M20 B3x Naturally Aspirated Stroker build past, present and future

[The Dark Side of Will]

Do you have a degree wheel? Sounds like one would make your refinement of your build MUCH easier. For example, you don't think the Cat Cams unit is actually has the specs they claim... you would be able to verify that with a degree wheel, which would aid your pursuit of building the better engine. I haven't read your whole thread, so apologies if you're already using one.

The GM LS community is demonstrating exactly what you describe with regard to cams.

The conventional idea of a "big" cam, and the associated lope at idle comes from the days when cylinder heads flowed for crap, cams were limited to flat tappet lifters and American MFG's just made their engines bigger to compensate... the 1960's.

Modern heads flow so well relative to displacement that medium duration, fast ramp, high lift cams with moderate lobe separation angles make superior torque curves across the entire RPM range compared to longer duration narrower lobe sep cams with more relaxed ramp rates. This is basically undisputed in the LS community and is so widely accepted that most people recognize that selecting a cam that lopes is... umm... ricey and only done for the sound.

The Ferrari 360 is another good example. It makes peak power at 8500 RPM, but because it has 5 valve heads which flow stupid stupid amounts of air for the displacement, it actually has fairly modest duration compared to what "old school" thinking would expect for an 8500 RPM engine.

[digger]

Do you have a degree wheel? Sounds like one would make your refinement of your build MUCH easier. For example, you don't think the Cat Cams unit is actually has the specs they claim... you would be able to verify that with a degree wheel, which would aid your pursuit of building the better engine. I haven't read your whole thread, so apologies if you're already using one.

The GM LS community is demonstrating exactly what you describe with regard to cams.

The conventional idea of a "big" cam, and the associated lope at idle comes from the days when cylinder heads flowed for crap, cams were limited to flat tappet lifters and American MFG's just made their engines bigger to compensate... the 1960's.

Modern heads flow so well relative to displacement that medium duration, fast ramp, high lift cams with moderate lobe separation angles make superior torque curves across the entire RPM range compared to longer duration narrower lobe sep cams with more relaxed ramp rates. This is basically undisputed in the LS community and is so widely accepted that most people recognize that selecting a cam that lopes is... umm... ricey and only done for the sound.

The Ferrari 360 is another good example. It makes peak power at 8500 RPM, but because it has 5 valve heads which flow stupid stupid amounts of air for the displacement, it actually has fairly modest duration compared to what "old school" thinking would expect for an 8500 RPM engine.

this is the old engine ive been using with a catcams since 2008, i did not use a degree wheel when setting up the cam but i did roughly set it up based on the relative lift at TDC of inlet and exhaust on the bench which is a bad way of doing it given it assumes the cam is correct. i subsequently dialed it in on the dyno and gave the engine wants etc stopping at 8 degrees advance as the topend would have started reducing had i went further. i could setup a degree wheel and plot it out but i dont think ill get around to that

ive plotted and seen another couple different catcams plotted out they are are often on a wider centres than what the cam card says and as a consequence ive seen about 5 engines 2.7/2.8 strokers make no torque (i.e less than or equal to stock m20b25) below 3500rpm hence my theory. i would never recommend catcam for a street engine there is too much tradeoff for my liking.

i do have degree wheel for the new engine though

[digger]

So I pulled the plugs the other week and 3 of the ignition leads pulled out leaving the connectors on the plug what a waffleswaffleswaffleswaffles.

pic of old rubbish wires



The wires were made by a shop when i went to wasted spark and weren’t cheap. i think they are accel wires based on the markings. Found out the fuckers over charged me big time after doing some googling plus they are shit quality.

The 8mm accel wires were supposed to be 500ohm per foot but all the wires 2ft long ohmed at about 15k i know they do break down but within a year? lol

found some cheapo bosch stuff for the interim to get me back on the road

Anyway did some research and seemed like moroso ultra40, MSD 8.5mm superconductor, magnecor & Firecore50 8.5mm were the best for the pushrod folks who have much more demanding applications than mine.

Moroso: were out the window given they made the junk wire set that VAC sell which didnt work when they arrived and the replacement set caused misfires after a year

MSD: well their MSD 6A did absolutely SFA except make the radio interference screw up the AM band so not wanting to try their stuff.

