Building up an Engine
Discussion
Always wanted a decent engine for my mini something like a 1340/1380 ideally above 90bhp at the fly
Had the idea of building one up myself to save money as I can do a bit more as money comes in and as a sort of project to keep me interested.
Just wondered what do i need to get started just a knackered 1275?
Also what books are usefull for help as I only have extremley basic car knowledge only engine rebuilds I have done are on 2t scooters which are a lot more simple.
If anyone does have a spare 1275 or something for cheap please let me know
Had the idea of building one up myself to save money as I can do a bit more as money comes in and as a sort of project to keep me interested.
Just wondered what do i need to get started just a knackered 1275?
Also what books are usefull for help as I only have extremley basic car knowledge only engine rebuilds I have done are on 2t scooters which are a lot more simple.
If anyone does have a spare 1275 or something for cheap please let me know
Rebuild a bottom end - for 85-90hps it is not that important to what bore. Next oversize is enough. Or if You can get a healthy engine, its the best. But bottom end needs to be ok.
Examine the camshaft. If not worn, use it. Save Your funds for a good "stage one kit" and a decent cylinder head. If You aim for 90 hps, I would say go for medium-modified head with 35.6mms inlet and 31mms exhaust valves (done by a recognised specialist). Raise the CR to 10.5:1. Have it set up on the dyno, and woila!
Examine the camshaft. If not worn, use it. Save Your funds for a good "stage one kit" and a decent cylinder head. If You aim for 90 hps, I would say go for medium-modified head with 35.6mms inlet and 31mms exhaust valves (done by a recognised specialist). Raise the CR to 10.5:1. Have it set up on the dyno, and woila!
camelotr said:
Rebuild a bottom end - for 85-90hps it is not that important to what bore. Next oversize is enough. Or if You can get a healthy engine, its the best. But bottom end needs to be ok.
Examine the camshaft. If not worn, use it. Save Your funds for a good "stage one kit" and a decent cylinder head. If You aim for 90 hps, I would say go for medium-modified head with 35.6mms inlet and 31mms exhaust valves (done by a recognised specialist). Raise the CR to 10.5:1. Have it set up on the dyno, and woila!
That would be unliklely to give a genuine 90 bhp at the flywheel. The standard cam really is not good enough even with a reasonable head. Examine the camshaft. If not worn, use it. Save Your funds for a good "stage one kit" and a decent cylinder head. If You aim for 90 hps, I would say go for medium-modified head with 35.6mms inlet and 31mms exhaust valves (done by a recognised specialist). Raise the CR to 10.5:1. Have it set up on the dyno, and woila!
Of course, 'Stage 1' really means not a lot as different people understand different things and it's really only a sales expression used by the vendors.
To get a true 90 bhp you need:
A well gas-flowed head with the bigger valves, a decent cam such as a 276 timed-in accurately with offset keys or a vernier sprocket, an improved inlet manifold with an HIF44 (or HS6) carb, an LCB or 3-into-1 exhaust manifold, a 1.75" Int. dia exhaust system with good exhaust boxes, 10.5:1 CR, a better distributor and a good engine build quality.
With just the head and exhaust system and a standard cam it would be hard to get over about 75 bhp. With an MG Metro cam you could get up to around 85 bhp, maybe slightly more with a better distributor.
Cooperman said:
camelotr said:
Rebuild a bottom end - for 85-90hps it is not that important to what bore. Next oversize is enough. Or if You can get a healthy engine, its the best. But bottom end needs to be ok.
Examine the camshaft. If not worn, use it. Save Your funds for a good "stage one kit" and a decent cylinder head. If You aim for 90 hps, I would say go for medium-modified head with 35.6mms inlet and 31mms exhaust valves (done by a recognised specialist). Raise the CR to 10.5:1. Have it set up on the dyno, and woila!
That would be unliklely to give a genuine 90 bhp at the flywheel. The standard cam really is not good enough even with a reasonable head. Examine the camshaft. If not worn, use it. Save Your funds for a good "stage one kit" and a decent cylinder head. If You aim for 90 hps, I would say go for medium-modified head with 35.6mms inlet and 31mms exhaust valves (done by a recognised specialist). Raise the CR to 10.5:1. Have it set up on the dyno, and woila!
