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Slow250XC

Pick me a cammy for my crossy

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Hi all,

giving my motor a freshen up while swapping the auto for a rail.

Also swapped from lpg back to petrol and want to ditch the lpg grind cam thats in there at the mo.

 

Whats worked for you guys with engine combo's similar to mine?

30thou 8cc pistons, ported ironhead and redline manifold, 500 holley, xe ignition, balanced etc etc and a 2.92 lsd

 

I live out of town so something with a powerband of 2k up would be great, lots of nice little country roads to play on around here. Was thinking something along the lines of a camtech 528 or crow 650.

 

Lemme hear your thoughts gents :)

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Crow 650 is going to be much more than just a "freshen up". It's advertised at 292/292 and lobe lift is 0.302" which on a 1.73 rocker gives 0.522" at the valve. Anything much over 0.5" lift, ditch the stock valve train. This cam will need springs, roller rockers and if going stud-mount, guide plates too. True, it has a wide lobe separation but that bleeds compression at low rpm. It will need a decent carb, extractors and exhaust. Also compression will need to go up by 0.5 of a ratio minimum.<br /><br />If you just want a sensible upgrade using stock parts, I'd suggest keeping it close to 0.5" lift with a 602 or 603 grind. These are single pattern, 270 and 280 deg respectively. At 0.050" they are 208 and 214. My first cam was the same as a 602 and it had great torque from 2000-4000. My current one is a 666 (dual pattern 270/280) and despite clevos apparently liking the dual pattern more, I think I took a step backwards with that choice. Anything bigger than the ones I mentioned, you need some serious work to make it come alive.

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Should have added already done new valves, springs retainers etc.

And i have been haggling with a supplier over some street terra rockers,

Exhaust is extractors to 2.5 inch pipe,a 2 chamber muffler and out infront of rear wheel so flows pretty well.

Compression ratio as worked out when i did the lpg build was 10.6.

Im a whiskey drinking redneck in the nz countryside, ain't nothin sensible 'round ere haha

 

Happy friday guys, drink up!!!

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They can rev and do it easy and still be useable but people seem scared to go for it. Here's 7700RPM to top gear skid and a 4500 transbrake launch after the car drove well over 1600km's with zero mechanical issues bar a door handle.

 

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stock rockers can run up to .550", but rollers are nicer on valve train.

I'd start at looking from a 214o @0.050" up. will make power from 1800-4500/4800rpm

10.6:1 will suit the 230ish cams 2300-5300rpm, I have a Camtech 510 237@0.050'' .550'' in a engine I'm building, hoping to put on the dyno next month.

my daily runs a dynotec 214" @0.050" 495" 111LSA in a std xflow with ported weber, extractors/exhaust,

drives like a stocker but with heap more torque, till valve float around 4000 due to valve springs, & gets 11.08lt/100km highway

has towed 15 cars, & does it well (except for big hills),

 

slydog you forgot, its 7700 skid, 4500 transbrake, triple webers, 6x 12.0's , 1600km & similar economy to 400rwhp LS :D

not too scared,just too broke.  :unsure: 

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With the extra info you provided, yeah your initial spec for the cam or the one above might be what you're looking for. I was under the impression that your bits were fairly stock.

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Yeah sorry about that i also forgot to mention the adjustable double row chain. And probably something else too haha.

Have sent the grind number off my current cam to the guys i got it off so will see what im playing with. Been a long time but i remember its very mild.

 

Cheers

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Whats worked for you guys with engine combo's similar to mine?

30thou 8cc pistons, ported ironhead and redline manifold, 500 holley, xe ignition, balanced etc etc and a 2.92 lsd

 

I live out of town so something with a powerband of 2k up would be great, lots of nice little country roads to play on around here. Was thinking something along the lines of a camtech 528 or crow 650.

Just my experience of having 2 falcon's with 2.92 diff gears and living in a place where in every direction I travel every road is 100km/h less than 1km from my house.....

