SATAN

iTrader: (2)

The reason I put this in forced induction, is because I need 8000rpm to trap in the 160mph range and this will be a turbo LQ4 to achieve that.

8000rpm
26" tire (bigger wont fit without rear end mods)
Powerglide with 3.7:1 diff

8000rpm = 167mph
7500rpm = 157mph

If I switch to a 3.54 diff, then I get...

7500rpm = 164mph
8000rpm = 175mph


From what I have searched, getting the bottom end to 8000rpm is not that bad. Pretty much just a decent forged and balanced rotating assembly coupled with proper machine work should do it. But what about a stroker with 4.0" stroke? Can that do 8000rpm?

The top end is where I am researching and finding the area that needs attention though. It seems that if you want to keep the hydraulic lifters, then 7,500rpm is right around your limit, and 8,000rpm is really pushing it. Anything after that and solid lifters start to come into play. Now, I know this also greatly depends on your cam profile as well. I also know that springs will have to be changed regularly. Right around every 30 or so passes correct?


What experiences do you guys have that you would be willing to share on this subject?

WheelsUp84z

iTrader: (14)

At that high of RPM, things you will run into is valve float and of course weather or not you want to keep it hyd. lifter or not. I'm gonna say plan for a nice free flowing exhaust and some valve springs that will be able to keep up with that sort of RPM. I dont know if I would chance a hydraulic lifter/cam setup to 8k. In your case i would just gear it down to keep your RPMs around 7500ish. The lower gear will also allow to you put a little more in it off the line without annihilating your tires.

stevieturbo

Why do you need 8000rpm, when a 3.54 diff and less rpms will do ?

You're building a turbocharged engine, power will dictate whether you can trap 160 or not regardless of rpm's available.

And I wouldnt try a 4.0" stroke to 8k. But then I also dont see why you would ever need to try.

Just make more power at lower rpm.

And as you're turbocharged, again you dont need a stupid camshaft to make the power required. Just opt for a moderate-low lift cam which will be easy on the springs and whatever timing and duration required etc to make it rev.

Proof in point you dont need a big cam to go fast

http://www.yellowbullet.com/forum/sh...d.php?t=417721

stevieturbo

Why do you need 8000rpm, when a 3.54 diff and less rpms will do ?

You're building a turbocharged engine, power will dictate whether you can trap 160 or not regardless of rpm's available.

And I wouldnt try a 4.0" stroke to 8k. But then I also dont see why you would ever need to try.

Just make more power at lower rpm.

And as you're turbocharged, again you dont need a stupid camshaft to make the power required. Just opt for a moderate-low lift cam which will be easy on the springs and whatever timing and duration required etc to make it rev.

Proof in point you dont need a big cam to go fast

http://www.yellowbullet.com/forum/sh...d.php?t=417721

6techniques

iTrader: (7)

you dont NEED to double post! lol

Im not sure what car Satan is driving or his exact combo will be, but Skinnies car has a weight factor to it, so I wouldnt run a really aggressive cam in it either.
My car on the other hand, needs a cam that will support higher rpms due to my small cid/large turbo/high cr setup. I wouldnt be able to run my car like I want to with a cam like the one Skinnies ran in his 7.

I think more info is needed before we can really point this lil devil in the right direction.

gnx7

iTrader: (28)

sounds like he has a Datsun Z car.

Put in a custom diff with useable gearing. There is no need to spin it much beyond 7200-7500rpm unless you are made of money. Turbos like engine load. Meaning a 3.08 gear would probably serve you best.

SATAN

iTrader: (2)

I understand that I need power to get to 160mph in the 1/4 mile. I would think that would go without saying. However, since you asked, plans are approximately 900-1000whp and 1000rwtq.

From everything I have read, you CAN take a 4.0" stroker to 8k. It is not the bottom end that has problems. It is the valve train. Again, this is just from what I have researched on this site though.

I probably will go with the 3.54 gear simply because big engines that wrap out just don't seem natural... And here starts the debate

I am very aware of Skinnies car. He is one of my inspirations. I am also aware that he said this.

He has a lot of tire working for him. That gets him to his 164mph trap right when he lets out at 5800rpm. That is where the bigger cam would come into play. If you look at skinnies power band, he makes massive torque right off the bat. His power really starts to dwindle at the top end. He is only wrapping out to 5800rpm. Imagine if he had to go to 7,500rpm! This is where a larger cam comes into play. The larger cam would allow the engine to breath more on the top end.

My car is a 1985 z31 300zx. Race weight will be 3000lbs. I don't have that option of a 33" tire. My tire size is 26" x 10.5", therefore I have to run a minimum of 7500. Unless I can squeeze a 28" tire in there. That with the 3.54 rear, and I would only need 7000rpm to get a 160+ trap. hmmm...

SATAN

iTrader: (2)

Actually, going back and looking at it, his HP line stays pretty damn flat until he lets out of it! It's his torque that drops off. But that is on any gas engine. Makes me wonder how long he could stay in it before power would start dropping off?

Thanks for the replies guys. Different points of view always help.

