Redtop sprint

[mbellinger]

Ian

My car used a standard Astra/Cavalier GSi 16V exhaust manifold, the bottom of which had been cut, turned 90 degrees and very neatly welded for in line installation. The car would rev happily to the limiter at 7250rpm still pulling.

The way the car drops straight back into the powerband with each upward gearchange is spot on, and is one of the joys of the conversion.

Are you sure the cause of your failure was not over-fuelling? This can wash the oil off of the cylinders, and these engines tend to fail on number 1 as it seems the weakest pot in terms of pressure from the oil pump. SBD have confirmed the latter to you, and they know these engines well. I would check your fuelling just to be sure.

Pleased that she is up and running again.

[iandollysprint]

Well done mate, sounds like its all coming together nicely. I noticed when stripping my spare Carlton engine for that pickup that theres no baffle at all in the standard sump and that the pickup is right at the front, which would indicate the possibility of oil surge on hard starts, however mine has had an oil pressure guage from day one, has done more than a few very hard starts (I dont mess about on the dragstrip when the red mist descends!) and so far not so much as a flicker so I would say you can rest easy on that score. I think the manifold is surely what is restricting performance over 5k rpm, my car, with its cast manifold and partsbin (part Skoda!) rather small bore exhaust system runs out of puff quite abruptly at 4500. Swapping out the ecu for an uprated Cav one made almost zero difference to it! I'm now on the hunt for a Sprint sports system but will probably delete the rear box in favour of a bit of drainpipe! I may have to bite the bullet and buy just the front box and cross axle pipe from the folk in Lincolnshire, Dammit! Steve

Aha! Only been to 5000rpm to protect the engine. Need to put some more miles on it before I explore beyond this. Can't believe my home brewed manifold will flow well at higher rpm, it certainly dopesn't look like it will Does fly up to 5000rpm mind.

My pick up is bang in the middle of the sump so is probably in a better position than the original!

If you hang on until next year you can have my sports sytem! I am looking to have a 2.5 inch manifold made up this year and then a 2.5 inch exhaust system to match next year when funds allow.

Ian

[iandollysprint]

Ian

My car used a standard Astra/Cavalier GSi 16V exhaust manifold, the bottom of which had been cut, turned 90 degrees and very neatly welded for in line installation. The car would rev happily to the limiter at 7250rpm still pulling.

The way the car drops straight back into the powerband with each upward gearchange is spot on, and is one of the joys of the conversion.

Are you sure the cause of your failure was not over-fuelling? This can wash the oil off of the cylinders, and these engines tend to fail on number 1 as it seems the weakest pot in terms of pressure from the oil pump. SBD have confirmed the latter to you, and they know these engines well. I would check your fuelling just to be sure.

Pleased that she is up and running again.

Hmm, interesting that it flows good at high rpm. Yours does look slightly more matched than mine though... Mine has totally unequal length primaries for cylinders 1 and 4 and is very crudely welded up.

Over fuelling - possibly but struggling to see how this would effect conrod bearings? Can you elaborate here?

Thanks

Ian

[Carledo]

If you hang on until next year you can have my sports sytem! I am looking to have a 2.5 inch manifold made up this year and then a 2.5 inch exhaust system to match next year when funds allow.

Ian

Thanks mate, I'll take you up on that, just let me know when and how much! Regards Steve

[Carledo]

Thought your 5k rev limit might be self imposed! Mine does rev happily to the limiter (about 6850) but it seems to drop off the top of the powerband very early, on the other hand the bottom end torque is massive and there almost from idle. The drop off in power is particularly noticeable on the strip in 3rd gear when the rev counter needle races to 4500 then dawdles up to 6000 and the next shift, I even tried short-shifting at 4500 but it didn't help my times. Also it won't pull at all over 4500 in 5th gear, (about 100 mph, oops!) its faster in 4th (with a bit of room to wind up). I do have a better head and cam to install over next winter and also an adjustable fuel pressure reg which may go on sooner but I reckon most of the problem is down to the engine being strangled by the exhaust. Steve

[iandollysprint]

Achillies heel the manifold I believe...

