mk1-forum.net

Hi all,

I have obtained a low mileage original 1300GT engine and wish to re build this into a nice period piece for my Mk1. I intend to do some 12 car road rallying as well as general B road blatting. I have not stripped it yet but anticipate having to go to 1293 and first undersize on the crank

This will be mated to a s/c pot joint box (courtesy of Guru which runs ST ratios and a 3.44 diff. I have a pair of 1.5" SU's all rebuilt which I would like to use unless folk think that might be overkill. The other option is the 1.75" HIF which is currently on the standard 1275 engine in the car now (the existing lump is a std 1991 Cooper lump)

I do not want to go silly on this engine and would like to keep it fairly mild, the aim being good torque and around 85bhp. I was thinking of keeping the head standard and was looking towards the cam for most of the power gain. I would like it to be fully balanced and perhaps a lightened flywheel. I would re use the existing LCB and RC40 twin box system

The questions for the forum I guess are what would be a good package of mods to achieve this? The most obvious question is the cam choice - I do like a slightly cammy engine and would like a 'period feel' from the car if that makes sense.

Thanks folks.

Jono wrote:Hi all,

I have obtained a low mileage original 1300GT engine and wish to re build this into a nice period piece for my Mk1. I intend to do some 12 car road rallying as well as general B road blatting. I have not stripped it yet but anticipate having to go to 1293 and first undersize on the crank

This will be mated to a s/c pot joint box (courtesy of Guru which runs ST ratios and a 3.44 diff. I have a pair of 1.5" SU's all rebuilt which I would like to use unless folk think that might be overkill. The other option is the 1.75" HIF which is currently on the standard 1275 engine in the car now (the existing lump is a std 1991 Cooper lump)

I do not want to go silly on this engine and would like to keep it fairly mild, the aim being good torque and around 85bhp. I was thinking of keeping the head standard and was looking towards the cam for most of the power gain. I would like it to be fully balanced and perhaps a lightened flywheel. I would re use the existing LCB and RC40 twin box system

The questions for the forum I guess are what would be a good package of mods to achieve this? The most obvious question is the cam choice - I do like a slightly cammy engine and would like a 'period feel' from the car if that makes sense.

Thanks folks.

..I pers like the H4,s..i got the cylinder head highly modified by a specialist Pat Howe and would deffo do the same again on another car..a qual cam,crank etc etc all lightened balanced run in and rolling roaded is always the way to go !!...re using the existing exhaust is fine but I don't think u can beat a new maniflow ?!..as and when I get another exhaust it will be the same again.. the quality is just a tad better I reckon.. foxy52

I have a 1293 which was built for - well doing the monte so we had to build a drivable and torquey motor

twin 1.5 hs4
modified mk 3 S head 10/1 cr
1.5 keith dodd rockers
1293

have the old cooper 997 cam in it
helical box
sc drops

and a 3.1 diff

very nice and capable engine

pad

I guess we are talking flywheel HPs?

Well, considering the engine needs a wide RPM range (ie it's not out & out race circuit use) I'd suggest a slightly modified head, not too big in the ports, but maybe big valves (not biggest though!), cam duration of around 275 - 280 degrees, but if you go for the longer duration cam, advance it's timing a few degrees from that recommended, only about 4 degrees. Push the static CR up to around 10.5 to 11:1 (Ideally, you'd work to a Dynamic CR of around 8.8:1 - out with the graph paper for that one!).

Now Carburation. The twin HS4's will do the job for sure, but for a more flexible engine, I'd suggest either twin HS2's or the single HIF44. These will give considerably better low RPM Torque and (though probably a very secondary consideration) better mileage too.

Look to the SU HP Chart for some guidance;-



Also consider that 90% of the time, you won't be using all ~85 HP's, so even a little sacrifice at this end will give much bigger gains at the lower end. Remember too that all engine combinations are a compromise so the ~85 HPs at the high RPMs will come at an expense somewhere else in the rev range.

