Hey guys, not sure how to navigate the forum as im brand new. But I have questions. I’ve got a 98 ex coupe with a stock y8. Im planning to a vitara build but im unsure what im up against. Any input and advice would be appreciated. Im ready to order the Speedfactory no notch rods and vitara pistons, but should I build the head as well? What do I need to do in order to put down as close to 400hp as possible?

 

400whp is a lot to ask for from a single cam but no impossible. If that's what you're actually shooting for, your best bet would be to work with whomever you've chosen locally for tuning.

Also, why 400hp in particular? Boosted single cams making 250 realistic and reliable WHP are very quick. 400 on a single cam becomes unusable and, without properly building the motor, unreliable.

Headwork? With the head off, that's a good time to do it. At the very least a quick port-match, freshen up the valve seats, new valves, guides, seals, springs, and mild turbo cam will be necessary if you actually want 400hp.

What turbo are you planning to run? 400hp on a Y8 will require a fairly large compressor to be efficient enough on boost to make that kind of power, effectively making your power band narrow and peaky and more or less terrible for street driving.

What's your plan for fueling, engine management, and tuning?

 

I’d be happy with less than 400whp. Just want the most reliable, streetable, power I can make without going crazy expensive. I’m not sure about fuel yet, my last turbo car was running the walboro255 and dsm injectors, and turned on chrome. But those areas along with the valves, springs, retainers, and cam if needed are actually where I need most advice. If I don’t need it, I don’t want to buy it, but if the part is needed, I’m completely ok with buying it.

 

Sure, that makes sense. No sense spending where you don't need it.

It's been a very long time (17 years ish) since I worked with SOHC turbos, but from my memory hitting anything over 250-275whp on a stock head and relatively stock block with low compression Vitara pistons would've required a lot more boost which starts to get diminishing returns when trying to push more boost/air through a restrictive head. This would also make for a pretty laggy powerband that could make big (relatively) peak power but only at the very end of the curve. Ultimately, what I'm saying is you'd be better off shooting for a smaller whp number with a smaller compressor on a stock head to retain drivability or spend the money for decent headwork (flow) where you could get more power throughout a more usable range.

You could also look at doing this in steps. D-series heads in a relatively uncluttered engine bay should take no more than half-hour to hour to remove so getting the car up and running and tuned with your Vitara pistons and rods. Start with a stock head and tuning and see where you're at. If you still want more power after that, then pull the head, send if off for some flow work, then put it back on and retune.

 

Thanks, I have decided to move forward with the bc valves, springs, and turbo cam. I’ve gotten a lot of back and forth on using the stock retainers or the bc retainers. But I’m certainly going to go ahead with the valves, springs, and cam. What should I use to tune it on? Or should I contact a local tuner and see what they prefer?

 

Stock retainers and keepers are fine, but I would confirm with BC that they're compatible with their springs. Otherwise, the BC springs/ti retainers package for $290 seems very reasonable, budget permitting. Most importantly with the head would be cleaning up the ports, bowls, valve seats, guides and seals, so if your budget is tight, do that before springs and retainers.

For tuning, definitely check with your local (trusted) tuner and see what they're familiar with and what fits your budget.

 

My budget is definitely tight, but I’d rather bite the bullet on round 1, rather then have my feelings hurt on dyno day with low hp #’s, or have them hurt with something I cheaped out on durning the build letting go and having to go round 2. So I’ll definitely check on those bc retainers and make some calls to the tuner for his preferences. Thanks again, and any advice you may have for me as well, I’m open.

 

Yup. Nothing more expensive than going cheap in this game.

Definitely find a good tuner even if you have to travel a bit for them. They should be able to get you on the right path for what you want.

Only thing I would note from your expectations and your list is perhaps looking to pistons with a bit more compression than the Suzuki pistons. If I recall correctly, those Vitara pistons in a y8 make something like 8:1 compression, if that. That was good for us back in the 90s/early2000s when tuning was still very crude and we needed a wide margin of error. These days, however, a good tuner working with with a good turbo and solid bottom end can reliably tune a D16 turbo with quite a bit more static compression that than ... say 9.8-10.2:1, which wold net you more power and a much more linear power curve. Not a requirement, but something to think about.