About rebulids...

[jkyle69]

If anyone is really concerned about engine rebuilds, why not take the car to a specialist motorsport engineer, get them to drop the compression ratio down (10:1 perhaps), get some custom parts (i.e. follows) made out of higher grade material etc. This will drop the power a bit but should reduce stress on the engine and will make it an easier car to drive at lower speeds I should imagine. Has anyone tried this as I was speaking to some engineers about these problems and that is what they recommended what does anyone think.....?

[nelly1]

jkyle69 said:

... This will drop the power a bit

I suppose an engineer would say that!
The BIG Motor Co. I work for is full of 'ologies, and we stopped building 'fun' cars about 10 years ago

By the way, what's a rebulid?

>> Edited by nelly1 on Saturday 21st May 08:29

[yzf1070]

This is my perspective on the subject having read the numerous threads on the S6 engine.

The failures I believe have nothing to do with compression ratio's or horse power levels. The failures, I understand, are to do with material quality and perhaps design imperfections. From what I have read, it seems the cam lobes, finger followers and valve guides wear out prematurely.

I have a late Mk1 S and have not (yet....!?!) experienced such a failure, but if I do I will likely take the car to one of the few specialists for repair and glean as much info as I can regarding the failure/s, before I make a desicion to keep it or sell it on after the repair.

Until if and when that time comes I shall enjoy the car for what it is......awesome fun.

[Mr Freefall]

yzf1070 said:

This is my perspective on the subject having read the numerous threads on the S6 engine. The failures I believe have nothing to do with compression ratio's or horse power levels. The failures, I understand, are to do with material quality and perhaps design imperfections. From what I have read, it seems the cam lobes, finger followers and valve guides wear out prematurely. I have a late Mk1 S and have not (yet....!?!) experienced such a failure, but if I do I will likely take the car to one of the few specialists for repair and glean as much info as I can regarding the failure/s, before I make a desicion to keep it or sell it on after the repair. Until if and when that time comes I shall enjoy the car for what it is......awesome fun.

So how do you drop the compression then????

This is an ally engine, most engineers will skim the head to make sure it is flat before the put it back on. The heads tend to warp alittle once the stress is taken off them ie removal, = raised compression...

Only way to do it (lowe compression) is increase the engine capacity, by removing some material from the pistons (put a concave in the middle), or take some material out of the dome in the head).= weaker engine.

Only real way is lower compression pistons made for the job, but then you have a complete rebuild, not just top end, polish crank, +10thou bearings, hone block etc etc etc...

My theory. Put a 7k rev limter on them, I'm sure its in the MBE system somewhere, and Im sure my MK Tuscan only rev'd to 7ish, not 8k plus like the 3.6. sort the cams out, Kent cams should be able to make a profile for you, sort the bloody fingers out, there was a thread somewhere with a solution, to this, just needed someone to make them in bulk. Make sure the valves line up from the stems right, double srung value springs, reseat valves, bolt back together. Oh and for good measure, balance the whole engine.

But, Im not a mechanic, so I might be talking out my arse.

Mr F

[jkyle69]

Just my fiancé had been talking about supercharging the Tuscan engine but using a forged crank, different pistons and con rods, but was recommended to drop the compression ratio to 10:1 down from 11:1 to try and reduce the amount of stress generally on the engine. She would still be able to get up to 800bhp with a chargecooler supercharger but didn't want the whole thing explode into small bits. Should do excess of 210mph but not really sure that the aerodynamics of capable of keeping the car on the ground. I have a couple of engineers in Sweden who I am thinking about looking of changing the front end of the car to improve the aerodynamics first as I am not sure if there is any point doing this if the thing is not going to stay on the ground....

[venom500]

800bhp!...should get even higher mileage from your speed six engine then!....err..not!
I think your talking out of your bottom mate!
Yawn......
Yawn.......
Yawn........