 

My previous daily XE wagon was 200ci with 4 speed singe rail, 2.92 diff with 205/65/14 tyres(24.5 inch diameter) on 14x6 mags. Don't think engine is standard due to how well it performs but have no info on the engine and havn't pulled it apart to conform if it has a cam. Was a fun car but was quite sluggish to get moving due to lack of torque from the 200ci and 2.92 diff gears, but 2nd and 3rd gears were fun. Also the car never really had a lot of throttle response, seemed more to just gain speed, I didn't have a tacho so don't know what working rev range was.

 

My weekender is an XE sedan with worked 250ci 4 speed single rail with 2.92 diff and 235/60/14 tyres (25.1 inch diameter) on 14x7 mags. The cam in this car works from low 3000rpm up to 6000rpm but the engine is making shit loads of torque and the torque curve is really flat so that means I have loads of torque available from 2000rpm. The car cruises effortlessly at 100km/h doing 2550rpm and once the car gets on cam it the diff gears don't matter (283RWHP will do that). Below 3000rpm the car feels rather sedate kind of like the daily XE wagon on take off, but because the sedan has so much torque the car still moves pretty well. I know people will say that the car is sluggish below 3000rpm due to the big cam but when driving the car you can feel the torque of the engine trying to push the car when off cam, I honestly think it's the diff gears holding it back and I will be testing this theory soon enough. The cam in my sedan is a solid roller cam with 256@50thou

 

The reason for the above is to give you an example of 2.92 diff gears because I think that is going to have the biggest bearing on your cam selection. With a 4 speed you just need to make sure you get your tyre size right and the car will be fine to drive at 100km/h for extended periods but will still give good fun car. The biggest thing with 2.92 diff gears is that the car won't feel super responsive and will lack a bit of throttle response, but the car will still be fast.

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Yet another reason to throw a 3.23 disc brake lsd in then :)

Pretty sure the rears are 255.40.17 will check when i head outside next.

Seemed like a good idea running big rims when i was 18, would love a set of 15s these days haha

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I wasn't saying that 2.92 are bad but rather you just have to make sure you are aware that if you pick a cam that is going to be lacking torque down low and you have 2.92 gears it will be a bit sluggish off cam.

255/40/17 tyres are 25 inch diameter so are actually smaller than my 235/60/14 but only by 1/10th of a inch. If you pick a cam that has more top end the cam manufacturer always recommend gear change anyway like Camtech recommend for the 528. If you picked a cam more in the middle then you can use the torque of the cam to drive the car with 2.92 gears and still have a fun car to drive, this will reduce the sluggishness and give better throttle response as well.

 

But it comes down to your expectations of your car, if you want a car where you stand on the go pedal and it bursts into wheel spin then 2.92 gears aren't for you. But if you like to drive especially in corners taller gears are more beneficial as it allows the engine to hold gears for longer, be smoother with throttle application and use the torque to drive into and out of corners.

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Economy is for prius owners :P this wont be a daily its meant to be entertaining.

3.7s haha my ears ring already without that much revs. I like your style of thinking tho!!

Ive been contemplating putting a 3.23 in for a while as disc brakes would be nice, just storing all this info in the brain bank for now.

 

Guess its time to wait for camshops to email back during the week... guess i may as well have a whiskey while im waiting :)

 

Cheers for all the good oil fellas

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I already have a slight ringing in my ears all the time, so Im guessing 32-3500ish revs at 110kmh and an exhaust 2 feet behind me will get annoying fast. Havent done the maths to work out revs though, it's sunday lol

 

Used to run a pair of dellortos on a starlet years ago. That ute with triple webers has me rethinking the holley situation. Ahh the sweet sound of sidies doing their thing.

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If you're going 3.27s, make sure when you get a rail you get a V8 one with the closer ratios. I got 3.27s but a with 6-cyl T5 and the lower gears are painfully short, like driving a truck. 302 rails have a nice spread, perfect for a warm 6. Coming out of one gear puts you right in the meat of the torque curve for the next.

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