Streetport 12a with stock nikki, any point?
 

If I were to give my 12a a mild streetport (on both intake and exhaust) but retain my nikki and racing beat exhaust (the one that will accomodate a cat) will I see any improvement? I have emissions testing to worry about thats why I ask.

Yes. Keep in mind a streetport is only 10-20% more power - Max.

yes about 10hp more peak power but a slight reduction below 3000rpm, but with the significant cost of having a streetport done it would be far better if you had the Nikki modified. You would then have some 30-40hp

ok 10-20% using an aftermarket intake setup right? What kind of gains would I see with my stock carb? only a few hp at most I would guess.

would a modded nikki still pass smog?

A Nikki moddified to match a mild streetport will pass. With larger porting and more flow requirements, then the mods required may give you problems.

But you will have the same problem with any performance carb. At this point you can go efi at more cost and get up to 225fwhp and pass smog.

Yea thats what I figured. Ideally I'd like to go with a N/A FC engine and retain the EFI, but money is tight, and I have 2 spare 12a's, both have issues, but could be combined to make one useable engine. Guess I'll have to give this more thought.

I know that this is slightly off topic, but what kind of gains would I get from a moddified nikki on a stockported 12A? Would this be able to pass emissions?

With a stockport adding a good exhaust system and a modified Nikki should achieve about 145-150fwhp and still be legal. This set up gives a significant improvement across the whole powercurve.

Going for a mild street port and more mods to the Nikki will get you up to around 180fwhp. However, the power curve is tilted dropping off at the bottom end. In fact the streetport will have less power under about 3500rpm compared with the improved stockport. It only comes into its own if you normally use the top end of the 3000-5000 rev range.

Not so sure about that. It's the lack of cats in the exhaust that'll keep you from being legal. You won't get the full potential power with a restrictive exhaust

I suggest that you get rid of your nikki carb and go with EFI if you plan on doing any hard cornering. On corners the nikki has a tendancy to hickup and your car just doesn't get the right mixture. Plus their really finiky and hard to keep set.

On a stock Nikki due to its design there can be a problem on a flatout left hand turn while racing using high revs. However, this does not occur on a modified Nikki with a a baffle mod to overcome this limitation . Search on Sterling's posts for a detailed response.

The Nikki is easier and requires less equipment than efi to set up. The conversion of a 12A to efi is very difficult to justify in cost terms.

Lee Lyons- I fully agree with your viewson another thread when you said after looking at efi you would stick to carb due to cost as it would take a 100 years to pay off the debt.

I also looked at the option and it came in around US$3000, but then rates of pay in Canada must be low as I know costs are high having a son at uni in Montreal!

ya I just I was thinking of going with a modified nikki but I talked to my dad first hes an excellent mechanic ands always tellin me about his 67 firbird with 625hp. but ya as soon as I mentioned nikki carbs he was like theres a problem waiting to happen. hes been around cars his whole life so now I have to think about what carb I'm going to get now. but if I had the cash I go EFI but their just to damn expensive. I know that I've really had to rethink what carb I'm going to use now I don't want my rex to sputter and cough around a tight corner. pump money into your engine with bridgeporting and turbo then get a carb that coughs and chokes around corners, just doesn't make sense to me. but hey thats just me.

The problem is only on left hand bends taken at high g, and would be very rare on street tires on the street.

I drive fairly fast on windy rural roads with bends down to 25kph advisory keeping the power in the 4000-6000rpm range, I have never reached the g level to get fuel starvation. On a track you may reach it. But a fully modified Nikki overcomes this problem.

We are getting off the thread subject, but for bridgeport or turbo then you start looking at a Weber if you need large cfm flows beyond a Nikki.

ok so in order to see any kind of gains from a porting the carb will have to modded to accomodate the changes. I might scrap the idea of porting due to the fact that the torque curve moves up. The torque is already a bit too little, I wouldn't want any less down low. I'll have to rethink this project a bit.

I would suggest modifying the Nikki as a first step as this would match the RB exhaust. It would improve power and torque across the powerband for a relatively low price. The cost of cutting the port is about the same but is small compared with stripping down the engine and installing the rebuild kit needed in porting.