Diff gears to go with cam?

[robbyj]

Just throwing this idea out there. If i can pick up this job im after ill be earning enough money to justify a cam + tune.

However i dont have much of an idea of what im up for.
So..

I don't care for top speed, would rather have torque. And that lumpy idle sound (if they go hand in hand..)

I was thinking of a Crow "Hi Torque" cam purely because of the name.
But im sure someone can mention a similar/better cam for torque

So questions.

Will a 'high torque producing cam have a lumpy sound?'
A different gear ratio will help with torque? is it worth it if i get a cam+tune
Will i need associated cam gear like valve springs etc? if so, what.
Will diff gears alone produce better torque as a worthy upgrade
Whats the best ratio for what i'm after

And what are the associated costs,
id expect around $1500 for cam+tune
(thats without taking into consideration associated cam gear)
Have no idea about costs of diff gears

Sorry about the questions but i want to gain enough knowledge if this goes ahead.

Thanks.

[frd906]

Read Montys build thread

[ebxr82nv]

Look further afield than crow for a cam, I'll leave it at that.

[SXR6]

Originally Posted by ebxr82nv

Look further afield than crow for a cam, I'll leave it at that.

+1

[Stattic]

also +1

[blueoval]

What is said below is based on personal experience. This is by no means gospel and everyone will have their own opinion on the matter.

Will a 'high torque producing cam have a lumpy sound?'

If you mean high torque as in producing torque 'down low' in the rev range, then NO would be the answer to this question. Generally lumpy cams have tighter lobe separation angles to produce the 'lumpiness' you often hear of in V8's. Generally speaking, and I mean generally, the lumpier the cam, the higher the rev range the engine will make power/torque. This in turn means you will either need a manual or high stall converter to make the car use the designed power the cam is intended for. Don't get me wrong, the car will still run, but it will be 'doughy' at low revs till the revs pick up and the cam is working in its designed rev range. Histalls and diff gears gets the engine to that desired rev range much sooner than stock.

A different gear ratio will help with torque? is it worth it if i get a cam+tune

Absolutely if you are looking for faster take offs from stand still. Also this will aid the engine to reach the cam rev range the cam is designed for, faster. Thus in turn, achieving the power quicker. In fact, I would not consider running a bigger cam without diff gears, OR if the cam upgrade is a mild upgrade, you may be able to run stock running gear ok.


Will i need associated cam gear like valve springs etc? if so, what.

This depends on if you are getting a reground cam, or new billet. As a rule of thumb, I recommend a new set of valve springs for a cam that is significantly designed for a lot more power. For a mild grind, you can get away with using stock valve springs if the manufacturer specifies it as ok. Consider asking the cam manufacturer for recommended valve springs at the time of ordering. Every brand is different so there is no real way of saying yes or no.

Cam regrind requires shims based on how much of the cam was ground in the first place. The supplier will recommend what size shims you need.

New cams do not need shims, but are more expensive


Will diff gears alone produce better torque as a worthy upgrade

I wouldnt say diff gears 'produce' torque, but rather assist the existing torque of your engine to come on earlier in the rev range. If you care about getting to a given speed fast, diff gears will certainly give you this. Be aware there is a trade off. Your engine will rev a bit higher at cruising speed, fuel consumption will be affected.


Whats the best ratio for what i'm after

I was told that for a street setup with auto trans go with 3.7 ratio. For a street setup with manual gearbox - 3:45 ratio will suit very well. Of course this will be argued due to everyone having different setups to suit different applications. But as a guide, the above ratios will suit a good street style setup.

And what are the associated costs,
id expect around $1500 for cam+tune
(thats without taking into consideration associated cam gear)

With this, it can vary. Depending on if you went reground cam or new billet. Plus who does the fitting and tuning and what other items you need to get the most out of your cam. Don't just think throwing in a cam and a tune is all you need. You need to work out what you want your car to achieve. Is it for towing, street driving, circuit racing, drag racing, general daily driving....what? This will be the first thing the cam suppliers will be asking. Then they will need to know what stall speed you intend on running, diff gears, max rpm speed, wheel diameter size, tire size, the list goes on. Don't be one of the knobs and stick a massively lumpy cam in for 'fully sick' reasons. It will drive like a complete dog and your fuel consumption will suck at best, with no power when you most need it. Be smart about what cam you choose, and be honest about the application you intend you car to be used for.

