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NA 3.1L=>head & camshaft questions. No shortcuts, max


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No word since last week. Dave hasn't received the prospective billet crank yet, and doesn't know when he will. No luck in used LD28s, either.

 

I've thought a lot about 3.0 vs. 3.1 vs. 3.2, and I've landed on... who cares? Very surprised that I landed on that, given how important each detail / choice has been, given some of my statements and sentiments above.

 

Why the shift? I don't have a single, simple answer. It's big-picture... and when I zoom out and assume that I'll have the car another 18 years, then it doesn't really matter what configurations it passes through along the way. I then saw the block the same way I saw the intake: it's been not-ideal for years, and I kept it why? Because I enjoyed the iterative changes and how different each dyno plot is when go-fast parts are swapped out. I enjoyed the control of comparison against the last engine.

 

So... "who cares" more accurately translates to no changes for now. This iterative changes philosophy is no doubt very odd from a competitive or financial perspective. This is neither. This is the journey, the experience. "Enjoy the ride." (Not the finish line!)

 

My heart wants to finish building the 3.1L that I set out to build so many years ago. Yes, I want to be competitive, but neither the suspension nor driver are dialed-in with each other yet, so at this point in my experience, class entry is moot. I'm racing the clock.

 

I know that "one day" I will probably move to ITBs. That may not be until I want to be more competitive, so maybe a 3.0L would make more sense at that point in time.

 

Bottom line, I simply woke up one day and wanted to keep things the same. For now, anyway...

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I'm not a good case study of how to spend money on a head. Jim made three custom cam grinds doing the R&D on my N42 cylinder head. As an example, I'm running valve springs that have 25% less sea

And final assembly drew near. I literally started at 9pm that night, and in these pics it was about 9am the next morning. I was leaving for the airport at 11am and had to wrap this up, get it running

Sounds yucky.

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  • 2 weeks later...

Slow but steady progress: billet crank is out, stock LD28 it is!

 

The prospective billet crank finally arrived at Rebello. Dave's assessment: "It's a nice crank. It's not one of ours... but it's nice." It's made of solid 4340 and arrived knife-edged. All parties were surprised that the crank weighs in at 51 lbs, with stock cranks coming in around 52-54 lbs.

 

The vendor for the crank: Thomas Thorman of Sugar Hill Speedshop (GA), (678) 546-6055, https://www.facebook.com/Sugar-Hill-Speed-Shop-1001732356563108. I spoke to Thomas; this is a new part for him and he is still getting the details (mods?) up to speed. I'm not sure what his plans are, but the price I was quoted in its current, raw form was $2,575, "pre-balanced within a gram."

 

For me, this is too much cash for too little performance upgrade at this time. I want more strength, less mass (or improved CG) and more stroke for that kind of money, but that's me. Below is a picture. On the left is the new crank in question, and on the right is a Rebello crank for his 3.2 kits. Really makes a case for Dave's bottom ends! Maybe one day, okay very probably, but not this year...

 

That said, I still rely on experts, and oversights continue to cost me a lot of time and money. Had I known my crank was shot six months ago, I wouldn't have ordered custom pistons and would almost certainly have purchased a 3.0 or 3.2 bottom end from Dave knowing what I know now.

 

I sincerely hope my experience is helpful to someone in the future. :iospalo:

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Edited by zredbaron
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The prospective billet crank finally arrived at Rebello. Dave's assessment: "It's a nice crank. It's not one of ours... but it's nice." It's made of solid 4340 and arrived knife-edged. All parties were surprised that the crank weighs in at 51 lbs, with stock cranks coming in around 52-54 lbs.

 

The vendor for the crank: Thomas Thorman of Sugar Hill Speedshop (GA), (678) 546-6055, https://www.facebook.com/Sugar-Hill-Speed-Shop-1001732356563108. I spoke to Thomas; this is a new part for him and he is still getting the details (mods?) up to speed. I'm not sure what his plans are, but the price I was quoted in its current, raw form was $2,575, "pre-balanced within a gram."

 

 

 

Interesting.  I wonder what the stroke is and what the rod journal sizes are.  Maybe I'll ask them.  I am planning on running Honda sized rod journals.  I'll be needing 90 mm of stroke though. 

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  • 3 weeks later...

Well, as unpleasant and uncomfortable as it was and still is, I paid an exborbitant price for a used LD28, and the ball is once again rolling.

 

The new-used LD28 passed its magnaflux test and will be balanced / polished this week. Main bearings are being sent off for coating now that the journal sizes are finalized, too.

 

So... barring any unforeseen challenges, final assembly and dyno tuning are all that remains. I don't have a date set yet, but it looks like there's a decent chance that "July 2016" might be the month I officially get to try again! :2thumbs:

 

 

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  • 2 weeks later...

Getting closer. Block is assembled. Pics of coated pistons and new L24 rods below (Eagle). I don't know the weight difference yet.

