Moss Motors, Ltd

Hello,

I have a 69 AH Sprite MkIV 1275. Seems this is a very popular motor. All the photos, drawings, and part numbers pertain to this motor.

However, i can't find too many sources for higher compression, and how to do it.

I would like to run around 10.5 compression ratio. I have found stock to be 8.8 and only one other place has 9.8s.

 What about the aluminum head by Moss or some other guy has one but it is 12 lbs. How do you put in 2 more main bolts? Are these already modified to increase the compression ratio?

Where on the west coast can one send the block for boring 0.020" over and putting in new head studs (and add 2 more)?

Does anybody make a "stroker" crank for this motor?

I prefer to run this car natually aspirated, so I'm sticking with higher compression and modified head.

I also understand that this is the popular motor for Mini track racing. Can I use information from those sites for modifying this engine?

Does anyone know what is the reasonable limit of HP one can expect from this motor?

Thanks

If I am not mistaken, the 1275 is the same engine as the MIni. The difference is the crank/flywheel/clutch setup. Pistons, rods, head, etc is the same. Check in Mini oarts pages. You can even get a twincam head and street usable engines with about 100 HP.

Alfonso 

I used APT in north Riverside when I lived in LA. 800.278.3278 www.aptfast.com David Anton is a good guy and will turn you on to someone if he can't do a particular machining operation for you. Be ready to pay. Dave (or Dennis) does his own work so you will be paying an American worker to do the job. But you also know the work is done correctly and they will stand by their work.

My Longman head has the extra head stud holes. I don't use them as a more experienced guy said they make only a little difference. That's just what I heard.

I accidentally got a "stroker" crankshaft from David instead of the stock-stroke I ordered. It's an easy mistake because Dave machines cranks using the longer stroke Marina units. This mistake became troublesome as the pistons popped out of the block at TDC. I ended up cutting about 1/8" off the crowns of the Mega .040 pistons. The pistons didn't burn through or seem to have any issues with this topping.

I ran that 40 over, stroked engine (1352 cc) with 91 octane and 104+ octane booster for a few weeks. It was a beast of an engine with a compression around 250 psi and pulled strongly into the 7,000 rpm range. I also used the breaker points as a rev limiter because they float somewhere around 8,000 rpm. I found that I could stay in front of most anyone.

In the end this engine was not feasible. I couldn't get it to stop blowing head gaskets so I swapped in a standard stroke crank and bought new Mega pistons. Now I'm running 210 psi of compression. I guess this is a compression ratio around 10.5:1.

I don't know the horsepower of my engine but it is quite a bit faster as is. This engine makes a quick road machine. Looking back I would have opted for a softer cam than the Kent scatter pattern 286.

-Bill Bailey