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V6 3.1 build from 3400 LA1

Old 01-29-2019, 09:59 PM
  #1  
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V6 3.1 build from 3400 LA1

My intention is to build a 3.1 L V6 for street use, using basic OEM parts whenever possible … I’m interested in torque for street use, not high-rpm power.

And, my primary goal here is to build a very light engine … aluminum block, heads, intake. Don’t try to dissuade me from light weight … it is the ONLY reason why I have chosen to build this engine. I am thinking of buying a 3400 LA1 engine, with computer and wiring harness, from a 1999-2005 Pontiac Grand Am.

I will combine the LA1 engine with an aluminum V6 block that I already own. This is NOT a Chevrolet Performance block.This is a Chevrolet Experimental block produced in the 1980’s … it has an experimental serial number cast into the side of the block. The bore is 89mm … all cast iron sleeves in perfect condition (I will NOT attempt to bore this block out any further).The main journal size is the pre-1985 “small journal” size … 63.3mm. The main caps are 2-bolt cast iron caps … the included main bearings have NO wear (but, I will replace them, of course … along with the cam bearings). The block is only drilled for a starter on the driver’s side (for longitudinal installation). This is an experimental block, developed to Gen I standards … a precursor to the Chevrolet Performance block.

So, I think I can combine the LA1 top side with my aluminum block. What are the obstacles? This is what I see …
  1. I need to have the LA1 crank main journals turned down to “small journal” size
  2. I want to run a DIS ignition system, but my block has no place to mount a sensor to read the “crank position notch” in the center of the LA1 crank … I assume that I will have to mount an external pickup to read the crank damper, front pulley, or a front-mounted degree wheel
  3. I will need new 89mm pistons and rings
  4. I will need a flywheel … because it is unlikely that I will find an LA1 engine for sale, combined with a manual gearbox
  5. I will probably buy a stamped-steel oil pan … though I think I can use the LA1 cast aluminum pan, if I seal up the main cap cross-bolt holes
That's it. What do you think? Any ideas?

Last edited by TVRV6; 01-30-2019 at 01:52 AM. Reason: More updates to my cut-and-paste from Word.
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Old 01-30-2019, 05:28 AM
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Re: V6 3.1 build from 3400 LA1

Originally Posted by TVRV6 View Post
My intention is to build a 3.1 L V6 for street use, using basic OEM parts whenever possible … I’m interested in torque for street use, not high-rpm power.

And, my primary goal here is to build a very light engine … aluminum block, heads, intake. Don’t try to dissuade me from light weight … it is the ONLY reason why I have chosen to build this engine. I am thinking of buying a 3400 LA1 engine, with computer and wiring harness, from a 1999-2005 Pontiac Grand Am.

I will combine the LA1 engine with an aluminum V6 block that I already own. This is NOT a Chevrolet Performance block.This is a Chevrolet Experimental block produced in the 1980’s … it has an experimental serial number cast into the side of the block. The bore is 89mm … all cast iron sleeves in perfect condition (I will NOT attempt to bore this block out any further).The main journal size is the pre-1985 “small journal” size … 63.3mm. The main caps are 2-bolt cast iron caps … the included main bearings have NO wear (but, I will replace them, of course … along with the cam bearings). The block is only drilled for a starter on the driver’s side (for longitudinal installation). This is an experimental block, developed to Gen I standards … a precursor to the Chevrolet Performance block.

So, I think I can combine the LA1 top side with my aluminum block. What are the obstacles? This is what I see …
  1. I need to have the LA1 crank main journals turned down to “small journal” size
  2. I want to run a DIS ignition system, but my block has no place to mount a sensor to read the “crank position notch” in the center of the LA1 crank … I assume that I will have to mount an external pickup to read the crank damper, front pulley, or a front-mounted degree wheel
  3. I will need new 89mm pistons and rings
  4. I will need a flywheel … because it is unlikely that I will find an LA1 engine for sale, combined with a manual gearbox
  5. I will probably buy a stamped-steel oil pan … though I think I can use the LA1 cast aluminum pan, if I seal up the main cap cross-bolt holes
That's it. What do you think? Any ideas?

quite a bit of this can be explained in my sticky for a hybrid build in the v6 area. You will find alot more support over there. Although I used a iron 3.1 block gen 3 top the issues with dis and such are exaplained there. Honestly it's quite easy.

so what is the difference between this experimental block.... and a gen 1 block? You say it has the small journals of the mid and lower 80s? Wow that's a shame they would do that bit it was normal at that time I'm sure.

