The Project Pad

So, I don’t even have my replacement 7A up and running yet in my coupe and I’m already thinking of a possible future swap. This was the first time I’ve done a swap and I guess I’ve enjoyed the process somewhat.

As I continue to trip over and shuffle around a bunch of parts from my original 7A, I can’t help but think about what to do with it all. With the exception of some bent valves and a bent rod, I nearly have a complete engine and the accessories.

I remember seeing lots of threads over on MG about the “ghetto 20vt”, but never paid much attention to them. So recently, I’ve been reading a bunch of really old threads about pairing an NG/NF block with a 20v head.

Then today, I ran across a local Craigslist list ad for $100 Complete NF engine with good compression. Being an vintage Audi enthusiast in Oklahoma can be frustrating. Things don’t pop up on Craigslist or in the junk yards very often. I hear of people with a 3B or two or more in their garages just waiting for the next project, but that is just so foreign to me.

Are there any of you out here still running an N*/7A setup? Are there in long term issues with that configuration? Does the effort to get it up and running outweigh the simplicity of a just finding and swapping in a 3B?

Just to be clear, I’ve never had any stand alone tuning experience, but I find it interesting and am willing to learn.

Just trying to weigh my options and see what y’all think you would do in my position.

My goal would be a reliable, respectable engine that would pair well with the B3 coupe for a spot in the occasion daily rotation and fun weekend car. So, to me, that’s 300-ish awhp.

Thanks
Brent

Is there something better about the NG or NF than , say , a building a 7AT? I guess in your case part of that answer is what’s readily available if you don’t have a good spare 7A block.
I was just thinking the cranks are identical . You’d have to make an oil return /drain into the pan or something .
Typically I’ve always used AAN or 3B engine blocks but I understand they’re not as easy to come by anymore

Afterthought wrote:Is there something better about the NG or NF than , say , a building a 7AT? I guess in your case part of that answer is what’s readily available if you don’t have a good spare 7A block.
I was just thinking the cranks are identical . You’d have to make an oil return /drain into the pan or something .
Typically I’ve always used AAN or 3B engine blocks but I understand they’re not as easy to come by anymore

I'm not sure. By building a 7AT, do you mean beefing it up with stronger internals or just getting creative with HGs to drop the CR? Or some other method?

I do have a serviceable 7A block, but I'm cheap and don't like the idea of spending a ton of money on pistons for it and I don't want to make the kind of power that would require that. I'm intrigued by the N*/7A combination that drops the CR in the turbo-friendly area. I could use my 7A block and source just the rods/pistons from an NG or NF.

Am I correct to assume that the stock NF/NG bottom end should be strong to support the goal of 300 whp?

jbrentd wrote:

Afterthought wrote:Is there something better about the NG or NF than , say , a building a 7AT? I guess in your case part of that answer is what’s readily available if you don’t have a good spare 7A block.
I was just thinking the cranks are identical . You’d have to make an oil return /drain into the pan or something .
Typically I’ve always used AAN or 3B engine blocks but I understand they’re not as easy to come by anymore

I'm not sure. By building a 7AT, do you mean beefing it up with stronger internals or just getting creative with HGs to drop the CR? Or some other method?

I do have a serviceable 7A block, but I'm cheap and don't like the idea of spending a ton of money on pistons for it and I don't want to make the kind of power that would require that. I'm intrigued by the N*/7A combination that drops the CR in the turbo-friendly area. I could use my 7A block and source just the rods/pistons from an NG or NF.

Am I correct to assume that the stock NF/NG bottom end should be strong to support the goal of 300 whp?

Dana will probably chime in, he had, as far as I know, one of the longest running/most beat-upon ghetto 20vt setups. I'm planning on doing the same eventually in my 90.

