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> Question to the braintrust for motor building
Mikey914
post Nov 30 2021, 11:27 AM
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Looking to make a larger motor (4) planning on a 2665, as I don;t really want to go over 103mm to make cooling easier.

The 80 crank is available for stock rods not the Chevy rods. It is my understanding that the Chevy option offers a significant upgrade to the strength. I'm tempted to do the stock.

My question is : should I wait an indeterminate time for the crank with the Chevy rod option? What am I really loosing here? or is this just a must for the larger motors?

My 1st engine build.
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VaccaRabite
post Nov 30 2021, 02:22 PM
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What are your goals for the motor? Long drives, or short? Track use vs street use. Do you care if its somewhat short lived?

You've been in the game long enough to know a lot of this, but heat is your enemy and the big motors can produce a lot of it.

Zach
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914_teener
post Nov 30 2021, 04:07 PM
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QUOTE(Mikey914 @ Nov 30 2021, 09:27 AM) *

Looking to make a larger motor (4) planning on a 2665, as I don;t really want to go over 103mm to make cooling easier.

The 80 crank is available for stock rods not the Chevy rods. It is my understanding that the Chevy option offers a significant upgrade to the strength. I'm tempted to do the stock.

My question is : should I wait an indeterminate time for the crank with the Chevy rod option? What am I really loosing here? or is this just a must for the larger motors?

My 1st engine build.



I know it's not one of your questions but......

Just put in a six.

My 02.
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mepstein
post Nov 30 2021, 04:17 PM
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QUOTE(914_teener @ Nov 30 2021, 05:07 PM) *

QUOTE(Mikey914 @ Nov 30 2021, 09:27 AM) *

Looking to make a larger motor (4) planning on a 2665, as I don;t really want to go over 103mm to make cooling easier.

The 80 crank is available for stock rods not the Chevy rods. It is my understanding that the Chevy option offers a significant upgrade to the strength. I'm tempted to do the stock.

My question is : should I wait an indeterminate time for the crank with the Chevy rod option? What am I really loosing here? or is this just a must for the larger motors?

My 1st engine build.



I know it's not one of your questions but......

Just put in a six.

My 02.

(IMG:style_emoticons/default/agree.gif) You have a bunch of fours, time for a six.
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914werke
post Nov 30 2021, 04:37 PM
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Nickies?
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Superhawk996
post Nov 30 2021, 04:55 PM
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QUOTE(Mikey914 @ Nov 30 2021, 12:27 PM) *


My 1st engine build.


Seems like you're proposing a jump off the high dive, into the deep end, and planning to learning to swim once you're in the water.

Forgive me if that comes off as overly negative. It is not my intent to insult you by any stretch of the imagination.

You've asked a loaded question about big bore /4's which isn't an ideal build even or an experienced T4 builder. Not to mention the other aspects like rod choices, stroker crank, case modifcations, Nickies, RPM & inertia effects on the durability of a T4 crank and rods, etc.

I'm sure you can do it, it's not impossible. You just need to be aware of the negative trade offs associated with the big bore route and go into it with eyes wide open.
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Shivers
post Nov 30 2021, 05:34 PM
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80 mm crank, wow lots of torque. In my bug days the chevy rod mod was popular with guys building drag engines. With a crank that big a little extra weight on the rod should not be a problem. Like said before heat would be my concern.
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NARP74
post Nov 30 2021, 05:55 PM
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I just went though this drill. Met a guy with all the parts to build a 2300ish engine, all the parts machined and ready to assemble. I decided it was not right for me and walked away, but your situation might be different. I can make a strong case for either side of the argument, just depends on your situation.
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Mikey914
post Nov 30 2021, 08:04 PM
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Well my buddy Allen who is a factory trained mechanic is going to help me assemble the motor. He was aware of the journal mod, but didn't think it was that big of a deal.
The issue is crank availability.

As far as heat and thermal build up. The consensus we came to was no larger than a 103mm on the bore in this configuration.