Have no idea about costs of diff gears

Diff gears can vary. Speak to those who have already done it. Steer away from 2nd hand diff gears as they are prone to whining when fitted to aother diff. If you want to go second hand, seek a complete diff with gears, axles the lot from an xr model (assuming 3:45s are what you are looking for). I did this and found a diff for $500 with low km with 3.45 ratio. Fitted new diff oil to it and its fine apart from LSD needing to be repacked.

Hope this has helped.

[The Monty]

Id factor in 2k plus for the cam and tune.
Billet Cam (not regrind) - $600
Vernier gear - $220
If you want a big cam you will need:
Valve springs - $220 plus install - $300
Valve sring retainers
Xcal 3, chiptorque chip etc - $8-900
Custom tune - $600-1000

3.9 Diff gears, a LOKKA and install would be around the $1200 mark.

Ive done both, and can fully say with no hesitation that the diff gears are a 98683 times better mod.

Fastest AU other than Stiddy ran a 14.2 with standard cam, but theres barely a car under the 15 second mark without diff gears.

[blueoval]

Originally Posted by The Monty

.....the diff gears are a 98683 times better mod.

Agree with this. Gearing is just as important as the cam itself when it comes to the 'holeshot' advantage. They work hand in hand.

[SXR6]

Very well said blueoval.
The Monty is on the case aswell. Its about the cheapest and all you can do in that list before you start looking into things like head porting, engine rebuilds and all that kinda fun stuff.
I love these motors, more so than the twin cam barra motors. These engines have so much potential if done right.

[The Monty]

If you want to save money you can have my cam and Vernier gear, its a surecam cam, .535 lift, 218@.050 duration and 114 l.s. Comes on hard around 3500rpm, makes 410nm of torque, and will happily rev to 6400rpm. Vernier gear is a Crow Cams vernier gear. I also have a head here with the valve springs and retainers in it, but I would want that taken off by the person buying it. Whole lot for $750.

[blueoval]

Originally Posted by The Monty

If you want to save money you can have my cam and Vernier gear, its a surecam cam, .535 lift, 218@.050 duration and 114 l.s. Comes on hard around 3500rpm, makes 410nm of torque, and will happily rev to 6400rpm. Vernier gear is a Crow Cams vernier gear. I also have a head here with the valve springs and retainers in it, but I would want that taken off by the person buying it. Whole lot for $750.

Is that the same cam you showed me in your youtube clip recently?

Dammit, why couldn't you be in SA.

[The Monty]

Same Cam, yes. Ill send the cam and vernier gear.

[robbyj]

Sorry guys i have been away for a week.

Shav, love reading your replies as always. Thanks for answering everything. As you say not to chuck a cam in and be done with it. Yet to try find a job over the holidays, as i was actually on holidays, so just trying to research it a bit.

Thanks monty, just read your parting out the blue car thread and your cam came to mind instantly.
Ill keep researching and keep looking for a decent paying job before i make a decision. But ill keep you in mind.

It seems id be better off doing LSD and diff gears first however???

[The Monty]

Id do the diff gears first. If your thinking about racing it, Id steer clear of an LSD though, head for a LOKKA. If its for streetduties only, just get an LSD.

[blueoval]

Originally Posted by bobuleh

Sorry guys i have been away for a week.

Shav, love reading your replies as always. Thanks for answering everything. As you say not to chuck a cam in and be done with it. Yet to try find a job over the holidays, as i was actually on holidays, so just trying to research it a bit.

Thanks monty, just read your parting out the blue car thread and your cam came to mind instantly.
Ill keep researching and keep looking for a decent paying job before i make a decision. But ill keep you in mind.

It seems id be better off doing LSD and diff gears first however???

No worries mate. Hope I helped a bit. I would definitely consider how you drive your car and what your intention for it is. This will help determine the best way to go.

[FS5]

if you want more torque and excellaration go the diff gears like mont said .for an au there the best bang for your buck. if you got an auto you'l need some sort of tune to get it to work.manual is easy get them fitted and just have fun.
if your after more torque from your motor ,try an xr6 cam ,get a vernier gear and advance it about 5* it will pull hard down low and still rev out ok.
i take it you'd have all the usual intake and exhaust mods done already?

