Are you sure you wanna run flat tops!
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| What are the costs for this work to be done? https://www.ausmini.com/forums/viewtopic.php?f=2&t=14038 |
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| Author: | Gerard [ Thu Dec 15, 2005 9:28 pm ] |
| Post subject: | What are the costs for this work to be done? |
Hi All what would it cost to get this work done to a 1275 motor?
Crank machined and crack tested with new bearings. New oil pump. New water pump. New timing chain(double row) Cylinder Head machined and crack tested. Fitted with new valves,springs and seals. Cheers Gerard |
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| Author: | willy [ Thu Dec 15, 2005 9:29 pm ] |
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Are you sure you wanna run flat tops!
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| Author: | Gerard [ Thu Dec 15, 2005 9:34 pm ] |
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Dunno mate are they a good thing or bad??? Cheers Gerard |
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| Author: | willy [ Thu Dec 15, 2005 9:44 pm ] |
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in a 1275, these pistons will give very large compression. With some good chamber work, the compression can be lowered so you can run pump fuel without too much drama, but a good set of dished pistons and a shaved head (if it tickles your fancy) would be a much cheaper and "better" option. Depends what you're after tho - a streeter or a ball tearer 
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| Author: | Gerard [ Thu Dec 15, 2005 10:02 pm ] |
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so flat tops would put me in streeter or ball tearing territory??? Cheers Gerard |
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| Author: | Stuwey [ Thu Dec 15, 2005 10:07 pm ] |
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Jeez Will, who told you that? Set the comp. ratio with a choice of piston, not by shaving the head to suit the pistons you may have. You can easily replace the pistons, but once the head is shaved to suit your build, its shaved forever! You don't need flat-tops. Too much compression. I have ACL cast-type pistons. Nothing special at all. They have a 3cc dish and i have no issues with pinging, but just a touch more comp. than standard. BUT the head has hardened seats, and it ONLY gets run on Ultimate 98 fuel, no exceptions. |
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| Author: | LS1380 [ Thu Dec 15, 2005 11:08 pm ] |
| Post subject: | Re: What are the costs for this work to be done? |
Gerard wrote: Hi All what would it cost to get this work done to a 1275 motor?
Crank machined and crack tested with new bearings. New oil pump. New water pump. New timing chain(double row) Cylinder Head machined and crack tested. Fitted with new valves,springs and seals. Cheers Gerard Does this help for your pricing 
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| Author: | bigel nigel [ Thu Dec 15, 2005 11:09 pm ] |
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no 
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| Author: | drmini in aust [ Fri Dec 16, 2005 6:15 am ] |
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If you run flat tops on the street you will need to machine heaps out of the combustion chambers to get the C/R down to a sane level. My 1310 had Mahle flat tops in, I think the head volume was 28cc for 10.4:1 C/R. I did run it at 11.0:1 for a while but it was too high for the fuel available then (95-96 octane). With 98 octane fuel, I now find 10.7:1 works OK on the road with the RE13 or RE282 cams. But if running near stock cams, don't go this high. 
Of course for track use only you can go higher C/R as the motor will seldom be below 4000 rpm. |
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| Author: | minicranks [ Fri Dec 16, 2005 6:28 am ] |
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Hold on a minute, whether its flat tops or not it depends on where the piston is sitting at TDC as not all flat tops are designed to sit flush with the top of the block. So that will have a huge effect on what you compression ratio is. Also why bother with 60thou over why not just hit up for the 73mm pistons as they have the bore size and have a dish so compression ratio is not normally an issue, price is a bit cheaper for the 73mm pistons the rings are readily available and i personally think they are a much better piston (althou made in the same place) I have built a 1293 with flat tops and it sits with my 1380 on a 1/4 mile sprint (well almost) but its a dog to drive due to the pistons being flush the comression ratio being 12.5:1 but hey thats what my mate wanted and he uses it everyday to go to and from work.But it all depends on what you want ot use it for. start there and then work out what you need. |
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| Author: | drmini in aust [ Fri Dec 16, 2005 6:55 am ] |
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Yeah what he said...^^^ 1275 flat tops were for racing, and most motors had them set near flush. I built mine this time with Hypatec 73mm pistons (dished) and had to deck the head .050" to get the C/R back up. |
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| Author: | TheMiniMan [ Fri Dec 16, 2005 9:42 am ] |
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you need to talk with someone about the intended use for the car that person should be a mini specialist with plenty of years of experience building & servicing minis,,,don`t just go to Joe Blow mechanic, they will have no idea a full rebuilt 1275cc donk (to whatever size) should be completed as a """"package""" if you go out & buy some go fast bits & just bung them together then the engine just won`t be what it could have been if it were built as a """Package""" i would also look at doing up the gearbox & drop-gears to make sure all is nice there too,,,you won`t want a shabby gearbox spewing metal slithers up into your oil pump & crank bearings wrecking your nice new donk now would you??????????? flat top istons were originally intended for race use, the comp ratio is needed to be kept at about 10:1 (ish) maximum for road use,,,much above that & you have a dam good chance of detination inside the combustion chambers which will eat away at your head gasket & piston & also hammer piston ring lands & crank bearings,,,so basically it`s not very good to have pinging/pinking/detonation , a very well sorted cyl head , carb & distributor & exhaust system as a package is a must if higher comp ratios are to be used for road engines on pump fuel,,,Av-Gas for race engines is a whole different ball game & not allowed to be used on the road. That said,,,the bigger engines & engines with bigger cam shaft profiles can get away with a slightly higher comp ratio,,,in fact big cams really NEED big comp ratio for them to work properly, but again these sorts of things are set for more of a race engine than a roady Road donks are just that, ROAD USE,,,track or club race engines can be set with much "sportier" cam profiles & higher comp ratios & bigger valves etc, but at a cost of low down drivability & also premature engine wear from constant high revs etc etc etc Big cams will need strong valve springs which in turn can hold an engines power down somewhat & also tend to wear things out very much quicker, like cams, lifters, valves & rockers etc etc etc compromise is what`s needed here & you will need to look at what you`re going to use the car for , before undertaking an engine build with go fast parts i`d expect you should be paying about $4500 for a complete roady re-build including the box race engines are much higher cost than that happy??????????? |
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