2 camshafts have more duration though, and may be preferred for full race applications.
- Now of course, you could just BOOST the 420A. The dollar per horsepower really makes sense. You'll spend thousands on a naturally aspirated 420A just chasing the power of a low boost application. BUT, that's the easy way out and probably not why you're reading this article.
- You may also consider spraying it - and I don't mean with those rattle cans you sprayed your shitty calipers with . I'm talking about NITROUS! Now I believe this is also cheating... But indeed an easy way to increase output. Keep the shot small unless you want to pace around in search of your connecting rod remains. Forged pistons & rods are really preferred, which is why this modification conjoinment is not placed in the cheap category.
- This is the key to greatly increasing 420A output! Do some port work on your miserable cylinder head! Advice from experience: Be careful polishing the intake ports. You still want some texture for optimal fuel atomization. I found a 120 grit finish to work nicely. And also be careful how much material you remove from the intake ports. Adding volume can decrease air speed. You can go crazy with the exhaust ports though. Much is to be desired with those. Get them as smooth as you'd like to. I've actually noticed casting defects within the exhaust ports on multiple 420A cylinder heads.
Stopping here for now. Updates and additional information in the posts below. We still have much to discuss.
Now there are many ways to get more ouput from an engine. But due to the ONLY fuel efficient designing of the 420A cylinder head (undersized ports), it takes quite a bit of time & money for larger gains, and spending little money brings little or no gains. For a random example: if you were to put cheap long tube headers on a 5.0 Ford you could possibly gain 15hp just from the bolt on. But with a 420A I wouldn't expect more than a 4hp gain, if that. This is because, aside from having half as many cylinders, the cylinder head is a most restrictive factor. You could potentially gain more if the engine is properly tuned, but tuning a 420A with a cast iron manifold and tuning a 420A with an exhaust header doesn't look very different.
To kick things off I'm only going to name a few modifications that help with output (categorized as "cheap" or "best"). As I build more of these engines and come up with new ideas, I will update this article with more modifications and the specifications about them.
Mandatory:
- Obviously, start with maintenance and verifying engine health. Do not start modifying if you are due for engine repairs or maintenance. Focus on that first. Your engine will have zero output once it self destructs.
Cheap, output on a budget:
- As mentioned already, the exhaust header. $48 is the cheapest 4-1 that I've seen, but 4-2-1 can go upwards of $500. A 4-1 is your classic, cookie cutter, short exhaust header. The 4-2-1 is the closest thing to a long tube design you can get, are usually higher quality, and in theory would be a greater help to the mid RPM power range.
- Also to increase airflow, a cold air intake; or at least an intake that flows better than the stock airbox. $33 is the cheapest "CAI" that I've seen, but I do not recommend using an Ebay filter. I recommend assembling your own custom air intake. Get yourself a name brand filter, some quality aluminum piping, couplers and clamps. Route the filter as far away from the header/manifold as possible, but not low enough that it will inhale road puddles. If you car is not fog light equipped, placing the filter behind the fog light vent is optimal. You can also fiberglass wrap the pipes to prevent heatsoak from engine components.
- 60mm Jeep throttle body from the 4.0L models. $35 from my junkyard, or you can search for a used one online. This will require slight modification to the throttle body and the intake plenum. There is a 2gnt.com guide for this if the site hasn't died.
- Coils, ignition wires, spark plugs... See my posts below for more information on these. A stronger ignition system is key once you start adding fuel and adjusting ignition timing.
- One of the most popular starter upgrades: Cat-back exhaust system. The cheapest that I've seen is $115. Be careful with basic Ebay systems as they are low quality materials and may not last long. Quality systems can be pricy. 2024 update, options have dried up. The Yonaka is still a nice system that I use, but slightly undersized for very high boost applications.
- This will improve power to weight ratio, but not necessarily engine output!: Weight reductions. Remove emissions & accesories, EVAP system, vacuum lines, EGR, cruise control, A/C. If strictly a race car you may consider the power steering. This is free, you may even be able to sell parts for $.
BEST modifications, no more penny pinching:
- Let's get it tuned up - electronically. MegaSquirt MS3. $775 is the total bill for the components I installed, but a used MS2 can be sourced for cheap sometimes. This is required to tune the 420A, and is a bit time consuming to install & set up. If you want to fully delete the stock ECU you will basically need to make an engine wiring harness from scratch.
- Performance camshafts. Price depends largely on the grind and brand of the camshafts, but the cheapest that I've seen were $285 for the OBX camshafts, which are HORRIBLE quality and I do not recommend! They are produced from a soft scrap metal essentially and the lobes will round off as the journals become scored. High zinc engine oil may prolonged their failure but I would never install those in one of my engines. You want Brian Crower, Crane, or Crower which were quality brands for the 420A at one point but they have all stopped producing 420A grinds in 2024. You can still custom order any grind you want from Crower but expect a multiple week turnaround. I use the Crower Stage 2 camshafts and they perform exceptionally well. The Brian Crower Stage 2 camshafts have more duration though, and may be preferred for full race applications.
- Now of course, you could just BOOST the 420A. The dollar per horsepower really makes sense. You'll spend thousands on a naturally aspirated 420A just chasing the power of a low boost application. BUT, that's the easy way out and probably not why you're reading this article.
- You may also consider spraying it - and I don't mean with those rattle cans you sprayed your shitty calipers with . I'm talking about NITROUS! Now I believe this is also cheating... But indeed an easy way to increase output. Keep the shot small unless you want to pace around in search of your connecting rod remains. Forged pistons & rods are really preferred, which is why this modification conjoinment is not placed in the cheap category.
- This is the key to greatly increasing 420A output! Do some port work on your miserable cylinder head! Advice from experience: Be careful polishing the intake ports. You still want some texture for optimal fuel atomization. I found a 120 grit finish to work nicely. And also be careful how much material you remove from the intake ports. Adding volume can decrease air speed. You can go crazy with the exhaust ports though. Much is to be desired with those. Get them as smooth as you'd like to. I've actually noticed casting defects within the exhaust ports on multiple 420A cylinder heads.
Stopping here for now. Updates and additional information in the posts below. We still have much to discuss.
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