Of course, 'Stage 1' really means not a lot as different people understand different things and it's really only a sales expression used by the vendors.
To get a true 90 bhp you need:
A well gas-flowed head with the bigger valves, a decent cam such as a 276 timed-in accurately with offset keys or a vernier sprocket, an improved inlet manifold with an HIF44 (or HS6) carb, an LCB or 3-into-1 exhaust manifold, a 1.75" Int. dia exhaust system with good exhaust boxes, 10.5:1 CR, a better distributor and a good engine build quality.
With just the head and exhaust system and a standard cam it would be hard to get over about 75 bhp. With an MG Metro cam you could get up to around 85 bhp, maybe slightly more with a better distributor.
These seems like a decent spec to me and fairly affordable...
Any good books to buy to read to give me and idea about how to build such an engine up?
A couple of months ago I have tuned my friends bog standard 1275 mayfair. We did a dyno run before the modification. If was 62 at the flywheel.
I have intalled MG Metro inlet valves, carved the head a bit, put on a "stage one" kit (I mean an LCB, a 1.75 RC40, KN cone with a stubstack), raised the CR to 10.5:1. And nothing more. The second dyno was 81.6hps at the flywheel. We have put a 1.5 roller rocker set on it, but did not resulted in any gain.
The engine did 100k kms before, soo it was not in pristine condition. I have only used normal exhaust valves (29.3mms)plus I am not an expert of cylinder head modification. I assume a well ported head with 31mm exhaust valves should be in the 85-90 flywheel range. Even with the normal "Metro"-type camshaft. Though if one can afford, a good cam can even give some more on top. I would go for Minispares EVO or Swiftune SW5. But the Kent is also a good choice.
Although the key is the head, not the cam.
I have intalled MG Metro inlet valves, carved the head a bit, put on a "stage one" kit (I mean an LCB, a 1.75 RC40, KN cone with a stubstack), raised the CR to 10.5:1. And nothing more. The second dyno was 81.6hps at the flywheel. We have put a 1.5 roller rocker set on it, but did not resulted in any gain.
The engine did 100k kms before, soo it was not in pristine condition. I have only used normal exhaust valves (29.3mms)plus I am not an expert of cylinder head modification. I assume a well ported head with 31mm exhaust valves should be in the 85-90 flywheel range. Even with the normal "Metro"-type camshaft. Though if one can afford, a good cam can even give some more on top. I would go for Minispares EVO or Swiftune SW5. But the Kent is also a good choice.
Although the key is the head, not the cam.
camelotr said:
A couple of months ago I have tuned my friends bog standard 1275 mayfair. We did a dyno run before the modification. If was 62 at the flywheel.
I have intalled MG Metro inlet valves, carved the head a bit, put on a "stage one" kit (I mean an LCB, a 1.75 RC40, KN cone with a stubstack), raised the CR to 10.5:1. And nothing more. The second dyno was 81.6hps at the flywheel. We have put a 1.5 roller rocker set on it, but did not resulted in any gain.
The engine did 100k kms before, soo it was not in pristine condition. I have only used normal exhaust valves (29.3mms)plus I am not an expert of cylinder head modification. I assume a well ported head with 31mm exhaust valves should be in the 85-90 flywheel range. Even with the normal "Metro"-type camshaft. Though if one can afford, a good cam can even give some more on top. I would go for Minispares EVO or Swiftune SW5. But the Kent is also a good choice.
Although the key is the head, not the cam.
A standard Mayfair should not have 62 bhp at the flywheel, it is more like a true 55 bhp. So if the initial reading was 62, that's about 7 bhp too high, which would give a corrected final figure of around 75 bhp, whih is what would be expected from the spec you quote.I have intalled MG Metro inlet valves, carved the head a bit, put on a "stage one" kit (I mean an LCB, a 1.75 RC40, KN cone with a stubstack), raised the CR to 10.5:1. And nothing more. The second dyno was 81.6hps at the flywheel. We have put a 1.5 roller rocker set on it, but did not resulted in any gain.
