MADJAK's NA8 - 200+HP N/A

[Ice88]

I picked this engine up second hand from QLD, so I'm not sure on the hours it had done previously. I know it was run at Bathurst which would have been pretty hard on it and then had been sitting around for a few years. Myself I've done approx 20 hours maximum.

Looking at the logs and the failure, I suspect a few issues may have reduced the bearing life. When I first installed the engine it took a while to get oil pressure. It was just cranking but still the bearings were probably dry and it might have damaged the surface a little.

Secondly, I've been very hard on the engine, with a couple of mis-shifts before I installed the MR short shifter and a couple of over-revs in downshifts. I was planning a full rebuild at the end of this season anyway. I guess this just brings it forward a little.

The machine shop is doing a hone on the bore, and is going to clean up the rod. The crank that was in the engine was already at max grind so I've purchased a another crank from Automotive Plus (thanks guys). I've got new rings already on the way from the US and I've managed to source some ACL bearings of the right size in Aus. Other than that it will be all back together and ready to go again in a few weeks... hopefully!

I'm going to clean out the oil lines, pull the cams and check the head surfaces. There is no powdered bearing surface in the oil, only flakes in the sump. I'll have a look in the oil filter and see whats in it, but I don't think anything has gone through the rest of the oiling system.

I think I might up the oil pressure a bit and also start doing some oil testing.

Are you regrinding the crank? I think you'll find that they ground the crank to increase the bearing thickness

Will also want to make sure your tolerances are quite tight to spread the load over a wider area of the bearing. Will also help with oiling

[ralt]

Hi.
Make sure you pay careful attention to thrust washer tolerances.

[madjak]

The existing crank was already at the limit of the grind running 0.5 bearings already. So I've ordered a replacement crank from QLD that should rock up in time, and I've checked that it hasn't had a grind on it.

The bearings I've ordered are the ACL STD bearings to match that new crank.

In terms of thrust bearing, I'm not sure how you set that up. I'll have to have a read up on it.

[zossy1]

It's pretty straightforward - feeler gauge between the thrust bearing and the main cap. You're looking for tolerance - 0.006" to 0.009". 0.010" is too much.

[madjak]

Got most of my parts now... just waiting for the crank and some gaskets to rock up (hopefully by the end of the week).

Whilst I'm waiting for the engine rebuild, I figured I'd tidy up the wiring in the car and sort out a few electrical issues whilst it's easy to access. I've installed 2 x 1000 PSI pressure sensors in the brake lines. I figured this might be useful to see how much fluctuation there is in the brake pressure due to the booster. Looking at my logs from the weekend, my g-forces under braking are far more consistent without the booster connected. I also set my fastest time without the booster so I figure it's definitely quicker. It will take a while to get used to stepping on the brakes harder on that initial application but once on the peddle I couldn't feel much difference. I'll experiment a little more before removing the booster entirely and I should have some data now to verify the feel. Ultimately I'd like to install dual masters, but that's a project for another day.

I've also installed a oil pressure gauge so I have a backup option to the digital gauge. I've set up my shift lights to give me a check engine light if there are any pressure drops below my set thresholds.

As part of the re-wire, I'm going to shield the CAS wiring with some foil. Is there other wiring (like the injectors) that should be shielded as well? The TPS on the ECU is shielded, but my wiring to the TPS isn't. I've just twisted them together.

[madjak]

The crank I got shipped from QLD from a certain race shop has a spun big end bearing! I asked if the crank was standard even got them to check it before shipping! Even without unwrapping the glad wrap I could see it was screwed. This means I now have 3 cranks all with spun bearings... Also, the std sized ACL race bearings that I scrambled to get are now useless to me and sourcing race bearings is impossible ATM with both Kings and ACL out of stock anything oversized.

So... I'm going to fall back to the crank I had ground. I'll have to run stock bearings for now.

And I'll have to send this crank back across the country... Just a little pissed off. Luckily I had my spare crank ground otherwise I'd be missing the Nationals.

[Old Grey]

You set end float by standing the engine nose-up with a dial and magnetic base resting on the nose, and then lift the crank up with a screwdriver.

Do all the cranks have the same burnt journal - it would indicate an oil gallery feed problem. I modify oil galleries like they have been designed with a flowbench - radius corners, removing sharp entrances and exits on the pump, matching bolted-on parts, etc. Check pump for scratches.

You need to cut open the filters regularly and look for debris.

https://www.google.com.au/search?q=oil+ ... pgod8nIFmQ

You could raise the comp. I would be running 12:1 minimum with such a large dur cam and E85.

Bearing clearances are very critical for race engines - lose is safe for high rpm -. You need to measure the old stuff, get the clearance they used, and then supply the rods and new bearing to the grinder so he can assemble them and measure them, and then grind the correct custom clearance.

[NitroDann]

Id be way into the 13's at least.

