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Race engine refresh
https://www.ausmini.com/forums/viewtopic.php?f=5&t=88650		 Page 1 of 1
Author:  69cooper [ Tue Feb 17, 2015 11:16 pm ]
Post subject:  Race engine refresh
Guys, I have pulled my race engine to repair drop gear bearing, I was also going to put a new set on main and big end bearings in while it is apart , I have inspected crank journals and they looks fine, cam lobs look fine and their is only light markings on cylinder bores.

Would it be worth chucking a new set of rings in ??, currently GR piston with Hasting Rings

Engine has done two seasons of SES sprints , so that's around 12 events/yr x 4 runs/event x 10min per run = 120 min per year, which gives me around 2-3 hours running each year at 6000-7500rpm :twisted:

The engine does suffer from a lot of blowby, but I assumed this was due to high revs :?

Cheers Mal
Author:  drmini in aust [ Wed Feb 18, 2015 10:32 am ]
Post subject:  Re: Race engine refresh
I'd give the bores a light hone and replace the rings, use GR's Nippon rings if available. They hold their tension better than the Hastings do if racing.
Author:  FNQ [ Wed Feb 18, 2015 7:44 pm ]
Post subject:  Re: Race engine refresh
Mal what was the state of the timing chain..... just curious as to how much slack is introduced in such driving conditions ( low lms but harsh) Darryl
Author:  69cooper [ Wed Feb 18, 2015 10:02 pm ]
Post subject:  Re: Race engine refresh
No timing chain :twisted: , I run genuine Italian made trigger belt drive , I have been considering a upgrade to vernier adjustable set up :wink: , to get a couple more Horses out of the engine, dr vizard book states that even three degree out will sap HP.
Author:  MiniVLT [ Wed Feb 18, 2015 11:17 pm ]
Post subject:  Re: Race engine refresh
Why not get a couple of different offset keys to dial in your cam?
Got to be a cheaper way than buying an entire new vernier set yeah?
A bit more fiddly, but way cheaper!

Cheers Shane
Author:  drmini in aust [ Thu Feb 19, 2015 9:08 am ]
Post subject:  Re: Race engine refresh
I agree. Offset cam keys work just fine.
I don't like the dowel pin vernier BD kits, I've seen them come loose. The slotted ones are better.

What's the latest on belts for these Trigers, is the loose Chinese one the only available here now?
I'm running a Mini Mania kevlar one, expensive yes but they fit well and last longer. Postage to Oz can be a bit rich though! US$18.43 to US$129! Lower price is US Mail, at least they will now use them again.

These belts are made by Gates in Japan for MiniMania, but Gates here know nothing of them.

http://www.minimania.com/part/C-AJJ3328 ... evlar-Race

[edit] I have just ordered a Gates 195L075 timing belt from the USA, according to UK forums they fit and work fine.
We'll see how well it fits.
Author:  Besser [ Thu Feb 19, 2015 9:46 am ]
Post subject:  Re: Race engine refresh
On the blowby it's a function of lots of factors. Honing done properly will have the first stoning produce the oil retension valleys and the angle is relevant to the rpm target, a steeper angle will retain less oil and give less friction but less sealing. The second honing is simply the ring bed-in scratches to the peaks of the first scratches and will flatten to a polish after limited mileage. Using one stone to do both "over" wears the rings and can micro chip them or it doesn't hold the oil for sealing and cooling. Unfortunately the rattle-can engineers around will single "hone" the cylinder, spray the block a nice colour and make you pay for a premium job, then make you pay through shortened engine life so you come back for more over paid rattle-can engineering.

If your bores are glazed, then you need a better warm up procedure, the scratches are full of junk and will give lots of blowby. A rehone is needed
If the bores are polished, you've run out of hone and need a rehone
If patches of polished zones appear this is where blow-by will mostly be occurring, the block wasnt warmed and stressed prior to honing, you need a rehone (this is very common in well kept but not prep'd race motors, road engines wear around the top ring land on the bore first)
If you dont mind the blowby no hone needed :)
Author:  69cooper [ Thu Feb 19, 2015 12:06 pm ]
Post subject:  Re: Race engine refresh
I have managed to get a couple of Pirelli belts out in Italy NOS for trigger set up, just jump on ebay Italy and us the google translator.

Thanks for the detail regarding honing interesting information on hone pattern

What is the recommended clearance on piston for race engines, mini spares quote 0.0022" - 0.0025"

mal :-)
Author:  Besser [ Thu Feb 19, 2015 10:21 pm ]
Post subject:  Re: Race engine refresh
Forged Pistons normally have a higher clearance say 2x cast due to thickness and expansion. The top of the Pistons are round with the under ring section an oval that expand into a round at operating temp. Go with the clearance on the piston/ in the box the manufacturer does lists of calls and testing. You can sacrifice life by cut back the skirt and taper it back to the pin if you avoid the wear area. The rings do the sealing not the piston, keeping the piston square in the bore helps the rings seal but big clearance and the off set of the wrist pin swaps the tilt of the piston tdc and bdc breaking seal so a tighter clearance is better to avoid the tilt.
Author:  FNQ [ Mon Feb 23, 2015 5:04 pm ]
Post subject:  Re: Race engine refresh
Mal , i can just see you on ebay italy bidding on all sorts of things.... good stuff and go the $AUD/euro exchange rate.
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