[robbyj]

Originally Posted by blueoval

No worries mate. Hope I helped a bit. I would definitely consider how you drive your car and what your intention for it is. This will help determine the best way to go.

Yea thanks mate, sort of in 2 minds at the moment, over the next few of years ill be looking for an AU XR8 as a weekend car.
Cant hurt to research it tho.

Originally Posted by FS5

if you want more torque and excellaration go the diff gears like mont said .for an au there the best bang for your buck. if you got an auto you'l need some sort of tune to get it to work.manual is easy get them fitted and just have fun.
if your after more torque from your motor ,try an xr6 cam ,get a vernier gear and advance it about 5* it will pull hard down low and still rev out ok.
i take it you'd have all the usual intake and exhaust mods done already?

Yea extractors, CIA all that basic stuff. So looking into next step.

Would it really need a tune? that turns me off the idea now haha

[The Monty]

I think he means regarding shiftpoints and speedo recalibration. I didnt get a tune for a while after getting diff gears done. Youll just hit the rev limiter sometimes on WOT. I didnt have this problem as my lmiter was raised so when it was changing gears I was still doing the same speed as I normally would be, just at a higher RPM.

[robbyj]

Originally Posted by The Monty

I think he means regarding shiftpoints and speedo recalibration. I didnt get a tune for a while after getting diff gears done. Youll just hit the rev limiter sometimes on WOT. I didnt have this problem as my lmiter was raised so when it was changing gears I was still doing the same speed as I normally would be, just at a higher RPM.

Ah k thanks
more to think about. Seems the next stage you have to start throwing some money at it.

[The Monty]

And none of it is worth it. I had fun doing it, but if there is a next time, I would deffinately go boosted.

[robbyj]

Well thats what i always thought, strap a super charger on and be done with it.
Although of course there is still need for intercooling tune etc etc.

[The Monty]

If your after 200kwish there isnt a HUGE need for intercooling. Handy for sure, and deffinately worth it.
And you would need a tune.
For me, its like this:
Cam and associated bits and peices - $2400ish, if you want a ported head to match, $3500.
Supercharger and tune -From $5k.
Not much difference, and one ends up with 50kw more than the other.
dont get me wrong though, I have no regrets doing the NA way, heaps of fun, but money for the gain wasnt worth it imo.

[robbyj]

Yea, it was interesting reading your builds, some great work. Also with N/A its like you didnt 'take the easy way out' by just bolting something on.

But if i was to do either id prefer the s/c

[MGM]

would 4.11's be ok for an auto xr8 ute towing a tool trailer everyday ??

[blueoval]

Originally Posted by MGM

would 4.11's be ok for an auto xr8 ute towing a tool trailer everyday ??

It would be more than ok. V8's have plenty of torque as it is to tow. Going with diff gears like that you will find the car is revving harder than it needs to. Fuel consumption will be compromised.

[MGM]

The car is on LPG to, so when towing it struggles to tow the 1300ish kg's plus the heavy car, I know it will rev at 2400rpm. It pulls the trailer fine but only getting up to speed is very slow

[blueoval]

I would consider a capa flash tune for your LPG so you can customize power for towing over diff gears.

[MGM]

I was told for LPG tune that I have to get a custom tune on both fuels first so that would be around 1500, I've already got a capa box from my old car to

[blueoval]

Originally Posted by MGM

I was told for LPG tune that I have to get a custom tune on both fuels first so that would be around 1500, I've already got a capa box from my old car to

As long as it isnt an xcal 1 you will be fine. To some degree that person is correct. If you use LPG 90% of the time, you could effectively get away with running 1 custom tune up until you switch it from LPG to petrol. Then you would need to revert straight over to the petrol tune. A bit of rooting around. If you have to start the car on petrol, I would be inclined to pull over, reflash on petrol tune. That is the way I see it. Some one else here could possibly shed some light.

[MGM]

yeh i run lpg most of the time, petrol is only really for driving to the srevo when i have run out of gas, mabey 10km a week or so, il find out more about the tunes then, dont want to have to re-flash it everytime