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October 17, 2026, 05:46:48 AM

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[MarkZE]

My new bottom end build up reached a major milestone today.  I finshed the lightening of the crank and will send that off to get balanced reground nitrided etc after the new year break.

See pictures here.





I have some H beam BA falcon style rods ready for it too and will order some CP pistons first thing after new years also.  Hoping to have it running by the Mini Jam in March.

[BigNorm]

by removing that much metal off the crank, how strong is it?

[CortinaD]

thats sick.

be interested to see how much it weighs.

[Oscar of Markoz]

Mark, did you end up getting the bits off Gauci for the front of the block and the crank girdle?
900hp, thats gonna be an animal man.

[TE_JET]

Nice Mark. now do you want me address to send it too?

[MarkZE]

Oscar - I haven't got one of Joes front head bolt plates yet.  I am not 100% convinced I like the idea yet.  Have you fitted yours yet?  What stops water leaking through around the head bolt once you drill the thread out of the block?

I called Joe about the crank girdle and his is designed for 200 crank not 250.  I have drawn my own which clear the conrod on the 250 crank and allows me to keep the stock oil pump in the bottom of the block.

Crank weight 25.03 kg now but I am not sure what it started off at.  I know is is definately lighter than a stock part counterweighted crank and WAY lighter than what is was originally.  I'd say around 5kg came of it.

I don't believe I have weakened the crank because I have not removed any material betwen the main journal and the big end which is essentially where the force is transmitted.  Grant at brisbane Balancing reckons it looks good and he has done a lot of research and testing on engines with harmonics issues etc.

[CortinaD]

cant you rubber o-ring the bolt?

[MarkZE]

Brisbane Engine balancing took about 53 grams of material off the 3 & 4 counterweights to get it to balance up to within 0.3 of a gram.  The crank is now ready to be nitrided and reground to final sizes.

The 86DA block was measured and checked with the following key measurements:

Bore thickness:  On average 0.220” thick walls.  Cyl #1 non thrust side 0.160” which is still acceptable.

Deck height: 9.389”

Allowance for decking block was decided as 0.007”

Final Deck height (after machining): 9.382”

Engine Stroke: 3.910”

Conrod Length: 6.060”  (Spool BA Falcon H beam rod with 0.866” floating gudgeons)

Bore:  3.680” (Still Standard and not very worn)

This allowed us to calculate the piston compression height.  We were working on having a “zero deck”, piston flush with the top of the block which gave the following piston specs:

Compression height:  1.367”

Bore: 3.700”  (0.020” oversize)

Gudgeon size: 0.866” floating

Dish: 22cc

Piston specs have been added to a drawing and will be sent to CP for a set of custom forgies to be made up.

We decided to go up to 9:1 from the previous 8:1 as I now only use the good quality C16 fuel.  The extra compression should help get the engine up on boost if I decide to go to a bigger turbo and will help make more power with less boost.

Moving the pistons up to being flush with the block and reducing piston dish from 27.9cc to 22cc was enough to give 9:1 with my 56cc chamber volume.

With the pistons flush and the dish smaller I should get better combustion properties and I hope to run the same amount of ignition timing without pinging even though the compression ratio is one point higher.

Main stud length was calculated.  The new engine will use ARP studs, and a girdle which clamps over the caps.  The caps are now machined flat to suit.  The following measurements applied to the stud length:

Block thread depth:  1”
Main Cap height: 2.2”
Girdle thickness: 3/8”
Nut and Washer grip length: 9/16”
Exposed threads above nut:  Approx 3/8”

A 7/16” UNC x 4.5” long ARP stud will be required.  So far I am told a 308 Holden V8 head stud should be the right size and thread to suit.

The block is currently getting acid bathed and crack tested and I will have that back tomorrow.

Next step is to get the, conrods, mains studs, main girdle, bearings torque it all up and measure the bearing sizes to get the finished sizes for the crank grinders to work from.

The timing belt drive is underway with some 4140 material on order for the crank sprocket and cam drive sprocket.  Some 140mm OD aluminium has already been roughed out to size for the outer section of the cam pulley.  All the drawings are now finished for the timing drive and the alloy cover plate will be sent off for water cutting next week.

When I get the timing belt drive looking like something worth showing I will get some pics of it.

Looks like the timing belt drive will require some mods to the front of the sump so I have a stock Cortina sump and pickup coming soon to make a start on that too.

[MarkZE]

Six hours on the lathe last night at my mate's workshop and not much to show for it.

I have bit of 4140 machined into a hub with a flange to fit on the front of the cam and a block of aluminium round bar that looks roughly like a pulley without any teeth on it.  The ally block slips nicely onto the hub and will eventually allow me to adjust the cam timing whithout pulling anything apart like you would with a DOHC engine.

I still have to get the keyway cut, hone the bore to be a neat fit on the front of the cam and then start on the crank pulley which at this stage is just a lump of 4140.

I have a cover plate being water cut from ally on the way, that will close of the timing cover section of the block and keep the oil behind it so the pulleys can run totally dry.

I didn;t fell much like taking photos at 3am but I will get some soon.

[Oscar of Markoz]

Nar mate, I haven't fitted my front plate as I haven't continued with my motor. Iam doing work on other parts of the car 1st and will get back to the motor later on. Money is an issue plus the order I want to do things in with the car now.

Gee, your thing sounds like its gonna be some serious peice of work. Lots of development gone into it. Are these ideas that you have just thought of or things that you know of others doing with the crossflow?

Can't wait to see the Zoom feature though, let me know what issue cause its not a mag I usually buy unless theres a corty in there.

Do you think you'll ever come down to WSID to race?

[MarkZE]

You shouldn't have to look too hard for my Zoom article because I am told my car will be on the cover.  I had to do an extra photo shoot specially for the cover shot so it better be there.  I think it might be March issue but I am not 100% sure yet.

Some of the ideas are just what the speedway guys have ben doing for years, i.e light weight crank shaft and good quality componets well balanced and carfully assembled.

The belt drive idea is basically a rip of of what Jesel and similar companies use on V8 Fords and Chevs for supercar and Nascar, pro stock type engines.

Rods and pistons are just a something I need to do to keep it reliable at the higher 6500 rpm rev limit.  Revs kill rods not outright power.  If you kill a rod due to outright power it will bend not break.

The extra work I will do on the head is farily typical, stronger lighter valves and good springs and some more porting, basically what a serious speedway atmo engine would have done to it.

I have a few ideas about harmonics etc that I hope to address so I can get rid of damaging vibrations that lead to bearing and block failure.

[MarkZE]

Timing belt drive from engine side (in progress)


Timing belt drive from front (in progress)


Main Cap Girdle showing caps machined flat



Main Cap Girdle and complete engine

[corty666]

so did u finish it yet?