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420A Reliability Build?

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Spoolin6er

Probationary Member
16
0
Apr 4, 2022
Detroit, Michigan
Hi everyone. I'm pretty new here - joined a few months ago when I started looking for a 2g. I Finally found one but the engine is knocking. I pulled it last weekend and I'm starting the tear down this week, but I've got a few questions first:

Goal for this car is a cool looking, summer daily. Obviously more power would be nice, but since this is never going to be that impressive, I'm more focused on reliability and maybe even things I can do to improve fuel economy. I know, that's probably never been talked about here, but I figured I'd ask anyway haha.

1. Anything specific to 420a's look out for on the tear down? I've rebuilt several engines, but just wanted to check if there are common internal issues to look out for?

2. I'm following the build guide on 2gNT and it's pretty thorough but there a few questions i've got:
- he spec'ed out PT cruiser lifters and rockers, but didn't say why? I did some research and found that they help with oiling at high rpm. Any opinions on if they are worth it for a street build? I'll have to look into going prices...
posting this here for future folks searching: https://2gnt.com/index.php?d=Rockers
*Edit*
** well, looks like they are all discontinued. Also like $18 piece where you can find the rockers... Maybe junkyards are a good option?
**I wonder how these type replacement lifters do? Maybe cleaning OEM junk yard ones would be better?https://partsology.com/products/set...dbrIu3HaBKXFn-d3WQOBBmLYg5dYG6d8aAptVEALw_wcB
- he talks about a "long rod" setup. How long is it? I'm probably just going to stick with stock rods since I don't plan on boosting it, but a longer rod and higher compression ratio is an interesting thought to boost power a bit. Guessing it's not worth it though unless there are cheap parts that fit?
- Looks like he got most of his parts from Howell Automotive. The site looks like it was made 20yrs ago haha. They still a good source? The standard rebuild option doesn't offer much info of what kind/brand of parts you're getting.

3. I've heard that the stock timing tensioner is trash and should be replaced with a mechanical tensioner. Is that only for boosted/sustained high rpm applications?

That's all I've got for now. Let me know what you'd do for an ideal daily 2GNT build...
Thanks!
 
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Any advise? Maybe I wrote too much or more likely my thread title didn't interest anyone.

Mostly trying to answer these two things now:

- I've heard that the stock timing tensioner is trash and should be replaced with a mechanical tensioner. Is that only for boosted/sustained high rpm applications?
- Anything specific to 420a's look out for on the tear down? I've rebuilt several engines, but just wanted to check if there are common internal issues to look out for?

Ay this point i'm just trying to get it running, but figure simple things like the mechanical tensioner might be worth it since I have the engine out. (I picked up a "running" junkyard engine for $250 rather than doing a full rebuild for now as full rebuild costs were snowballing)
 
If you can find the necessary parts to do so then I would go with a mechanical tensioner. I had a new hydraulic tensioner fail with 7k miles on it. I just ended up installing a new Aisin tensioner and calling it done because I didn't find a mechanical assembly when I briefly looked. But if I ever have to do the job again I'll get a mechanical one.

Other than that, the 420a is a solid engine. As long as you get everything done properly then you should have no issues. I actually tried to kill a 420a once and couldn't. Before I dropped in my built engine I ran the hell out of the internally stock one. Held at rev limiter multiple times and doing hard down shifts, it never gave me any issue. I sold it as a running engine with around 180psi compression across all cylinders.

Since you said it's a junkyard engine you're using I would do a full once over on it to make sure it's healthy. Compression test, leakdown test, and pull all of the rod caps to check for bearing wear. If everything looks good I would still reseal everything and replace necessary hardware. (main seals, valve seals, headgasket & head bolts, valve cover gasket, oil pan gasket etc...) and get the head resurfaced if you pull it off. I would probably replace the oil pump too just because you don't know the age of it or if it's making any oil pressure. It's significantly easier with the engine out.
 
Thanks for the reply, sounds like solid advice!

Yeah, the engine was supposed to be "running" out of a dude on marketplace's car, but on further inspection, there's no way. Had to be from a junkyard - cut hoses and wiring, I should have noticed 😞 I knew I was taking a gamble when I saw there was no timing belt. Guy made an excuse saying we was going to start tearing it down to build it and then stopped. Marketplace is the worst, he was originally asking $600 for this pile LOL.

Anyways, did a leak down, and was getting air from the exhaust ports. Pulled the head, bearings look great so that's a plus. Two bent valves! Interestingly I see no witness marks in the piston or on the valves from a collision...

Current plan is to put some valves from a different head I have (bad cam bearings), lap them in and through the head back on and re-do the leak down test. Hopefully the used head gasket will hold 100psi, I think it will.

Also, found these mechanical tensioners.. not sure I trust them, but options seem limited.
https://www.ebay.com/itm/363860313614
 
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You can get a decent brand tensioner for a dodge neon DOHC. You do have to do some modification to make the tensioner work on the 420a tho. I can remember exactly what it was. You might try searching on the 2GNT forums. I believe that is where I saw the write up.
 
Yeah, I have heard about a "mopar" mechanical tensioner as well, but haven't found anything about it at 2GNT... but maybe I suck at searching LOL
 
I didn't see it either but lots of information was lost back when photobucket screwed everyone and stopped allowing linked images and moderators deleted posts that relied on the images.

Anyways here are two diagrams first is the neon timing belt and the second is the 420a timing belt. They use the exact same engine block so the tensioner should bolt right up to the block. Where you will probably run into issues is with clearance of the motor mount or the timing cover. If you go this route please take pics and do a write up!

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