Opel 2400 CIH Engine
Discussion
Is there anyone else using a 2400 cih engine for his racecar? I have one in my Manta and it is already pretty fast, but i like to keep developing this old cast-iron dinosaur, as i'm still running the original cast iron exhaust manifold, i'd like to know if a tubular manifold can help to raise the power a little further.
The specs so far: Bored to 2511 cc, big valves, Cat Cam, 12:1 compression, DCO/SP 48 webers and a Simons group-A exhaust system.
I use the car for the Dutch timeattack series and this year i will be in the super-pro street class.
The specs so far: Bored to 2511 cc, big valves, Cat Cam, 12:1 compression, DCO/SP 48 webers and a Simons group-A exhaust system.
I use the car for the Dutch timeattack series and this year i will be in the super-pro street class.
Edited by Keesjr on Saturday 11th February 16:47
Edited by Keesjr on Saturday 11th February 21:30
Edited by Keesjr on Saturday 11th February 21:30
I'm guessing you're the one who emailed me about head porting. In a few months when I've moved house and settled in to somewhere new I'll think about taking on new work again. I hate cast iron heads though. So much work to port properly and you breathe in all the dust and crap. Might be fun to do a new head though.
You're right, thats me. And i agree, a cast-iron head is a lot of (very) dusty work, but also rewarding in terms of power.
I have always ported my own heads, but when you can do a head for me and make my old Manta just fast enough to win against much newer turbocharged stuff like skylines, evo's etc.....
I also think that the stock cast iron manifold is already a good design, just a little too small in the inside diameters, the bigger downpipes helped to bring the torque up a bit, i think a custommade manifold with bigger diameters and maybe even anti-reversion cones welded in (dv-trick) will add some power over the entire rev-range.
Risse motorsport does shortened 24V heads for this engine, but i'm really into the cast-iron old-school stuff, and it is also part of the fun to get the maximum performance out of this engine ;-)
I have always ported my own heads, but when you can do a head for me and make my old Manta just fast enough to win against much newer turbocharged stuff like skylines, evo's etc.....
I also think that the stock cast iron manifold is already a good design, just a little too small in the inside diameters, the bigger downpipes helped to bring the torque up a bit, i think a custommade manifold with bigger diameters and maybe even anti-reversion cones welded in (dv-trick) will add some power over the entire rev-range.
Risse motorsport does shortened 24V heads for this engine, but i'm really into the cast-iron old-school stuff, and it is also part of the fun to get the maximum performance out of this engine ;-)
Edited by Keesjr on Sunday 12th February 13:38
I will dyno it before and after, every modification gets tested on the dyno to see if it works, cam and ignition timing, jetting of the carburettors, different exhaustpipes, filling the inlet ports, all these things are already tested, i'm about to test a new camshaft, but before that one gets fitted, first re-baseline the power, then change the cam and test and tune again.
Because if you change more than one thing at a time, you never know what works and what doesn't.
One thing is for sure, i'm staying with carburettors and a distributor-type ignition.
Because if you change more than one thing at a time, you never know what works and what doesn't.
One thing is for sure, i'm staying with carburettors and a distributor-type ignition.
I will be running a brand new 2.4 crate engine in my A series manta soon.
My other opel Mantas run 2.2 Rekord engines.
Risse do a 16V head conversion for the CiH engine, link below !
http://homepage.ntlworld.com/david.jackson17/cih_1...
My other opel Mantas run 2.2 Rekord engines.
Risse do a 16V head conversion for the CiH engine, link below !
http://homepage.ntlworld.com/david.jackson17/cih_1...
I'm keeping the stock cast exhaust manifold, just going to make it a little bigger on the inside an remove as much as possible sharp edges, gasket match it to the cilinderhead, and fabricate the biggest possible downpipes, maybe make a bigger diameter exhaust system from the downpipe backward, it is now 2,5" but i don't really expect a power increase from a 3" system.
Just a lot of trouble making it and keeping it from hitting the floor and the rear axle.
50 mm Webers, a bigger cam and a lot of fine tuning should bring some extra power to the old cast iron furnace though!
About the downpipes, going up in size from 1,75" to 2,0" gave a nice increase in torque and power.
But before and after all the fiddling and testing, at 6500 rpm the power drops off immediately, which is very clear at the power graphs, it seems to hit the wall there.
Is it possible that the original ignition system has a built in electronical controlled retard feature or something?
I also have fitted an Omex rev limiter with a "soft-cut" but that is adjusted to start at 6800 and really limits at 7000.
In normal racing circumstances i never go above 6500 because there's no point in going higher.
I'm really serious about making the fastest possible Opel 2.4 / 2.5 engine on carbs, just love those old 8-valvers.
Just a lot of trouble making it and keeping it from hitting the floor and the rear axle.
50 mm Webers, a bigger cam and a lot of fine tuning should bring some extra power to the old cast iron furnace though!
About the downpipes, going up in size from 1,75" to 2,0" gave a nice increase in torque and power.
But before and after all the fiddling and testing, at 6500 rpm the power drops off immediately, which is very clear at the power graphs, it seems to hit the wall there.
Is it possible that the original ignition system has a built in electronical controlled retard feature or something?
I also have fitted an Omex rev limiter with a "soft-cut" but that is adjusted to start at 6800 and really limits at 7000.
