Tomei valve springs

[kunsx]

Hello Iam building my engine up again after I had to get a new crankshaft with new bearings. Working on my head at the moment. Bought Tomei valve springs and will install exhaust cam on the intake side and adjustble camgears. Iam not an expert so I have to ask about the springs. I see the Tomei springs is a bit shorter than the original ones,between 2-4mm shorter(I dont have them in front of me at the moment) but can I still install them or do I have to put in some shims under the springs?

Ronny, Arendal Norway

[nissangirl74]

I asked one of our CA moderators to check out your question. Good luck!

[themadscientist]

From the Tomei site.
http://www.tomei-p.co.jp/_2003web-catal ... pring.html

http://www.tomei-p.co.jp/_2003web-catal ... pring.html

Nothing listed about special retainers so they should be good. They are perhaps a harder spring to compress so are not as tall uncompressed. Do may sure to put the stock shims back in before dropping the springs in. The aluminum head need to be protected from the steel spring.

If you put the exhaust cam on the intake side, how are your exhaust valves going to open silly?





J/K, I did that to an RB20 with good results.

[float_6969]

They are shorter to allow for more lift before the coils bind. IIRC the stock springs bind around 9mm of lift. I don't think the Tomei springs bind until 11mm of lift. To achieve this, they use a much stiffer spring material with fewer coils, but with a shorter "resting" height.

[kunsx]

Thank You guys for the answers.

One of you asked about the opening of the intake valves with a exhaust cam: intake cam has a duration of 240 and 7.8 lift and the exhaust cam got 248 durtion and 8.5 lift. So I hope I will notice the difference

[themadscientist]

You will. As I said, I did the same thing on an RB and the power shift was very noticeable and I know some 4AG guys doing the same thing. That's where I got the idea back in, crap, 98'. Has it been that long?

[float_6969]

in '98, i was 17 yrs. old and unless that cam had a vagina, I wasn't interested, lol!!!

[datso]

LOL - Cam-SHAFT you mean

Im stuck with using local spring manufacturer for 12mm lift and they reckon their single springs will do the job but I feel twins would be better?

[float_6969]

twin springs have more to do with dealing with spring resonance than overall lift. At certain RPM's there is a frequency that doesn't allow the spring to work properly and you can get valve float. The purpose of a dual spring is that they have 2 different resonant frequencies, and so you have less risk of valve float. This honestly isn't an issue with most modern spring materials and technologies and a single spring should be fine.

[datso]

yet dual springs would allow better distribution of forces thats for sure and still just sounds better we can even get triple spring for old A series yet its not easy to get twins for a ca18det yet the place that quoted me for singles only wants 170aud.

[tommey]

What about RB25 springs from supertech?
Cheap and should be good for 14mm lift.
Thats not something i know for a fact, just something i have heard.

[datso]

Yes with a supertech price, great quality though but you can make max power at just under 8500rpm maybe the extra 100grams of retainer weight wont be such a parasitic hp issue?