miata cams

[mzdamx3rsdohc]

hey im getting my new rocker cover gasket today. how hard is it to install the miata cams as i cant find ne write up on it. i already have the cams.ne thing else i should do while im in there?waterpump,timing belt. i would prefer not to do either as ive found that half of aftermarket waterpumps ive installed on my cutlass supreme,s10,etc. needed to be replaced within a week as they were faulty parts. what do i look for on the timing belt for wear? ne help would be greatly appreciated thanx

[torpedan]

Dont buy cheap parts, you tend to get what you pay for. Also it would be atleast worthwhile to inspet the timting belt. If it shows signs of age (Crqacking, missing teeth, looks corded) it would be worthwhile to change it while you are in there.

[mzdamx3rsdohc]

thanks a lot for the reply. so ill definatly look at the timing belt for those signs. but i was also wonderin what about timing belt tensioner? is there one on the mx3 id imagine so. any signs of wear on it? and has neone done this b4 that could just allow me to kno what to expect as it looks like i will be doing this this weekend and if i get no info, ill just do the rocker cover gasket and inspect the timing belt.

[torpedan]

Yes there is a tensioner. ITs best to purchase a whole kit and replace them as well. The whole timing assembly-- belt, tensioners, and water pump, are all developed with the same lifespan in mind. So when one is going to go, the others are likly about to as well.

[Josh]

you cant run stock Miata cams!

they are different lift and duration from exhaust to intake side. exhaust is always bigger when it comes to stock cams. you can only do the swap if they are the same lift and duration, almost all aftermarket cam sets are same lift and duration for ex and in.

unless you got 2 Miata intake cams and cut off the distrib notch off of one of them. BUT you might actually loos alittle, due to the smaller lift and duration, so your best bet is to get aftermarket cams. or go and get another Exhaust side B6DE (MX3 DOHC) cam and cut the end off and put that in there. that way you taking in more air into the engine, more air more power. might not be much but its something. maybe 5hp increase.

[mzdamx3rsdohc]

that doesnt sound right. i thought i read that the exhaust miata cam went on the intake cams spot on the mx3 and vice versa

[torpedan]

that doesnt sound right. i thought i read that the exhaust miata cam went on the intake cams spot on the mx3 and vice versa

funny you should mention that


http://www.mx-3.com/phpbb2/viewtopic.php?t=16307

[Josh]

^^^

ha ha Thanks

like i said, its easier and you will make more power if you just go get another MX3 DOHC Exhaust cam, and cut the toothed distributor portion off, and swap that into your intake side of your DE motor. that way you only have one cam to play with, when it comes to timming. and you will make more power. probably somewhere around 5 to 7 WHP if you have like intake and exhaust.

[JWMotorsports]

If you are using nitrous you'll see more power with a larger exhaust cam. You can also use this combo on turbo cars and it can be a nasty setup with adjustable cam gears. The reason is because the exhaust volume becomes much much larger and hotter than on NA engines. NA engines like similar size cams with a bit larger duration than Forced Induction engines as you don't have as large of a pressure wave reverberating back at un real speeds like forced induction cars. If you run to much overlap on Forced Induction engines you'll actually lose cyl. pressure due to the really large pressure wave generated. The only time large duration cams are good for anything are when your reving the engine to 10,000+rpms with short Intake runners or ITBs. Forced engines perform best of short to mild duration cams with the most lift physically possible. See the HKS 2JZ-GTE cam comparrison dyno charts. The 264 duration cams walk all over the other cams in nearly every rpm range from about 3,000rpms to upwareds of 8,000rpms. The 272 duration cams as you can see from the dyno suck compared to the other cams until about 8,000+rpms! The runs were at only 1.05 kg/cm2 of boost (15psi) in which it appears the turbo was running out of compressor efficiency...other wise the power wouldn't have fell off at the top end. It would have peaked and gradually increase, with the exception of the 272 cam would have started out running the other cams at 8,000+rpms.

http://www.hksusa.com/images_products/1440.jpg
http://www.hksusa.com/images_products/1441.jpg
http://www.hksusa.com/products/?id=656

[Josh]

well from what i understand, by the manufactur of the cams i have, and the turbo guys iv talked to, and th eresearch iv done, that for Turbo motors you want more lift over duration, as the larger lift gives you power in the high end, and if you want power for the low end then you want a cam with more duration. just like in old school muscle, thats why they see 500 hp at 3000 RPM, its large duration. if you compair BPT cams to BP cams, the BPT cams have less duration and more lift than the N/A BP cams. becaus the turbo motors love the air in the top end when the turbo spools. there is a fine line when choosing cams for a turbo motor. they have to be just rite. like the cams i have, have to be 114deg from TDC and 114 deg BTDC on the exhaust side. n/A they are 112 deg. but still thats just a general rule of thumb for timming from the company. it could be more or less. but generally Big lift small duration is more of a turbo cam. if your going N/A and looking for some low end torque and power, then big lift isnt for you. all you do is push your power up in the RPM's

[JWMotorsports]

Large duration isn't good for low end torque. At slower rotational speeds large duration cams have HUGE overlap. Thats where the lope sound comes from on large V8's. During overlap you have massive intake charge contamination from the exhaust pulses reverberating back up into the cylinders. Not only does this reduce the oxygen content of the cylinder but it also reduces the cylinder pressure. This is enough to cause a car to fail emissions even with a cat. Slight overlap can be used to cool cyl temps via a small controlled amount of dilution. Large cam overlap doesn't idle well with stoich AFRs either, big V8s with large overlap have to idle as rich as 12:1 AFR to obtain smooth idle. Leaning further at idle casuses idle speed surging & hunting along with poor AFR control and stumbling. The faster you rev the engine, the smaller the overlap becomes. Overlap is basically timed like fuel injectors. The faster the engine revs the less time you have in milliseconds to inject the fuel...same principle with overlap which is largely contributed to by the cam duration. Some overlap can be made smaller via adjustable cams but it has its limits as I described before. The valve lift is what determines the low to mid end power. The further you open the valve, the larger the shot of air in that same time frame equating to increased torque & HP via faster cylinder fill. Duration adds power mostly at the top end of the rpm band. As you have less milliseconds to inject a shot of air the duration increases the time frame in milliseconds by holding the valve open longer.

Yes, short to mild duration with large lift for Forced Induction.
For NA cars you want large duration for peak power but you also want large lift. Both of which I mentioned previously. Additionaly, the duration purtains mostly to the RPM range your targeting your powerband for. Thats why V8 guys like to rev the NA engines so much higher. The higher you can rev the engine the more cam duration you can get away with. It also increases the volumetric efficiency of the engine as piston speeds increase.

The size of the valves are also something helpful, more so in Forced Induction because NA engines can lose port velocity if to large of a valve is used. Forced Induction cars love large valves...unless your using a really laggy turbo and trying to make really big torque at really low rpms, then you want to use valves more along the lines of a NA car.