In normal racing circumstances i never go above 6500 because there's no point in going higher.
I'm really serious about making the fastest possible Opel 2.4 / 2.5 engine on carbs, just love those old 8-valvers.
Edited by Keesjr on Friday 2nd March 20:05
You can play with the torque a bit with the position of the last merge into one pipe. It is quite a long way away from the Manifold on the Manta B GTE, On my A series I moved the collector closer to the manifold and it altered the feel of the car quite a lot, it felt more perky low down the revs. I think it lost torque at the top end of the useable revs.
Have a play with lengths and see what feels good, do not be tempted to go for a really large bore pipe for the exhuast but try to get what you have as free flowing as possible, no baffles in the silencers seemed to make my GTE go better, cherry bombs in the system so it flows but is not really loud !
Have a play with lengths and see what feels good, do not be tempted to go for a really large bore pipe for the exhuast but try to get what you have as free flowing as possible, no baffles in the silencers seemed to make my GTE go better, cherry bombs in the system so it flows but is not really loud !
Thanks again, the system is already a Group-A with 2.5" pipes and free flowing silencers, so that's good enough to at least 260 bhp, so still some development to do before that becomes an issue.
Playing around with secondary pipes in different lenghts sound like a good idea, just fabricate shorter downpipes and test them to see what happens to the powercurves.
I'm going to make one which is 2 inches shorter before going into one pipe, and an other one 4 inches shorter, if it works: great!
If it doesn't work: it was worth the trouble to find out.....
Playing around with secondary pipes in different lenghts sound like a good idea, just fabricate shorter downpipes and test them to see what happens to the powercurves.
I'm going to make one which is 2 inches shorter before going into one pipe, and an other one 4 inches shorter, if it works: great!
If it doesn't work: it was worth the trouble to find out.....
Pumaracing said:
I'm guessing you're the one who emailed me about head porting. In a few months when I've moved house and settled in to somewhere new I'll think about taking on new work again. I hate cast iron heads though. So much work to port properly and you breathe in all the dust and crap. Might be fun to do a new head though.
Mr. Baker, if you like to do a cylinder head for a really fast Opel please reply.I'm in the proces of building a 2.7 litre engine 97,25 x 90 millimeters bore & stroke.
It will be equipped with bigger valves, DCOE 50 weber carburettors, the biggest Cat Cam camshaft, ported/polished cast iron exhaustmanifold, etc.... and a puma head?
The current engine is a 2.5 with 48's /head /cam / etc.... which at it's best times made 190 bhp @ the wheels at my local rolling road.
With the 2.7 i hope to go over the 200 mark @ the wheels.
Not much done to the Manta's engine due to busy work at my garage and the autograss BX taking a lot of time too ;-)
But having bought and read David Vizard's books on cylinder heads and building horsepower some new ideas came up, like some small but effective modifications to the head and exhaust system.
I might be a little too enthousiastic or fanatic but hope to het the 2511 cc engine above 200 bhp @ the wheels without going to insane rpm levels for the old cast iron lump under the bonnet.
But having bought and read David Vizard's books on cylinder heads and building horsepower some new ideas came up, like some small but effective modifications to the head and exhaust system.
I might be a little too enthousiastic or fanatic but hope to het the 2511 cc engine above 200 bhp @ the wheels without going to insane rpm levels for the old cast iron lump under the bonnet.
The books from David Vizard about porting and flowing cylinder heads have been a very useful source of information and ideas to get more power from the old Opel.
The first thing was to file the plugs and also index them, it runs better at idle, but also responds better to the throttle.
Next step will be the exhaust manifold, it is already flowed and polished on the inside and the holes to the downpipe have been tapered to make a smooth transition into the downpipes, i just have to grind the floor of the ports in the manifold down 3-4 mm to make an anti-reversion step.
When this is done, it's a trip to the rolling road to test and if necessary change ignition, jets in the carburettors, and maybe the timing of the camshaft.
Then i will have a new baseline to work from.
Next on the list will be the intake ports, no big changes, but just some nice little attention to the details, then back to the rolling road again to test again.
If this is succesful, there are two possible tings to try, a 4-2-1 manifold which will be tested before an eventual change to a bigger cam (more duration on the intake)
With a little luck i hope to get over 200 bhp @ the wheels, the next thing will be making the bodywork lighter, with glassfibre wings, doors and bootlid which should save about 100 pounds.
The first thing was to file the plugs and also index them, it runs better at idle, but also responds better to the throttle.
Next step will be the exhaust manifold, it is already flowed and polished on the inside and the holes to the downpipe have been tapered to make a smooth transition into the downpipes, i just have to grind the floor of the ports in the manifold down 3-4 mm to make an anti-reversion step.
When this is done, it's a trip to the rolling road to test and if necessary change ignition, jets in the carburettors, and maybe the timing of the camshaft.
Then i will have a new baseline to work from.
Next on the list will be the intake ports, no big changes, but just some nice little attention to the details, then back to the rolling road again to test again.
If this is succesful, there are two possible tings to try, a 4-2-1 manifold which will be tested before an eventual change to a bigger cam (more duration on the intake)
With a little luck i hope to get over 200 bhp @ the wheels, the next thing will be making the bodywork lighter, with glassfibre wings, doors and bootlid which should save about 100 pounds.
Edited by Keesjr on Sunday 29th December 21:17
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