Tomei Camshaft Selection

[davidricardo86]

I am in a little situation right now where im trying to figure out which camshaft profile im going to end up chosing. If anyones been following my buildup, youll know that im running 83mm CPs, balanced assembly, and stock rods and crank. Im building the head now and having trouble deciding on camshafts. I will be using Tomei springs and camshafts, rebuilt lifters, and oem guides and seats (if they are still within spec). If i can find a better deal on the springs, which i know some of you guys have, i would probably go with that unless its better to stick with the same manufacturer or cam/spring combo. Also i plan on a upgraded t25 -> t28 wheel conversion or buy a s14 t25. I just dont want to use the oem ca t25 because of efficiency. I want to use my 370cc injectors to start off. Then once i feel i am ok/confident enough to upgrade and increase hp, it will be done accordingly. I know its a preference thing and no one can choose for me but i wanted to hear some opinions on this and share some light on the subject.

Tomei Camshaft options:256 degree 8.5mm260 degree 8.8mm270 degree 8.8mm

The car's purpose is to be a weekend warior mostly, mostly concentrating on track-like racing, touge, highway, overall response and balance. Im not trying to build a race car, just a really mean street car with realiability in mind with the ocassional drag race here and there. Take into consideration this is my first engine buildup and i am rookie driver. This will be a learning process.

I was thinking 270 degree 8.8mm for intake and exhaust. I like the idea of my engine making hp past 6400rpm. Also torque will be higher in the band aswell but i want to be able to go to 8000rpm without a problem and actually make power. With this type of setup some torque will be sacraficed...

[float_6969]

IMHO, and I have no experience on this, is that the 270's would be a bit big for the T28. Also, it's generally thought that running a longer duration exhaust cam will help with the spool up.

I would either go with a 256° IN and a 260° EX, or a 260° IN and a 270° EX.

You are basically going to have a stock style powerband, only it will be moved up farther into the rev range, resulting in more power. As I said before though, to make power with the 270° cams, you'll need to rev the motor and that T28 may not like it. At least not at anything more than 14psi.

[davidricardo86]

You know i was worried about that. These are big cams and they will most likely not idle to well and loose too much low end that can be used on the streets/short tracks like my fav touges. I was reading some stuff on cams and got worried about the overlap these cams are going to produce in the low rpms. Maybe something like 256 IN and 260 EX would be more than enough highend for me because i wouldnt be sacrificing too much low end torque? Or even 256 IN & EX and adjust timing seperately starting with the exhaust side. I am going to be using adjustable cam gears.

I was reading that high rpm motors use a lot of overlap especially at the high end, thats how they make most of the power by having to rev higher. They recommended staying close to stock duration for turbocharged engines becuase of overlap and reversion. See i want to avoid that too. I dont want to be contaminating my fresh intake too much. Uh man im so confused, i think im going to purchase Dyno 2000 Engine Simulation and mess with some ideas.

[dattodude]

Tomei 270x8.8mm sound a little meaner, that's all. It does almost nothing to the idle, despite popular forum belief. I had some on my CA18, you really wouldn't know from the idle, that they were anything special.

I'll be putting a pair of 270x8.8 on ebay in the next couple of months. I'll be sure to get a shipping quote to both sides of the US, before I put them on. I'll definitely be undercutting the bozo with his HKS cams trying to screw everyone on price.

I've gone 270x9.25 with solid lifters. I am a bit nuts though.

[float_6969]

As datto dude said, you don't need to worry about the idle too much. None of those cams will effect it that much.

Also remember that the 256's from Tomei are already indexed. So if you were to run them as a pair, you wouldn't need cam gears.

Just some food for thought...

[bentvalves]

what do you mean if purchased as a set they are already indexed and wont need adjustable gears. Is that only with the 256's, please explain.

Greg

[Kouks]

they are set-up to work with each other, and do not require one to advance/retard the timing to fine tune them. Also, the lift of the cam, more so than the duration affects the idle.

I agree with float, 270 are too long duration for a t28. With a t28 i would go with a 260 IN/256 ex, spool up will already be fairly quick, and more midrange torque will be felt with your bigger intake cam. Fine tune them with cam gears.

[float_6969]

As Kouks said, when Tomei designed those cams, they already took the cam timing into account, so you don't need cam gears. That is ONLY on the 256° cams though, so you would have to use the 256° IN and EX cams as a pair. They're supposed to be a decent upgrade, give a wider powerband and not be too peaky. They are designed to be used with an upgraded turbo of somesort, from the info that I can gather, nothing major. A T28 would probabally work nicely with them.