This motor will be utilizing heat dissipating and ceramic coatings, as well as some new biral cylinders we are working on.

It will have lots of sensors monitoring each cylinder for EGTs and multiple head sensors. We will be running fuel injection with a new setup that we are trying to make more plug and play for larger motors.

Will probably spend as much as a 6 when Im fone. But if it works as planned will be a blueprint for turnkey larger motors.

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NARP74
post Dec 1 2021, 12:06 AM
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Sounds like you are on the right track. Making it affordable, reliable and not needing a rebuild in 30k miles are the next big steps.
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BeatNavy
post Dec 1 2021, 07:15 AM
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QUOTE(Mikey914 @ Nov 30 2021, 10:04 PM) *

But if it works as planned will be a blueprint for turnkey larger motors.

Just tell me when the group buy is scheduled, Mark (IMG:style_emoticons/default/laugh.gif)
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Superhawk996
post Dec 1 2021, 07:31 AM
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Other big bore considerations beyond thermal effects:

T4 Crank only has 3 bearing journals to carry loads. Not ideal for lots of power reliably over long durations of time.

Rotating inertia of the crank increases as a function of mass and stroke^2 (exponential). Rotating mass and/or inertias may increase substantially due to bigger pistons and wrist pins, stronger rods, the added mass from the stroker crank depending on the components you use.

In addition to those inertial loads you now have more combustion based torque load applied to the crank with each combustion event.

Horizonallly opposed 4 cylinder engines - although they have perfect primary and secondary balance, the non overlapping combustion events contribute to torsional oscillation of the crank. Normally a harmonic damper would be used to damp these out. Not aware of a harmonic damper for T4's. The more power the engine puts out, the more quickly the crank will be fatigued by the increased torsional vibrations.
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Shivers
post Dec 1 2021, 07:40 AM
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QUOTE(Mikey914 @ Nov 30 2021, 06:04 PM) *

But if it works as planned will be a blueprint for turnkey larger motors.



Have you considered a possible short stroke version, for people that like that type of power. A counter balanced 1.7 or 2.0 with 103's , a well breathing induction system
with the horse power a little higher on the band.
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Superhawk996
post Dec 1 2021, 07:43 AM
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delete - duplicated post
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Mark Henry
post Dec 1 2021, 09:03 AM
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Toss the stock rod idea, they're heavy and a wider journal further weakening the crank. Chevy 2.0 journals and H beam rods are the way, one cam lobe where it meets the rod still needs major clearancing with 80mm. For longevity and an easier build I'd recommend the 78mm crank with type one journal size rods, the beefier T1 rod journal makes for a substantially stronger (less flex) crank.
Although there's no replacement for displacement depending on expectations I try to to talk peeps into a reasonable margin for safety.
My own engine (in a '67 bug) I built 78mm x 102mm (2.6L, nickies) mostly because I planned to put many street miles on my engine. When building my engine I had both a 78mm and an 80mm crank, I chose the 78 and sold the 80mm.

Biral cylinders...why?
Porsche abandoned biral's after only a couple years and LN found to make them properly they cost almost as much as nickies and also abandoned biral cylinders after just a couple of years. If the aluminum fins aren't perfectly (and I mean perfect) cast onto the steel it will have voids, at which point you may as well run no fins at all. LN found material separation to be be a huge problem in manufacturing. A china supplier working at a reasonable price point will fuch this up and a domestic supplier will be way too expensive. You will only be able to tell this by Xray and/or ultrasound of each and every cylinder further driving up costs.
I won't build a Biral cylinder engine (except stock 911), I don't give a flying fuch who made them. I'd rather walk away from the job.


QUOTE(NARP74 @ Dec 1 2021, 01:06 AM) *

Sounds like you are on the right track. Making it affordable, reliable and not needing a rebuild in 30k miles are the next big steps.


For a street car my engines require a valve job at 60k and the bottom end must be good for 2-3 times that. An 80mm crank engine requires a full teardown at 50-60K regardless. The slightly detuned 2.6-2.7 engine is a much better overall investment.

