200+ WHP NA build

[BluDestiny]

Bluestag, you should PM burkeys now that he's on this forum, since he was the guy who was closing in on 200rwhp with SU's. He's a great guy and will answer any of your questions.

 

You're likely going to lose power because of that auto trans. I've heard horror stories about how much they suck, but I've also heard how much they don't suck. Not sure what to believe on the internet these days lol.

[Tony D]

didier does bring forth the most pertinent point in the difference in HP potential between carbs and EFI. The restriction of the venturi necessarily limits the airflow to the engine costing you horsepower.

 

Our Bonneville engine, all other items being identical, peaked power 750 rpms higher when we went to EFI. We also gained 40HP at that higher point. somewhere about 16-20HP at the former peak with 45DCOE's (7500rpms)

 

Recently with a new Isky Cam we've duplicated our previous HP, but back closer to the old Carb RPM peak point. Ron has some ways to do things that make L-Engines BREATHE! 278HP at well under 8,000rpms. Amazing (Thanks Ron!)

[HowlerMonkey]

As compared to the SU setup with twin 44mm venturis on stock manifolding, the single 50mm throttle body flows substantially more air regardless of the pressure drop across the venturi.

[z-ya]

Recently with a new Isky Cam we've duplicated our previous HP, but back closer to the old Carb RPM peak point. Ron has some ways to do things that make L-Engines BREATHE! 278HP at well under 8,000rpms. Amazing (Thanks Ron!)

 

WHP I am assuming.

[BlueStag]

 

You're likely going to lose power because of that auto trans. I've heard horror stories about how much they suck, but I've also heard how much they don't suck. Not sure what to believe on the internet these days lol.

 

No doubt I am. Autoboxes are inefficient in a number of ways, not least that there is more friction in one than in a manual box.

 

But the thing most aggravating about an autobox is its hesitancy to let you spin the motor very fast. Horsepower is dependent on spinning the motor quicker (broadly speaking) and my slushbox rarely permits the L26 to spin much faster than 3500, which is just where the hp and torque are beginning to happen.

 

I could get a 5sp for next to nothing, if I ask around nice. And I don't need a competion clutch. I could enjoy the car a little more if I was rowing thru the gears. But this is LA and I do like the auto box out on the freeway.

 

I am wondering what sort of low-end torque brute could be built with an L28 and SUs? Seems to me the first item to consider would be the cam.....

 

Or just find a turbo.

Edited May 30, 2012 by BlueStag

[Tony D]

Did you connect the WOT microswitch from the Datsun? That will hold the autobox in gear longer, and frustratingly kick it down out of gear to get rpms up.

 

Talking with Bernard may also help as there are shift kits available that will alter how all that happens as well. It's an old mechanical slushbox, some drilled holes to fill accumulators faster, some springs to make things grip tighter, you can have quite a fun time with a Juicebox if you want to spend an hour or two dropping the pan and valve body to put in another shift plate!

[HowlerMonkey]

Definately leave alone your current transmission other than hooking up the kickdown.

 

It works now.

 

The transmission will kick down when +12v is applied to the terminal on the kickdown solenoid.

 

It makes a huge difference in performance.

 

Shift kitting a transmission that old will surely run you into issues as I found out in the early 80s when I was getting my 3n71b shift kits from B&M.

Edited May 30, 2012 by HowlerMonkey

[BlueStag]

Did you connect the WOT microswitch from the Datsun? That will hold the autobox in gear longer, and frustratingly kick it down out of gear to get rpms up.

 

Talking with Bernard may also help as there are shift kits available that will alter how all that happens as well. It's an old mechanical slushbox, some drilled holes to fill accumulators faster, some springs to make things grip tighter, you can have quite a fun time with a Juicebox if you want to spend an hour or two dropping the pan and valve body to put in another shift plate!

 

I don't think I would alter this transmission, not until I had a back-up. There is a slightly more modern one that is electronic in its shifting and has an ECU.

 

Yes, I have installed a switch, which the throttle peddle should activate. But the carpet is in the way. I need to engineer something mounted on the balance tube and have the switch there. Some sort of cam that comes up as the throttle rotates. And make it adjustable such that I don't need to go to WOT to get the downshift.

 

And I have a switch to drop the OD (this box came out of a Maxima with OD), but it is a bit of a reach.

 

The ergonomics of the Stag are a problem for me. Tony, you should have taken me up on the offer to drive it. But I respect a policy of not driving other people's cars. So much grief avoided.....

 

I find if I set my seat such that I can reach the console controls, that my right leg is bent back and my ankle fatigues quickly. (The steering wheel is adjustable for rake and reach) I set my seat all the way back, despite the fact that I am not at all tall (5' 7")

 

Re-engineering the switch. Not too daunting nor expensive. A thing to do when next business slows down. Probably next week.

[Tony D]

A microswitch works for that kind of setup. Long stainless lever and away you go!

[BlueStag]

A microswitch works for that kind of setup. Long stainless lever and away you go!

 

I'm picturing it now. Just next to the throttle cable cam that you asked me about.

[HowlerMonkey]

Did your entire drivetrain swap come from a first generation maxima?

 

If you're set on keeping an automatic, then the 4n71b is sweet.

