Valvetrain Questions

[Phax]

Guys,

I'm going to be doing an SR20 swap in the next 6 months. Per someone else's suggestion, I've reposted part of a question that I put up in general. I look forward to any of your insights. Thanks.

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Engine:

I've read enough to know to get the front clip. I'm going to try to find an S13 with the high-port head. My initial goal is approx. 300whp. Before the engine goes into the car, I'm going to do the clutch and lighten the flywheel, have the head pulled off for a metal gasket, and to inspect the pistons. While the head is off, I'm considering some cams (HKS and Toda both seem to make a set with around 264 degrees of duration), adjustable sprockets, and upgraded valve springs. So, two questions.

A local where I live at who has done some SR swaps, says that the engine will spin to 9k all day long with an upgraded valve train. True?

How many horsepower are cams and sprockets generally worth? Of course that's dependent on a lot of things like turbo sizing and what not. I'm not going to be running anymore than 1 bar for a while. This car is going to be a street car, that I can hopefully go spank some M3's and Audi's at the track with.

[Tai Mai Shu]

Oi... when ricers invade nissan, not a good thing...at 9k your engine will be making crap power, so why even put your car threw that? why?

[Phax]

Oi... when ricers invade nissan, not a good thing...at 9k your engine will be making crap power, so why even put your car threw that? why?

What do high RPMs have to do with rice? Other than VTEC kicking in at high RPMs? I guess F1 cars are kinda rice like following that train of thought. Those things spin to ~15000 RPMs all the time. I think the word you were trying to use is through, as in... we came through the spot.

What will cause the engine to be making crap power at high RPMs? Will the longer duration cams be flowing too much? Will the 14 pounds of boost not be enough pressure to carry up to those high RPMs?

Tai, thanks for the thought provoking questions bro.

You know, I try to be mellow, especially in public forums. And although the following might make me look like a prick, to the very people I'd like answers from... yet, it's gotta be said.

Go F*** yourself with that lame a** ricer comment. Where the f*** did that come from?! I'm trading my 71 Datsun 510 project for a 240SX project. I drive a 5-Series BMW during the week. I care less about quarter mile and 0-60 times, and lots about suspension setups and weight reduction.

[lucky]

The question is....will your car still make power at 9k rpms? There is no point to spin your motor that high if you aren't making power. It won't happen on a stock turbo...that's for sure. Cam sizes really depend on what you want out of the car....if you are putting a smaller turbo on the car, use 264 cams at the most. I'll be conservative and say you could get 35 - 50 HP out of cams but that depends on alot of variables. Stick with stock cams if you are running the stock turbo and spend the money elsewhere. I would recommend getting some titanium retainers and rocker arm stoppers while you have the head off.

edit: if you really want to go all out, get some over-sized valves and have the head ported and polished.

[Phax]

The question is....will your car still make power at 9k rpms? There is no point to spin your motor that high if you aren't making power. It won't happen on a stock turbo...that's for sure. Cam sizes really depend on what you want out of the car....if you are putting a smaller turbo on the car, use 264 cams at the most.

I'm doing the buildup in stages, and one of the main considerations I'm putting into it is how often am I going to have to open the motor? I want to get the motor internals fortified before it goes into the car. From what I've read, the stock bottom end should take ~400chp, and I'm only looking to make ~300-350whp.

I guess the question I should ask is, will doing the cams and springs significantly hamper stock turbo driveability, for the 6-12 months that I'll be running on the stock turbo?

Quote »... I would recommend getting some titanium retainers and rocker arm stoppers while you have the head off.[/quote]

Those help hold more boost, right? Do the stock retainers and rockers start to have problems around 1 bar or so? Or maybe up at high speeds, like 7k+?

Quote »edit: if you really want to go all out, get some over-sized valves and have the head ported and polished. [/quote]I'm only looking to make 300-350whp. At what sort of hp / tq numbers, does head flow start to become a problem?

[Ace]

There are plenty of parts you can purchase before you should get cams. One idea is when you take off your head to put in the metal gasket, inspect the cylinder walls and the pistons. If they are in good shape then leave them alone. 300 hp won't hurt them. The rocker arm stopper is to keep the rocker arms in place when going into high rpms. You may want to put in strong valve springs if your going to put in cams. Titanium retainers are lighter and stronger then stock thats about all they do. I am rambling about a bunch of stuff, but basically do a metal head gasket, rocker arm stopper, possibly valve springs, and take the head to have at least a valve job done if you don't want it ported and polished. Then once you upgrade your turbo, and if that doesn't deliver enough power then get some cams. Camshafts are very easy to put in, and don't require you to take off the head to install them.

Camshafts kind of get annoying in everyday drivability. I had some in my Acura and they had some power, but it was a trade off with driveability.

[ItzGenX]

Cams cause bad idling probs for driveability and low RPMs because the driver chose the wrong duration for the application. Use 256 cams if it is mainly for street. 264 will have rougher idles and possibly bogs during low RPMs, even stalls.