Recently, I did swap out a set of twin HS4s for a chap, to a single HIF44, his car was putting out 83 HP's at the wheels, in the Dyno session with the Twins and the same with the HIF, but it was way more drivable on the HIF (also allowed it to come on the cam ~400 RPM sooner) and drinks less fuel now, so happy days for him. The Dyno Graph also showed improvement at the lower RPMs with no cost anywhere, so clearly even with around 100 HPs at the flywheel, the Twin HS4's were over-carburated.

foxy52 wrote:

Jono wrote:Hi all,

I have obtained a low mileage original 1300GT engine and wish to re build this into a nice period piece for my Mk1. I intend to do some 12 car road rallying as well as general B road blatting. I have not stripped it yet but anticipate having to go to 1293 and first undersize on the crank

This will be mated to a s/c pot joint box (courtesy of Guru which runs ST ratios and a 3.44 diff. I have a pair of 1.5" SU's all rebuilt which I would like to use unless folk think that might be overkill. The other option is the 1.75" HIF which is currently on the standard 1275 engine in the car now (the existing lump is a std 1991 Cooper lump)

I do not want to go silly on this engine and would like to keep it fairly mild, the aim being good torque and around 85bhp. I was thinking of keeping the head standard and was looking towards the cam for most of the power gain. I would like it to be fully balanced and perhaps a lightened flywheel. I would re use the existing LCB and RC40 twin box system

The questions for the forum I guess are what would be a good package of mods to achieve this? The most obvious question is the cam choice - I do like a slightly cammy engine and would like a 'period feel' from the car if that makes sense.

Thanks folks.

..I pers like the H4,s..i got the cylinder head highly modified by a specialist Pat Howe i and would deffo do the same again on another car..a qual cam,crank etc etc all lightened balanced run in and rolling roaded is always the way to go !!...re using the existing exhaust is fine but I don't think u can beat a new maniflow ?!..as and when I get another exhaust it will be the same again.. the quality is just a tad better I reckon.. foxy52

also.. top quality 1 and a half hi-lift roller rockers were a good buy at the time of rebuild as well......foxy52

go for a decent modified head, and one SW5 cam if you like a smooth engine, sw10 or re13ot if you want one engine with more caracter

i have done the following spec for one happy custumer

1293 10.5cr
sw5 cam
nice head with 35.7/29 valve, open chamber and ported
fully balanced
3.44 box with cr gear
X pin diff
rc40/lcb
HIF44 carb

nice engine to drive with good torque at all the rev range

I love the excitement and rush that a cammy engine provides. You have a decent gearbox to make the best out of it. I had a 1340 with a 286 and it was fun. I also had a 1275 with a 649 and that was even more fun.

If you want something smooth, powerful, quiet and well mannered, get a Corsa Ecoflex.

In the shed wrote:I love the excitement and rush that a cammy engine provides. You have a decent gearbox to make the best out of it. I had a 1340 with a 286 and it was fun. I also had a 1275 with a 649 and that was even more fun.

If you want something smooth, powerful, quiet and well mannered, get a Corsa Ecoflex.

Custom pistons??

All very good suggestions.

I would recommend a 'race' light-weight steel flywheel.
-With the other changes, and the careful assembly and balancing, it'd make it nice and lively.

andy1071 wrote:All very good suggestions.

I would recommend a 'race' light-weight steel flywheel.
-With the other changes, and the careful assembly and balancing, it'd make it nice and lively.

Yep ,.. good point I have one of those to an steel backplate..!!!...as one other said the headwork is key as the basis of a nice engine...everthing else follows if yr budget allows,ie a nice cam,crank,carbies..all lightened and balanced, run in properly and rolling roaded.....happy mini-ing !!! I,ve been out in mine today !!! Overstrand to Holt and back in the beautifull Norfolk countryside !!!!...foxy52

Thanks for all your thoughts and suggestions chap - some food for thought there!

Rgds

Jon

Chaps...just a final thought

The 1300GT rods looks a bit heavy! Are A+ rods a direct substitute and would this be a worthwhile upgrade?

Cheers

Jon

PS: what would the best/most appropriate pistons to use be?

Jono wrote:Chaps...just a final thought

The 1300GT rods looks a bit heavy! Are A+ rods a direct substitute and would this be a worthwhile upgrade?

Cheers

Jon

PS: what would the best/most appropriate pistons to use be?

a far better rod to use and a straight swop

for a fast road engine the p21253 are very good

..thanks for that.

...does anyone have a set of A+ rods for sale?

Jon