The Junkyard Dog is back!!

[Guest norm[T12SDSUD]]

I got the old Z back on the road today.

I went ahead and went back to the old setup I used to run with two head gaskets and a .015" shave on the dished pistons.

My compression ratio is right around 10.5:1 CR now, so that is a little more manageable than the 11.6:1 CR setup that had an APPETITE for Destruction!! I had that sucker apart 4 times in 6 months due to broken piston ringlands!!

 

I found a good set of pistons and rods sitting out in a junkyard. The engine was sitting in a big junkpile with the spark plugs removed but thankfully it was tilted to where no water got in the engine. I removed the pistons and rods and the salvage yard owner let me have em for free so that was a good score.

 

Basically it only ended up costing me $40 to get the old junkyard dog back on the road again!!

 

My plans are to hopefully break a 7.99 in the 1/8 mile this year. I am thinking new slicks ,an MSD or Crane mutiple spark ignition box, some stub stacks on the SU's and maybe an X pipe with a dual exhaust system might help me achieve this goal.

Hopefully I will make enough money to buy all this crap! LOL

 

Anyway, it was good to drive the Z again tonight after 3 weeks of down time!

 

Later,norm

[Guest Zpeed]

niiicceee good to hear..

[Dan Baldwin]

Great to hear your back in bidness, Norm!

Man, this guy gets more done in less time for less money with the most outstanding results of ANYbody in the Zworld!

 

You might try dual exhausts, but I don't think and X-pipe would do anything for ya.

90-degree crank v8s use 'em because they firing sequence for each bank is all outta whack. Flat-crank V8s don't connect the two banks at all. The inline 6 should work best at high rpm as two inline 3s, with no crossover, I *think*.

 

Dan Baldwin

'71 240Z 3.1

COMSCC #7 SPB

[DAW]

Norm,

I love junkyards and a good one is a great find. I've used a lot of pistons harvested from the core engine pile and you can also see weak points in the engines, like L24 rods with 8mm bolts break, even if they are ARP bolts.

If you've got the Nissan SUs, have you considered cutting the stock airhorns out of the aircleaner housing base?

I think your exhaust idea is good. The header should have equal length primaries grouping 1-2-3

then 4-5-6 into separate collectors, as the firing order (1-5-3-6-2-4) is then split into equal volumes and by ignition interval. From what I've read the way to make the optimal balance in the secondary pipes is to make the exhaust all the way back as your dual system then put an "H" pipe between the two by painting the pipes on the sides that face each other, drive the car, then look at the pipes: the hottest spots where the paint is burned is what needs to be bridged with thw H-pipe. Actually, I think a two-into-three one's-into-one type exhaust would be better for flow balance and low-end torque: 1-6, 2-5, 3-4, but the 3:2 is more practical.

 

Oh BTW, of the dished L28 pistons I think the turbo pistons are drilled under the oil ring rather than slotted which adds strength, and the top rings and lands are different on the turbo pistons which may make them a better choice for a high compression n/a engine. DAW

[Guest norm[T12SDSUD]]

Yeah what got me interested in the X pipe was an article my buddy read on the old M3 4 cylinder BMW's.

He said that they gained over 17 HP with the X pipe over seperate dual exhaust systems.

 

BTW, DAW that is interesting on the L24 8mm bolt breaking thing.

How many engines have you found that have had this problem?

 

LAter,norm

[DAW]

I know that NISMO recommends that only the 9mm bolt-rods be used for competition. I thought about using a set I have anyway, but I came upon a freshly built L28 with L24 rods and Sterling pistons (#12149P which have a lower compression ht. than stock to allow use of 133mm rods) which had a hole in the block where #2 rod cap and fragments of the broken ARP 8mm bolts went through. Seeing one convinced me. DAW

[Guest norm[T12SDSUD]]

I got to go racing tonight at Shadyside in Shelby and the old Junkyard dog was running strong.

I had my best ever street tire run tonight.

 

My previous best street tire run was an 8.44 with mucho wheelspin and that was with the 11.6:1 motor, so it looks like I've not lost anything with the new 10.5:1 setup.

One thing nice is that the lower compression motor doen't light the tires up everytime I hit 2nd so that helps quite a bit.

 

With regular old street tires I ran a best of 8.39 @ 84.48 mph.

 

Once I get some new slicks the quest is gonna be on for 7.99's!

 

LAter,norm

[Mike C]

I love it Norm! I'm amazed at the power you've coaxed from your 'Dog! Keep us updated. What kind of cranking compression does your 10.5 motor have? I'm not convinced my new motor is as high as my buddy said, and he can't remmeber what pistons he used when he rebuilt. WIth the stock L28 cam what should I see?

[Guest norm[T12SDSUD]]

With 11.6:1 I was eeing close to 230 psi.

With the lower 10.5:1 motor I am seeing about 210-215 psi.

As far as cranking pressures go I could advance the cam 4 degrees and boost the current cranking pressure up to 225 psi, but then I might encounter detonation again and it makes more HP in the retarded position anyway.

 

BTW, I think a stock 280 motor cranks at 145 psi when set in the #1 cam position.

 

Later,norm