Stroker Motor with Stock Bore questions

[Maticus]

So, I just built a new engine with good used parts and some mild speed parts (mostly valvetrain related) and let's just say a mysterious noise got out from under me and toasted a rod and my crankshaft, so I need to replace them. I believe that because I run a full flow oil filter and shut off the engine immediately when the pressure dipped below 10psi, that nothing else was damage by the metal particulate. Further inspection upon opening up the case showed that everything else was in perfect condition, besides the cylinder 1 rod and and crank journal.

So with, my need to replace the crank anyway, should I just go ahead and throw a stroker crank in there? I read through a couple of other posts somewhat similar to this topic (but not quite as specific) and shopped around for good stroker cranks. I was really interested in CBs Super Race Cranks as they seem to be the more affordable, but still quality, alternative to a welded crank. There are no price differences between the different stroke sizes and if I'm going to get the clearancing done for say an 82mm, why not go with an 84 or 86 stroke? I am considering CB's "chevy" H-beams as well to make case clearancing less of an issue. Aircooled.net's Engine Article shares similar sentiments on choosing stroke (go big if possible). My biggest concern is that (for the meantime) I'll be using stock Mahle 85.5 cylinders. I've not built a stroker motor before but a lot of reading suggests that the standard pin location on the pistons and the longer rods I'll be needing to use could potentially cause issues. If the only "problem" I'll be running into is an engine that's a little wide, that's ok for fitment related issues (the body on this car is trashed, a little death wheel action in the bay won't bother me none).

So, what would be my best bet in stroke choice? I'd like to get the biggest crank I can in a 1600 case without doing crazy modifications and hacking a lot of material out of it. My gut feeling is leaning towards the 84, but if I can use the 86 (both using chevy H-beams) I'll definitely go with that. I'm also planning on adding either 92 or 94 cylinders later but for right now I'd like to just stick with the 85.5s if possible. This is an ongoing project so tearing down the engine at a later date for machine work, redoing all the deck heights and other rebuild related tasks isn't much of a problem. Any thoughts and suggestions are welcome.
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[FreeBug]

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PostPosted: Tue Mar 21, 2017 7:26 pm Post subject: Re: 1699 vs 1776 Reply with quote Report this post to Moderator/Admin.
The proper order to build things is

bore it first

and

if there's $ left over, stroke it too.

A stock bore stroked engine will get left in the dust but a stock stroke bored engine, all else equal.
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[Maticus]

While I agree with bore first then stroke, there's no point in boring my case when I don't have a usable crank in the first place. Hence my question regarding the stroker crank being the priority.
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1969 Rust Bugget AKA "Blitzkrieg"

[FreeBug]

If you must use stock cylinders (this is crazy, btw), the 78-82 mm stroke is about the limit. That's going to have some BIG spacers (like 4.5mm+). Someone else here might talk some sense into you.

76 or 74 mm stroke with stock P/C makes more sense, but really, do it once and do it right. I know, money, time, life, but otherwise, there WILL be regrets...

Hope I don't dampen your enthusiasm, but you will be happier in the end.

Hope this helps.

[pyrOman]

Agree with Free! I went with the 78 x 85.5 because like you, I already had the 78 and did not want to machine the case. Plus I figured why not put it together and "see" what I got out of it. Though I am now very happy with the result, I also have to say that if I was to have the clearancing done at a machine shop I'd had gone all the way and have it bored to at least 92. I don't have the tooling to bore it so if I was to pay $$$ for that might as well do the boring too.
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[Floating VW]

"A stock bore stroked engine will get left in the dust by a stock stroke bored engine, all else equal."

I love that expression. I wish I had a dollar for every time the guy on the other side of the parts counter said that to me when I was building my own stock bore stroked engine. The only problem with it is that it's missing a bit, which I think should be, "A stock bore stroked engine will get left in the dust by a stock stroke bored engine, but only at the big end of the quarter mile, all else equal."

I get the whole "go big or go home" thing, and I can appreciate the need for speed just as much as the next guy, but what if you don't want to live life Toretto style all the time (Toretto style is "a quarter mile at a time," in case you're like me and don't get to the movies but once every 20 years)? Sometimes it's nice to just have something simple and smooth, that really pulls hard down low in a real-life situation, like when you suddenly find yourself in the wrong turn lane and need to get off the line fast so you can cut over when the light goes green. Mini-strokers are perfect for that. All of the power, all of the time. That's what I'm talking about. Check out the "mileage motor" build that Hot VWs did a few years ago for an idea of what you'd be getting into: www.cbperformance.com/Featured-Articles-s/142.htm

And don't forget, as I recently learned the Porsche 356 Super 90 was built around a 74X82.5 mini-stroker, so how's that for street cred!

As far as how much you should stroke it, I suppose anything is possible, but with those pistons I'd limit myself to 76mm, maybe 78mm at the most. It would make life a lot easier on you than trying to stuff an 82mm or 84mm in there.

Good luck, man.
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[FreeBug]

I hear ya, Floating VW, I drove a 76 X 85.5 for two years or so, and I liked it! A lot!