And if that isn't a good enough description follow the link below and then click on "Poncam" at the top.http://www.tomei-p.co.jp/_2003....html

[r34 gtr]

the intake cam on the turbo CA is a little lower lift than the exhaust cam, right? i cant remember but i seem to remember 248/7.8 for the intake and 248/8.5 for the exhaust. just wondering (and dont by any means mean to thread jack). might help with the final decision. ive got a questionable intake cam in my engine and it has definitely affected the idle and torque curve. duration and lift? wish i knew.

[dattodude]

Quote »It is all based on the progress of technology when has not beer realized in the past.[/quote]I knew beer was important..

Interesting reading, but I doubt that with the precision at which a cam is ground, that only the poncams are ground to 0 degrees. This is explicitly said for the poncams, which are the 'user-install' cams of the tomei range. But this not being said for the procams makes it an assumption either way.

Actual Poncam link:http://www.tomei-p.co.jp/_2003....html

With such a relatively expensive investment, you need to think a little into the future. If a fella is so keen that he rebuilds his engine in his living room.. :-) I don't think it will be long before he finds himself upgrading the turbo.

The big advantage of the poncams is that you can sell them off to anyone else.

[davidricardo86]

Hahaha i saw the beer thing too...

Well it gives me confidence when you guys say that the idle wont be affected too much or atleast in anyway that it will hurt something. Also i am thinking about this in the long run aswell thats why i wanted something a little bit bigger. In the future, i will be upgrading the turbo(s), and increase fuel aswell but i want to start small and work my way up once i feel comfortable.

Hey dattodude, how were the 270 8.8mm cams? How did they feel compared to stock ones (if you've experienced stock ones)?

Kouks & Ryan, what are you guys using and what do you think of your current setup? From experience, what would you change? What would you leave alone?

I am 99% sure im going with Tomei cams, but i said i wanted to use my oem valves, retainers, and keepers (also guides & seats). I was also planning on using the Tomei uprated springs to go with the new cams. Im worried about valve float too. If i used stiffer springs, wouldnt there be a greater chance of floating if i used the oem valves (instead of lighter material valves)? Or i can obviously keep it to a safe limit and not go past xxxxrpm and be fine. From all the info ive read on the CA, i read somewhere that 7-8k rpm is safe on factory valvetrain, it just doesnt produce anymore power. I appologize if it seems like im not understanding this but the fact is thats it isnt so easy, plus its a lot of money and time spent.

[dattodude]

I can't tell you what they felt like too much, as I didn't dyno them. They felt better. As expected, they were maybe a little boggy down low, but with a 3.45 diff, it's expected to feel that way. It didn't affect the boost curve, and truthfully didn't feel much different. But with a full dyno tune, I'm sure they would have made use of my larger turbo (Garret equivalent GT2540). I'm looking for max power, not economy. I run an autronic, and am confident that the choppy idle will not be a problem.

Valve springs are needed for 6800+rpm. Lightweight valves..nah..total waste of cash while you are running hydraulic lifters.

With my engine, I've pretty much got a triple cheesburger meal upsized to the max.

I'm on the seach for 3.9 LSD tomorrow (ex-R31 skyline).

[bentvalves]

but wouldnt all camshafts be setup to work with each other?

A matching set of 256's, paired with adjustable cam gears, would not see any benefit in being able to advance/retard ignition timin? s15 t28, .020 bigger pistons, z32 maf, power fc etc.
Modified by ks13 at 8:41 AM 12/3/2006

[float_6969]

the intake cam on the turbo CA is a little lower lift than the exhaust cam, right? i cant remember but i seem to remember 248/7.8 for the intake and 248/8.5 for the exhaust. just wondering (and dont by any means mean to thread jack). might help with the final decision. ive got a questionable intake cam in my engine and it has definitely affected the idle and torque curve. duration and lift? wish i knew.

FAQ FTW Tim; IN 240° @ 7.8mmEX 248° @ 8.5mm

...Interesting reading, but I doubt that with the precision at which a cam is ground, that only the poncams are ground to 0 degrees. This is explicitly said for the poncams, which are the 'user-install' cams of the tomei range. But this not being said for the procams makes it an assumption either way....

I don't think they're saying that the Poncams are ground @ 0°. I think they're saying that they adjust the paired cams to have the optimal overlap with out the use of cam gears. Now what they have decided is "optimal" is probably geared twords good mid range, with decent top end, and mild loss in bottom end.

I think the Procams don't really have that taken into account as they assume that if you are going to purchase cams with 260/270° of duration (a considerable amount over stock), that you are building a powerful enough motor that you will be running cam gears and will be tuning the cams to your specific needs.

To index the cams (pre-set the overlap w/o the need of adjustable cam gears) they have to actually modify the placement of the dowl pin and bolt holes on the end of the cam. To figure out the best index, they would have had to ground a set of cams at 0°, put them on a CA w/cam gears, dyno the motor multiple times to find the optimal cam timing, and then grind all of the retail sets with the dowl pin and bolt holes moved to put this indexing in place already.

