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ANOTHER Datsun Z/LS3/T56 Swap Thread


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Posted (edited)
1 hour ago, 280Z-LS3 said:

Did you ever figure out the soft pedal issue?  A friend mentioned bleeding dual masters is a real challenge while discussing my brake setup.   What method did you use?

 

Every method I could conceive.  I pressure bled them multiple times, and also did so by pumping the pedal while doing the fronts simultaneously, then the rears.  I tapped on the calipers with a plastic mallet to knock air bubbles loose.  I bled them with the pistons in different positions....

 

Gradually the pedal got better and better....now it is rock hard, like standing on a brick.  I wish I could tell you which step was the magic one....but I don't know.  It was a PITA though, and it doesn't seem like it should be that difficult...

 

The switch to .75/.70" master cylinders also helped a ton.  My prior setup was just...all wrong.

 

I also switched to Carbotech XP20 pads in an effort to improve cold bite.  I only briefly drove on them before starting the exhaust re-do, but I can tell you they REALLY bite.  Even completely cold, it almost felt like I had power brakes again.  I need to break them in and test them a lot more to know the full picture....but they definitely work when cold.  They also were squealing like I couldn't believe....but that might be due to lack of break-in.

Edited by Ironhead
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Finished the stitch welding....nice to have that chore done....and moving forward at my normal glacial pace.   Started building the supports for the main hoop of the roll cage.  I included c

Thanks for the kind words Vanilla.   I spent most of the day today getting the passenger side door hoop bent.  It really fought me.  To make it fit decently, bends in multiple planes are nec

Calling the cage done, at least from the dash back.  Also hit the tubes and welds with Scotchbrite so they are ready for primer.          

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15 minutes ago, JMortensen said:

If I ever redo my headers I'm going Tri-Y out to the side pipes. Looks good! Did you dyno with the previous ones? Would be curious to see numbers on both.

 

I didn't.

 

I've read several opinions that the Tri-Y design is likely to offer benefits over 4 into 1 on LS engines, but this was really a "how can I make things fit better" exercise rather than a quest for more power.  

 

I too would be curious about the differences between each design, but nowhere near curious enough to actually do it.  The headers can be swapped with the engine in the car, but it requires some dismantling on both sides and is a bit of a PITA.  Also, the 4 -1 headers won't mate up with the updated downstream exhaust.

 

 

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Took the car out in 95 degree weather a couple of days ago, and it wanted to over heat.  Nothing catastrophic, but it started to get a bit warm when driven hard and I question it's capacity to withstand a warm day on track.

 

My oil cooler location seems like an obvious first place for improvement.  It clearly impacts airflow to the radiator, particularly once the oil is hot and the air passing through to the radiator is going to be very warm.  There are a thousand other places I can put an oil cooler...and I figure it is time to experiment.  The only real problem is that I will probably need a differently shaped cooler.  Or a coolant/oil based heat exchanger.

 

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Opinions?  While there is no question the radiator will work more efficiently with the oil cooler elsewhere, do you think it would be a huge difference or a subtle one?  I know this is not the first application wherein an oil cooler is mounted in front of the radiator, but that is a damn big oil cooler.

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I would build a duct from the front bodywork to the rad to force all the air that goes in to pass through the radiators, and then put the oil cooler on the backside of the rad. That's how I did mine after emailing with one of the oil cooler companies about it. Can't remember which company I was talking to (C&R?), but the idea was that the oil gets hotter than the coolant, so you want coolant first. They also steered me away from a rad/oil heat exchanger.

The main point I got out of it was that the bigger the temp difference the better it will cool, so by putting your oil first you're raising the temp of the cooling air hitting the rad rendering it less effective, and done the other way there will still be a significant difference between the air exiting the rad and the hotter oil, so it will still have enough capability to cool the oil, assuming all the rads are sufficient size, and it looks like that's not a problem. 

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Agree that front end air ducting would definitely help.

 

Putting the oil cooler behind the radiator would require massive modifications to the build in my case, as with fans and radiator plumbing there is almost no room.

 

What do you think about a wide/short air-oil cooler in the opening in the air damn?  That would clean up the flow to the radiator and also offer unobstructed airflow to the oil cooler...

 

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Sure, separating the flow entirely would work too. I wouldn't put it right at the air dam though. Oil is a surprisingly big fire hazard, so I'd set it back and keep your frame work out in front to protect it. You don't need that much open space to cool the car either, I'd block the top grill entirely (with black material recessed a bit if you don't want it obviously blocked off, and then split the opening at the bottom to feed both the rad and the oil cooler.

