What cam- for a blown lump?

topcatcustom · Post by **topcatcustom** » Wed Sep 24, 2008 8:41 am

I am very tempted to stick with a new standard cam for my 3.9 blown lump, but saw this and wondered if the extra £100 would really be worth it as I am not modifying much else on the engine and want to keep prices low- thought it may just be a couple of extra bhp for racers that need every little bit

http://www.v8tuner.co.uk/product.php?id=483

And I know cheap is normally bad but is this cheap and nasty or cheap and good for the standard cam?!:
http://cgi.ebay.co.uk/LAND-RANGE-ROVER- ... 18Q2el1247

Blown v8 · Post by **Blown v8** » Wed Sep 24, 2008 7:56 pm

it doesnt say what the lobe seperation is !
you want between 114 -116 degrees with more duration on the exhaust side if possible
too much overlap and the "charge" blows straight out of the exhaust valve

stevieturbo · Post by **stevieturbo** » Sat Sep 27, 2008 3:13 pm

Blown v8 wrote:it doesnt say what the lobe seperation is !
you want between 114 -116 degrees with more duration on the exhaust side if possible
too much overlap and the "charge" blows straight out of the exhaust valve

Myth.....that depends on the overall characteristics of the cam, not just the LSA.
There is a lot more going on than just LSA.

It will also depend on type of blower, amount of air being shifter, driving characteristics you want etc etc....

In short though, mild cams work great. Bigger cams can also work well....more so with PD blowers, as the air is always getting pumped the right direction...but go big, and idle gets a bit lumpy.

topcatcustom · Post by **topcatcustom** » Sat Sep 27, 2008 11:09 pm

Its a 4-71, on carbs. (or under) I think I will use std pattern unless there is a massive gain to be had with the V8 tuner one (anyone advise?) as I cant justify the extra money!

Can anyone advise on what the quality of the cheap ebay one may be like?!- I know its cheap so normally a bad sign or is it a good deal?!

stevieturbo · Post by **stevieturbo** » Sat Sep 27, 2008 11:28 pm

If in doubt...stick with what you have.

Blown v8 · Post by **Blown v8** » Sun Sep 28, 2008 7:30 pm

poppycock !
B&M spent 100 of 1000s of dollars perfecting cams for there roots type blowers (which Mr. Topcat has) and low and behold. they came to the conclusion 114degree lobe centres !
a coincidence ? I dont think so !
a turbo motor requires a different cam to a blown motor !

The old adage says turbos suck !
I would rather be blown

topcatcustom · Post by **topcatcustom** » Sun Sep 28, 2008 7:39 pm

Erm....
Just noticed that the V8 tuner cam has a 1.2mm lift- isnt that a little too much for my std head set-up?

stevieturbo · Post by **stevieturbo** » Sun Sep 28, 2008 7:46 pm

Blown v8 wrote:poppycock !
B&M spent 100 of 1000s of dollars perfecting cams for there roots type blowers (which Mr. Topcat has) and low and behold. they came to the conclusion 114degree lobe centres !
a coincidence ? I dont think so !
a turbo motor requires a different cam to a blown motor !

The old adage says turbos suck !
I would rather be blown

Unless they tested his engine on a dyno with every cam variation possible.....then they cant say which cam is best.

They may have tested some setups.....but is everyone using the same ???
Does everyone want the same idle, power delivery, emissions characteristics ??

Soild roller, hydraulic, what rockers, what lift ???

Doubtful they did.....so its very naive to say 114LSA is the best, when there is a hell of a lot more to valve events, than just LSA !!!

Blown v8 · Post by **Blown v8** » Sun Sep 28, 2008 7:58 pm

i have in my possession 5 different books on supercharging,on cam selection they all recomend between 112-116 LSA !
I concur nothing is set in stone
when i had mine made.it took a lot of try and error !
i ended up with over 500 lift, and more duration on the exhaust side
if you want to talk cam dynamics,please do !
unlike a lot of people i didnt go the easy route, and buy of the shelf.
who wants a KIT engine

Boosted LS1 · Post by **Boosted LS1** » Sun Sep 28, 2008 9:23 pm

Which books are these?

Also have you proved their recommendations work? How so? Did you run with many different cams before settling on the optimum?

As an aside, for a conversation on cam dynamics I'd suggest you go over to ls1 tech. That'll keep you busy for most of the winter.

Also, B&M are sales people, just like M&S but I don't buy M&S tasty meals;)

JP. · Post by **JP.** » Mon Sep 29, 2008 2:12 pm

Blown v8 wrote:.........a turbo motor requires a different cam to a blown motor !

The old adage says turbos suck !
I would rather be blown

Here you say it your self.........the cam we are talking about is a ...according to the advertisement on the given link....

V8 Tuner wrote:Rover V8 SUPERCHARGER or TURBO Camshaft

How can this cam working on both engines

Id stick to the Viper Hurricane on my blown 3.5.

Blown v8 · Post by **Blown v8** » Mon Sep 29, 2008 3:10 pm

i ran more than 1 cam ! i had 3 made , and settled with the 1 that made the power by 5800rpm !
420bhp on a street engine is enough for me in a car that weighs 2100lb

topcatcustom · Post by **topcatcustom** » Sat Oct 04, 2008 7:22 am

Soooo..... Is the extra £60 odd going to give me a lot more horses or not by using V8 Tuner's SC cam over standard one?!?!

stevieturbo · Post by **stevieturbo** » Sat Oct 04, 2008 8:28 am

A well matched uprated cam does have the potential for more power everywhere. Yes.

Dont forget you will need to buy new cam followers too.

kiwicar · Post by **kiwicar** » Sun Oct 05, 2008 10:16 am

With a supercharged engine as with any engine it is important to match cam to heads to compression ratio and exhaust headers. As a supercharged engine that is "roughly right"will give more power regardless and generally stop a motor with too much overlap from coughing and farting at idle it is more difficult to to get the right set up.
That cam is still pretty mild, but has some more timing than normal, and because of the greater LSA it probably has similar overlap to the standard cam so should run at idle pretty well with a supercharger without blowing all the charge out the exhaust. However this is assuming you have uprated the heads to make use of the extra lift and duration, if you are not going to upgrade the heads stick with with the standard cam. It also assumes you are going to use a CR that will not detonate when the boost comes in.
If you want to use that cam I would look for an engine spec for a normally aspirated engine that uses a similar inlet timing and about 108 deg of LSA and copy it but reduce the CR to about 8.75 to 9.25 to 1 (depending on boost guessing at 7 to 12 PSI). I would think you want fully ported heads (or some Merlin heads) probably with extra work on the exhaust side.
If it is a basically standard or stage 1 head engine go for the standard cam.
Mike