L28 - Bigger Valves?

[TheCrazySwede]

Dear Forums,

I'm currently rebuilding a stock L28. I was looking at the DSI Big Valves ($408) but was questioning myself whether or not it's worth it. http://datsunspirit....=dsi-big-valves

The Intake is 1mm larger, and the exhaust is 1.5mm larger. Looking at my own head, I noticed that the stock valves are already pretty large, and was wondering if bigger valves are worth the extra dough and if they are safe. Also, on that website, it states that the valves are longer. What would I have to change to accommodate for the extra bit of length? I'm planning on running a higher lift cam, but it's still a mild cam and not some crazy .560 racing cam.

What are your thoughts on this?

Cheers!

[madkaw]

That 400$ can be better spent. I doubt you are going to build a motor that would require more breathing than what the stock valves offer. Spend the 400$ at rebello porting the head

[73str86]

There are other companies which sell oversize stainless steel valves in the $180-220 per set range. Which head are you using? As much money as I spent on getting my E88 ported, I didn't want to skimp and figured I might as well go for stainless/oversize valves.

[Diseazd]

Good question CrazySwede......If the valve is longer, how do you compensate for the longer valve? With the P79/P90 head, when you shave the head .080 inches, you shim the the valve springs .080, the cam towers .080 and use the early L28 valves which are .080 inches longer. Therefore, the distance between crank sprocket and cam sprocket remain the same as stock....in other words, the engine remains at stock geometry in regards to the valve train and chain distance. With the DSI longer valve, if you shim the valve spring, without shimming the cam towers, wouldn't you throw the geometry of the valve train haywire? And, if you shimmed the cam towers, wouldn't you screw up the chain distance, unless you shaved the head by that much more? No doubt that the longer valve would be a big help for retainer to valve seal clearance on higher lift cams and bigger and lighter is definitely a plus.

Edited April 18, 2014 by Diseazd

[TheCrazySwede]

I'm glad to see you here, Diseazd, because if I remember correctly, you got your motor touched up by DSI.

Things that I'm planning on my rebuild are mostly Cam (Including rockers, retainers, springs), new pistons and proper balancing (within 0.5 grams) I wanted to get the Kamaeri pistons (Pardon me if I miss-spelled that) that weight 160 grams lighter than stock, but I would like to keep the stock 86mm size.

Could I expect a powerful L28 without a turbo or a stroker while keeping the bore the same? What are your guy's thoughts on the subject?

Here are the current valves. The car had a broken head gasket, so there's a bit of coolant and oil running amok.

Here are the dished pistons, that will get replaced.

Edited April 18, 2014 by TheCrazySwede
Added photos

[TheCrazySwede]

There are other companies which sell oversize stainless steel valves in the $180-220 per set range. Which head are you using? As much money as I spent on getting my E88 ported, I didn't want to skimp and figured I might as well go for stainless/oversize valves.

I'm using a N42 head. I didn't really have any desire to port my head, unless it became necessary. I would like to reach a 200HP number, although power is not really my goal. Instead, it's how it delivers the power. My current 280z has EFI, but the L28 I'm rebuilding is carbed. Triple Weber setup, lightweight flywheel and propshaft, along with a 5-Speed tranny and a diff upgrade already satisfies my needs. If I could dish out a little more juice out of the powertrain, I would love that, but I don't want to go out of my way to do it.

[Diseazd]

http://www.classiczcars.com/forums/engine-drivetrain-s30/34448-new-l-28-my-72-a.html

Pretty much explains what I do Crazy......plenty of power....lots of fun!