21 replies to this topic

[spritey]

As my oil pressure is low and don't know how long it's gonna survive im looking at building a new engine with a bit more power


I've got a 1275 sitting here but would like advice on what bore and Pistons gear ratio and diff to buy
I've got a hiff44 already and the car will be used as a town car with some distances to shows via motorway to would like it to cope with the motorway

I'm thinking 1330 for reliability but if you engine builders could help me decide as my Knolledge is limited which bore and Pistons etc to go for , I know head is a easy thing that can be upgraded in the future

Edited by spritey, 17 May 2015 - 04:41 PM.

[mini-geek]

I'm by no means an engine builder..

But why not just go for a 1293 (leaves loads of life in it and if it doesn't need it leave as is)

If your on a budget MiniSport stage 3 head if not spend s bit more on the head..

Then stick an MG or similar cam in with verniers

You've got the right carb... Makes a nice little engine...

Maybe lighten and balanced crank..

[gazza82]

I think most of our engine experts would say NOT to go straight to 1330 as this is the max. Does it need a rebore? If so go 20+ to 1293 first. Gives you two more standard rebores before you resleeve. I have fitted minispares mega pistons to my 1330 but it's still in progress so can't comment on reliability etc yet.

Edited by gazza82, 17 May 2015 - 05:20 PM.

[Cooperman]

As above, bore to the next possible oversize.

Use 21253 pistons.

Use 35.6 mm inlet valves and 29.5 mm exhausts in a head which has been slightly cleaned up in terms of gas flow. Measure, calculate and set the compression ratio to between 10:1 & 10.3:1.

An MG Metro camshaft is very nice to drive with combined with an LCB ex. manifold and 1.75" Maniflow exhaust system. The inlet manifold should be an allow one cleaned and matched to the head ports.

Use new cam followers and new oil pump with a re-ground crankshaft and new main & big end bearings.

Set crankshaft end float to between 0.002" & 0.004".

Time the cam in very accurately using either vernier sprockets or offset woodruff keys and fit a duplex timing chain.

Fit an Aldon 'Yellow' distributor.

Usually good to fit a new water pump.

Use a BK450 head gasket.

Assemble it very accurately and carefully.

 

I hope this helps.

Edited by Cooperman, 18 May 2015 - 11:35 AM.

[spritey]

Thank you so in terms of head if I buy the parts you specified the engine machine shop will just match my head and engine bore to them ?

[nicklouse]

I think most of our engine experts would say NOT to go straight to 1330 as this is the max. Does it need a rebore? If so go 20+ to 1293 first. Gives you two more standard rebores before you resleeve. I have fitted minispares mega pistons to my 1330 but it's still in progress so can't comment on reliability etc yet.

Typo? 1380 (73.5mm Pistons or slightly more with 74mm Pistons) is the biggest bore.


BUT whatever size you go for plan ahead if you need to go bigger make sure it has been bored to allow you.
Then the CCs in the head what you want for 1293 is not what you want for 1380 so don't go mad.

My only comment on coopermans post above is electronic ignition. Don't know if the Alcon yellow has got rid of the points if yes good but a black box of mappable ignition curves can really do wonders in terms of drivability and tick over.

But as with most things engine realated your engine builder needs to be your best friend. So you know what you are getting is right. Buying x from a and y from b and z from c and hoping it all works.......... Yes that word Hope.

If you have the head already give it to the guy doing the short motor so he can make it to match and visa versa.
Ignition give them the info of the engine and you will get something very close to right. Final tuning on the rolling road/dyno.

[gazza82]

Cooperman: are the cam float numbers correct?

[gazza82]

 

I think most of our engine experts would say NOT to go straight to 1330 as this is the max. Does it need a rebore? If so go 20+ to 1293 first. Gives you two more standard rebores before you resleeve. I have fitted minispares mega pistons to my 1330 but it's still in progress so can't comment on reliability etc yet.

Typo? 1380 (73.5mm Pistons or slightly more with 74mm Pistons) is the biggest bore.


BUT whatever size you go for plan ahead if you need to go bigger make sure it has been bored to allow you.
Then the CCs in the head what you want for 1293 is not what you want for 1380 so don't go mad.

 

 

I meant just STANDARD bores .. not going offset yet. Also we don't know yet if it needs re-boring and we don't know if it's already been re-bored. Still sticking to my original suggestion of simply going up one size.

 

If it's already at 1330, then it probably will need offsetting or re-sleeving back to 1275 first.

[Cooperman]

Cooperman: are the cam float numbers correct?

Hi Gazza, I think you mean crankshaft float. 0.002" to 0.004" float at new build is ideal. The float will increase as the engine puts miles on, so start with a good accurate fit and NEVER start from cold with the clutch pedal pushed down.

By mixing & matching with standard and +0.003" oversize thrusts the float can normally be set very accurately, unless you have over 0.010" at trial build in which case very thick +0.030"thrusts will need to be machined down to get the float correct.

You are right about re-boring. Always go to the next size up. After 1330 cc it is best to sleeve back to 1275 cc.

 

To Mr. Spritey, personally I would never leave a machine shop to co compression ratio/combustion chamber calculations. Do them yourself by careful measuring and calculating. The formulae are all on here and it's not difficult. It is best to do the actual build yourself and, as a classic car person, you should be able to do this - unless you have 'loadsa money' to pay specialists. Most of us have to do our own work due to the hourly rates necessarily charged by specialists. It takes around 25 hours to properly build an engine. Yes, it can be done in less but it won't be as thorough a job. At least one 'trial build' is needed before final assembly, sometimes two are needed. 25 hours at, say, £40 per hour is £1000 in labour, plus machining costs.

[gazza82]

Sorry, that's what I meant but in your previous post you had .02 to .004 .. guessed you'd lost a zero somewhere!

[Cooperman]

I'm sorry about that - a typo (again!). I had better go back & edit it.

 

Edited to add that it's now edited  .

Edited by Cooperman, 18 May 2015 - 11:36 AM.

[spritey]

I've decided to go for 1293 as you guys have advised , I've got a minisport fast road cam set (is it worth using this can or going for a different one )and duplex timing gear , I will change water pump oil pump ,gaskets , fit a centre oil pick up and use my hiff 45 carb my maniflow lcb, is it possible to just use stock head to save costs and upgrade in the future ? Also I'm unsure on setting valve clearances and end floss and compression , I've searched on the forum but can't find anything...

[nicklouse]

No idea what can that is but if it is anything like the topic heading suggests then you really are wasting your money not doing the head.

A height lift cam is wasted on a standard head. If anything I would go for the head before the cam. Opps that is what I did do back in the 80's.

But at the same time you need to make sure block build suits the head. Compression etc...

[Cooperman]

As 'nick...' so correctly alludes to it is pretty pointless changing the cam, or much else really, unless the head is properly gas-flowed with the optimum valves for a road engine (35.6 mm inlets & 29.5 mm exhausts), the C.R. increased to c.10.3:1. An improved head is the basic key to making the A-series engine give more power and more torque.

I have no experience of working with Minisport came and I always work using the Kent offerings. The Kent 266 is about ideal for a road engine and gives really good torque at mid-range revs.

Make sure you fit a really top quality oil pump and time the cam in very accurately.

[nicklouse]

Personally I would not bother with the 266. Did like my 276 on the road though. And my 1380 with a 286 was wickid as they used to say but I would not go that far on a 1293 or for a road use engine now.

As per Mr Cooperman I tend to stick with Kent fir the cams. Did have a play with Piper but did not get on with whatever it was.