I have a bare 1275 from a Morris 1100s that I plan on building.
Engine number 12ydtah13121
I need to buy some main caps for it.
Any recommendations/experience with 4 bolt caps?

https://kentautodevelopments.com/products/kad-mini-steel-main-cap-set

Would these suit my block? (listed as suiting 1300 A+ and GT blocks only)

Cheers Gordie


ps- yes I know it will need line boring

Gordie, I have have two 1100's engines with MED four bolt mains , thrust washer face width is different to cooper s , if you are using std 1100's crank you will be fine .

Mal

I am planning a buying a new a+ crank, would that work?

Hi Gordie, I confess if you were a customer of mine I would be asking you why you need the 4 bolt mains. How much hp and how hard do you intend to rev it. My max for the A plus would be 7500, and even that's a bit excessive imho.
The crank, caps and line boring will set you back nearly $2000 odd, IF you can find someone in TAS to do the machining , and it may end up with loose timing chain and rear and front oil seals that leak as the crank position in the block will most likely change ., also affecting idler gear.
this may sound harsh, but I feel its reality.
The most powerful A series I have had was 200hp supercharged, A plus crank, std centre,cap just not over revved .
Cheers Lindsay Siebler
In the end it is totally your decision .
I have also just reread your post, does it mean you have no caps ? , in which case I suggest you find another block with caps, as still the same situation as above applies.

_________________
1967 EX works rally mini restoration virtually complete OBL45F
1965 Mk1 Cooper S
1970 Colt 1100F SS
2014 Mitsubishi Imiev fully electric daily driver
1948 Allard M coupe Olds 215 v8 project
1971 Twin cam Escort ex Uk championship winning rally car project

Thanks for your input Lindsey, I understand where your coming from.
Correct I have no caps, my thinking was as I need to get caps I may aswell get 4 bolt ones.
The engine is going in a Group Nc mini. (Over reving is a possibility )

What is a better option - spending 2k on this block (virgin bore) or buying another block with caps ($?)
Either option will be getting a new crank, h beam rods and pistons etc.

Hi Gordie

Lindsay has far more experience and knowledge on this one, but i would support his assertion. I know the theory behind the 4 bolts but i have concerns that there isn't really a lot of meat in the block around the centre,so whilst theoretically pulling down across a wider plane makes sense, not if you weaken the underlying structure. I have seen lots of racers ( Group Nb and Nc) using standard caps, and they do pull high rpms, but i strongly suggest ARP bolts .... there are probably just as many out there who are converts for the 4 bolts !!!!!

For what it is worth, spend some of that saved money on a well sculpted and lightened crank ( hint chat with Lomin some more). Cheers Darryl

Hi, what a complex issue this is. You can spend $10000, to $50,000, and to some degree the more you spend the more expensive the blow up is. I also have another theory. If you learn to drive a slow car fast, you will be great in a quick one. Short stroke high revving , light cars, low diff ratios, will be hard to beat, and they are NB cars., but that also costs You cannot rev an A plus crank hard (over 7500) safely it is too heavy to spin up fast. I think an NB car would be cheaper and faster. Graham Russell in his NC is an exception, but there is an amazing amount of work and $ there.
The power is in the head and Cam. This is my suggestion. If you can find a couple of large journal 1100S cranks, you can get it converted to S dimensions and short stroke it too the max you can. Use Chinese billet H beam rods, will have to have buttons made for the pins, bore it to 73mm hypatec pistons, balance, super light weight flywheel and then you will have an engine bottom end that will rev to 8000 all day for not a lot.
Spend the money on a good torquey cam that goes to 7500, and great race head. Then choose the lowest diff ratio for the circuit.that suits. I also think another block its best by a mile. thick flange 1100S, no sleeves. Have you realised how much a roll cage is ? make the car light.
I have made a couple of assumptions, so forgive me I have got it wrong. I have assumed you are new to racing, and wish to race on a budget.
cheers Lindsay Siebler

_________________
1967 EX works rally mini restoration virtually complete OBL45F
1965 Mk1 Cooper S
1970 Colt 1100F SS
2014 Mitsubishi Imiev fully electric daily driver
1948 Allard M coupe Olds 215 v8 project
1971 Twin cam Escort ex Uk championship winning rally car project

Ok, I will rule out a a+ crank.
By Chinese rods do you mean Maxpeeding Rods? A few guys down here are using them with good resaults.

Car is caged and logbooked.