WAWUZAT Northstar build thread (lots of pix) (Page 2/16)
AJxtcman APR 18, 07:52 AM
If the bore is not square and you can help it become square without oversizing it out of clearance spec then a light hone is good.
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First you need to scrub down the block. I use liquid floor soap "simple green" this is a water based degrease. I use scotch brite pads either the green or maroon pads. You will need to wash the block off with lots of water and then apply a moisture displacement oil. I used CRC for years in 55 gal drums. WD40 will work. I now dry the block and spay it with ATF. Now you can get an accurate reading. It is amassing how much is built up on the cylinder walls and how much the reading vary from before the block was scrubbed.
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If you find the tapper at .002 - .003 I would not be concerned.
If you find the Out Of Round at .002 - .003 you could hone .001 out if the piston clearance does not go above .002
If you find the Out Of Round at .003 - .0039 you will be OK, but do not touch the block.
If you find the out Of Round above .004 You will need to do something else. another block? I have an alternative repair.

--Piston Clearance @ 41 mm below deck face ........0.0008-0.0020 in

--Cylinder Bore Out-of-Round -- Maximum ...............0.004 in

--Cylinder Bore Taper -- Maximum ..........................0.004 in
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.004 is junk as the industries standards is .002. This is the service spec for a Northstar. Before I started at this dealer they had a Machinist would come in and measure the bores. He found them all junk. He was looking at .002 or less as a rule of thumb.
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----=-Cylinder Bore Taper Measurement Procedure
#1 Measure the cylinder bore along the thrust surfaces (perpendicular to the crankshaft center line) at 5 mm (0.20 in) below the deck surface and record your measurement.

#2 Measure the cylinder bore along the thrust surfaces (perpendicular to the crankshaft center line) at 102 mm (4.00 in) below the deck surface and record your measurement.

#3 Calculate the difference between the two measurements. The result will be the cylinder taper.

#4 Compare your results with the engine mechanical specifications. If the cylinders exceed these specifications, replace the cylinder block.

--------Cylinder Bore Out-of-Round Measurement Procedure
#1 Measure both the thrust and non-thrust cylinder diameter 5 mm (0.20 in) below the deck surface. Record your measurements.
#1B Calculate the difference between the two measurements. The result will indicate out-of-round at the upper end of the cylinder.

#2 Measure both the thrust and non-thrust cylinder diameter 102 mm (4.00 in) below the deck surface. Record your measurements.
#2B Calculate the difference between the two measurements. The result will indicate out-of-round at the lower end of the cylinder.

#3Compare your results with the engine mechanical specifications. If the cylinders exceed these specifications, replace the cylinder block.

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Cadillac Tech
ASE MASTER TECH since 1988

86 Northstar Fiero
85 RX7 former SCCA car
56 TR3 small mouth 6.0L
Formerly Washougal WA Resident
A.J. Whiteley

AJxtcman APR 18, 02:26 PM
This would be a nice cylinder bore gauge
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This is a middle of the road gauge and the one I use.

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This is a cheap one and it will take some extra time to get acurate readings

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Instructions from central tools.
WAWUZAT APR 21, 08:04 PM
Had a machinist friend come over today and we measured most everything. In return, I did some welding for him. I've yet to analyze the numbers ... will plug & chug 'em using an Excel spreadsheet ... but the bore diameters are all within 0.0015" of each other at high/mid/low locations in both longitudinal & transverse directions. I also found an error in the spec's listed in the GM factory service manual. More details on that later.

Finished silver-brazing & painting the plug I made from the old oil level sensor.


A few years back, I fit a 3800SC engine into a buddy's Fiero (all I did was get the engine in the car, modify his cradle & fabricate the motor mounts, he did all the outfitting work). During that swap, we decided to keep the 3800SC's serpentine belt pulley arrangement, and just modify the PS pump's plumbing. What we did was route the high-pressure line right back into the tank with a small orifice fitting inline to provide some fluid restriction (keep turbulance & foaming down). This time with my N*, I got a little more brave and disassembled my PS pump. Turns out that I can remove the pumping vanes, plug the holes, fill it halfway with oil, and ditch the reservior tank. Another photo ...

[This message has been edited by WAWUZAT (edited 04-21-2007).]

WAWUZAT APR 22, 11:23 AM
OK, now I am somewhat concerned, and not sure what I should believe. I'm losing confidence in the GM data.

The GM manual says the cylinder bore is "93 mm (3.66 in.)", but when I convert 93 mm to inches, I come up with 3.6614 in. All of my cylinder bores measure 3.664" to 3.665" diameter at (near) top/mid/bottom locations in both longitudinal and transverse directions.

On another page, the GM manual says the (crankpin) rod journal diameter on the crankshaft is "53.995 mm (0.069 in.)" WHAT??? By my calculations, 53.995 mm equals 2.1242 in. All of my rod journals measure 2.124" diameter.

