What is a 355? - LS1TECH



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What is a 355?

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Old 04-19-2017, 03:50 AM   #1
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Default What is a 355?

As the title says, what is a 355 and what exactly do you need in order to build it? I've been searching but haven't found a definitive answer on any forum, and I can only find 383 stroker kits on eBay.

Perhaps someone could take the time and explain this to me in layman's terms?


I bought my dream car - my Formula LT1 - because I wanted something to tinker with and spend some time on, and after countless hours (years) of browsing I think I have finally found what I would like to do with it, and that is to build a 355! I'm not talking about starting this build today, but somewhere down the line I would like to do it. For now I would just like to know what a 355 is and what you need for it. All info is appreciated!

I have zero experience of any kind of engine work and I haven't done anything like this before (well, I did Pacesetter LT's last year lol), but I bought this car with the intent of learning. My car is my hobby and I have been a car guy for as long as I can remember. Cars in general, and f-body's in particular is my life!

Looking forward to answers!

/E

Last edited by ErikFormula; 04-19-2017 at 03:55 AM.
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Old 04-19-2017, 04:18 AM   #2
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The bore and stroke on a stock lt1 is 4.000" x 3.480"

This means the diameter of the cylinder bore is 4.00" and the amount the piston travels up and down the cylinder is 3.480". A 355 is when you remove 0.030" from the cylinder walls for a rebuild but still retain the stock length of stroke. A 383 is when you remove the 0.030" from the cylinder walls but also change the crank to one that has a stroke of 3.750".

the reason why you don't see 355 kits really is because it just requires a larger diameter piston where as a 383 requires different pistons, rods, and crank.
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Old 04-19-2017, 04:43 AM   #3
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The bore and stroke on a stock lt1 is 4.000" x 3.480"

This means the diameter of the cylinder bore is 4.00" and the amount the piston travels up and down the cylinder is 3.480". A 355 is when you remove 0.030" from the cylinder walls for a rebuild but still retain the stock length of stroke. A 383 is when you remove the 0.030" from the cylinder walls but also change the crank to one that has a stroke of 3.750".

the reason why you don't see 355 kits really is because it just requires a larger diameter piston where as a 383 requires different pistons, rods, and crank.
This is exactly the kind of answer I was looking for, thank you very much! So a 355 build only needs a larger piston? It sounds so easy, why go through all the trouble for that? What kind of gains will I see from it?
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Old 04-19-2017, 07:14 AM   #4
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This is exactly the kind of answer I was looking for, thank you very much! So a 355 build only needs a larger piston? It sounds so easy, why go through all the trouble for that? What kind of gains will I see from it?
truly 355s are done mostly for the point of rebuilding when the cylinder walls of a block become damaged to the point of needing to be enlarged to remove imperfections from the bore.

cubic inches increase the potential for power since more space inside the cylinder can equal more power with the proper compression ratio and supporting parts like a larger camshaft and better flowing cylinder heads. Changing the piston allows you to run a different design to influence the compression ratio like more compression for a naturally aspirated build or one using higher octane fuel or lowering the compression ratio for forced induction.
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Old 04-19-2017, 08:36 AM   #5
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truly 355s are done mostly for the point of rebuilding when the cylinder walls of a block become damaged to the point of needing to be enlarged to remove imperfections from the bore.

cubic inches increase the potential for power since more space inside the cylinder can equal more power with the proper compression ratio and supporting parts like a larger camshaft and better flowing cylinder heads. Changing the piston allows you to run a different design to influence the compression ratio like more compression for a naturally aspirated build or one using higher octane fuel or lowering the compression ratio for forced induction.
Damn, I have learned more today than I have in weeks googling about 355 builds, thanks again friend!

So if I buy a LT1 rebuild kit with a new crank and some new larger (forged?) pistons, and a mail order tune, is that all I need? My car has 77k miles on the clock btw.

How much money are we talking about?
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Old 04-19-2017, 08:51 AM   #6
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Buy this before spending anything else
https://play.google.com/store/books/...FRZHDAodObYCoQ

Read it a few times, then start planning a motor build.
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Old 04-19-2017, 08:59 AM   #7
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Buy this before spending anything else
https://play.google.com/store/books/...FRZHDAodObYCoQ

Read it a few times, then start planning a motor build.
Very nice, I definitely need that. I'll order it next week! Thank you!
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Old 04-19-2017, 09:07 AM   #8
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if lookin to get more power and you got long tube headers already then head and cam would be a good place to start. with 77k on the block it should be in great shape. that is as long as its not been abused. le2 head job from elliotts with a custom cam from him is a good path to take. if you dont have one i would recommend you pick up a factory service/shop manual for your year.
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Old 04-19-2017, 09:32 AM   #9
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if lookin to get more power and you got long tube headers already then head and cam would be a good place to start. with 77k on the block it should be in great shape. that is as long as its not been abused. le2 head job from elliotts with a custom cam from him is a good path to take. if you dont have one i would recommend you pick up a factory service/shop manual for your year.
Yeah I've been looking at the LT4 hot cam kit since I bought this car so a cam swap is already part of the plan! The reason for the hot cam kit is because it seems to include everything that is needed.

After doing the LT's I swore that next time I do anything I will pull the engine, and if I do that I might as well give the block some love while it's out in the open. Thinking about it still gives me chills along my spine.. it took me 6 weeks to do the headers, not one weekend as the people here on the forum said lol!