The engine did 100k kms before, soo it was not in pristine condition. I have only used normal exhaust valves (29.3mms)plus I am not an expert of cylinder head modification. I assume a well ported head with 31mm exhaust valves should be in the 85-90 flywheel range. Even with the normal "Metro"-type camshaft. Though if one can afford, a good cam can even give some more on top. I would go for Minispares EVO or Swiftune SW5. But the Kent is also a good choice.
Although the key is the head, not the cam.
A Mayfair on a standard cam with only head and some exhaust mods is rather unlikely to give over 80, especially with a standard distributor. I built a 'fully-blueprinted' 1330 A+ engine with new MG Metro cam timed a 2 deg advaned from recommended, Aldon dizzy, 10.4 CR, 'worked' head with 35.6 mm inlets and 30.5 mm exhausts, RC40 system at 1.75" ID, HIF44 on gas-flowed inlet manifold, plus some other little tweeks and that only gave 84 bhp at 5700 rpm.
I have checked my photos, and just found that it was a carb cooper ('90) not a mayfair. But the dyno data is correct. This dyno I use usualy gives less than factory data not more (not many people like to go there for this reason).
And again, I am petty sure that a decent gas-flowed head would give much better result.
Soo if professionaly modded head or good cam is the question, I would go for a good head. Especialy if You add that a good cam mainly offers its extra power above 5000, which on the road is not often used.
And again, I am petty sure that a decent gas-flowed head would give much better result.
Soo if professionaly modded head or good cam is the question, I would go for a good head. Especialy if You add that a good cam mainly offers its extra power above 5000, which on the road is not often used.
camelotr said:
I have checked my photos, and just found that it was a carb cooper ('90) not a mayfair. But the dyno data is correct. This dyno I use usualy gives less than factory data not more (not many people like to go there for this reason).
And again, I am petty sure that a decent gas-flowed head would give much better result.
Soo if professionaly modded head or good cam is the question, I would go for a good head. Especialy if You add that a good cam mainly offers its extra power above 5000, which on the road is not often used.
Those 1990-1 Coopers were strange as no-one seems to know what cam they had as standard. I was told by a guy who worked at Rover that they had whatever was on-the-shelf due to the cam manufacturers often not delivering due to their bills not having been paid. I can believe that as when I dealt with Rover back in the late 80's it took them 180 days minimum to pay after receipt of invoice. That would explain why some cars are better than others. It believe the cam should have been the MG Metro, but with 33.5 mm inlets and a bit less CR than the Metro.And again, I am petty sure that a decent gas-flowed head would give much better result.
Soo if professionaly modded head or good cam is the question, I would go for a good head. Especialy if You add that a good cam mainly offers its extra power above 5000, which on the road is not often used.
With a better flowing head, and the standard ones were dreadful, plus the MG cam a good improvement would be seen. Interestingly I have a Haynes manual which lists a 1990 Cooper as having 35.6 mm inlet valves, so when I built one which had to comply with regs for competition I used the bigger valves with the Haynes as confirmation of the legality of my engine.
There are no logical explanations for the workings of Rover's engineering Design Dep't. One might suspect that that dep't had 2 brain cells but only one worked at any one time.
My son, who works in F1 design, can never believe the poor engineering standards when compared to other mainstream manufacturers. No wonder they went 'belly-up' in the end. The basic problems with Rover went right back to the 60's and you only have to look at the vast engine and model range compared to Ford and Vauxhall to see why they failed in the end.
My son, who works in F1 design, can never believe the poor engineering standards when compared to other mainstream manufacturers. No wonder they went 'belly-up' in the end. The basic problems with Rover went right back to the 60's and you only have to look at the vast engine and model range compared to Ford and Vauxhall to see why they failed in the end.