[jkyle69]

So just out of interest why would it be not possible to get that much power out of the engine with better components? I think after 1200 miles between 2 rebuilds I think you might as well give good reason to have a rebuild and would therefore have no complaints - also it is cheaper to buy an entire engine and cylinderhead than have a rebuild (£4500 for an engine with 15000 miles). So might as well have 2 engines - one for track days and one for driving around normally.
Higher power out of the SP6 seems to be pretty straight forward, charge cooled supercharger, forged crank (not the crappy cast one that is currently in the car, uprated lightened con rods and pistons, a thinker copper head gasket, uprated oil pump & cooling, uprated fuel pump, tremec TKO600 transmission (good for 600lb/ft torque) and custom adapter plate, racing clutch, lightened flywheel along with a load of other bits and pieces.

[powerlord]

Mr Freefall said:

My theory. Put a 7k rev limter on them, I'm sure its in the MBE system somewhere, and Im sure my MK Tuscan only rev'd to 7ish, not 8k plus like the 3.6. sort the cams out, Kent cams should be able to make a profile for you, sort the bloody fingers out, there was a thread somewhere with a solution, to this, just needed someone to make them in bulk. Make sure the valves line up from the stems right, double srung value springs, reseat valves, bolt back together. Oh and for good measure, balance the whole engine. But, Im not a mechanic, so I might be talking out my arse. Mr F

yeh, rev limiter kicks in at 7200ish (found out when I mistakenly set the rev lights too high and was waiting for the red light to come on and got the rev limiter...oops.

stu

[R666 TUS]

Had mine on a rolling road on Saturday
and the rev limiter cut in at 7526.

Col

[powerlord]

I stand corrected. Didn't think it was as high as that as my lights were set to 7000/7500/8000 and only the first one came on.

more to the point... what were the results of the rolling road ? got a graph you can post ?



stu

[R666 TUS]

I do have a graph and will post it Tomorrow
if I get my scanner to work. Best run of three
was 360.7bhp at 6854 rpm and highest torque
was 310.3 lbft at 5262rpm.
It was a good day out with the west lancs TVR lads
at Tunit in Chorley, they have a very nice 1000bhp
rolling road. We had a lot of different TVR's on it
including a 4.7L Cerb ! I videoed all the runs but
they are a bit large to post.

Regards, Col

[HarryW]

R666 TUS said:

I do have a graph and will post it Tomorrow if I get my scanner to work. Best run of three was 360.7bhp at 6854 rpm and highest torque was 310.3 lbft at 5262rpm. It was a good day out with the west lancs TVR lads at Tunit in Chorley, they have a very nice 1000bhp rolling road. We had a lot of different TVR's on it including a 4.7L Cerb ! I videoed all the runs but they are a bit large to post. Regards, Col

Out of interest what did the cerb make .

You could alwasy edit the videos downa bit and save them as a lower res wmv and out them up on PHTV too .

H

[powerlord]

R666 TUS said:

I do have a graph and will post it Tomorrow if I get my scanner to work. Best run of three was 360.7bhp at 6854 rpm and highest torque was 310.3 lbft at 5262rpm. It was a good day out with the west lancs TVR lads at Tunit in Chorley, they have a very nice 1000bhp rolling road. We had a lot of different TVR's on it including a 4.7L Cerb ! I videoed all the runs but they are a bit large to post. Regards, Col

thats not bad then. that a standard tusc ? how did it sound ? I have a rolling road near me, but I'm petrified of putting the tuscan on it... you hear folks cars on it and they sound like they are gonna explode.

plus... I'd be disappointed if it came out lower than it should be :-(

stu

[R666 TUS]

The Cerb managed 350bhp but was not running
as sweet as it should have been so the chap
is going to sort it and have another go.
Powerlord it was quite scary and the noise
at 191mph(no wind to slow you down)was amazing.
I would have a go if I where you.Mine is a standard
4.0 having done about 2700miles since rebuild.
It was good to see nothing nasty coming out the
cans at high revs, by nasty I mean smoke, oil,valves
etc

Col

[R666 TUS]

He is a pic of the graph from the dyno session

Col

http://img24.echo.cx/my.php?image=rollingroadgraph3po.png

[Leadfoot]

Odd graph, the power & torque line cross at the wrong point.