Northstar rebuild: Will style (Page 30/119)
Will SEP 01, 11:17 PM
Pistons are at Calico being coated. I got a big chunk of the bill for pistons, rings & coatings... ouch. Doing it right hurts.

I haven't been keeping track of machine work here... the align hone was completed and the block was decked just a teensy bit to straighten it out. The deck height came to 8.840".
The stroke is 3.307 and the throw is 1.6535.
The conrod is 5.943.
8.840 - (1.6535 + 8.840) = 1.243

I'm setting the piston up 0.005 in the hole, so the compression height I ordered from CP was 1.238. I plan on using 0.030 Cometic MLS gaskets, but I need to verify the piston/deck relationship before I order those. A Cometic rep told me it would take three days to make the gaskets (they already have a pattern on file) before they could be shipped.

[This message has been edited by Will (edited 09-01-2006).]

THE BEAST SEP 02, 11:51 AM

quote
Originally posted by Will:

CP pistons are on the way. Total Seal Diamond Finish rings will be coming with. The pistons will include pins, which will be 2.25" long vice the stock 2.48" long. I still would have liked to have ceramic aluminum pins, but Hank the Crank was having "problems" last I checked.

I built a spreadsheet to look at quench numbers, but I kept on getting unexpectedly small numbers, so I decided that I didn't have enough info to calculate that directly.

However, I have been told that a 350 with 4340 rods and comparable quality pistons can run as little as 0.032 quench to 7200 RPM.

With a 3.48" stroke and 5.700" rods, the piston acceleration at TDC at 7200 RPM is...

R = 5.700"
T = 1.740"
S = 120 RPS

a(t) = 754t
da(t)/dt = 754
(da(t)/dt)2 = 568,489

A(t)|t=0 = -1,291,128 in/sec2
= 3,362 g's.

With 6.000" rods, this would be 3,322 g's (~1% difference).

At 7200 RPM, the Northstar pistons experience 3,130 g's.

So if the pistons weighed the same, The Northstar should experience the same rod stretch at 7640 as the 350 does at 7200.

HOWEVER, the pistons do not weigh the same. CP has given me estimates of the Northstar piston weights. I need to call them back and get a number for a comparable 350 piston and do a bit more arithmetic.

However, in the mean time I've decided to go for 0.035 quench. I'm going to set the pistons up at 0.005 in the hole and use an 0.030 MLS gasket (stockers are around 0.065 compressed(!)). If I decide I can get away with it, I may drop to a 0.027 gasket.

The CP pistons will be fit at 0.003 bore clearance, while the Ross pistons required 0.0045 bore clearance. That should give a clue about the difference in engineering between those to brands.


Concision is for Cliff Notes.




So I will have to have the block machine to .0095? .005 over for the pistons plus .0045 for the clearance= .0095 right?

JG
THE BEAST SEP 02, 12:00 PM
Hey, if this # are right then I will only have size down the rings .0005

JG
toddshotrods SEP 24, 03:40 PM
Had to float this one back to the top. Boy, do I have a lot to learn! I also forgot how deep Will digs

------------------
toddshotrods.com - wanna ride?
crazy projects, features, articles, art & more

Will OCT 30, 09:37 PM
Pistons are done & at machine shop.
Rings are done & at machine shop.
Block machine work is finished.

I'm having some issues with getting the crank balanced the way I want it done. I left my best crank (the one that was in the engine I had been running) with the shop that did the block work. They don't have crank machinery on site, so they sent it off to a crank specialist with my instructions, which were to turn material from the outside radius of the counterweight until the balance was close and then balance by conventional methods (drilling to remove weight). The crank shop apparently wasn't as experienced as was implied, because they cut OVER .500 from the radius of the counterweights. There wasn't enough left of the weights to put enough Mallory metal in them to bring them back up to weight. Scratch one otherwise perfrect Northstar crank. Grrr....

I had another crank that I thought hadn't been messed with, but it needed a journal job. Ok, I handed that one over and got the undersized bearings ($180 for the rods and $70 for the mains) and had the journal job done. Once that was done, the shop put the crank on the balancer (check first!) and found it to be out by 125 g/end. Based on the difference in bobweights, I had calc'd that it should be out 270 g/end. @#%@%@#@#$.... So now I have to figure out WHY this crank is lighter than I think it ought to be and pull a crank out of one of my parts engines to compare the factory balance holes to the ones in that crank. SIGH....
S8N OCT 30, 11:12 PM
Doh, that sucks. I have found that there are fewer and fewer shops that really know how to performance balance a crank or rotating assembly. I take it you want to do first and second harmonics? How many N* do you have laying around?

-Chuck
'87 Fiero spread across three states and six counties.
carolinajoe OCT 31, 07:00 AM
Hey Will

Where you been, trying to get ahold of you.

I just went and checked ebay there was a brand new
crank on there but looks like it sold.
That sucks, what you are going through with the cranks.
Will OCT 31, 09:40 AM

quote
Originally posted by S8N:

Doh, that sucks. I have found that there are fewer and fewer shops that really know how to performance balance a crank or rotating assembly. I take it you want to do first and second harmonics? How many N* do you have laying around?

-Chuck
'87 Fiero spread across three states and six counties.



Since this is a street engine, I was going for a neutral balance. If it were a race engine, I might consider overbalancing, but it isn't. I have enough rebuildable cores lying around that I'm not going to run out of cranks soon, but not getting it done the way I really want it done is annoying.



quote
Originally posted by carolinajoe:
Hey Will

Where you been, trying to get ahold of you.



Did you try email?
I've done enough with ebay cranks. The last time I tried that, the crank showed up in a great big cardboard box, packed in styrofoam peanuts....
Will DEC 31, 02:00 PM
I pulled apart two parts engines that I had in the shed. One was a '00-'03 engine and the other was a '96-'99 engine. Both had the same pattern of holes in the counterweights as the crank I sent off to be worked on. I'm waiting to hear back about the depths of those holes, but in all probability that crank has not been worked on. Hmm... So if that crank has NOT been worked on and is half as out of balance as I expected it to be, then my math must be wrong.

Good news: probably don't have to send another crank off.

Bad news: not sure where I went wrong and don't want to go forward until I know.

Good news: the crank balancing guy gave me the number for an engineer with a balancer manufacturing outift with whom I could discuss the math of balancing.
AJxtcman DEC 31, 02:38 PM
Will I have 3 spare cranks in good shape. One may have slight surface rust. I must have 4 sets of rods. One set is an early set. The stock rods are OK to 13K "I question that". I have 1 block left after I installed the other in my Fiero. I have 1 set of 00-02 heads with Y cams. I just let a 04 engine go that had a bent rod and hole in the block. It had ingested water. It had a good set of 9 heads. The caddy dealer I work at has 4 separate shops the first has all windows the second is my shop I work with two other guys the third is half mechanical and the other half body the fourth is all body shop. The reason I mention this is I have 4 stalls and the other 2 guys share 4 stalls. I have only been there 3 years the other 2 have been around 14 and 18 years. I have been having issues with my Fiero parts in the shop and finally think it is really about all the free parts I get. I passed on the last engine parts. I come across a lot of parts let me know if I can help. When I started they went though and cleaned out the old engine sitting around. I would guess about 10 engines got scrapped