 

I ran a 1984 4n71b in a maxima in which I simply swapped the turbo manifolding to the l24e and the transmission lasted 20k miles behind that setup through some really hard driving.......after 225,000 miles before the turbo was done.

Edited May 31, 2012 by HowlerMonkey

[BlueStag]

Did your entire drivetrain swap come from a first generation maxima?

 

If you're set on keeping an automatic, then the 4n71b is sweet.

 

I ran a 1984 4n71b in a maxima in which I simply swapped the turbo manifolding to the l24e and the transmission lasted 20k miles behind that setup through some really hard driving.......after 225,000 miles before the turbo was done.

 

No, the current engine is an L26 with a pair of SU's.

 

It is all very nice and all, but I am seeing no more than 125hp at the flexplate. Which is comparable to what the 3.0 V8 of the Stag produced. Possibly a bit less torque. The OD trans is out of a Maxima, yes.

 

Obviously, wherever you can mount a L26, you can pretty much mount an L28ET. That package can be easily juiced to give 200hp and similar torque. Hardly even trying. Which will certainly get my Stag moving down the road.

 

So I'm inclined to use the tougher 4sp attached to many of the V6's, including the 300ZX.

 

Oh, I did need to reshape my trans tunnel to get the trans in there. I'm not eager to go thru that again, so the E4N71B might be the final choice. They certainly are available.

Edited June 1, 2012 by BlueStag

[BlueStag]

A microswitch works for that kind of setup. Long stainless lever and away you go!

 

Finally mounted a micro switch. Long lever with a roller end. It is mounted on the balance tube and closes when the screw holding the throttle arm to the shaft turns to WOT. Had it set up to act at about half throttle and went out on the 5 with it. Wow, did it honk along!

 

I'm trying to set it to kick in at more than 3/4 throttle, but before full open.

 

I am very much happier, it does keep the trans in lower gear as I am accelerating and drops it when I want.

 

I think I am going to be enjoying this much, much more. This ease the pain for a turbo engine.

[burkeys]

 

Try THESE numbers for 'runs and doesn't blow apart guidelines' (and we haven't actually floated a damn valve yet):

 

12,500 for an L20A

9750 for an L28

8700 for a VO7 Stroked L29

 

And in EVERY case above, we stopped because either the tachometer didn't log higher or we were plenty past the power peak that we've determined further increase would be pointless other than to know we just need a bigger cam or more boost to make even more power at the higher rpms.

 

8K with an L24 isn't even getting STARTED as far a 'maximum allowable RPM's'!

 

Tony, what are you guys using to keep your timing chain tension happy?

 

I recently had all of my exhaust valves kiss the pistons. This happened when my throttle linkage became stuck causing the engine to idle at 4k. I drove to a open late Walmart to buy an allen wrench to fix the linkage. On the way, the engine saw extended higher rpms with more abrupt than normal street rpm changes. After the linkage was fixed the valve train was louder. Found 2 cracked intake valve spring retainers, which is odd because none of the intakes touched the pistons. Pulled the head to change all of the Schnider springs and retainers to Isky and found nicks on the pistons. Could have been valve float but I suspect the chain tensioner may have momentarily been over come by chain tension creating slack. I doubt the engine saw anything over 7500rpm that night, I doubt it went over 7k but it is possible. I have about 8000 miles on the build.

 

@bluestang the best I could do with SU's, L28, stock crank and flat top pistons 10.25 comp ratio, ported slovers N42 head was 191 rwhp with about 180 fpt. Very streetable, idle at 1000rpm.

 

Scott B

[Tony D]

Do you know your piston-to-valve clearance? Chances are good they mechanically interfered the first time you fired up and after that it ran just fine.

This has been known to happen, just because a piston nicks a valve doesn't mean either is affected by it other than some cosmetics. Polish out the nick (er...'install clearance retroactively') and call it done!

 

Which valve is open furthest as piston is near TDC or approaching TDC? Look at your cam card to find out, these truths will become self-evident!

 

I think you are on the right track in thinking some cam timing change from drive chain slack may have caused some unholy valve-piston osculation...

 

But what do you do? Spend $500+ for a mechanical tensioner. We haven't yet, but could if we were road-racing. As you postulate relative change and acceleration/deceleration is what throws slack into a chain. If you're running Bonneville or Top Speed, you're ON IT and there is none of the radical throttle position changing like in street driving or roadrace. (Reference John C's snapping of oil pump drive shafts, JeffP spinning the timing drive gear, etc...) When you throw impulse in an opposite direction in a back-and-forth manner you can shake things loose.

 

Then again, we have been running at Willow Springs just to get seat time...still no issues though!

 

Just breathe easy: It could have been worse!

[BlueStag]

 

 

@bluestang the best I could do with SU's, L28, stock crank and flat top pistons 10.25 comp ratio, ported slovers N42 head was 191 rwhp with about 180 fpt. Very streetable, idle at 1000rpm.

 

Scott B

 

190 wheel hp is pretty damned respectable off what is basically a very dated design.

 

 

It sure as hell would get my 2700 lbs Stag moving.

 

Been driving with the down shift solenoid working, and boy this is a very different car. On flat acceleration, the trans does not down shift until 5000 rpm, which must be nearly the peak hp for a stock L26.

 

I'm struggling to get the down shift to happen more like 3/4 throttle than 2/3rds. It is kicking in just a bit early for my taste just now, but I am liking it!