Geo

Before I changed ISPs I had a web site I maintained that used to have a series of articles on the build. I know a few friends copied the site and hosted it, but I don't have the URLs. I'll try to find it. In the meantime...

The engine was the Nissan SR20DE and the car was a Sentra SE-R. The engine I built was a 99.5% clone of the one Mike Kojima built for Sport Compact Car's Project SE-R. I bought a spare engine with a bad bearing (and thus a bad crankshaft) and originally was planning on a relatively mild build with 300ZX pistons creating an 11:1 CR. About the time I started the build, Mike was posting on the SE-R list about his build. We quickly started talking and my build got wilder and wilder. Mike's engine made 171 wheel hp on a Dynojet in the same configuration as mine.

OK, so what did I do?

New crankshaft - since the bearing clearance under 10/10,000, machining the old one was not a great idea.

Micropolished journals

Crank, flywheel, main pulley all balanced as a set

Rods (stock are forged) were straightened and balanced. I considered polishing, but that would require re-stress relieving

Low mass aluminum flywheel

Low mass pulleys

1mm overbore - bored with torque plates to ensure the bores are round when the crank girdle and head are bolted on. Final honing finish on the cylinder walls was done using the same process as the factory (nearly impossible to find).

300ZX NA pistons with the domes shaved off (yields 10:1 CR). Piston crowns coating with Swain Tech Thermal Barrier Coating and the skirts coated with their Poly Monly anti-friction coating. Stock 300ZX rings.

Block was machined and tapped for factory piston squirters (standard on the factory turbo engine - SR20DET). At the time, nobody was doing this.

OK, top end....

DPR (Dan Paramore Racing) head. Port and polish. Combustion chambers were welded up and reshaped to add quench which makes the head more detonation resistant, and also increase CR from 10:1 (with flat top 1mm over bore) to 11:1.

Intake manifold was ported and polished and port matched to the head.

Special very trick valve springs. These were developed by a guy who consulted on engine development for Roush Racing. The wire the springs were made from is only available from one mill in the entire world. These were critical. On an otherwise stock engine, these valve springs added 4 hp! Sounds crazy, but true.

Cams were a pretty radical street grind. Without some serious ECU programming they would lope like crazy and throw a MIL. Thankfully, the folks who did the programming also sold the cams. Oh, also had a set of adjustable cam gears.

The ECU required some serious programming. The maps looked very similar to a turbo engine map. The car ran on the edge all the time. I not only needed to run 93 octane, I could only run Texaco 93. All other 93 would ping and the ECU would pull out timing.

State of the art 4-2-1 header with high flow Random Tech cat. GReddy exhaust. Tuned Cold Air Intake.

I've probably forgotten some things, but this is a pretty good run down.

The epilogue:

I never got it on the dyno. I was chasing some minor tuning issues over the course of a year. Then I all of a sudden heard a strange noise when driving next to a wall. Changed the oil thinking the bearings might be going. No brass. Still heard the noise. The next week I went to change the oil again. I never poured out the pan from the prior week. As I was pouring out the oil, the bottom was lumpy. Oil isn't supposed to be lumpy. It was metal. Lots of metal. In the end, it turns out the head was FULL of 0.020" and 0.040" steel shot. Best guess is that DPR (who was HORRIBLY behind) sent the head out to be cleaned and it was thrown into a vibration tank and DPR never cleaned it when it returned. After a time, the shot started working itself loose and digested the engine. Six grand shot to hell. The only things salvageable were the header, the pulleys, and the ECU. Everything else was NFG. I thought about having the head repaired, but that never happened. It was going to cost nearly as much as the head was worth.

sm

Let’s revive this thread. What’s the current state on a high revving 968 NA motor?

951and944S

You ready to grind those cams eh...?



Saw this thread bumped to the top and I was like, "hey, this'll make for some good reading" while we are under flash flood watch and waiting out 2 more hours until clock out for the weekend.

Talk about flash back from the past...., I hadn't seen some of the contributors around here in years.

Geo once gifted my son a subscription to RL because he was impressed that he restored his own car at age 16 (with a little help from me ), a really good guy.

Now, SM, define, "high revving"...., are you talking about the level of the OP, 8500...?

T

sm

Once I determine the overall plan, yes, cams will be ground!

I would be happy with 7500 RPMs. 8000 would take me over the moon!

Arominus

Buy the RSbarn chip, it will give you 7100. Hes got cams coming soon too, those + VEMS+ Exhaust and your 68 motor about the best boost it can, that said if all you want is more RPM, just chip it for 7100. VEMS is a full standalone so you would need to be able to play with tuning. Actually, just call RSBarn and get up to speed there.

sm

RS Barn already has cams for sale, but if he has a new profile in store, I’ll contact him.

ptuomov

Another bump, has anyone actually gone to 8500 rpm and what did they actually have to do to get there.

