1275 A+ : MG Midget Forum : MG Experience Forums : The MG Experience

Re: 1275 A+ #21
Speedracer Hap Waldrop Greenville, SC, USA 1967 MG MGB "The Biscuit"	Posted: March 22, 2012 11:51AM Registered: 7 years ago Posts: 20,337

A good SCCA, or vintage inline race engine puts out 140-150 hp at 9000 rpms, and A+ blocks are not allowed in most US racing, so those fiqures are for normal inline 1275 . Almost all A+ blocks were made for FWD, the few they were not are pretty scarce, and none of those engine were ever imported to US by the factory, it was mostly post 1980s in Mini, they have some additional webbing on the block, larger rod journal, so differnet connecting rods, to convert a FWD A+ block to inline RWD, it can be done, but it's lot of work and you need a inline block for part, crank, main caps rods, and engine plate to make it happen, it will special machine work, drilling and tapping on the blcok to accomplish this. Is it worth it for even a highly built street or race engine, nope. As for 4 bolt center main cap, they too require a bit of prepartion,and machine work to install, and the only time I suggest them is for a full out high rpm race engine.

AS for aftermarket heads, none fo them flow as good as stock out of the box, so for performacne gains they need to be ported.

I plan on working with David "Gundy" that post here, on a 1380cc 10 psi boost A series engine over the next winter. It should make some very interesting HP. cool smiley

Hap Waldrop
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Edited 1 time(s). Last edit at 03/22/2012 11:53AM by Speedracer.

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Re: 1275 A+ #22
Egodriver71 Thomas Mann Jacksonville, FL, USA 1998 Dodge Dakota 2004 Chrysler Pacifica	Posted: March 22, 2012 11:55AM Registered: 1 year ago Posts: 216

In reply to # 2019162 by Speedracer I plan on working with David "Gundy" that post here, on a 1380cc 10 psi boost A series engine over the next winter. It should make some very interesting HP. cool smiley

Thanks for the info Hap. 9000rpm is pretty stout for a 3 bearing motor!!!

I'll be watching intently on your build. I wasn't necessarily wanting to go as far as 1380, but 10psi sounds about right were I was looking at!!!

Thomas Mann
Jacksonville, FL

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Re: 1275 A+ #23
Speedracer Hap Waldrop Greenville, SC, USA 1967 MG MGB "The Biscuit"	Posted: March 22, 2012 12:03PM Registered: 7 years ago Posts: 20,337

In reply to # 2019168 by Egodriver71

In reply to # 2019162 by Speedracer I plan on working with David "Gundy" that post here, on a 1380cc 10 psi boost A series engine over the next winter. It should make some very interesting HP. cool smiley

Thanks for the info Hap. 9000rpm is pretty stout for a 3 bearing motor!!!

I'll be watching intently on your build. I wasn't necessarily wanting to go as far as 1380, but 10psi sounds about right were I was looking at!!!

At 10 psi, we going to make custom JE 8.0 to 1 pistons and use Total Seal gapless rings.

Hap Waldrop
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Edited 1 time(s). Last edit at 03/22/2012 02:12PM by Speedracer.

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Re: 1275 A+ #24
trevorwj Trevor Jessie Louisville KY, USA	Posted: March 22, 2012 12:17PM Registered: 5 years ago Posts: 2,295

I need to check my notes, but I think I ended up at 8.4:1 and the manifold boost is 9PSI.

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Edited 1 time(s). Last edit at 03/22/2012 12:19PM by trevorwj.

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Re: 1275 A+ #25
Egodriver71 Thomas Mann Jacksonville, FL, USA 1998 Dodge Dakota 2004 Chrysler Pacifica	Posted: March 22, 2012 01:04PM Registered: 1 year ago Posts: 216

My idea was to stay around 8:1, maybe as high as 8.2:1 and boost between 10-12psi using water/meth injection.

Thomas Mann
Jacksonville, FL

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Re: 1275 A+ #26
trevorwj Trevor Jessie Louisville KY, USA	Posted: March 22, 2012 01:23PM Registered: 5 years ago Posts: 2,295

You might need an over sized crank pulley to reach that boost level.

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Re: 1275 A+ #27
trevorwj Trevor Jessie Louisville KY, USA	Posted: March 22, 2012 01:25PM Registered: 5 years ago Posts: 2,295

Going back to your original post. If you want to push the envelop, forget the SC and go for the turbo.

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Re: 1275 A+ #28
hpmowog Karl Keiger Covington, LA, USA 1959 Austin-Healey Bugeye 1960 Austin-Healey Bugeye 1962 Austin-Healey Sprite	Posted: March 22, 2012 01:52PM Registered: 4 years ago Posts: 1,994

In reply to # 2019173 by Speedracer
At 10 psi, we going to make custom JE 80.0 to 1 pistons and use Total Seal gapless rings.

Now that's compression!!! tongue sticking out smiley

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Re: 1275 A+ #29
Speedracer Hap Waldrop Greenville, SC, USA 1967 MG MGB "The Biscuit"	Posted: March 22, 2012 02:13PM Registered: 7 years ago Posts: 20,337

In reply to # 2019256 by hpmowog

In reply to # 2019173 by Speedracer
At 10 psi, we going to make custom JE 80.0 to 1 pistons and use Total Seal gapless rings.

