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Rebuilding my 7A vs 1.8t AEB swap

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 Post subject: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Mon Mar 20, 2017 6:51 pm 
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Hello,

My 7A, (1990 90 20v Quattro) has bottom end issues, and it's been out of commission for almost 4 years. I am weighing the costs/advantages to rebuilding the 7A bottom end, either myself or professionally, versus swapping in a AEB from an 'early' B5. I have yet to do either an engine swap or bottom end rebuild, so both would be learning experiences. My upfront budget is less than $1000, with more trickling in over time. Through a quick search on CL, I've found suitable donor B5's for around $750, this comes with the bonus of bolt-off bolt-on, ie; included turbo, electrical, and potentially interior parts.

I would be taking the 7A out and putting her on a stand for a full rebuild to come at a later date; I have a hard time switching to a smaller-displacement turbo engine, especially from the 20v and its beautiful torque curve.

I'm looking for suggestions, criticisms, anything you may have to offer on the subject. I'm trying to get started sometime next month.

Cheers


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Tue Mar 21, 2017 9:12 am 
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Speaking as someone who has done the AEB swap, and owned a dozen 5 cylinder cars, here are my thoughts:

Putting an AEB into something that had a 5 cylinder, is the whole reason i didn't put a 5 cylinder in my b4. there is a lot of work, and a lot of parts to buy. Radiators, accessories, mounts, ect.

I wouldn't replace a 5 cylinder with anything but a better 5 cylinder.

Now, 1k budget isn't that bad. I'm not sure where you are located but with some luck you can get a 3b or aan engine (WITH CAR) for that type of money. If you buy a c4, and it has a good bumper, you can sell the bumper for 500 alone pretty easily, to help 're coup' some of the costs. Also selling the c4 interior will get you some cash, and fenders, and numerous other bits.

Now alternatively, rebuilding your 7a block or sourcing a different one are also options. I have a few 7a's floating in my garage, id happily let any of those short blocks go for 100 bucks, all were from running driving cars.

The other option you have here is also go with custom pistons, or source NG pistons for the 7a. which will make it more 'boost friendly' and turbo that bad boy and enjoy it.


I love the 5 cylinder, and while I have done the 4 cylinder swap, i wouldn't replace a 5 cylinder with a 4. you have a lot of options, good luck!

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Tue Mar 21, 2017 5:42 pm 
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More work, but better outcome. I vote AEB > 7A.

Agreed that 3B > AEB.

My dad and I are debating this exact swap for this 1982 FWD Coupe. He already has a 4000hp 3B 4Ktq so we want something different and fun to do. Please post what you end up doing!

Thanks, Eric


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Wed Mar 22, 2017 5:54 am 
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7A rebuild! hands down! I can't justify going smaller displacement especially that good sounding 5-banger. Like Hybrid_Hatch said if I take out a 5 cylinder it is for a better 5 cylinder (i.e 07K).
I guess the better question is what are your power goals?

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Wed Mar 22, 2017 7:55 am 
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ejfluhr wrote:
More work, but better outcome. I vote AEB > 7A.

Agreed that 3B > AEB.

My dad and I are debating this exact swap for this 1982 FWD Coupe. He already has a 4000hp 3B 4Ktq so we want something different and fun to do. Please post what you end up doing!

Thanks, Eric



You mean 400 hp I'd wager ;)


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Wed Mar 22, 2017 12:47 pm 
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Well, my 20v has some goodies installed, like 034 injectors, adjustable FPR, racing radiator, 034 big MAF and stage2 ECU tune. Along with the flowmaster, it ran pretty damn good. The idea of finding a replacement 7A short block is the most appealing, I just have to find something in Oregon or southern Washington. Of course I would probably jump at the opportunity to get either a 3B or AAN too...


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Thu Mar 23, 2017 5:34 am 
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solidengineering wrote:
Well, my 20v has some goodies installed, like 034 injectors, adjustable FPR, racing radiator, 034 big MAF and stage2 ECU tune. Along with the flowmaster, it ran pretty damn good. The idea of finding a replacement 7A short block is the most appealing, I just have to find something in Oregon or southern Washington. Of course I would probably jump at the opportunity to get either a 3B or AAN too...

by the way what bottom end issues are you having? there is not much down there that can go wrong

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Thu Mar 23, 2017 12:34 pm 
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When I turn the engine over by hand, I hear some 'clank' in #1 cylinder.

I'm guessing a broken connecting rod, probably fried main bearings, and potentially a warped crankshaft?

A few years ago, I took it up the hill without checking the oil, which there was basically none, and felt loss of power during hard acceleration. Clankclankclank sound coming from the bottom end.