The GM manual also says the crankshaft's main journals should be "64.358 mm (2.52 in.)". Again, I calculate 64.358 mm to equal 2.5338 in. All of my main journals measure 2.5330" to 2.5335" diameter.

My pistons still show the original machining surface around the skirts, and I have 0.0015" to 0.002" of clearance between the pistons and cylinder walls. The bores have no more than 0.001" out of round or taper in them. When I compare the crankshaft main journals against bearings inside the torqued down block & crankcase, I have 0.002" clearance. When I compare the crankshaft rod journals against bearings inside the torqued down connecting-rod & cap, I have 0.002" clearance. I haven't measured thrust dimensions yet, but after seeing the minimal wear on all these components, I'm not concerned about it (though I will double-check it when I assemble the bottom end).

If any of you have opinions on these findings, please chime in.

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GT40 rebody on an '85 GT ... soon to have N*-power // '05 Excursion // '05 Mustang // '06 Harley

WAWUZAT APR 22, 06:57 PM
Got the modified PS pump reassembled, and now it functions only as a pulley.
WAWUZAT APR 23, 08:43 PM
I had a thought about another aspect of the N* swap. The front cradle crossmember must be moved forward. No big deal in and of itself, and fabricating a crossmember should be a breeze. Years back, I modfied the cradle to lower the car. But since the Northstar will require a cross-over tube for the cooling system, I'm curious if anyone has given any thought to making that front cradle crossmember function as the cooling system's crossover tube? I'll decide later whether to use round or square steel tubing for the crossmember, but sealing its ends, and plumbing in some hose connections could free up a little space at the forward end of the engine compartment.
Totty APR 24, 01:19 PM
i used 1" round tubing and welded some mandrel bends into it. turned out real nice and i can still fit factory style radiator hoses over it.
WAWUZAT APR 24, 09:02 PM

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Originally posted by Totty:

i used 1" round tubing and welded some mandrel bends into it. turned out real nice and i can still fit factory style radiator hoses over it.



Totty - Are you saying you used 1" round tubing to make the front crossmember in the cradle? 1" O.D. tube or 1" NPS? Either way, I would think something more substantial would be needed. I'll probably use some square tubing (size yet to be deternined) and weld on some hose connections to route the coolant through it. I also like the idea of having that square tube penetrate through both walls of each side-rail in the cradle ... have it protrude to the outside of the cradle a bit to allow for more stiffness. This will also allow me to weld on a 90-degree hose fitting on the right-hand side, then use a fairly short rubber hose to connect to the under-chassis coolant pipe.
WAWUZAT APR 25, 09:07 PM
I've gotten to a point where I can install the NS300L head bolt inserts I bought via eBay. You can find those inserts on eBay by doing a search for "Northstar inserts" ... and I've heard several folks (and GM technicians) claim they're much better than Timeserts.

When I disassembled my engine, all the head bolts broke loose with a definite crack-crack sound. None of them eased out, which would be an indication of bad threads in the block. Being the cautious type, I wanted some sort of thread insert for when I torque the new head bolts down. The last thing I want is to wait until that time to find I really need them. It is so much easier to do it now while everything's disassembled, and cleaning out the drilling & tapping debris won't be a tedious task.

In the past, I've tapped holes that were 1/2" diameter and smaller. But I needed a larger tap-holder to use the taps that came with the insert kit, something that would accomodate a 3/8" square. I shopped around locally, but what I found was way too expensive ($70) for a tool that will only be used one time. Instead, and as shown in the following pix, I cut up an old broken 3/8"-drive socket extension, and welded it to a 1/2" diameter by 12" long round bar (a scrap piece I had left over from some other project). It's not pretty, and I have to tape the tap to the "driver" to keep it from falling out, but it works like a champ.
WAWUZAT MAY 01, 08:39 PM
A week ago Sunday, we had a crew here replacing the front porch columns, posts & rails. I spent many hours over the last week caulking, sealing and painting the new stuff (composite columns & wood everything else). So, I've been away from the N* for awhile. Tonight, I gave the bores a very light scuffing with a hone (enough to break up the glazing), then did a final blow-out of the holes with compressed air, hosed off the block, and used the air again to dry everything. Then I lubed the cylinder sleeves (steel), put a plastic bag over it, and called it a night. I am now in assembly mode.

The photo below shows the amount of aluminum that got drilled and tapped out of the head bolt holes in order to install Norm Huhn's inserts ... which will be installed tomorrow evening. More importantly, the photo shows a relatively inexpensive item that saves a LOT of mess getting on the floor. I paid about $45 with shipping for that catch-all pan that rests on the legs of the engine stand. It caught all sorts of gook & oil during disassembly, the aluminum as shown, and will keep assembly oils from reaching the garage floor. This thing is well worth the money.