[soe8m]

Overfueling is a too rich mixture by a faulty carb or setup. The fuel condensates and goes, especially in a new engine with new rings, into the sump. The oil becomes thinner and does not lubricate well anymore in your new engine. A new engine does use some oil and when the fuel is going in the sump you will notice it immediately on your dipstick.

Jeroen

[Carledo]

I think if this IS happening, Jeroen, Ian will notice a drop in oil pressure from the thinning oil. I put a 5w/30 semi in mine by mistake and nearly sh*t myself when it got warm and lost most of its oil pressure! Having petrol in the oil would have much the same effect! Fortunately I worked out what was wrong quickly and changed it again for the correct 10/40. Steve

[Carledo]

Achillies heel the manifold I believe...

I sure would love a 4 branch, thats for certain but a bespoke one is a bit out of my rather limited price range. I think we've had this convo before and someone said try German e-bay, think I might give it a go! Steve

[soe8m]

I think if this IS happening, Jeroen, Ian will notice a drop in oil pressure from the thinning oil. I put a 5w/30 semi in mine by mistake and nearly sh*t myself when it got warm and lost most of its oil pressure! Having petrol in the oil would have much the same effect! Fortunately I worked out what was wrong quickly and changed it again for the correct 10/40. Steve

I was talking about what WAS happening. He didn't had an oilpressure gauge at that time.

Jeroen

[Carledo]

I think if this IS happening, Jeroen, Ian will notice a drop in oil pressure from the thinning oil. I put a 5w/30 semi in mine by mistake and nearly sh*t myself when it got warm and lost most of its oil pressure! Having petrol in the oil would have much the same effect! Fortunately I worked out what was wrong quickly and changed it again for the correct 10/40. Steve

I was talking about what WAS happening. He didn't had an oilpressure gauge at that time.

Jeroen

Yeah but the engine IS new (again) and AFAIK he hasn't altered the carb settings so if it happened before it will happen again, only this time he will get a warning! Steve

[iandollysprint]

Overfueling is a too rich mixture by a faulty carb or setup. The fuel condensates and goes, especially in a new engine with new rings, into the sump. The oil becomes thinner and does not lubricate well anymore in your new engine. A new engine does use some oil and when the fuel is going in the sump you will notice it immediately on your dipstick.

Jeroen

Thanks, I follow that as a possible cause.

Ian

[iandollysprint]

Overfueling is a too rich mixture by a faulty carb or setup. The fuel condensates and goes, especially in a new engine with new rings, into the sump. The oil becomes thinner and does not lubricate well anymore in your new engine. A new engine does use some oil and when the fuel is going in the sump you will notice it immediately on your dipstick.

Jeroen

Also not seeing anything on the dipstick re fuel but worth checking the set up as you suggest. Don't want it to happen again of course!

Ian

[mbellinger]

Ian,

Jeroens explanation is spot on.

Essentially, the fuel condensates and literally "washes" the oil off of the bearing. You may be overfuelling on all cylinders but because, on these engines, pot 1 gets the least oil supply pressure it is that bearing that spun. On the ohv Triumph four cylinder it is pot 4 that gives way under the same conditions, for the same reasons.

I had to scroll back in the thread, but see you are using bike carbs. You can therefore set the fuelling fairly accurately for each cylinder. The more I think about it, the more I would suspect this as the cause of your original failure.

[soe8m]

Maybe with some factor X petrol in the oil the lubrication quality decreases more than the viscosity so maybe even before an oilpressure loss is noticable the lubrication is very bad.

I have no experience with bike carbs on a car but how is the fuel supply? Is it on the original bike just a line from the tank and now you have a petrol pump? If this is the case your floatneedles are not designed for a pump pressure and the mixture is while driving way too rich by little flooding.

Jeroen