[madjak]

Yeah if it was a new engine I'd be at 13:1. I don't even know what this one is. Has the Wiseco 10.5:1 pistons but the head has been decked a lot. It should be around 11 - 11.5:1

Ok so thrust bearing is measuring at 0.006". Plastigauges are telling me around 2 thou across the board. I think thats in the right specs so I'm going to start final assembly. Still waiting on the rings but they should be here early next week.

I love playing with engines. Shame they are so expensive!

[Old Grey]

0.002" sounds right.

The only other thing is rod bolts. We stopped using torque wrenches 20 years ago, because the torque required changes with lubrication, so we switched to ARP bolts and use a stretch gauge instead.

https://www.google.com.au/search?q=stre ... 80&bih=965

Would I be asking to much for the valve sizes, and cam specs, and some pics of the ports.

[madjak]

Yeah I've picked up some arp bolts instead of the crowler ones. They might have stretched on the rod that run a bearing. The arp bolts come with their special lube stuff that helps them torque correctly. I don't have a stretch gauge so I'll just have to torque it as per the specs. Engine needs to be run in this weekend.

Doing a rebuild in 3 weeks is pretty tight, especially when stuff has to come from the US.

Valves are oversize 2mm on intake 1mm on exhaust (I think). When setting up the lifter clearances I heard a ticking when turning one cam. It was the valves touching as the other valves were half out. I hadn't thought they could touch... with te overlap these cams run, it makes it even tricker to make sure nothing hits when you have to avoid cylinder heads and the other valve!

Cam specs are unknown (I don't know them because they are a full custom grind and came with the engine) ... but are over 305 degree.

[Old Grey]

It's good to torque up and loosen new bolts a few times to remove the fur off the thread, so that they torque correctly. Rods should be closed and honed when changing bolts because they can go out of round.

Valves are usually 1mm oversize because the seat runs off the std seat insert - I guess they are the usual 35mm 31mm -, I was just wondering if they did something fancy like new seats and larger valves with a worse DC, due to it being cam limited.

Bigger cams have more lift at TDC, so can hit if you're not careful. You could fit the head without the cams, and the pistons ½ way down the bore, and assembled it after the head is bolted on. If the head is fitted with the cams they can spring back on the stiffer springs, so keep an eye on that.

Just measure the height of the lobe and subtract the width, and that gives you the lift.
305º is seat to seat, so I suppose it's something like 255@0.050". I was just wondering if they reduced the exh lobe to make up for an exh port that flows too much.

All race motors should have the oil primed before start. I've seem too many race engines trashed when brgs get wiped due to no priming. A NASCAR engine must be fully assembled with only 2 revolutions of the crank because repeated revs wipe assembly lube off parts.


If you're handy with a drill and have an old LPG cyl, just fit a tyre valve near the top and extend the pickup to be to the bottom. Fill with oil, pump it up, and screw into pressure sender. Then fill the engine untill it comes out of the cams while spinning the engine.

If that's too hard, at very least crank the engine without the spark plugs until oil comes out of the cams and pressure builds up.

[madjak]

The rods have been honed by the machine shop. He stretch tested the old bolts and they tested fine however for $100 i figured a new set would be safer. The instructions for torquing the rod bolts say to torque to a low setting on all then straight to target torque in one go.

When I measured the valves the intake is certainly more than 1mm oversized. I think it was closer to 1.5mm than 2mm. They are a custom valve so the seats must have been modified. The valves hit each other at something other than full lift so I have to be carefull to make sure where the other cam is sitting before rotating.

In terms of piston clearance i'm about 3-4 degrees clear on both exhaust and intake. So its all pretty tight in there. It would be tricky to raise compression further with these cams.

The intake and exhaust are identical specs as far as I know. I think 0.05" duration is around 250 degrees but it could be more.

In terms of building pressure, I was planning on crank it without plugs. I'm using good assembly lube on all friction surfaces and I'll also try and prime the oil using an AN oil cooler line and gravity. I actually suspect thats how I damaged the bearings in the first place. When I first got the engine it had been sitting for ages. It took far longer than I expected to build pressure and the bearings possibly had dried. Bit silly in hind sight but I didn't want to pull it apart before I had run it.

Engine will be in as soon as I receive the rings. Head is ready, block is ready.

[Old Grey]

When it's assembled tip it on it's side and pour oil in from the oil filter mount.

Race brgs have the soft babbitt embedability layer removed so that the brgs can handle more load - they changed from silver colour to dull grey -, so you have to be careful and prime engines because they can't self heal when wiped any more - self healing is not ideal in a race motor anyway -.

You can get the valve relief's deepened, and then you can raise the comp.

[madjak]

Whist waiting for my rings to rock up I figured I'd hack up a valve cover and trial a new breather setup. Basically the entire Mazda baffling is removed, ports are drilled and tapped for -8 fittings and the baffle plates cut in half and screwed back on.



The idea is to open up the airways so that there is less velocity in the air so the breathers pick up less airborne particles. With the E85 I'm picking up a fair amount of moisture combined with some sludge so I'll see if there is much difference. I saw the scotch bright option but I'm not that keen to put an abrasive in contact with the oil. If I find I'm getting too much oil I'll pack some SS scrubbing material under the half baffles.