Thank you for your answer, I will search eBay for a shop manual!
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Old 04-19-2017, 09:38 AM   #10
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Word of advise, stop looking for one stop purchases.
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Old 04-19-2017, 10:07 AM   #11
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Word of advise, stop looking for one stop purchases.
Meaning?
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Old 04-19-2017, 10:23 AM   #12
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hot cam setup is not all that great. doing the lower end is not as easy as it sounds, lol, and can cost a pretty penny. check around your area machine shops and see what they charge to bore your block. building an engine, its not hard to spend 5k real fast. about 1700 bucks for elliotts le2 job, cam and port intake. probly lookin at about 2500 for these and the gaskets, 1.6 rockers, pushrods and various parts.
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Old 04-19-2017, 10:43 AM   #13
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hot cam setup is not all that great. doing the lower end is not as easy as it sounds, lol, and can cost a pretty penny. check around your area machine shops and see what they charge to bore your block. building an engine, its not hard to spend 5k real fast. about 1700 bucks for elliotts le2 job, cam and port intake. probly lookin at about 2500 for these and the gaskets, 1.6 rockers, pushrods and various parts.
Yeah I believe you, but as I said before - this is not something I will start doing right away. This has been my dream car since I was 14 and I plan on keeping it for a long time. It's a never ending project to me!

First of all I'm gonna build the rest of my exhaust, and when that is done I will move on with the suspension (probably Koni STR.T or KYB AGX). After that I will move on with the body and rims. I'm about to be a father in a few months so the car is pretty far down on the list. ^^
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Old 04-19-2017, 10:59 AM   #14
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kool, being a dad is so overwelming at first. yah i picked up some used heads and found a new crate short block to build while i drove the car. once engine was ready i just switched engines, well engine and trans, picked up a nice setup from patc. it was about a year process but could have drug it out for more with no issue.
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Old 04-19-2017, 11:34 AM   #15
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kool, being a dad is so overwelming at first. yah i picked up some used heads and found a new crate short block to build while i drove the car. once engine was ready i just switched engines, well engine and trans, picked up a nice setup from patc. it was about a year process but could have drug it out for more with no issue.
I was also thinking about having a spare engine on a stand that I could build while driving the car, and swap them when I'm done. A nice little project when I want to get away from the family for a few hours!

Anyway, thanks a lot for the help, and btw your car is badass!
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Old 04-19-2017, 05:39 PM   #16
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Meaning?
conveniently packaged kits, though not always, are usually underwhelming in quality or value. Unless you're looking at advanced inductions or lloyd elliot, pretty much all the LT1 "heads/cam" kits are pretty underperforming. The same can be said with alot of the rotating assemblies (pistons, rods, crank, etc.).

When looking at rotating assemblies stay away from cast cranks unless using a GM crank. Hypereutectic pistons are fine unless you're planing a lot of compression, forced induction (turbo/supercharger), or nitrous.
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Old 04-19-2017, 06:29 PM   #17
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Do a heads/cam swap as mentioned... 77k should mean the bottom end is in good shape and not in need of a replacement.

Doing a heads/cam swap will gain you alot of valuable experience in disassembly/re-assembly and how the motor goes together. Depending on the setup, you should end up between 350-400rwhp realistically, which will equate to a fun street car. Once you get bored with that, figure out the next steps. Some people move on to nitrous or forced induction (supercharger or turbo).

At that point, start considering what bottom end to run.
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Old 04-19-2017, 06:44 PM   #18
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Do a turbo setup, I hear a guy on here makes really bad *** kits.
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Old 04-19-2017, 11:29 PM   #19
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Originally Posted by myltwon View Post
conveniently packaged kits, though not always, are usually underwhelming in quality or value. Unless you're looking at advanced inductions or lloyd elliot, pretty much all the LT1 "heads/cam" kits are pretty underperforming. The same can be said with alot of the rotating assemblies (pistons, rods, crank, etc.).

When looking at rotating assemblies stay away from cast cranks unless using a GM crank. Hypereutectic pistons are fine unless you're planing a lot of compression, forced induction (turbo/supercharger), or nitrous.
Ah yes, now I understand!

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Originally Posted by RealQuick View Post
Do a heads/cam swap as mentioned... 77k should mean the bottom end is in good shape and not in need of a replacement.

Doing a heads/cam swap will gain you alot of valuable experience in disassembly/re-assembly and how the motor goes together. Depending on the setup, you should end up between 350-400rwhp realistically, which will equate to a fun street car. Once you get bored with that, figure out the next steps. Some people move on to nitrous or forced induction (supercharger or turbo).

At that point, start considering what bottom end to run.
After I'm done with the suspension I will start looking for a cam. Maybe even a complete H/C package from Lloyd. Can you swap the heads and cam while the engine is still in the car?

I forgot to mention that I live in northern Sweden so ordering parts are very expensive with import charges and all that. My Pacesetter LT's and y-pipe sat me back close to 500 bucks in additional charges.
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Old 04-20-2017, 05:01 PM   #20
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.... Can you swap the heads and cam while the engine is still in the car?
Yes. The head removal will be somewhat easier than the cam, because after you remove the intake manifold and valve train parts, the heads will then lift straight off. The cam is a little trickier, as the radiator and a/c condenser have to be gotten out of the way. The radiator isn't too hard, but you probably don't want to evacuate the refrigerant from the a/c system, so getting the condenser out of the way could be tricky. Keep in mind, the camshaft is basically as long as the engine is, so you need that much clear space in front of the engine, in order to remove it.
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