Now that's compression!!! tongue sticking out smiley

LOL , my fat fingers strike again grinning smiley

Hap Waldrop
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Re: 1275 A+ #30
prop46 Prop Black Hole Midget Missouri, USA	Posted: March 22, 2012 02:52PM Registered: 2 years ago Posts: 2,582

What are you going to do with this engine...

Or more the point, what do you plan to do for a drivetrain, suspension, brake, and wheel/tire system as well as a safty roll cage system

A hot engine is great but you still have to stop, steer, and keep it planted to the road and do all that safely

Not to mention reliability, cause im guessing the ribby 4 speed and the rear axle will detonate like an afgan IED well before 9000 rpms

Prop

Edited 1 time(s). Last edit at 03/22/2012 02:56PM by prop46.

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Re: 1275 A+ #31
Egodriver71 Thomas Mann Jacksonville, FL, USA 1998 Dodge Dakota 2004 Chrysler Pacifica	Posted: March 22, 2012 04:50PM Registered: 1 year ago Posts: 216

I'm not expecting to pull anywhere near 9000rpm. I'm thinking stock redline, about 6000rpm.

Trans would be the 210 5spd. Rear, I haven't thought about, but I see people doing Ford 7.5 and RX7. I've also seen stout axles in Moss' catalog, but no research on those yet.

Suspension would be stock, but slightly lowered with uprated front and rear swaybars and rebuilt shock from Peter most likely.

Brakes would be at least the Spitfire rotors and B calipers, but most likely 4-pot calipers.

Don't worry, I've spent many years playing with cars and hot rodding them. The '87 Shelby Lancer I just put together is upped from 10.25" front and 11" solid rear disc brakes to 11" front and 11" vented rear disc brakes to handle the 300 whp 2.5L turbo engine going into it. The engine has a Garrett Super 60 turbocharger upped from the stock 50 trim turbo, using a 3" swingvalve into a full mandrel bent 3" MagnaFlow exhaust over OE 2.25" swing valve and 2" exhaust.

I've though it all through, except the rear axle, I'm just wanting to see if the A+ block was really worth exploring!!!

Thomas Mann
Jacksonville, FL

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Re: 1275 A+ #32
metalhead Andrew F NSW, Australia 1970 MG Midget MkIII 1977 Mazda 3 1979 Ford F-250	Posted: March 23, 2012 12:47AM Registered: 2 years ago Posts: 414

I built my engine with a guy over here who specialises in A Series engines and has built a large number of them for boost, both turbo and supercharger. My engine was built entirely to his recommendations for the 15psi (with water injection) of boost I plan to run. Quality (but not forged) pistons, 9.2:1 compression ratio (he routinely runs very high 9s on <10psi applications), very well balanced, and ARP studs throughout are the main strength features. I am still running standard rods and crank (though cleaned up and balanced of course) and 2 bolt centre main. His opinion was that a 4 bolt centre main is a waste of money, though he was more than willing to do it if I wanted ("it's your money" were his words)! The engine hasn't seen boost in the car yet, as I misjudged the pulley sizes (I'm using a home built setup with Toyota SC14 blower) and it made 25psi of boost by 2000rpm when placed on the engine dyno. So while sorting out and finishing off the rest of the car I have just been running a 45DCOE. The engine also has a heavily ported head, is bored 60thou to 1330cc, roller rockers, race extractors, and a long duration short overlap (specifically intended for supercharging) cam. With just the Weber and not the blower it made 121bhp at 7000rpm (which was as high as it was run) on the engine dyno, though we all know dyno readouts don't mean a lot. This same engine builder has built several supercharged engines running ~9-10psi of boost using the Moss kit, built to the same specs as my engine but with a little more compression and with lesser extractors (my extractors have a long straight shot out of the head that doesn't fit under standard SU manifolds or the Moss kit) that have made between 150 and 160bhp depending on which dyno they are on.

If you're interested in the limits of what can be done with the A Series, Mini forums are often where it's at, particularly for forced induction. There are a number of turbo cars here and in the UK running up around the 200bhp mark...

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Re: 1275 A+ #33
Speedracer Hap Waldrop Greenville, SC, USA 1967 MG MGB "The Biscuit"	Posted: March 23, 2012 11:56AM Registered: 7 years ago Posts: 20,337

In reply to # 2019318 by prop46 What are you going to do with this engine...

Or more the point, what do you plan to do for a drivetrain, suspension, brake, and wheel/tire system as well as a safty roll cage system

A hot engine is great but you still have to stop, steer, and keep it planted to the road and do all that safely

Not to mention reliability, cause im guessing the ribby 4 speed and the rear axle will detonate like an afgan IED well before 9000 rpms

Prop

Prop, the 9000 rpm claim was mine and about race engines, the point I was trying to make if it we can race prep a normal inline 175 block to these levels, anything one can do with one on the street, short of 15 pis of boost it can handle.

Just for grins, at the 2001 SCCA runoffs my super duper trick dog gear racing gearbox decided to stick into 3rd gear on the first lap, at first I thought I would just retire the car, but I thought to myself, what the hell, I just drove the entire race in 3rd gear, I started catching and passing cars after dropping to the rear fo the field, I ended up 14th in 30 car field, and was going down the back straight at mid Ohio in 3rd gear at 9300 rpms, and did this every lap for 18 laps in a row, the engine was no worse for wear when it was all over, these engines are tough as hell when put together right.

Hap Waldrop
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