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V6 3.1 build from 3400 LA1

Old 01-29-2019, 08:59 PM
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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 12:52 AM. Reason: More updates to my cut-and-paste from Word.
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Old 01-30-2019, 04:28 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 04:32 AM.
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Old 01-30-2019, 11:53 PM
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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, 12:08 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, 04:22 AM
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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 04:30 AM.
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Old 02-03-2019, 02:23 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, 07:50 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, 12:05 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, 05:17 AM
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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, 01:49 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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Old 04-02-2019, 03:46 PM
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Re: V6 3.1 build from 3400 LA1

Welcome! I highly recommend you start a build thread in the V6 section. Where did you get such a rare block, and what vehicle is it going in?
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Old 04-04-2019, 02:49 AM
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Re: V6 3.1 build from 3400 LA1

Originally Posted by Sierra6 View Post
Welcome! I highly recommend you start a build thread in the V6 section. Where did you get such a rare block, and what vehicle is it going in?
Hi,

The engine will be going into a TVR, replacing the existing 2.5 L Triumph TR-6 inline 6 cylinder (the V6 and T5 5-speed will be WAY lighter). I found the block on Craigslist ... the guy sells a lot of old/used racing parts and equipment (although, this block is NOT a strengthened racing block ... it is a duplicate of the original GM 2.8 V6 block, but cast in aluminum, with iron cylinder liners, and cast iron 2-bolt main caps ... and it carries Chevrolet experimental identification markings in the casting). I will be building basically a stock engine ... a duplicate of the LA1, but in a 3.1 liter size, because the bore size restricts me to that capacity ... I am not going to mess with those liners ... they are basically like new ... not ANY wear at all. The LA1 heads and EFI intake will give me an engine that breathes very well and is astoundingly light. It will be a simple street engine of maybe 200 hp ... but, I don't really care about horsepower, I want the torque in the 3000-4500 rpm range.

Once I get started I will definitely write up the build for ThirdGen. At the moment I'm working thru the details of the engine swap with the Department of Environmental Quality, here in Phoenix. Phoenix is not like the rest of the USA ... the rules are different in this county, and very strictly enforced. Here in Phoenix you could buy a car from somewhere outside this county, or state, and NEVER be able to license or drive it here.
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Old 04-04-2019, 08:02 AM
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Re: V6 3.1 build from 3400 LA1

you probably just need to sell that block to me then
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Old 04-04-2019, 09:15 PM
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Re: V6 3.1 build from 3400 LA1

Originally Posted by Sierra6 View Post
you probably just need to sell that block to me then
I don't think so. That block is a keeper. I was unbelievably lucky to stumble across it, and the seller lived just a few miles from my son's house, 2000 miles away.

Here in Arizona the DEQ is strict, unyielding, but once you get past all of the hearsay about the emissions rules it all begins to make sense. They are good rules ... carefully thought out. Once you talk with them face-to-face you can see how most everything that you want to accomplish is actually possible ... but, only if you follow the rules to the letter. My first meeting with the DEQ showed me that most of the hearsay that you pick up on forums is wrong, and confusing.
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Old 04-05-2019, 08:04 AM
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Re: V6 3.1 build from 3400 LA1

Good luck with it. I look forward to seeing/hearing it when you're done. make plenty of youtube vids.
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Old 04-05-2019, 10:40 AM
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Re: V6 3.1 build from 3400 LA1

Originally Posted by TVRV6 View Post
I found the block on Craigslist ... the guy sells a lot of old/used racing parts and equipment (although, this block is NOT a strengthened racing block ... it is a duplicate of the original GM 2.8 V6 block, but cast in aluminum, with iron cylinder liners, and cast iron 2-bolt main caps ... and it carries Chevrolet experimental identification markings in the casting).
THAT is a cool little piece of Chevy history!
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Old 04-08-2019, 03:18 AM
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Re: V6 3.1 build from 3400 LA1

Originally Posted by Sierra6 View Post
Good luck with it. I look forward to seeing/hearing it when you're done. make plenty of youtube vids.
I'll keep you updated. I'll post all the details on what I have to do to pull this off ... hopefully it will be fairly simple. We'll see.

But, I've never posted a YouTube video ... I'll probably just type it up.

AND ... before all that takes place .... I've got to pay my taxes! That's the first priority.
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