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nothing wrong with a STF engine, but a big bore stock stroke engine will out perform a stock bore stroker engine.

If you are re-using engine parts you already have that's another story, compared to not having bought anything yet.
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[Pruneman99]

Besides the grossly over widened engine, tins not fitting, exhaust not fitting, having to hack up your engine bay, and pistons hitting the crank, more CC's than the valves can flow, nothing is wrong with a 82mm+ crank and stock pistons..

Personally I feel 76mm is the farthest I would go with stock pistons. I have only done a 74 though. Anything longer, and you need bore just to unshroud the valves.

[Maticus]

First off, thank you all for your responses and knowledge. So what I've gathered from this is a) I can stroke with stock bore, but not as much as I'd like to (considering all the strokes are the same price) and b) If I'm going to go big, I might as well go BIG for the cost of some pistons and machining. I just called a small local VW guy who will do a package deal on machine work and pistons, except for the clearancing work. I'll either have to bust out the ol' Dremel or find another shop (or use my school's CNC if I wanna go the extra 20 miles) but that's for later.

So, with these new considerations in hand, I guess I'm looking at an 84 or 86 crank (insight welcomed here) with 92 or 94 pistons. I'm leaning towards the 92 thick tops for longevity, or if I ever get around to an EFI turbo setup, but I digress. As for clearancing not regarding the case, at what stroke does the cam come into play? From what I've read it's usually either 84-86 and up, which are my target strokes. However, I might just get a new clearanced cam anyhow because the 2280 would most likely no longer be sufficient for the engine.

Regarding parts selection, everyone seems to have their own 4340 forged crank with nice things like 8 dowels, nitrided journals, already balanced, etc. and H-beam rods. They all say they're made in the same factory so brand really isn't a thing in that respect, regardless if its CB, DRD, Scat, or Cip1 (assuming they really are all the same, correct me if I'm wrong). I'm asking because if I don't have to pay more to, for example, buy a "CB" crank, I'll get the more affordable option, IF the quality is in fact the same.

So, how big on stroke can I go with big bores (92/94) instead of stock bore, what clearance issues will I run into if I say go with an 86 over an 84, and are all 4340 cranks and H-beams made equal?
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1969 Rust Bugget AKA "Blitzkrieg"

[mark tucker]

probably bigger than your wallet will permit.....and dont forget the rest of the vehicle it's going into.

[Lingwendil]

If I were planning a stroker (and I am) I would go 2180. 82 stroke, 92 thickwall pistons (94 head register). Deck your case, and set CR with barrel shims and head CC volume. Could go 84, but I wouldn't bother.

Go with either a DPR or CB Performance crank.

CB Performance Los Panchitos, DRD, or Mofoco heads.

Apply camshaft to taste, depending on exact choice of heads, exhaust, carbs, etc.
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[Pruneman99]

82mm crank, B pistons, and stock length rods makes a very close to stock width engine. Tins fit, exhaust fits, and you can actually fit it in the car. Your choice on piston size. Done.

[vwracerdave]

Just because all the cranks are made in the same country DOES NOT mean they are all made in the same factory. There is major quality control differences between the brands. You buy cheapest price and you'll get the cheapest junk. For a 1st time engine build 82mm is the max you should go. It takes an experienced engine builder to fit a 86mm crank into a stock case. Power is in the heads and not the length of the stroke.
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[slalombuggy]

There is a TON of clearancing to fit an 84 or 86 in a stock case, even the cam needs to be clearanced or buy a preclearanced one and check it. 82 is as big as I would go even with chevy rods for your first stroker build. If you want to go big, just send your case to Rimco and get the full meal deal including clearancing. OR, save your money, buy a CB bubble top and be good to go out to 86mm.

Don't forget to think about beefing up the tranaxle and mounts, maybe bigger brakes, bigger fuel supply lines and pump as part of your engine build.

brad

[Maticus]

This is really good information, thank y'all. Ok, so no 84+ stroke, 82 it is with B pistons of course. I'm probably going order from DRD. I feel as though they're a trustworthy company, their prices are fair, and I've heard they make some killer heads, but the same could be said for CB. I have a T3 IRS transmission for the meantime (I hear its 4.12 R&P is more stout than the Beetle variety), and the harder rubber mounts from Wolfsburg West. I also just redid all of my brakes very recently. They're still drums, and will later be swapped for discs, but I can lock up the wheels if I want to, so braking is ok.

So, if I have decided on the stroke at 82, should I also go with longer connecting rods? Longer is better after all, but can you go too long? I think 5.5 rods would be a happy medium in this case and like I said earlier, I'm shooting for deck height in the 0.040" range.
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1969 Rust Bugget AKA "Blitzkrieg"

[modok]

I'm a bit late but I'm going to tell you max stroke 76mm, and I'd probably go with 74
78 maybe but use a custom cam on tight lobe center.

With stock size valves it can't breath, and doesen't want more stroke, so unfortunately the 85.5 stroker pistons and 82 stroke is mostly useless, unless it's a rock crawler buggy. If it is a rock crawler buggy go for it.

[Maticus]