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Posted (edited)

Blocking off the empty fresh air duct holes would help as well. Air is surprisingly adept at making its way around a heat exchanger if there is a path with less resistance. 

 

Edit: Ducting the radiator like Jon said is definitely the first priority, though. There's a lot of space for air to get between the splitter and lower core support, so that's where a ton of air is going.  You could do what Jon said, but I think an easier route would be to just add a flat plate to the top of your bumper/splitter support structure, and then fill in the gaps behind and on the side. It doesn't have to be beefy stuff as long as it's secured well. I've  used 1/4" plywood before, and that worked perfectly along with being light. 

Edited by calZ
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What radiator design are you using, single or dual pass, tube size, overall core thickness?

Does the fan shroud allow for air flow when fan is not active?

 

The location of the oil cooler is very common, there must be an easier solution than relocating.  And as others have said, ducting more air toward the radiator seems like a good idea.  Maybe some light aluminum or stainless sheet metal could be formed into a polyhedron (big word, had to Google that one) to funnel air to front of radiator. 

 

The C7 fan I plan to use has 7 flaps which are pushed open when air pressure rises and get sucked shut when air pressure is low enough when fan is needed/active.

 

IMG-5516.JPG.86873b5b277326d6e25cc61a7d343b69.JPG

 

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On 7/7/2021 at 12:54 PM, 280Z-LS3 said:

What radiator design are you using, single or dual pass, tube size, overall core thickness?

Does the fan shroud allow for air flow when fan is not active?

 

The location of the oil cooler is very common, there must be an easier solution than relocating.  And as others have said, ducting more air toward the radiator seems like a good idea.  Maybe some light aluminum or stainless sheet metal could be formed into a polyhedron (big word, had to Google that one) to funnel air to front of radiator. 

 

The C7 fan I plan to use has 7 flaps which are pushed open when air pressure rises and get sucked shut when air pressure is low enough when fan is needed/active.

 

IMG-5516.JPG.86873b5b277326d6e25cc61a7d343b69.JPG

 

 

The radiator is a two row, 1.25" tubes, dual pass, 2.50" core.  It has two huge Spal fans, but it seems more like airflow at speed is the issue.  It holds temp very well at low speed and idle.

 

I am going to start out with relatively simple ducting, and keep testing to see when adequate cooling is achieved.  First step is to use some adhesive foam strips to seal the top and bottom of the radiator so air won't flow around the core.  

 

 

 

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Please report back with results after you seal up all the alternate air flow paths in the radiator core support.  Your cooling equipment choices are almost identical to what I have sitting in the garage waiting to be installed.

 

Way back when building a 1969 Camaro (should have kept that car...) called up Ron Davis for the radiator.  Went with an with a unit with an integrated oil/water cooler.  Worked well.  One thing he did stress is sealing the radiator core support holes, radiator to core support gap and also the fan shroud to radiator (for low speed cooling) so only path for air to travel is through radiator.

 

 

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On 7/9/2021 at 1:33 PM, 280Z-LS3 said:

Please report back with results after you seal up all the alternate air flow paths in the radiator core support.  Your cooling equipment choices are almost identical to what I have sitting in the garage waiting to be installed.

 

Way back when building a 1969 Camaro (should have kept that car...) called up Ron Davis for the radiator.  Went with an with a unit with an integrated oil/water cooler.  Worked well.  One thing he did stress is sealing the radiator core support holes, radiator to core support gap and also the fan shroud to radiator (for low speed cooling) so only path for air to travel is through radiator.

 

 

 

Will do.  

 

I think Ron Davis' advice is pretty much something that I should have followed from the beginning, and which I knew I should have followed, it's just sort of a PITA to actually do, so I let laziness prevail.  

 

I am starting off by moving the oil cooler and sealing the airflow gaps around the radiator with adhesive backed polyurethane foam.   Then I am going to test it and see how much improvement is noted.  If it still gets too warm, next step is going to be increasing amounts of aluminum ducting to further force the air through the radiator.  I'm just hoping that step won't be needed, as it will involve some significant fabrication time that I would just as soon skip.  Laziness again.

 

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If what you've just done doesn't work and you want to test the effectiveness of ducting, just do it with some stiff cardboard and duct tape. You could seal and duct the whole area in probably half an hour, and it would give a good idea of if the aluminum fab time would be wasted or not. 

