7MGTE cams - when to and when not to replace the stock bump sticks?

[boxh34d]

Hi there all.

Has anyone here got any thoughts one way or another on whether changing the 7M cams to optimise a 500hp package has any benifit, and / or at what levels they really start to shine?

Have you gone into grinding cams, and if so, how much can be gained from the stock castings by grinding the base circle and using thicker shims to gain more lift and / or more duration? Whilst I'm very green when it comes to camshaft theory, the stock 7M cams seem to be very mild - both in lift and 50thou duration. Or are these perfectly fine due to lazy nature of the 7M preferring not to rev.

I've spoken to Wade cams on this one, and they aren't sure on the specs of the stock cams and how much room there is to play. They don't have the stock details, and whether they can do it or not as they haven't done one in a long time.

I've been doing some looking around on the net, and the US forums are (as usual) close to useless with little info or details of these things, due to people either sticking with a basically stock package, or going for the biggest bad-est turbo they can find, running huge boost, and making eleventy billion HP with no real desire for midrange manners and driveability. Also, I find it hard to work out how their power levels from dyno runs compare to ours. Everyone can seemingly make 400RWHP with highflowed standard turbos and piggybacks. This doesn't really translate to what we find - 400 odd engine HP would normally be closer by my experience.
That said, the general vibe is that the stock cams are good for 800HP. . . . . . I'm sure there has to be benifits to be had from cams or other airflow mods rather than just outright boost.
If there is some worthwhile readings that I've missed, please point them out.

My current setup is running around 325RWHP @ 1 bar, with the highflow CT26 turbo looking like it's starting to run out of puff.
Next step (after some swaybars and control arm bushes) is looking like an exhaust manifold, and something in the GTX3071R or GT3076R range for around a max of 500 engine HP, with as much bottom end and mid range grunt as I can get. I'm thinking that maybe cams could help at this stage.

For reference, my car is primarily driven on spirited drives through the hills where its linear power, flat torque curve from 3000 to 5500rpm and 180RWHP from 3000rpm comes in really handy, with the occasional stint down at Winton thrown in for good measure.

Thanks for any input.

[boxh34d]

Anyone?
10 char

[andrew_mx83]

your 2 options are to buy toda/hks/bc etc cams in 264 or 272 duration (usually about $1000) or to do regrinds for about $300. have done the 268deg/8mm regrind on 7m-ge's that pull seriously hard from 3500-4000 onward.
280/8.5mm is the max available without welding (expensive)

the problem here is how to make up the base circle reduction and keep the valve clearances in check. one option is to get thicker shims made up, but they stick out a long way and you run the risk of them spitting out with high revs or lift

im currently working on a shim under bucket conversion which will safely allow heaps of revs and very aggressive cam profiles, as well as being lighter than the standard shim over bucket system. hoping to have these ready to sell in the next couple of months, will possibly do them as a package with reground and lightened cams

[whatthe?]

The exhaust ports in standard form also breathe like a clogged drain, so some work there would be recommended if you're going to install some bigger bumpsticks.

My old 7M engine (now running in Blacksupra's soarer) makes 450rwkw @ 1.5 bar with an aggressively ported head and TED cams which are 272 and 8.9mm lift (which doesnt mean any expensive welding and still runs shim over setup). The bottom end also had extensive work but if your goals arent quite that high the standard bottom end should get you there

[boxh34d]

Thanks very much guys.

Andrew - I was hoping you'd chime in.
I've seen the various off the shelf offerings for the 7M as you suggest, and am happy to look at it as an option and take recommendations one way or another. I have to ask though: is it just me, or do they all seem very much the same as every other 'stage 2, stage 3' cam out there regardless of engine specifics? I'd have thought that a long stroke 7M would benefit from a different cam profile to a short stoke 1JZ or is that being naive or simple?

The grinds sound interesting - any chance you have some more specs and or a company contact? Are they just ground stock cams, or new blanks? What kind of lift @50thou compared to the stockers and what did you do about making up valve adjustment - thicker shims, or is this the purpose of the shim under setup?
I'd be interested to hear some numbers on the shim under conversion even if just for interests sake - feel free to pm me.

Whatthe - I rebuilt my engine a while back with probe forged pistons, final comp around 8.7:1 (IIRC) and the head was mildly ported along with the manifolds. Cleaned up casting marks mainly and relieved a bit around both the exhaust and inlet - so hopefully that should have it covered.
I must admit, I almost had a heart attack when I saw the power that blacksupra got with your engine at only 1.5bar, and yes your right, it's a fair bit more serious than I'm looking for. Very interesting that a lot of yanks say not to remove material out of the exhaust as it doesn't really gain much and loses mid range. Your results make me glad I took it with a grain of salt and just left my engine builder do what he thought was best.

Any more thoughts on any of the above?

Anyone else care to add?