That's a lot of work and I don't think they would do that for what they would consider a "race" cam that you're probably going to put cam gears on and index anyway.

...Kouks & Ryan, what are you guys using and what do you think of your current setup? From experience, what would you change? What would you leave alone?

...I was also planning on using the Tomei uprated springs to go with the new cams. Im worried about valve float too. If i used stiffer springs, wouldnt there be a greater chance of floating if i used the oem valves (instead of lighter material valves)? Or i can obviously keep it to a safe limit and not go past xxxxrpm and be fine. From all the info ive read on the CA, i read somewhere that 7-8k rpm is safe on factory valvetrain, it just doesnt produce anymore power. I appologize if it seems like im not understanding this but the fact is thats it isnt so easy, plus its a lot of money and time spent.

I'm on stock cams right now, but I do plan on changing them. I kinda wish Dee was around right now to chime in as he's played with A LOT of different cam setups.

As for the stock springs, it depends on the cams that you end up using. I think the general concensus is that on the 256° and 260° cams you're fine with stock springs as long as the lift stays below 8.8mm.

As far as the actual valves are concerned, don't worry about it. They're fine for just about any power level.

The valvetrain in stock form is generally agreed to be good to 8K w/o problems. The only reason it doesn't make power up that high is because of the cams.

8K RPM is FAST. I know that Honda has got a 10K RPM redline on the old S2K's, but that is a 5yr old motor w/VTEC. Remember that even though this is an exceptional motor, it's still 20+year old technology. You can build a 10K RPM redline CA and have it make great power, but it won't be streetable.

but wouldnt all camshafts be setup to work with each other?

A matching set of 256's, paired with adjustable cam gears, would not see any benefit in being able to advance/retard ignition timin? s15 t28, .020 bigger pistons, z32 maf, power fc etc.

Modified by ks13 at 8:41 AM 12/3/2006

Were not talking about ignition timing. We're talking about cam timing, or "indexing" as I like to call it as it helps to reduce confusion. This is the actual timing of when the intake and exhaust cams open in relation to eachother and the crankshaft.

Indexing helps to decide where the motor will make power with a given set of cams.

[pnblight]

BUY TOMEI CAM WHEELSi am also building a couple of CA motors at the moment but my experience with RB26 poncams tells me there is a great deal of power and response to be had tuning cams properly on my rb26 we made over 100rwhp tuning the cams the overlap didn’t change a great deal but dialling them into the crank did and by advance the exhaust cam only 2deg (crank timing 1 deg cam timing) we were seeing 30rwhp at the top end. So the wheels aren’t there to run different timing so to speak but as much to adjust the differences between motors and get the same actual timing to the crank right.What mean is in mass production every component has tolerances and if you get motor with for example a tall block with tall head etc etc its cam timing (cams to crank) will be different to a motor with short block and short head etc etc. And there are many other component tolerance that affect this relationship (just giving a couple for example) and with 1 deg on cam rotation making a 30rwhp difference you can see it doesn't take much to make a difference. A 2mm thick aftermarket head gasket will affect the timing on its own.So i would most defiantly buy adjustable cam wheels you may gain a little or a lot but on ever motor i have tuned has responded to cam tuning.

As for selecting cams i have found tomei reference to cams for the turbo kits for the Rb26 very interesting as they use all the same duration cams but just adjust the lift for the hp requirements. They suggest 260deg inlet and exhaust with different lift levels .The 260deg poncams for the RB26 9.15mm lift(solid) have been very good street ability response and out right power makes the idle sound tuff without causing any items. the 260deg 8.8mm (lash) is very very close to the same lift (a the solids run a ~.4mm clearance and only actually lift 8.75mm) So personally i think you couldn't go wrong with the 260deg 8.8mm inlet and exhaust. I know the 270deg will make more power but you'll be losing street ability that’s why tomei don’t recommend anything over 260deg for street application

pete

[davidricardo86]

After all the opinions and information i got from here i think im going with 260 8.8mm and stiffer springs because i dont want to loose too much low-end (hopefully). I will be using adj. cam gears too, and lifters rebuilt w/ the help from Ryan. Hopefully this will hold up nicely with what i have going now and provides some good reliability.

[float_6969]

I still don't think you'll need the springs, but it certainly won't hurt! I should have those lifters tomorrow, right?

[pnblight]

i don't think you can go wrong with combo, good balance and covered your bases with spring and lifters.best of luck with itpete

After all the opinions and information i got from here i think im going with 260 8.8mm and stiffer springs because i dont want to loose too much low-end (hopefully). I will be using adj. cam gears too, and lifters rebuilt w/ the help from Ryan. Hopefully this will hold up nicely with what i have going now and provides some good reliability.