Last edited by fasteddi; 01-30-2019 at 05:32 AM.
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Old 01-31-2019, 12:53 AM
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Re: V6 3.1 build from 3400 LA1

Thanks Fasteddi. I wasn't sure where to post my question. I'll take a look at the V6 stuff.

As to your question about my block ... I am pretty sure that it is a duplicate of the cast iron Gen I block, but cast in aluminum, rather than iron.

Thanks for the lead. I'll look at it now.
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Old 01-31-2019, 01:08 AM
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Re: V6 3.1 build from 3400 LA1

Fasteddi, I'm new to this forum. How do I find the "sticky" that you mentioned? What do I search for in the V6 area to find the hybrid build that you mentioned?

Thanks.
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Old 01-31-2019, 05:22 AM
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Axle/Gears: Strange S60 4:10s
Re: V6 3.1 build from 3400 LA1

Go to the sub forum for the v6 area here https://www.thirdgen.org/forums/v6/

and here is one of the stickys I made back in my v6 prime. https://www.thirdgen.org/forums/v6/7...eddis-set.html

The stickys are on the top of the sub forum (v6) page

Now my sticky is basically how to affix a gen 3 top end to a gen 1 bottom end which is what you have to a extent.

Last edited by fasteddi; 01-31-2019 at 05:30 AM.
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Old 02-03-2019, 03:23 AM
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Re: V6 3.1 build from 3400 LA1

Thanks fasteddi. Perfect. Exactly what I needed. Great info!
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Old 02-03-2019, 08:50 AM
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Re: V6 3.1 build from 3400 LA1

Originally Posted by TVRV6 View Post
Thanks fasteddi. Perfect. Exactly what I needed. Great info!
Not a problem. Let me know if you have any questions. Hopefully me or a few other gear heads on the v6 sub forum can help.
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Old 02-05-2019, 01:05 AM
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Re: V6 3.1 build from 3400 LA1

I have a general question about CPU's/ECM's.

As I mentioned, I plan to pull a 3.4 V6 from a 1999-2005 Pontiac Grand Am, to get an LA1 version of the V6 engine. I was thinking of using the ECM computer from the Grand Am to control fuel and ignition.

BUT ...
  • I'll be building a 3.1 engine, NOT a 3.4 engine
  • My car will be about 1000 lb lighter than the Grand Am
  • The Grand Am will probably have an automatic trans, but my car has a 5-speed manual gearbox
My question is this ... can the Grand Am ECM be updated/modified for my use? Or, would it be easier to just buy, install, and tune a new Megasquirt system?
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Old 02-05-2019, 06:17 AM
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Transmission: Hughes TH350 Trans Brk.PTC5KStall
Axle/Gears: Strange S60 4:10s
Re: V6 3.1 build from 3400 LA1

Originally Posted by TVRV6 View Post
I have a general question about CPU's/ECM's.

As I mentioned, I plan to pull a 3.4 V6 from a 1999-2005 Pontiac Grand Am, to get an LA1 version of the V6 engine. I was thinking of using the ECM computer from the Grand Am to control fuel and ignition.

BUT ...
  • I'll be building a 3.1 engine, NOT a 3.4 engine
  • My car will be about 1000 lb lighter than the Grand Am
  • The Grand Am will probably have an automatic trans, but my car has a 5-speed manual gearbox
My question is this ... can the Grand Am ECM be updated/modified for my use? Or, would it be easier to just buy, install, and tune a new Megasquirt system?
Personally I would either use a 7730 ecm with a $59 mask, which is what I used for dis, my turbos, etc. Or just go with a ms system. Depends on how well you are with gm obd1 systems. But the $59 mask has lots of options and can do everything you talked about
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Old 02-09-2019, 02:49 AM
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Re: V6 3.1 build from 3400 LA1

Thanks fasteddi. Good info. Exactly what I needed.
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