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Supercharged 1293 - Rod & Piston Choice, And Expected Power


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#1 supermog

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Posted 20 September 2016 - 01:43 PM

Hello,

 

New to the forum but not the A-series.

 

I'm starting to plan the engine build for my Morris Minor (hope you Mini chaps don't mind) and have a few queries regarding component choice for a supercharged setup.

 

Engine is a 1275 Midget block with EN16T crank, planned spec is listed below.

 

1st question regards piston and con rod choice. I have three avenues in mind:

 

1. Original AEG625 rods lightened and polished, with Minispares MEGA pistons

2. Original AEG625 rods lightened and polished, with Omega cast pistons

3. Forged rods (SC, MED or Arrow) and Omega forged pistons

 

What sort of power and boost can each combination handle? I'm hoping for at least 120bhp, but ideally aiming for 150bhp+

 

At what bhp would the original rods become potentially unreliable?

 

The engine build is going to be expensive and it's going to be a road car, so reliability is key, even if it comes at additional original cost.

 

 

2nd question realtes to the power I can expect from the engine. Full proposed engine spec is below, but in brief it would be 1293 engine, Eaton M45 blowing through HIF44 with Podifold manifold. The space available in the Morris engine bay allows for fitment of a large IC which would hopefully overcome the inefficiencies of the Eaton at high boost.

 

What sort of boost figure is sensible assuming a large IC?

 

I've read numerous posts quoting quite low power figures from supercharged A-series, but most of these are suck through and not IC'd. I'm hoping blowing through and an IC will release greater potential from the SC.

 

I've read many an argument that suggests turbo has more potential than SC, and I know there are numerous easy ways to increase power in a Morris with engine swaps, but I am steadfast on sticking A-series and SC'd not turbo.

 

Any help much appreciated.

 

Proposed engine spec below:

 

All components to be uprated versions (valve guides, ARP bolts etc) and crank/rods/pistons/damper/flywheel to be balanced.

 

Head:

12G940

35.6/29.2 valves

DIY ported as per Vizard

CNC combustion chambers to lower CR

Rockers TBC

Manifolds to be matched to head

 

Block:

Bored +20 to 1293cc

EN16T crank, wedged and cross drilled

Steel main caps, inc. 4 bolt centre

Conrods TBC

Pistons TBC

 

Cam:

TBC

 

Ignition:

Aldon dizzy or mappable with crank pulley sensor

 

Fuel & Induction:

Eaton M45 super charger, blow through set up

HIF 44 carb

Podifold manifold

Intercooler

 

Potentially convert to injection at a later date

 

Exhaust:

Maniflow LCB

1.75" straight exhaust

 



#2 mini13

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Posted 20 September 2016 - 02:05 PM

All looks good to me,

 

I would go for the cast Omega's and leave the rods std, charged engines are not usually high RPM engines, and to be honest thats what stresses the rods. Plenty of turbo guys have seen 200hp plus on cast Omega's, also I'd leave the steel caps, its an expensive machining proces thats not really needed. what you save on the rods and caps, put towards a cam and getting the head done professionally.

 

dont go crazy boost wise with an eaton charger as they get inefficient, with an intercooler I'd aim for 12-14psi, with a good head and cam you should see 140-150 hp. Kent 274I should be a good cam 



#3 supermog

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Posted 20 September 2016 - 05:44 PM

Thanks for the comments, that's really useful.

 

Good to hear the cast Omega's can handle that sort of power, nearly £200 cheaper which will help.

 

The engine will only see road use, so its probably unlikely I'll be revving over 6000. If I'm seeing 140+bhp are the rods really up to it?



#4 Gr4h4m

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Posted 20 September 2016 - 07:35 PM

The rods will be fine for that power.

When looking for power the head will make the biggest difference, and a cam that works with your setup. I used turbo Phil for the head and he delivered the goods with my suck through 1060. He would also advise on the valve sizes.
The cam might be harder as less people have run the podifold setup...

#5 mini13

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Posted 20 September 2016 - 09:34 PM

Standard a+ rods are pretty bomb proof, heard of them being used at 9k once stress relived etc, and they are lower quality steel than midget rods, it's worth going for arp rod bolts though, although the std ones are fine,or at least a+ ones are... They aren't new any more and to be honest I tend not to trust repro stuff, so 80 quid on a set of ARPs is worth it for fit and forget imo

#6 supermog

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Posted 21 September 2016 - 11:33 AM

Thanks guys, that's good to hear and very useful.

 

Looks like Omega cast pistons and then lightening the standard rods as per Vizards guidance.

 

I'll look into the cam choice when all other components are finalised, asking advice from Kent etc.

 

Will be using ARP's throughout the engine. Though I'm curious if anyone has tried using other high tensile fasteners? I wonder how much of the price tag is related to the ARP brand, I know HT bolts can be bought at a fraction of the price elsewhere. Does ARP have some magic ingredient?!



#7 Gr4h4m

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Posted 21 September 2016 - 06:58 PM

Reputation, quality control and recommend torque/stretch settings with the supplied lube. Why go anywhere else?




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