 

Also included are pics of the coated E31 head. Combustion chamber, valve faces and exhaust port all received a TBC (thermal barrier coating, SwainTech). Not yet assembled.

 

Sounds like coordinating a window to use the engine dyno is proving difficult. Best case another delay, worst case chassis dyno only. Not sure what to expect. At this point, it's been so long (again) I'd just assume wait until the engine dyno can be utilized. "August?" B)

 

I think I've busted my budget by about 300% or so, too. Couldn't have afforded all this without the year of waiting to pay for it, wow!

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I found two for $900. One ended up being a dead end, and the other left me with the opposite of a warm fuzzy (I wanted it magnafluxed; he wanted a cash deal.). I ended up going with one from SoCal from a fellow racer who had been hanging on to it and was Johnny-on-the spot with communication and prompt pics of it being magnafluxed, video of it turning in a block, etc. I paid $1,300 primarily because I had wasted too many hours on it and wanted to have a chance to get one autocross event before the end of the season.

 

With the cost of custom pistons and new rods.... a full kit that's already balanced and is truly an upgrade is definitely the way to go in my opinion.

 

That said, there's no question this is a custom motor. Is it worth the cost just to be custom? Probably not. Helps me be less frustrated, though. Driving would help, too.

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  • 1 month later...

More challenges and a bit more progress.

 

Rockers. According to my builder, the CNC Rockers from ZCCJDM aren't a viable OEM replacement rocker at this time. Something about the ratio not being correct. Probably contributed to the last engine failure, but that doesn't excuse the previous builder from ensuring proper clearances. Joe is working with Brian to help him update his design. Back to OEM rockers for this guy!

 

Springs. Short version is that valve springs that have been ordered and reordered multiple times yet still do not produce the expected seat pressures from the cam spec sheet. Joe presented me with the springs he uses in his L4 motor, and we are proceeding with those. More pressure than the cam spec sheet calls for, but less pressure than other options. Still retains an outer-valve only design. Might raise the RPM limit slightly. (Not sure how one would test that safely?)

 

I still do not have a dyno date set yet, but very little assembly remains.  "Six minutes, Turkish."

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Nice Snatch reference. :) Mark what size are your pistons? I missed that in the thread, (just kinda skimmed it quickly.) I wanted to share something I read on Les Collins website. Evidently very few blocks whether N42 or F54 can handle the 3mm overbore. If you are going 89 make sure you get the block sonic tested as Les Collins states that only 1 in 6 blocks can handle the 3mm overbore.

 

http://lescollinsracing.com/engine/projects-engine/3435cc-z-racer

 

Surprising whats true and what gets passed around as truth.

Edited by Chris_Hamilton
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  • 2 weeks later...

If only 1 in 6 can handle the 3.1L overbore, why don't we hear warnings from the unhappy owners of the other 5 of 6? Interesting claim, but I'm with Steve -- I don't buy it either. I don't think our community would be silent on that kind of a failure rate.

 

Gettin' close and looking good! Head and valve train assembly complete, only minor assembly remains. No idea when the engine dyno will be scheduled...

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Edited by zredbaron
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Gathering the final details. Need to order a best-guess DCOE venturi (choke) for my upcoming engine dyno pulls. 

 

Engine Dyno approach:

Phase 1 - 40 mm DCOE, 36mm venturis (already installed)

Phase 2 - 45 mm DCOE, 36mm venturis (came with the new 45mm carb bodies)

Phase 3 - 45 mm DCOE, ?? best-guess venturis

 

Joe's experience with road-race DCOE engines lent him toward 41-42mm chokes. I asked the question about torque band, about how drivable these road-race DCOE engines are in lower-RPM ranges and varying throttle positions. His natural instinct is that this won't be an issue, as this motor will not lack for torque. True, but I still want to be confident in selection.

 

Since drivability is more important than peak hp, I posed the question: Is it better to start big and see what the engine likes or wants? Or better to start conservatively (~38mm?) and open up the venturis as needed?

 

Now that I've slept on it, the cost of venturis is, well, less than the cost of having a dyno crew and engine builder on the clock.

 

Then I think about why I waited so long and why I'm being so thorough with the engine dyno phase to begin with. To do it right. To share, and contribute. I'm here for the experience, after all...  I didn't know it until just now, but  it turns out I want the experience of open R&D.

 

If it isn't too lofty of a dyno-pull list, I now intend to add a couple of choke sizes. Any thought and experience here is appreciated!

 

Wouldn't that be some nice data to watch 36mm, 38mm, 40mm and 41mm? It's not like I can't sell the almost-new parts afterwards.

 

In honor of John Coffey. His R&D is in my E31 head, after all. This is how our community "lives."

Edited by zredbaron
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Great plan. I currently use DCOE 40s with 36mm chokes on my stoker and can't wait for you numbers and thoughts on drivability with the different combos. What's the biggest useable size in 45s? 41 choke? I would start at a 40 choke. Betting that's going to be the best fit but can't recall how much head work has been done. Big breather?

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