So it was down to magencor or firecore50

Never found a bad thing said about firecore50's i liked the fact that people had said they have put them on and pulled them off dozens and dozens of times and not had any wires pull out and the wires are only 50ohm resistance. They are well reviewed especially on yellow bullet. family owned business not looking to cut manufacturing costs at expense of quality like many others

Custom set of 6 with choice of connectors and length was $145, the guy even rang me up as i screwed up the form and suggested something better, comes with warranty of 12months

As per site the wires ohmed at 50ohm which must be better than 15000? im using resistor BPR6ES plugs not sure whether non resistor plugs would be an issue. boots are nice and long so easier to grab hold of without burning yourself

installed them not long ago and they seem good, like lost performance has been restored. you arent going to gain heaps of power even though it feel like it does go a bit harder, engine seems quite happy and revs more crisply and cleanly than i seem to recall probably just end up with less losses. maybe placebo but some have dynoed and seen gains over other wire sets. im not interested in that too much but just wanted a good set of wires and so far so good.

if you're after a custom set i can recommend based on my initial assessment. same exact wire is used on street cars all the way to top fuel/nascar/promod etc so cant be a bad wire as those guys cant afford to put up with junk.

They also do some 7mm wire which will fit in the OEM plastic moulding if using a stock dizzy but not sure about the connectors at dizzy end if they stock those. Might be best getting an IE set if you a stock setup.

http://www.firecore50.com/

[CorvallisBMW]

That sucks about the wires, definitely sounds like they just made some garbage stuff and overcharged you for it.

Regarding the compression testing you did in an earlier post, does having the throttle open (WOT) really affect the numbers?

[digger]

ive never tried to see what effect closed throttle has

yeah the wires were cheap after doing research which is ok if you actually pay cheap prices. still very pleased with the new wires and i fully recommend for someone looking for a custom set with wasted spark or individual coils to give them a go

[Mfever]

digger can you post some pics in this thread, we need some eye candy man!

[digger]

pics of what?

[ForcedFirebird]

I do compression tests almost daily, and I have never seen any difference with throttle open/closed.

[digger]

presumably with single throttle at manifold entry there is enough volume in the system that it is negligible difference like FF said.
with ITB i imagine it may take a few more pulses though if throttle is at idle vs WOT since the blade is cracked less with ITB as its only feeding 1 cyl ata time instead of 2.5 at a time like the single TB

[ForcedFirebird]

with ITB i imagine it may take a few more pulses though if throttle is at idle vs WOT

Same with a single. Just one or two strokes more.

[digger]

yeah makes sense, main reason i put mine at WOT so flood clear is activated and no fuel is injected

[digger]

sorted out why the tacho wouldn't work after wasted spark conversion.

the shop just screwed up the pins when they reassembled the connector. they routed the boost control output to the tacho. i sorted this out after an hr or so crawling around under the dash checking wiring diagrams. this is the second issue i sorted due to something being pinned incorrect and i know SFA about electrons and their pipes.

[bmwmaster81]

Hi digger,

i read the whole thread and must say that your work is really amazing !!!
I also have built an m20 stroker but am using 272° Schrick cam.

Specs are M52 crank with high compression pistons.
Decked block so CR is 10,5:1

While cranking i have about 210 psi and think with another cam i could optimize my engine little bit.
Here in germany we have an company called schleicher. They offer cams for m20s and i find them quite interesting, but lack of my knowledge i can't realy judge if they will have good caracteristics in my engine. Maybe you could give me some advise ?

They offer 4 different cams with these specs:

270° 112 67/23/23/67 lift: 11.10 / 1.4mm @ tdc
274° 112 69/25/25/69 lift: 11.10 / 1.7mm @ tdc
280° 111 71/29/29/71 lift: 11.40 / 2.3mm @ tdc
288° 110 74/34/34/74 lift: 11.70 / 2.9mm @ tdc


Im thinking about to buy the 280° Schleicher cam to replace my 272° Schrick....what do you think ?

P.S.: Im running standalone ecu without MAF and car is just used on public roads.

[digger]

280/280 looks good for that compression, id set it up 2-4 degrees advanced though with a vernier cam gear. check piston to valve clearance as this will probably be a limiting factor

personally i wouldn't run a 288 duration on the street without a better intake manifold and ported head and perhaps a slightly higher static compression 11:1 is about ideal. many people have but you just wont get near the capability of the cam without those things but you'll still get the downsides.

[bmwmaster81]

Alternatively i could use asymetric 284°/272° Schrick with these Specs:

Schrick:
284°/272° 111/100 72/32/26/66 lift: 11.40/11,0 2.2/1,7mm @ tdc

Schleicher (for comparison again):
280° 111 71/29/29/71 lift: 11.40 / 2.3mm @ tdc

Which would you prefer?
It's not a daily driver. But i also don't like to rev the hell out of it, just sporty driving sometimes.

Could you maybe explain something about the asymetric point? does it make sense to use this kind of cams? advantages? disadvantages?

Thx