Edit; Note the china cranks are softer than OE, I'm expecting that a full tear down of the bottom end will be required before 100K to check for center main wear.
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Jack Standz
post Dec 1 2021, 01:14 PM
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Sounds like a very cool project. Best wishes with it. Similar to one we have planned.

Some things going into the 2.6 liter Type IV motor when time allows (so many projects to complete beforehand):

Type 1 Journal on crank - hard to find, but available 18 months ago when started assembling parts. Stroke is 80mm (78mm stroke crank wasn't available).

Nikasil cylinders with JE forged pistons, 102mm bore. Pistons are light, light lifters and valve train, along with lightened flywheel. Reducing reciprocating mass improves longevity, faster acceleration, more HP. Careful balancing very important.

Better than H-Beam rods (lighter and stronger):
https://www.thesamba.com/vw/classifieds/det....php?id=2342801
EMPI New Pro Series I-Beam Rods 5.5 Length with ARP 2000 5/16" Bolts in a VW Journal. These are lighter and stronger than the H-Beam Rods.

Aluminum push Rods, custom length.

Type 1 tool steel lifters (lighter than Type iv).

Custom cam with extra duration on exhaust stroke (helps control motor heat). Lead time can be a project killer though.

Keep compression low to aid with heat control. Initial spark setting,to be 14 degrees BTDC, with 28 all in...subject to tuning and optimization. Probably starting with carbs because they're so tunable and easy, especially since the car is already setup for them. Maybe later, like you, it'll have injection?

As you already know, heat is an enemy in larger Type IV motors. So, stay focused on that (in addition to careful machining and assembly) and can't wait to see how she turns out!
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NARP74
post Dec 1 2021, 01:23 PM
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Did anyone consider getting this project going again?
http://www.914world.com/bbs2/index.php?sho...=42456&st=0
Seems like some of the originals dropped out but might be salvageable.
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930cabman
post Dec 1 2021, 01:38 PM
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QUOTE(914_teener @ Nov 30 2021, 05:07 PM) *

QUOTE(Mikey914 @ Nov 30 2021, 09:27 AM) *

Looking to make a larger motor (4) planning on a 2665, as I don;t really want to go over 103mm to make cooling easier.

The 80 crank is available for stock rods not the Chevy rods. It is my understanding that the Chevy option offers a significant upgrade to the strength. I'm tempted to do the stock.

My question is : should I wait an indeterminate time for the crank with the Chevy rod option? What am I really loosing here? or is this just a must for the larger motors?

My 1st engine build.



I know it's not one of your questions but......

Just put in a six.

+1, my vote goes here. Plenty "O" power with durability
My 02.

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Mikey914
post Dec 1 2021, 02:19 PM
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Thanks all,
This was the kind of feedback O was looking for. Definitely a few things to think on. We were looking at makung the biral cylinders here and had an idea for a twist on them that could improve cooling. I get that voids would be an issue. My idea was to utilize a process that we could replicate, and if the results were consistent, we would only have to to QC on a few in each batch.

The 78mm crank is a good point.

I think we can develop a pretty solid motor. The testing will be the most fun.

Mark
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914_teener
post Dec 1 2021, 02:35 PM
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QUOTE(Mikey914 @ Dec 1 2021, 12:19 PM) *

Thanks all,
This was the kind of feedback O was looking for. Definitely a few things to think on. We were looking at makung the biral cylinders here and had an idea for a twist on them that could improve cooling. I get that voids would be an issue. My idea was to utilize a process that we could replicate, and if the results were consistent, we would only have to to QC on a few in each batch.

The 78mm crank is a good point.

I think we can develop a pretty solid motor. The testing will be the most fun.

Mark


Mark....

You are probably better off lookng at flame applied coatings rather than the biral cylinders.

There are some amazing thermal coatings out there now as I sure you are aware of being into aircraft.

This technology just wasn't as mature back when Porsche looked at it.

Kind of like the EV technology now.... (IMG:style_emoticons/default/hide.gif)
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