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Thu Mar 23, 2017 12:42 pm 
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yeah sounds like a spun bearing

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Thu Mar 23, 2017 1:26 pm 
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Hybrid_Hatch wrote:
yeah sounds like a spun bearing


Is this something that would be best addressed with a full rebuild? At this point, the block is looking a little crusty, and I'm skeptical that replacing a connecting rod and some main bearings would resolve my issues with any reliability. With the scarcity of 20v's, there's one about 500mi away in Reno, it seems that an AEB might fit into my timeline better.

There is at least one manual B5 here that would serve as a good donor car, and new engine mounts, radiator and supports, sounds like a small price to pay to get my rally car back in business. Especially if my 20v needs a full rebuild anyways, an AEB would be a good placeholder, only, if it didn't require any custom fabrication. Electrical work, I can do.

As it is, I just pulled out my radiator last night, and finally got some tape to start labeling everything. I found a youtube of some backwoods mfer's pulling a 20v with what looks like a pallet jack. This would save me money on an engine hoist ;)

cheers


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 5:12 am 
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You could get a good used 7a block and swap it over in a weekend. I cant see how that is not the easiest choice.

Swapping an AEB would certainly be cool to some people, and totally worth it, if that is your thing. However, to compare the two in ease, time and cost is silly. No comparison.

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 5:20 am 
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death 4kqt wrote:
You could get a good used 7a block and swap it over in a weekend. I cant see how that is not the easiest choice.

Swapping an AEB would certainly be cool to some people, and totally worth it, if that is your thing. However, to compare the two in ease, time and cost is silly. No comparison.


Agreed!!
anyhow the broken block needs to come out the car. no argument there. now if you are worrying about cost and save some money, open the block and see what you need to replace (maybe just rod and bearing) but you go a lot of scored parts, 1K is waayyy more than enough to get you a short block.

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 5:40 am 
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I probably wouldn't even bother trying to replace the bearing if it has spun. If the engine was rare, then yes. But when you can get a perfect 7a bottom end for $100, its not even worth replacing the bearing. Hell I have a couple 7a blocks sitting in my barn that I couldn't give away. I'm making one into a sculpture for my mailbox.

You will never get things installed and clearanced as well as the factory. Even machine shops seem to fail to assemble an engine that lasts as long as a running, factory assembled block.

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-1990 90q 1.9tdi swap w/holset turbo
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-1990 90q 20vt: 3b swap
-1990 90q 20vt: 11.7 @124.5
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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 10:46 am 
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Sound advice, just need to find one of these short blocks.


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 11:16 am 
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solidengineering wrote:
Sound advice, just need to find one of these short blocks.


again, i have 3 in my garage and i'm only a couple states away.

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 1:29 pm 
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Hybrid_Hatch wrote:
solidengineering wrote:
Sound advice, just need to find one of these short blocks.


again, i have 3 in my garage and i'm only a couple states away.


I've been trying to source something closer to home, as I am unfamiliar with the greyhound shipping method you have mentioned, but, it's getting closer to my allotted project time, therefore.. How does the greyhound thing work?


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 1:59 pm 
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Greyhound is normally 2 day service on the west coast. I drop it off at the local greyhound station, they load it on a bus, you go pick it up at your local greyhound station.

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 2:47 pm 
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What part of Oregon are you in? LOTS of Audi guys and parts in OR/WA. I think I know of a 7A or two up in the Seattle area.

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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Fri Mar 24, 2017 3:23 pm 
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I'm in Portland OR.

I'm going to try and source something a little closer, but If nothing pans out Hybrid, I'll pick one of those up from you. I still have a few weeks until this check rolls in.


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Thu May 18, 2017 12:44 am 
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So I got ahold of a longblock from somewhat nearby, but the cylinder walls have a noticeable wear mark right about where the rings are; about 3/8" from the top of the cyl and maybe 1/32" deep. The cyl walls on my block are far less worn, no perceivable lip.

I have basic literature for rebuilding engines, so would it be possible to tear into the bottom end and rob parts from the worn block, like rods, maybe crankshaft with basic tools? Guess I don't need this thing to run forever, just like to put if together right. If not, my next option is to take both blocks to the machine shop, and have them replace the broken internals with those from the worn block. Does anyone have an idea about how much this would cost?

Apparently, the 'new' block has new main bearings, but would those be replaced without replacing the piston rings? And per my manual, if the cylinder wasn't reamed then the rings probably weren't replaced. Right? I made a few rookie mistakes here, but I have two 7A's worth of parts and figure there's a way to get things done.

Thanks for any input, cheers.


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 Post subject: Re: Rebuilding my 7A vs 1.8t AEB swap
PostPosted: Thu May 18, 2017 4:31 am 
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you do not need a special to get in there.

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