If you're going to do pistons and/or rods than it doesn't really matter where you start, but the NF/NG 20v combo is perfect for the 300whp goal you're talking about, just don't let the torque spike too hard and you should enjoy many miles of smiles.

vt10vt wrote:Dana will probably chime in, he had, as far as I know, one of the longest running/most beat-upon ghetto 20vt setups. I'm planning on doing the same eventually in my 90.

If you're going to do pistons and/or rods than it doesn't really matter where you start, but the NF/NG 20v combo is perfect for the 300whp goal you're talking about, just don't let the torque spike too hard and you should enjoy many miles of smiles.

Thanks for the reply. I seem to recall Sam, Marc, and maybe some others have gone this route also. Do you have a project thread for your 90? If so, I'll be following along.

jbrentd wrote:
I'm not sure. By building a 7AT, do you mean beefing it up with stronger internals or just getting creative with HGs to drop the CR? Or some other method?

I do have a serviceable 7A block, but I'm cheap and don't like the idea of spending a ton of money on pistons for it and I don't want to make the kind of power that would require that. I'm intrigued by the N*/7A combination that drops the CR in the turbo-friendly area. I could use my 7A block and source just the rods/pistons from an NG or NF.

Am I correct to assume that the stock NF/NG bottom end should be strong to support the goal of 300 whp?

Yeah with the 7AT thing I meant like 034 does, with a compression dropping head gasket.
But, I didn't realize the 7A pistons were any different than AAN/3B other than size. If theyre not good for that much power , I dont know.

Be careful because I think this slippery slope is how I got all my AAN/3B's to begin with. Maybe things have changed a little (price/availability wise) but I have purchased a few AAN's from $500 reusable long block to $1700 for a good low mile runner pulled from the car. So I had ended up looking at what it would take money wise to get the 7A set up and then still need a harness and stuff and I just ended up getting the AAN which gained me the harness/ecu and the serpentine belt with all the accessories, intake and exhaust. But a lot of that you can get for next to nothing, and like was mentioned above, the crank is the same, and if you're doing pistons and rods it doesn't matter which block you start with I dont think .

If I recall correctly, the cast 7a pistons are good up to about 350 hp. I'd imagine detonation is the thing to keep in check for durability.

Afterthought wrote:Be careful because I think this slippery slope is how I got all my AAN/3B's to begin with...

Yeah, if I get my coupe running well, I should probably focus on refreshing the suspension and drivetrain.

under no circumstances would I ever deter anyone from doing a turbo! I mean you could look for a block ad just work on something on the side in your free time. Especially with your attention to detail and refinishing / painting / etc.
I did the vac booster conversion, boxter rotors, 2B/Koni suspension and the 5-lug swap on my coupe as well which was a nice all around set up.

I haven't started on my 90 and probably won't for a while. I think the 7a/NG/NF pistons all have about the same limit since they're cast, but using the NG/NF block gives you more headroom due to the compression drop.

Look for Dana's 90 build on Motorgeek (the 20vt one not the TDI one lol) and for McStiff's Coupe on here or Motorgeek, he has (had?) a super reliable 7at setup that made nice power. I think those are two of the best threads to read through if you don't think you'll go AAN/3B bottom end. pkw on Motorgeek also has a really interesting option that uses an MC2 bottom end and 7a head.

I have an MC2 bottom end laying around I might use instead of the NG but we'll see.

I just put NG pistons into my 7a block and ran it. It was a super fun car, I did feel like the off-boost power was noticably less than the 3b/AAN engines, but that could be cams too. Also, I never had a 3b or AAN car with anything other than a k24.

My plan was to replace it with a 3b with rods, but never got to it.

The car was reliable, engine went together once, and never gave me any trouble...The new owner blew a rod threw the block in the first week. The car was tuned on 93 octane and it happened on the first pull after filling with 91. I assume that killed it, but it could have also just been its time. Interesting to note that it appeared to be a rod failure, not a piston failure as most would assume with cast pistons.

I did tell him that it was subject to blow at any second, and he had plans to have 034 install a built AAN.