PF

Mr Mount has.
https://rennlist.com/forums/924-931-...-400hp-10.html

ptuomov

Yeah I recall that build. That build was “max effort” in terms of power production for the given fuel. However, maybe not everything in that build is needed to run 8500 rpm safely. Much of the stuff is likely for power production.

odurandina

i think someone should mention it:
What you're really attempting would beat most 944/968 enthusiasts
into the ground. We have a long history of people trying to build
similar engines, only to learn they built a very short life dyno motor,
but less practical for any kind of longevity.
There are some who've managed to come close, and are still driving their cars.
But such examples are rare. There's not many 968 or even SBC
or other American V8 combo's that can deliver what you're asking for easily.
But there are a few V8 combo's that can turn 83~8500 rpm,
and of course, smaller short stroke V8's that will come close.
not break the bank--or court failure.
A short stroke LS7 or destroked LS3 block will make it to the finish line.
http://www.superchevy.com/how-to/vem...oke-of-genius/

It'll fit--and it won't fail unless you (really) abuse it.
Is it the best small block V8 ever built? For performance
and longevity, it's very tough to beat.
This same block/crank/ rod/ piston combo running turbo's beat the Veyron
for the top speed world record in a production car in 2007,
and *held the record for 3 years.

i run the same exact forged engine (except mine is cammed and
rev limited for 6800.

My engine runs on 91-96 octane gas. But 95-96 octain is best.
When i ordered mine built, we found only 1 source for the rods and pistons,
so, it's a certainty i'm running the same stuff w/ my forged crank.
At the time, we didn't know that others were running the LS7 in 388c.i.






*The SSC Ultimate Aero held the title of the fastest production car in the world,
according to the Guinness World Records, from 2007 (when it was officially
timed at 256.18 mph (412.28 km/h)) until the introduction of the Bugatti Veyron
Super Sport in 2010.

ptuomov

Motorcycle engines rev above 8500 rpm all day and with enough money one could take a flathead Ford up there. I am interested in model specific information, what does it minimally take to get 968 engine (or the shorter-stroke 16V 944 engines) to operate reliably at 8500 rpm?

V2Rocket

the 944 (and 928) oiling systems are weak spots.
that is the primary obstacle to high revving.
the pumps flow fine but the oil channels are poorly shaped and the rod bearings are very soft.
filtered oil re-enters the block pointing directly at #1 main bearing and all the others are a hard 90 degree turn towards the back. perhaps tapping the block at each main bearing for external oil pipes would work?

new bearings are available which fixes a lot of that but the plumbing needs to be addressed to be sure; thats why most 7000+ stuff gets dry sumped because they can inject the oil wherever they want.

the rods are just old; you have had great success with the PPF rods found in the 944T but they are super heavy and often have an uncertain life history when bought used. Molnar makes brand new H-beams for the 944 (and with some mods they will fit 928) for $400/set of 4 so why bother with old ones anymore?

stock pistons are fine and strong, just very heavy for what they are. extra stress on the rod/bearings.
944/928 parts seem to have been inspired by the Porsche diesel tractor... lol

lighter valves and lifters help because you don't need as aggressive a valve spring to control them.
obviously new cams are required because the stockers peak by 6000rpm and they are generally tiny baby cams anyways.

ptuomov

My personal opinion: I think that the pickup sucking air is by far the biggest problem with wet sump 968/944/928. If the pickup doesn't suck air, then the oiling system works well. If the pickup does suck air, then the oiling system doesn't work well -- but hey what oiling system would?

Has someone computed oil flow velocity in the 968 block? The turns only matter if the oil flow velocity is high. If the oil flow velocity is low, then oil pressure is approximately equal everywhere in the system regardless of the turns in the channels. The only disruption comes from gravity, which will separate air to the top and oil to the bottom. Contrast this to the situation in which oil velocity is high: Now turns do matter to pressure drop and also act to separate air and oil.

michaelmount123

Addressing your original question:

- Use a properly designed dry sump oiling system (this is a subject within itself)
- Use a billet rod to maintain big end concentricity and limit stretch
- Use a lightweight piston with strutted skirt support (engineered for the application)
- Use performance rod bearings like Clevite H, or ACL H
- Convert to mechanical lifters to maintain valve control
- Limit oil to top end by blocking oil to followers

I can provide more detail, just ask.
MM

ptuomov

Thanks.

Questions:

”Use a properly designed dry sump oiling system (this is a subject within itself)”

If we take out the extreme g forces with slicks on track and limit ourselves to street cars on street tires, is the dry sump system necessary for a reliable 8500rpm with the 968 engine?

“Use a billet rod to maintain big end concentricity and limit stretch. Use a lightweight piston with strutted skirt support (engineered for the application)“

For the 928 crank and deck height, we found similar enough modern raw forgings for both pistons and rods that we could have the suppliers start from those and get the strength of forged parts. I wonder if the same is possible for the 968.

What ring pack runs reliably at 8500rpm with 968 stroke? I think that the stock 968 1.75mm ring doesn’t model well even for the stock 968 stroke and redline.

“Convert to mechanical lifters to maintain valve control”

Is this solid lifter conversion necessary because of the time spent on the base circle getting short or because the camshaft profile and 8500 rpm engine speed combine to large forces when opening the valve? Suppose that one would keep the camshaft lift low and duration long, would the hydraulic lifters work at 8500 rpm?

“Limit oil to top end by blocking oil to followers“

Is this only the case with solid lifter conversion or would you do that even with hydraulic lifters?