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13 minutes ago, calZ said:

If what you've just done doesn't work and you want to test the effectiveness of ducting, just do it with some stiff cardboard and duct tape. You could seal and duct the whole area in probably half an hour, and it would give a good idea of if the aluminum fab time would be wasted or not. 

 

Good idea.

 

I also definitely think the first place ducting would be of benefit is where you suggested above, to prevent air from slipping down and below the radiator.  Currently, the hood should keep most air pressure from escaping upward, and the sides of the chassis create sort of natural "fences" to keep airflow from escaping to the sides....downward is the biggest problem (I also need to plug the passenger side cabin fresh air intake hole).

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  • 2 weeks later...

Finished the revised oil cooler installation.  I thought it would be a one or two day job, took me about a week and a half.

 

Basically the (new) cooler now sits in the gap between the undertray and bottom of the radiator support.  This should get tremendous airflow, without in any way disrupting or heating the airflow to the radiator.  As a side benefit, this location also blocks off a major spot where a lot of the airflow that would otherwise go through the radiator could previously escape.  

 

BqlS3Cg.jpg

 

I installed a "T" fitting in the lower line to use to drain the cooler/plumbing when doing oil changes.  Might be a bit anal, but the cooler and plumbing hold well over a quart of oil, so I thought this was worthwhile.

 

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Since the cooler sits fairly low, I wanted to install screening to protect it from rocks and keep out leaves, bugs, whatever.  Otherwise the ducting would create sort of a trap for garbage to collect in front of the cooler and it would be a PITA to remove.

 

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Hopefully (I REALLY hope) this modification will solve my cooling issue by improving cool airflow to the radiator.  If not, I will have to add additional ducting to force more air through the radiator, which I don't really want to have to do.

 

Thanks for looking.

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Posted (edited)
17 hours ago, LLave said:

I will be very surprised if you do not see a noticeable increase in cooling. 

 

You may consider adding the OE hood seal that is on top of the core support, or something similar. The OE one is a little wimpy, buy sealing the hood to core support will probably help some, and its easy.

 

I drove it yesterday in 94 degree weather.  Temp stayed good, but cooling fans were going on A LOT, even when car was at speed.  Fans go on at 203 and switch off at 196.  Not sure, but still seems like it points to inadequate airflow, although no matter how good airflow through the radiator is, the fans would still increase it by creating a low pressure zone behind the radiator.

 

 Obviously I couldn't duplicate track conditions on public roads, but I drove it pretty hard.  Honestly, I'm not sure though that I will even track this car in warm weather.  My home track (Thunderhill) gets hotter than hell, and I have done summer track days in the past in my other car (no A/C)....really not much fun.  In addition to no A/C, the Z also picks up a lot of heat from the trans tunnel, and it gets...unpleasant....inside on warm days.

 

For summer I used to go to Laguna...but the noise restrictions there have pretty much 100% driven me away.

 

9 hours ago, 280Z-LS3 said:

Another thing to consider, if not already done, is a dyno tune.  Sub-optimal ignition timing curve can make engines run hot.  Finding a good LSX engine tuner can be a challenge but in NorCal you should not have to go far.

 

I could write a book on my experiences with dyno "tuners" from my other car, which has a highly tuned four cylinder engine.  None of it would be good.  I eventually learned to use the ECU logging function and tune it myself, which was my only salvation. 

 

One of the main reasons I went with a crate engine with GMPP ECU on this build was to avoid having to use those bozos.  I do know of one tuner I would trust, but it would involve taking the car to So Cal, full day rental of a dyno and payment for the guy's services.  As I understand it, he can work miracles, but it results in a $5000-6000 day.

 

Do you think any dyno tuner could improve upon the GM factory tune anyway?  As a crate engine, the tune is in no way compromised for emissions or mileage or anything else....pretty much just to run its best.

Edited by Ironhead
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I would look for other tune solutions too if the SoCal guy's tune day would cost $5K.

 

Full disclosure I have never tuned or had a EFI motor tuned but interest in doing so led me to research the process over the years.  Your previous experience with other race car puts you miles ahead of me.  Does your engine ECU allow for data logging or real time monitoring of timing, air/fuel and other engine parameters?  Not saying the GM tune is inadequate but just double check that things are working per spec.

 

LS1Tech.com is a great resource with plenty of brilliant people willing to help.

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