[dash]

a number of guys on sxoc saw a significant improvements installing ~260° intake cams only. I've read the testimonials.Old school u.s. cam grinders had more duration on their inlet than exhaust... and their turbo 4s were flyin' from way back then.

As far as revs, last 500hp turbo 1.6L 4ag owner/builder I spoke to ran 304° Toda? cams and shifted @ 10000+rpms on the street! 11k redline. Vtec that. Car featured on sdsefi.com project page.

[Kouks]

Yup I have read significant threads on this also, and when I got my CA, the owner had installed an HKS 256/8.5mm lift intake cam ONLY. Also HKS 1.2mm headgasket.

When I get my car dynoed,(which I was supposed to do a LONG time ago) you will be able to see my chart and compare for yourself. I wanna do a 272/264 combo or 270/260 tomei w/e, when I upgrade turboes and keep my intake cam bigger than exhaust.

Proper indexing is very key to a turbo DOHC 4 cyl especially being more "sensitive" in my opinion than larger motors as in old v8's of pushrod technology.

IMO, anything more than the 256/256 tomeis that float said, should be tuned properly with the cam gears.

[davidricardo86]

I still don't think you'll need the springs, but it certainly won't hurt! I should have those lifters tomorrow, right?

Yeah i probably really wont, but for my own peace of mind and me choosing these higher lift and longer dur. cams (260 8.8mm in/ex), i dont think they'll hurt either. I'd rather be safe then sorry you know. You should be getting the lifters today, so be on the look out for a UPS man. And ill be getting my Tomei adjustable cam gears today aswell. Oh YEEEAAH!

i don't think you can go wrong with combo, good balance and covered your bases with spring and lifters.best of luck with itpete

Thanks! As always i hope for the best and want to make wise and informative decisions.

a number of guys on sxoc saw a significant improvements installing ~260° intake cams only. I've read the testimonials.Old school u.s. cam grinders had more duration on their inlet than exhaust... and their turbo 4s were flyin' from way back then.As far as revs, last 500hp turbo 1.6L 4ag owner/builder I spoke to ran 304° Toda? cams and shifted @ 10000+rpms on the street! 11k redline. Vtec that. Car featured on sdsefi.com project page.

I thought about that, using a bigger cam on the intake side and knowing that it would give better low end grunt but if the stock cam is used on the exhaust youre still going to be loosing power at around 6400rpm arent you. So maybe upgrade both but keep the intake bigger than the exhaust.

500hp 1.6l 10k rpm 304 Toda cams 4age, man i assume it lags like a biotch? Must be scary to ride in that car once boost kicks in though. What car is it being used in? I assume its turbo'd because i havent heard of a 1.6l na putting that much. I could be wrong.

Yup I have read significant threads on this also, and when I got my CA, the owner had installed an HKS 256/8.5mm lift intake cam ONLY. Also HKS 1.2mm headgasket. When I get my car dynoed,(which I was supposed to do a LONG time ago) you will be able to see my chart and compare for yourself. I wanna do a 272/264 combo or 270/260 tomei w/e, when I upgrade turboes and keep my intake cam bigger than exhaust.

Proper indexing is very key to a turbo DOHC 4 cyl especially being more "sensitive" in my opinion than larger motors as in old v8's of pushrod technology.

IMO, anything more than the 256/256 tomeis that float said, should be tuned properly with the cam gears.

Do you have the dyno sheet of this? Id like to see. You should try out that combo so it could expose some info we might not know about right now. Oh and i will be "dialing in" timing w/ adj. cam gears.

[dash]

I honestly don't know the reasoning behind having more intake duration, but some experienced and sharp minds been practicing it for years, so there must be somethin to it. A dyno would surely reveal the difference, vs a 264/264.... maybe they've already seen it. For a street car, I personally would prefer boost and make torque as opposed to high peak hp and rpm.Bigtones outstanding 474 ft-lbs tq at flywheel td06/20g always stuck in my mind as the perfect ca18 street/strip monster.

http://www.sdsefi.com/features/jan064ag.htmyeah, that 4ag was nuts. He posted details of the buildup on club4ag. Amazing how relatively 'little' preparation resulted in those crazy revs and that the stock oil pump & crank survives it.You'd 'think' 304° cams wouldn't suit a boosted motor, but....... No 'quick spooling' turbo would allow that sorta powerband.Notice how veterans always luv their big turbos ?Anyway, they figured car would've hit 600hp if the tires didn't break traction on the dyno @8000rpm... even with three guys stuffed in the hatch!I'd liked to see the torque curve vs rpm.Interesting build nevertheless.A starlet gets that motor next. Frightening

[Kouks]

I havent gotten mine dynoed yet, mainly because i wanna make 250+whp before I do.