Setting new redline

[evm1024]

What sets the redline.... The obvious answer is where power is no longer useful. 5th gear, open road, WOT go as far as it will go. We can ignore that.

Let's take an example: 2 liter engine, stock crank (ground 1st oversize), Ritmo 105 pistons, lightened flywheel balanced with crank, dowel pins installed, "high rev" valve springs. Pistons and rods matched in weight to each other.

What is the limiting factor here? I'm assuming that the FI cars with a 5500 rpm yellow line and 6000 rpm redline would comfortably do the carb limits 6500 redline.

So what is a realistic redline for the example engine? 7500? 8000? Less? (Which of couurse brings us bact to where is the power...)

--Ethan

[engineerted]

Ethan,

The true red line is the point at witch the engine blows apart, in your example of the 2L engine, the pistons strength and the cast flywheel needd to be considered. I believe GC recomends not to spin it over 7200 rpm, other wise bad things will happen. Now if you want to build a motor that is capable of running to 8K+ , you are going to need forged pistions, new rods, steel flywheel, bigger cam, bigger carbs and oh lots of $$$. If you want to make your 2l rev higher and make more power in the upper revs it needs to breath better, bigger valves, bigger cams , higher compression, and bigger carbs. but like i stated there are limits to the strengths of the stock parts. This is why some of use here like the 1800 motor, shorter stroke, revs higher, but at the cost of low end torque.


Ted

[mbouse]

better breathing is the easiest key to achieve, whether it is fuel injected, or carbureted, 1800 cc or two litres.

you can take no more in that you'll be letting out, and visa versa.

[danaspider]

It is all about mass, momentum and air(gas). Higher redline is lighter and stronger components. Remember you are stopping the piston and going the other direction, same with valves. So redline is based on the point where they keep going in one direction, when you are expecting them to go in the other direction. Hence redline = stop.

Mike is right but his last statement sounds more like an older guys digestive system.

[evm1024]

Ah, thats right CG states that cast flywheel upper limit 7200 (page 97). Even with a lightened flywheel. So that sets the upper limit on this specific engine. If I want to spin it faster I'll need a steel flywheel. 7000 redline will be fine.

Making the torque is not the problem. Being smart about it is.

Regards, Ethan

[mdrburchette]

If you have a little money to spend you can go the route I did with the clutch/flywheel. I had one custom made here:
http://www.10000rpm.com/ It's extremely light and precise. My 1608 engine is built to withstand high revs up to 9k rpms but the powerband starts levelling off around 7500.

[evm1024]

Thanks for the link. (Server timed out BTW). The cast flywheel on this engine was sent off to PBS to be lightened a few years ago. I don't "need" to spin 9K just looking for the limits.The engine is a project that has been waiting for a car to go into. Got the car now so it is time to get back to the engine.

Lightened flywheel, Balanced to crank, Dowel pins installed, weight matched rods and pistons. 8mm dome pistons, no mechanical fuel pump lobe. Home made windage tray. Choice of heads. FI head with matched 50 cc chambers and a 2mm gasket, big valves and very minor porting/shaping. 80/40 intake cam, stock exhaust. Dual IDF. The other head is a stock FI head with fuel injection. Still need to measure the CC volume so as to select a head gasket to give a 10:1 CR. I'm undecided which to use at this point (too many things else to rebuild on the car first).

Regards, Ethan

[Jim DeShon]

I have to agree with engineerted. I prefer the 1800 motor. I like the shorter stroke. If you go to a long stroke motor, you increase the fpm on the rings. I'm no mechanical engineer but I feel you'll have a stronger motor this way. My 1800 is in pieces right now but I plan to keep it 1800 and focus on quality [balancing, good oil flow, lightening the flywheel etc.]. After all that, I can increase compression, cam timing, and air flow. ...J.D.

[So Cal Mark]

stock exhaust? cam or system?

[evm1024]

Stock exhaust cam. 421 exhaust. Currently no rear muffler and a stock resonator and cat. I'm thinking about plumbing 2" from the 2-1 part of the headers back, Cut it at the right place. But (a big but) I have not researched this yet. I think that I recall you speaking of 2" exhausts. And that got me thinking. With the reat muffler rusted out it makes the exhaust system an open book.

--Ethan

[So Cal Mark]

your exhaust system is going to be critical to how that engine performs. Do you have to keep the cat?

[evm1024]

No need to keep the cat. No testing for a car this old in WA state. I like a not too loud but Italian sound. What do you suggest?

--Ethan