1275 is better then 1340+, cause it is more reliable.. due to the amount of boring needed to do, the distance between the pistons is too small, which is v.bad if the car overheats... apparently
i prefer a small bores, but i kno how to get a 998 to 70+ bhp..
do this:
(1) 286 Cam (276-310 depending how choppy you mind the idle to be..)
(2) 180-280 lb valve springs, they raise your maximum RPM to 8,000-12,000 rpm (respectively, however staying over 8,000 rpm will eventually lead to burning out the piston rings) remember if the strength is too big, then you lose power.. (lose power, gain rpm and vise versa)
(3) Polish&port your head - DIY, get a dremyl, and polish the metal, and smooth out the heart-shape combustion area (dont remove the point between the valves).
(4) Hif 38 or 44 ( they are better then HS carbs since they are more efficient ).
(5) Stage 1 - Inlet and outlet manifold (straight through exhausts are better, btw, if the exhaust is too big you lose tonnes of torque, 1.5" is the best afaik) + K&N
(6) 1.5:1 rockers
(7) Lighten fly wheel, the problem with this is, that it makes the idle lumpier ( i personally dont like them)
(8) skim head, if you do this, then you need higher octane fuel (over 9.5:1 you need octane 98)
(9) Oil cooler (keeps your engine at the right temperature)
(10) high pressure fuel pump can help..
(11) racing/high rev carb needle
(12) right AFR - just a case of setting your carb up properly)
p.s I used a haynes manual to learn about rebuilding a engine..
hope this helps..
i prefer a small bores, but i kno how to get a 998 to 70+ bhp..
do this:
(1) 286 Cam (276-310 depending how choppy you mind the idle to be..)
(2) 180-280 lb valve springs, they raise your maximum RPM to 8,000-12,000 rpm (respectively, however staying over 8,000 rpm will eventually lead to burning out the piston rings) remember if the strength is too big, then you lose power.. (lose power, gain rpm and vise versa)
(3) Polish&port your head - DIY, get a dremyl, and polish the metal, and smooth out the heart-shape combustion area (dont remove the point between the valves).
(4) Hif 38 or 44 ( they are better then HS carbs since they are more efficient ).
(5) Stage 1 - Inlet and outlet manifold (straight through exhausts are better, btw, if the exhaust is too big you lose tonnes of torque, 1.5" is the best afaik) + K&N
(6) 1.5:1 rockers
(7) Lighten fly wheel, the problem with this is, that it makes the idle lumpier ( i personally dont like them)
(8) skim head, if you do this, then you need higher octane fuel (over 9.5:1 you need octane 98)
(9) Oil cooler (keeps your engine at the right temperature)
(10) high pressure fuel pump can help..
(11) racing/high rev carb needle
(12) right AFR - just a case of setting your carb up properly)
p.s I used a haynes manual to learn about rebuilding a engine..
hope this helps..
Cooperman said:
To get a true 90 bhp you need:
A well gas-flowed head with the bigger valves, a decent cam such as a 276 timed-in accurately with offset keys or a vernier sprocket, an improved inlet manifold with an HIF44 (or HS6) carb, an LCB or 3-into-1 exhaust manifold, a 1.75" Int. dia exhaust system with good exhaust boxes, 10.5:1 CR, a better distributor and a good engine build quality.
With just the head and exhaust system and a standard cam it would be hard to get over about 75 bhp. With an MG Metro cam you could get up to around 85 bhp, maybe slightly more with a better distributor.
I'd agree with this. I did one with an LCB.A well gas-flowed head with the bigger valves, a decent cam such as a 276 timed-in accurately with offset keys or a vernier sprocket, an improved inlet manifold with an HIF44 (or HS6) carb, an LCB or 3-into-1 exhaust manifold, a 1.75" Int. dia exhaust system with good exhaust boxes, 10.5:1 CR, a better distributor and a good engine build quality.
With just the head and exhaust system and a standard cam it would be hard to get over about 75 bhp. With an MG Metro cam you could get up to around 85 bhp, maybe slightly more with a better distributor.
Gassing Station | Classic Minis | Top of Page | What's New | My Stuff