Rebuild head or whole engine

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Jul 23, 2011
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Background: I have two 97s and Joey’s turbo is going on my favorite one of the two. But, very low compression in that engine (350k miles with orig HG) and much better in the other (160-170 on all with 385k but has had HG replaced). I’m stumped because I was trying to figure out if just a head job on my lower compression engine would do the trick instead of swapping the two eng/trans/transfer and avoiding a full rebuild (expense). Used a vacuum gauge off of brake booster port. Was hoping with a jab of the gas that tired engine would drop to 0 and then to 20 and settle at 20 (indicating worn rings) and the better compression one would drop to 0 and snap back to 24/25 then settle at 20. But, both perform identically - drop to 0 and then to 23 or 25 (depending kn how sharp the snap is) and settle at 20. So, is my thinking correct that a head rebuild and new gasket is likely to bring good compression back to the lower compression engine since it appears the rings aren’t worn out? Thanks in advance.
 
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What?

If you want to find out where your compression loss is just use a leak down test.
Thanks. Was under impression that a vacuum guage and the way it performs and reacts will diagnose many things including bad rings.
 
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I usually think of good compression numbers coming from good rings. And then good vacuum readings generally come from good valves. Which seems backwards from the way you are thinking about it. Though I may be the one who's backwards in my thinking.
 
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Thanks. Im going to try the leakdown test and in my rrading on that, I'm planning to use a stethascope to see if air escapes through intake, exhaust, oil filler (getting past rings into crank area), or radiator (indicating HG). I’ll report back but someone correct me if I’m off base.
 
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Thanks. Im going to try the leakdown test and in my rrading on that, I'm planning to use a stethascope to see if air escapes through intake, exhaust, oil filler (getting past rings into crank area), or radiator (indicating HG). I’ll report back but someone correct me if I’m off base.

This is correct. A leak down test can verify if you have a leaking head gasket, leaking piston rings, leaking valves, etc. Just ensure the piston is at top dead center with both valves closed.

There's plenty of documented information that can be found on google if you're confused on how to properly perform a leak down test.
 
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350k miles is a lot, even for a 1FZ-FE. Could the bottom end handle the turbo without a rebuild? Probably for a while, but the turbo is going to increase the stress on the engine and accelerate wear on what is already a high mileage engine. If I were going through all the time and expense of rebuilding the head and adding the turbo I'd want to be sure the bottom end is in good shape. At the very least the rear main seal is probably leaking and needs to be replaced.

You could send the engine oil out for analysis to get an idea of what kind of wear is happening to give you a better idea of what kind of shape the bottom end is in.
 
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If i rebuild, is this a project any longstanding engine builder shop tackle or does the 1FZ rebuild require experience with this particular engine?
 

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If i rebuild, is this a project any longstanding engine builder shop tackle or does the 1FZ rebuild require experience with this particular engine?
A good engine build shop / performance shop should be able to tackle it. The 1FZ is straightforward. If they had experience with cruisers and the 1FZ it would probably be better, just because. On the last 2 rebuilds that I considered I ended up going with a new block. I'm sure it wasn't necessary, but the cost in the end wasn't considerably more. YMMV, IMHO.

Also, if I was putting on a Turbo or a supercharger, I'd go with a new block. If I had 300K on a block, I wouldn't stress the motor with a turbo or a supercharger.
 
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A good engine build shop / performance shop should be able to tackle it. The 1FZ is straightforward. If they had experience with cruisers and the 1FZ it would probably be better, just because. On the last 2 rebuilds that I considered I ended up going with a new block. I'm sure it wasn't necessary, but the cost in the end wasn't considerably more. YMMV, IMHO.

Also, if I was putting on a Turbo or a supercharger, I'd go with a new block. If I had 300K on a block, I wouldn't stress the motor with a turbo or a supercharger.
Guys, on both of mine ('94 Toy and '97 Lex) the condition of the block deck was the main issue. I was able to ream the ridge, but I wouldn't trust the head gasket to block seal without a block deck milling, especially with a boost.

40head.jpg
 
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Good info and pic. Is that type of roughness typical on our heads? Maybe stupid question but can a shop mill the block deck in the truck (easier to trailer it to shop than pull the engine)?
 
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Good info and pic. Is that type of roughness typical on our heads? Maybe stupid question but can a shop mill the block deck in the truck (easier to trailer it to shop than pull the engine)?
This picture is of the 1994 LX450 with 284K. Not sure if head gasket was ever replaced, but I doubt it. My 1994 FZJ-80 with 315K was worse. The head gasket between cylinders blew out, partially due to the corrosion on the head, part the block. I'm certain the head gasket was never replaced on that one. I'm rebuilding the (OBDII) '97 for another project but I'm dropping a 7.4L BBC in the Lexus now.
 
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Good info and pic. Is that type of roughness typical on our heads? Maybe stupid question but can a shop mill the block deck in the truck (easier to trailer it to shop than pull the engine)?
No, a shop cannot mill the deck on the block in frame on the truck. The machine to deck the block is about the size of the truck.

The roughness appears to be fairly common on these based on this forum and the many photos posted.
 

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i would pull it and send it off. so there are 2 ways it can go...

1st way is something is bad and you fix it or buy a new short block. yeah that sucks but you caught it before you put a turbo on there and sent a piston to the moon. i had a cracked piston skirt i didnt know about. engine held pressure fine but it was time bomb waiting to go off.

2nd option is everything checks out good. they clean it up, slap some new rings and bearings in it and send you on your way knowing everything is great.

if you already dropped 6K on a turbo kit why not do it once and do it right?
 
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FYI, including machine work (boring out +1, decking) torque plate, replacing everything on the bottom end but the rods and the shaft in my locale is going to be about $800 cheaper than an OEM short block. Anticipated delivery date on all the parts sometime in late 2023.....
 
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Jul 23, 2011
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Thanks. Anybody have experience with AAA engines in LA (I see some good and bad reviews - just like every place you check reviews on - some people are unrealistic)? $4500 plus shipping seems a good option if its a well done rebuild. Anybody know pricing on the Jarco engines out of Canton, GA?
 

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