Of course I did NOT streetport the primaries. I feel diabolical1 missed the mark on that recommendation to you. No offense to him but he seems to sort of cruise all around the forum popping in here and there to offer advice. It's usually good but sometimes not so much. You know the old saying "jack of all trades master of none." He's sort of a jack of all trades over there. Him and that rxtacy guy. Great guys, very helpful, but sometimes incorrect like Racing Beat.
The rubbery low end of streetports? If they are all he's done over the past several years, then says he feels no difference from his streetports vs stock ports, how big are his streetports? Maybe really small, or super weak. When was the last time he drove stock ports?
Also you've gotta ask yourself who has done a half bridgeport recently? Who had awesome results? Who is just handing out armchair (or computer chair) advice? See what I mean? If you're gonna do streetports, there's a lot of advice out there. But if you're doing half bridgeports, and you seem genuinely interested in doing some, maybe follow my advice. I don't mean to sound conceited (or maybe I do). Results speak.
I've recently driven a full stockport with 12A turbo exhaust timing (we used 12AT housings so they were already ported from the factory). Then I drove a freshly built massive streetport 12A. Then the half bridge 12A with STOCK primary AND STOCK secondary port timing and mild ported exhaust. All three with Nikki carbs. The differences were very different, dramatic and very educational.
The fully stockport with 12AT exhaust timing was powerful in the low end and has plenty of high end too. Basically 4k comes up quick on the tach and you either upshift or punch it to open the secondaries and keep going. Nice, pleasant daily driver engine with some fun factor. Stock SA22C 30 pound flywheel by the way. Kinda heavy, but still usable. Some sort of header exhaust with a magnaflow out back.
The massive streetport 12A was the largest I had ever done. The exhaust ports were to the sleeves. This engine has a lot less low end. I wouldn't say rubbery. I'd say weak. It did get some great power up high toward 7k, though. Maybe not the best daily driver but it starts up quick and runs cool. This engine is destined to get a blow through turbo so its low end isn't much of an issue right now. It should improve a lot with a turbo. Stock 83-85 27 pound flywheel helps while NA especially.
Lastly the half BP.
I had something to prove with this. I wanted to prove BDC and peejay wrong and run an aluminum flywheel and still have great launching and driveability. They, or rather BDC recommends running a stock flywheel to help with launches possibly because the tiny bridges you're forced to do on 86+ engines suck, or maybe just HIS engines suck? Don't know.
All I know is you can do really big bridgeports on 85 and older engines, so that's what I did.
What were the results? Better than expected. The aluminum flywheel was just fine. It only had a little bit of brap at low load and low RPM, like around 2k, which stock carbed rotaries also get. The idle was right at 1100 which is fine as that's where my supercharged camden engines idle with an edelbrock. Plus the videos of half bridgeports I've seen all seem to have a slightly elevated idle with a little bit of brap as well. Perfect! The launching, even though it had the lightest flywheel I could get at only 7.5 pounds by itself, was better than expected. It didn't seem to lose any low end, infact had way more than the large streetport with its stock flywheel! This half BP is far more rewarding to drive! You get to have your cake (low end power) and eat it too (high end power), for free (no boost required)! How can you refuse that kind of awesomeness?
I could not compare apples to apples directly with the stock ported 12A above, as it had a stock flywheel and the half BP had aluminum, but I can tell you its launching would probably be about the same, then take it up to 4k, pop open the mechanical secondaries and hang on! Way more noticeable usable power than the stockport with its heavy flywheel. The aluminum really affected things in a positive way. Very few downsides.
I guess there was one downside. A slightly richer idle had to be tuned for the half BP to be happy. It caused the spark plugs to become slightly blackened with carbon after only four heat cycles. Oh they worked fine; it just made them darker more quickly than I was expecting. A good direct fire ignition like DLIDFIS would help a lot here I suspect. Also the engine took a few seconds of cranking to start. I suspect this will improve over time as it breaks in. j9fd3s said his P-port used to take a while to start until it broke in. Fare enough. Also the rotor housings of the half BP had some missing chrome. The engine ran fine before it was torn down so I knew they'd be fine to reuse if I got some new atkins apex seals. Who knows, it may have acted EXACTLY the same way even if it wasn't bridged, you know due to the worn rotor housings during its first few starts. Seems logical. You also can't get 12A housings anymore so you gotta reuse when you can.
Anyway I hope this has been educational and answered some questions you didn't know you had.
As for you specific questions, stock port timing on all four intake ports. Cleaned and smoothed castings. Bridgeports similar to group B spec on secondaries only. Exhaust ports ported up 3-5mm and 2mm bevel redone (can't remember exactly how high I went but maybe it's mentioned in the thread). Timing was leading at TDC. Trailing was 10 degrees after. So basically stock with a ten degree split. The Nikki was rejetted to work on a separate runner manifold. That means the large difference in size from primary to secondary jets was reduced. So from 92 to 94 primary. The secondary went from 160 to 150, but then I went to 170 because the secondary runners breath so much more now. I also reduced the size of the secondary air bleeds to keep feeding fuel up to a higher CFM (RPM) than stock. So it went from 140 to 120. Try to translate this over to your Holley if possible. Good luck. Oh and keep your runners separated! Secondaries must not ever communicate with primaries, ever! That's the key to a successful half bridge that nobody talks about. Well, trochoid kinda touched on it, but he was using dual carbs so it's not entirely applicable.
Gonna start a half BP thread like I did?