[lucky]

You won't run into any flow problems with the amount of power you're looking for so porting and polishing isn't mandatory. You can gain decent power by doing this and you will also help spool up your turbo faster. If it was me, I would do the head gasket, springs, retainers cam gears, and rocker arm stoppers and save the cams until after you get your turbo upgrade. When properly installed and tuned, you can get a near perfect idle even with 272 cams....

[Phax]

Guys,

Thanks for all of the information on the various valve train parts. One common denominator seems to be the rocker arm stoppers. I did a search and in one thread, some guy was talking about using Tomei RAS.

What brand have you guys been using, and what influenced your decision to go with that manufacturer?

I'm glad that I'm not going to have to open the head too much, with valves and what not. It seems like it just needs to be fortified a bit, to prevent floating valves and all that sort of fun stuff.

What kind RPMs do you guys with RAS, springs and retainers spin your engines to?

[lucky]

From what I have seen, most of everyone uses the Tomei RAS. It seems to be a quality product. I couldn't tell you anything about the RPMs because I have no experience with this on the SR20 yet.

[I H8 UR DSM]

Its RPM a biiiiiiig pet peave of mine : ), especially when you hear mechanics say it wrong : )

rotation per minute's really doesnt make sense : )

[lucky]

Fine...I'll start saying it right...rpms...err...rpm. This is gonna take some getting used to : )

[I H8 UR DSM]

thank you : )

High Rev Tuners say "rpms" hehe

[DonDonati88]

I'm looking for about the same horse power range and may or may not upgrade to a bigger turbo. Prolly going to safely max out the t25 to about 300hp at the crank. Other than the basics, i/e/dp/fp/fmic, etc what mods do I need to get to a guaranteed 300hp on the stock t25. Would ecu be the next logical step?

[1bad180sx]

I have an HKS rocker arm stopper, is really a cheap little piece of sheet metal on each side, doesn't matter which one you get - just go for price. I rev my car to about 7800-7900 on it. I stop making power around there with my little exhaust housing.

Quote »Oi... when ricers invade nissan, not a good thing...at 9k your engine will be making crap power, so why even put your car threw that? why?[/quote]Well, at 300hp, 9000 RPM is useless. But while running a very big turbo and hi-lift cams, 9000 RPM does have a use. My turbo, if I put on a large enough exhaust housing, would be quite useful up into that range. Once you have turbo lag that lasts forever, its important to make use of whatever power band you have. Many racers in japan take their SR that high after installing a lash killer kit.

What you need is a set of Cams, Valve Springs, Lash Killer, and Rocker Stopper. Your valvetrain will take 9000 RPM bursts, but not all day as stated by someone else. 8500 is a bit safer.

I have already built an entire head with this setup, just need to put it on my car.

I will reccomend Tomei to you. They make very nice valvtrain parts, better than the HKS stuff I have already. They are also cheaper. As long as you have a source in the states, go with Tomei.

[BuudWeizErr]

I have the Tomei RAS and I was originally going to get the HKS setup, but Wayne said that the Tomei unit was a little better, and after hearing that the HKS is just a couple pieces of sheet metal, I'm glad I chose the Tomei. It's a pretty solid piece of metal, and it's not near "sheet metal," it's fairly thick, and it doesn't bend.

$.02++

[nissanrcer240]

so about how much would the RAS be? I dont plan on upgrading the turbo(at least not anytime soon), i just want a reliable daily driver for the most part, but i want speed for when i go to the track occasionaly. intake, exhaust, fmic, koyo radiator, upgraded clutch, down pipe, boost controller...this is of course after upgrading the fuel system, pump, filter ect..... so for daily driving purposes, kind of like 'insurance'...valve springs, rocker arm stoppers, and a metal head gasket would be good to put in when i do the swap to then? anything im missing that would be needed to insure reliabilty when i put the motor in?

you guys still have the cats on your cars? or did you eliminate them? or get a high flow? what do guys reccomend given my situation? thanks

Nick

[SpeedRacer1]

RAS would be fine for a daily driver, valve springs and a metal headgasket could be overkill depending on what type of driving you will be doing and the boost you will be pushing.

Most just buy a test pipe. I have a gutted cat and a high flow. Dont let the name fool you, they dont flow more air, they are just cheap alternatives and some have larger piping.

[Onizuka]

I'm looking for about the same horse power range and may or may not upgrade to a bigger turbo. Prolly going to safely max out the t25 to about 300hp at the crank. Other than the basics, i/e/dp/fp/fmic, etc what mods do I need to get to a guaranteed 300hp on the stock t25. Would ecu be the next logical step?

Im sorry but there is no way in hell you will get even close to 300hp with the stock T25. It is tough to get that much out of a S15 T28.

About rocker arm stoppers, i got HKS Rocker arm stoppers for like 70 bucks or something, good deal.

[ItzGenX]

I have greddy ras, and it too is very good quality. It is thick and very hard to bend. I've seen the HKS one. I wouldn't call it sheet metal, but it is very close to it.