DOHC vs SOHC PnP w/reground cams

[BAC5.2]

Oh, I didn't know it was about a particular turbo.

This was a Forced Performance 18G, with a high-flow cat, 2.5" axleback, pump gas, top mount, and that was mostly it.

It was on TurboXS's Dynapak. That thing pulled like a motherfucker. It was sick. In the rain, it broke loose in 3rd... from a roll. Just roll into it in 3rd, and it'd light em up.

[Matt Monson]

272 duration cams seems like too much overlap for a turbo car to me. Maybe the issue is the duration in that case, as only at high rpm would would that be beneficial at all and would really kill the bottom end with boost blowing partially out the exhaust. Higher lift might be beneficial all around, but then you're going to need some real beef top end components for high rpm.

That was Mark's conclusion as well, even though there are a bunch of buys on NASIOC running those cams in their WRX's. Those cams now reside in Mark's high revving NA Ej25. It's a total kick to drive. It's got nothing until about 4000rpm, and then it's like V-tec as you come onto the cam and rocket up to 7500 and shift to drop right back onto the sweetspot.

[Matt Monson]

Oh, I didn't know it was about a particular turbo.

This was a Forced Performance 18G, with a high-flow cat, 2.5" axleback, pump gas, top mount, and that was mostly it.

It was on TurboXS's Dynapak. That thing pulled like a motherfucker. It was sick. In the rain, it broke loose in 3rd... from a roll. Just roll into it in 3rd, and it'd light em up.

The overall discussion wasn't, but I was answering the thread starter's question about his expected power levels with the parts he had chosen to use...

[Splinter]

Im conflicted again...

Turns out the performance shop where Im sourcing a lot of my parts has quite a skilled machinist

He says it'd be a hell of a lot cheaper for him to work the 2.5RS head plumbing than for me to get the 2.2 heads PnP'd

[free5ty1e]

That's an interesting trade-off to note.

This thread has some great info.

[Matt Monson]

Im conflicted again...

Turns out the performance shop where Im sourcing a lot of my parts has quite a skilled machinist

He says it'd be a hell of a lot cheaper for him to work the 2.5RS head plumbing than for me to get the 2.2 heads PnP'd

Generally is. Something many people don't realize is that there are castings on the backside of the DOHC Ej25 heads for the coolant and oil plumbing. They just need to be drilled out and tapped. They were cast as if they were turbo heads. You could do this conversion with all factory parts...

[mikec]

So much to think about... This is making me reconsider the plan to stick V3 heads on my turbo block later this year.

[Matt Monson]

So much to think about... This is making me reconsider the plan to stick V3 heads on my turbo block later this year.

Why, v3 heads flow a bit better than the Ej25 DOHC heads and require no machine work to make them work. They would even have the pumbing for an under-manifold straight through inlet...

[mikec]

Why, v3 heads flow a bit better than the Ej25 DOHC heads and require no machine work to make them work. They would even have the pumbing for an under-manifold straight through inlet...

True

[Splinter]

What about using an impreza 2.5 crank shaft to stroke it to 2.3

worth it?

[Splinter]

Also, if I switch to RS 2.5 heads, would I need to switch to the RS manifold, and if I do, is the TB in the same place? I want to plumb my front mount before I do the engine work if possible.

[Matt Monson]

I don't think the crank is worht it unless you are re-doing your bottom end to start with.

As far as the manifold, you will need a different manifold and the TB is in a slightly different place...