6techniques

iTrader: (7)

with that setup, 7500 (or lower) definitely sounds like where your max should be, did you try to squeeze a 28" in there? Is tubbing out of the question?

lol dont remember seeing a sig earlier, so a Z car is what the "other" devil drives lol.

black98ws6ta

iTrader: (77)

A larger tire should be the first attempt, even a 27'' tire. If it doesnt fit you should gear the car. There is no reason to spin the engine so high. It will just put more wear and tear on it.

98Z28CobraKiller

iTrader: (17)

There are other issues with spinning a 400+ cube TURBO motor to 8K RPM without even getting into the solid roller valve train required with an N/a, Nitrous or Blower combo. The ehaust needs to get out of the motor and at 8K RPM, there is lots of it. So you need a large frame T6 turbo to accomplish that. That means you gotta fit a trash can under that hood along with the V8 AND a 5" down pipe. You'll also need an intake that makes power up there and a cam that will breath up there. Both of which will cost you throttle response which in turn will require a really high stall (6K RPM). Turning those RPM's also doesn't help in keeping the heads on. See where I'm going with this?

SATAN

iTrader: (2)

I completely understand where you are going with this. This thread was not intended to be a budget build stock junk yard block. It was intended to tackle the main question at hand. "How to get LQ4 to 8000rpm semi reliably?"

Block would get the main caps pinned and the deck O-ringed utilizing ARP (or other) head studs. Maybe larger than OEM studs.

That is also why I mentioned a cam that will make power up that high and was wondering how high skinnies could turn that engine before power would start to fall off.

Although, I have no idea what you are talking about in relation to keeping the heads on vs. RPM's. I didn't think the two were related... at all.

RPM also does not dictate how much exhaust is coming out of the engine. The amount of power you are making dictates that. Just like the amount of fuel it takes to make said power. If you have an engine that only spins to 6000rpm but makes 2000hp, it will be pushing out more exhaust than an engine spinning 10,000rpm but only making 1000hp.

But, all that aside, I think you guys are right, just try to put a bigger tire on there and gear the rear end down. Seems talking about spinning engines fast around here stirs up too much of a hornets nest... my bad.

SATAN

iTrader: (2)

I have not tried a 28" tire yet. But I do think I may be able to fit it in there. I know a 33" tire is DEFINITELY out LOL.

For now tubbing it out of the question. I am not against it, just not at this time.

Yes, I have a 1985 300zx. I have been building the OEM engine for about 10 years now. Build it, blow it up, reapeat. I am tired of trying to make big power out of small displacement. So now I am going with twice the engine that takes up only slightly more room.

This is my car now. It is a 26" MT ET Drag on there in this vid. A 28" would be close as the 26 already comes close to rubbing.
http://www.youtube.com/watch?v=leUB4PCv0mU

Blown06

iTrader: (32)

What about the oiling system?

A solid valvetrain, good bottom end pieces and an engine management system up to the task should be all you need to go 8000.

SATAN

iTrader: (2)

I was going to replace the oil pump with one of the Melling oil pumps that offer 18% increase in flow. Anyone know anything about those? 18% is quite a bit! Did they just increase area 18% and say it flows 18% more, or do they actually measure their flow?

98Z28CobraKiller

iTrader: (17)

If you have all the answers, why ask the questions?

Do what you think and let us know how it works out.

skinnies

iTrader: (33)

I pulled that dyno pull short on that one as no reason to keep spinning it high on the dyno, we have other pulls to 6500rpm and the power doesn't drop off, at the track I'm shifting at 6500-6600 as my converter is too tight and it will lose 1200rpms on the shift.

I'd look at getting more gear out of it, I think you can make a more reliable setup that way that will get you what you want since you mentioned building/blowing up your oem motor and that is why you are wanting to do the lq4 now.

stevieturbo

Why complicate things ? What rear diff are you using ? The most sensible thing to do is just fit a taller diff.

Job done, no high rpm's required.

And I certainly didnt say you couldnt spin a 4" crank to 8k, but I just dont see why you would ever need to or want to when you dont actually need to.
it just makes more sense to use a shorter stroke for higher rpm's

And I'm assuming you already have an engine in place, or are you starting with nothing ?

stock48

iTrader: (17)

Is 3.54 the highest gear you can get?

bettonracing

iTrader: (3)

Thinking out loud here:

Keep in mind that higher rpm means higher GPM for the oil pump. You'd be adding 23% more (maximum) oil flow going from 6500 to 8000, so adding the 18% melling would be a whopping 41% increase over stock. Personally I'd be crunching numbers & looking up data to ensure I have the oil capacity (or adequate drainback - while averaging ~1G accel) to avoid pump starvation on the big end of the track.

All that said, more oil volume thru the same orifice means more pressure - meaning You'd prolly dump all that extra volume thru the pressure relief.

You may want to consider using the high pressure pump (or spring) to help counteract the increased bearing loads at high rpm.

Regards,

Kurt Betton

P.S. For the record, I'm another unsolicited vote for finding some way to gear the car more appropriately, instead of revving to 8k. Like skinny said, engine reliability was one of Your original project goals. Revving higher than 95% of the ppl using the new engine is completely contradictory to that project goal.