[andrew_mx83]

yeah i dont like the generic "stage x" labeling, i want to know what im getting.
in general, more duration and lift is good for a performance engine, from there you can tune the lobe separation angle with adjustable gears to get the desired result. by playing with LSA's you can do a lot with stock cams too.
however i believe that there is a cam for every application. that is why i march on down to my cam bloke, and tell him what i am doing with the engine rather than just buy something off the shelf. his 268/8mm grind is great for a streeter, still well mannered but pulls like a freight train up top. i cant wait to fire up these puppies and see how they go:





should have a nasty idle, be a pig until 4000 then just keep making power til it goes bang



noone seems to be able to get 7m blanks, so stock ones are reground by removing meat from the base circle and reshaping the lobe. if the valve height is bought up the match the reduction (which you need to do for valve clearance anyway) you can gain both lift and duration by REMOVING meat from the cam. the grind i posted above is apparently the max he can get out of them before welding the lobes up to add more meat then starting again.

i have 1 engine running the 268/8mm with custom made thicker shims. not a great option, the guy is difficult to deal with and it takes some time. if you get the numbers wrong and have to go back, its puts things another couple of weeks behind. i also still worry about it spitting a shim out at high revs, shit ive spat one out with standard cams/shims and there is a LOT of shim sticking out of the bucket when you make up the .060" lost in grinding.
there is another guy running the same grind with lash caps added under the bucket, having now put a lot of design time into proper shim under bucket i can see flaws with the lash cap idea.

the shim under setup is primarily to make regrinds more accessible to people (doing them for JZs as well) but also being lighter than standard is a benefit for those with any engine that sees high RPM

pricing wise looking at well under $1000 for all 24 buckets and lots of shims. also looking to package it up with lightened and reground cams, plus my adjustable gears.


stock cams down from 5kg/pair to 4kg/pair:

[whatthe?]

I'm not a fan of regrinds. Basically it means welding on metal to grind off in an effort to re-shape the cam profile and offers another point of weakness in a performance engine (where you want as few as possible weak points). Billets are worth the extra $ IMO

[andrew_mx83]

no, the cams pictured above are reground only, no welding. read the text.... im not a fan of welding either.

[boxh34d]

Whatthe:
I've heard some horror stories of welds done poorly and the new metal seperating from the main lobe. I'm sure that it can be done properly, but like you, I'd very much rather avoid the risk.

Andrew,
The shim under conversion sounds like a reasonable option. Your pricing seems like it would be very competetive as a complete setup with cams and gears compared with trying to source billet cams from the likes of Crower etc. Do you know when a change of springs is required? I'm guessing that the 268/8mm would get away with standard valve springs without too much trouble?

Can I ask who your cam bloke is? I wouldn't mind having a chat at some stage to see if he would recommend something slightly different for a turbo'd engine as opposed to your NA.
With regard to thicker shims vs lash caps: I assume that you source the shims or lash cap shims from precision in Croydon, or is there other suppliers out there?

Thanks again fellas. - rep'd.

[boxh34d]

Apparently I must spread love before i can rep you andrew.

[andrew_mx83]

no rep = no cam contact

na, i use Clive Cams in ferntree gully. i get along quite well with both the blokes there, Clive in particular really knows his shit. he actually started out as partners with Wade before moving into his own shop. afaik he is the only bloke left in melbourne that does regrinds. let me know when you go see him, i live 5 mins away might be good to catch up and have a chat. still got those cam gears here for you too.

again, the only bloke ive found in oz who will do custom size shims is Chris from Precision. see above for my experience with him, last motor i did was held up for over a month waiting on shims.
lash caps are available off the shelf for Yankee crap, but they only hold onto the valve stem but 1mm or less. due to the valve angle, you can imagine that if the valve floats/bounces any more than the engagement you run the risk of a cap coming off and falling outwards, getting suck between the bucket and retainer, possibly causing it to drop a valve and munch a piston. im not saying this will definitely happen, but i like to engineer things right and to me that is not an ideal solution.

in my shim under setup, the shim sits in a large recess in the underside of the bucket, a size for size fit at room temperature. as the engine gets to operating temp the thermal expansion will lock them in tight and they will never come out no matter how much the valves bounce.

ive not had the 268s past the factory ECU limit of 6500-6700 (still well on cam there), but my LPG 7m powered daily is running standard cams w/adjustable gears and pulls to 7500, i start to get a very faint noise from about 7200 which is reckon is the valves floating. ive since pulled back the intake cam so it runs out of puff at 7000 instead and gives me a bit more pull down low so i dont destroy it, this motor was built for torque more than revs

[TheStitt]

Subscribing for later

[Shifty]

Strengely, cams are one of the least-attended-to but most important parts of a performance turbo setup. Even a mild turbo setup will benefit greatly.

Yes you can make 500hp without them but you could make the same 500hp on a safer tune, or you can take the extra power instead

[boxh34d]

Andrew:
I'll probably call in to Clive's at some stage in the next month (I'm in Melb every second weekend usually) and have a chat about my engine and future needs. I'll be sure to let you know when I'm over that way to arrange to grab those gears and have a chat if your free. If your gas powered 7M is only using gears and still pulling strong to 7000rpm, I really think I need to find out where I'm restricted ASAP, and get the gears on.
As stated, I spoke to Wade's and whilst they do grinds, they haven't done a 7M for ages, and don't have the specs, so Clive seems like a better bet for a bit on info and possible job.

Shifty:
Have you got any insight as to what kind of cam numbers or hints / tricks I should be looking towards for this power level with the 7M?

[boxh34d]

Shifty: I just re-read my post and whilst it could be perceived as taking the piss or being sarcastic, I can assure you it's not the tone intended.

Damn this difficulty in conveying tone or context through letters. . . . . . . . . . . .and beer.