garagemahal76

ok, brief background to get you on the same page.

83 gsl
presumed stock port 12a
stripped nikki w/tunneled 80 manifold
fresh OG ignition parts and timing never touched since I have had it
rat's nest deleted including all emissions parts

here's my setup. it was cheap, easy to weld up, and has a nice deep tone.

pacesetter header - used
hollowed out cat
2 1/4" in/out
2 1/4" 24" total length glass pack (yeah I know)
reused pipe from old setup not stock, say 2 1/2" over axle area
into DC sports stainless fart cannon.

did a lot of mods all at once - rookie mistake. still have to mod my mechanical secondary link to go full tilt - the small spring I added wont stay put or loses tensile strength upon heating up to full engine bay temps. accelerator pump arm lengthened and tuned. comes on smooth, idles smooth, fires up quick, no backfires or popping upon coast down or engine braking down hills.

primary main jet taken up from 90 to 91 via stock jets out of spare carb. all other internals are stock but rebuilt on carb. venturis stock but booster "arm" cut off the supporting sides and castings smoothed out.

car doesn't seem to pull much from 4k rpms up, aftermarket fuel pump is 42 GPH at 2-3.5 PSI but only has the cohones right now before relaying power to it to get my pressure up to 2.5 psi. float levels need tuned, front is just below middle and rear is just about full - been fighting flooding issues since my noob *** made the mistake of capping off the vent fitting, and walnut shell remnants still in line from the blasting I gave it. really think from what I have read that it's too small a pump. does not starve it but i'm sure bowl height makes a big matter in tuning.

I am attributing the lack of low end grunt ( used to chirp tires grabbing gears) and really the lack of top end power too, to maybe this TOO LARGE of an exhaust. I am going to run better grounds from alt to irons to housings and daisy chain a good strap to ensure good grounds that might not be perfect due to corrosion between parts. I'm just at wit's end with this time vampire. making new intake gasket this evening since the one I bought new is now not happy with me taking things off and bolting back on again and again during this carb journey.

just want the damn thing to accept nicer parts and give me more hosses.

sorry for the long winded post! just wanted to explore all avenues.

Cookboy

iTrader: (10)

It's not your exhaust. Of your secondaries are mechanical and as they should be, you should be able to look down the throats and see a beautiful spray of gasoline when they crack open. If you don't, get that straight. Then timing. Then...

Jeff20B

iTrader: (13)

There isn't really any corrosion between housings. You're looking in the wrong places for power or lack there of.

Long primary is the only way to make real NA power with stock or near stock ports (like 74 spec or even a streetport).
Hogged Nikki with mechanical secondaries is the only way to make power with a Nikki.
Free flow air filter and massaged but not port matched intake manifold are next. You need an anti-reversion lip, so keep it!
Fuel system should also be corrected along with the carb and manifold mods.
Direct fire ignition comes next.
What's after that? I'd say a light steel flywheel. If you go aluminum, be aware they're not as good on a daily driver; you end up fighting it too much. With the light steel, you don't.

After that, well, I'm fresh out of ideas.

garagemahal76

fixed the mech. secondary link, bent the tang in on the outside arm to take off with the inside arm that's linked to primary shaft. BOOM. fixed. cut out the stock air cleaner lid base to open up all around minus the strap areas for the lid. K&N filter added. engine sounds better and idles smoother with the 80 manifold. kept the ports the same @ the gasket. made a new gasket out of kerropak paper.

before the manifold swap I was not using the vacuum ports at the reusable base, I had to attach the dizzy vac (teed off ) to the port above the air mix screw for strong vacuum signal. this made some headway but its STILL not pulling as hard as it did with stock manifold and small pipe. going to take the noisy **** off and weld on a chambered muffler where the ***-pack is right now. it's like I dropped a seal or some **** but I am getting 60 psi on all faces.

Samito Built

iTrader: (38)

60 psi doesn't sound like a healthy motor. I can assure the exhaust modification would not take power away.

garagemahal76

i'm going to bet it's a timing issue. like the mechanical advance isnt working or it's stuck, vacuum advance helped the idle and smoother starts but it acts like it runs outta oOMPH at 4k rpms

rotornoob

iTrader: (2)

Timing may be off, but if hes only showing 60psi on all faces, then he needs a rebuild or a new engine. It should be around 90psi on all faces iirc. Timing dont mean jack if the compression isnt there...

peejay

I just ran 13.69 on an engine that has no compression on two faces of the rear rotor when cranking...

2 1/4 isn't too big but it is not necessary. If you didn't port the collector of the header, it is choking power compared to a stock exhaust manifold. (Tests have shown a 10% power drop compared to the box manifold)

Mechanical secondaries is a poor modification. There is also no need for it, all you need to do is remove the spring and the secondaries will open as necessary.

LizardFC

iTrader: (1)

I ran a 2.5" exhaust with nothing but a magnaflow behind it and didn't have that issue. I think your main problem is a lack of data. You need to invest in a wideband 02 and a timing gun. I'd go as far to say that most mods are useless without at least the wideband. Also with those mods you probably need to rejet. .90 to .91 is inconsequential, and if it's falling flat above 4k then your secondaries probably need more fuel. Although you won't know this for sure until you get... wait for it... a wideband!

60 PSI on all faces... what were the readings on the other rotor? If it's low for both, it might be testing issues - throttle not open all the way, weak battery/starter.

peejay

Falling flat over 4k is also a symptom of fuel starvation from a weak pump or plugged filter.

Pumps make flow, not pressure. Internally regulated pumps will be able to flow their rated volume at their internally regulated pressure. If the pump cannot make the regulator pressure even at no flow, then the pump is garbage and is the source of the problem.

I usually ran 1.5-2psi with a Nikki, but always with sufficient volume flow. Meaning a Holley Red that was regulated down to appropriate pressure. I never had to relaty the pump, either, the original wiring was more than sufficient.

LizardFC

iTrader: (1)

Holley Red with the regulator is a good choice. I had to rewire mine, it kept blowing fuses.

garagemahal76

well guys, it was timing. damn thing woke up and feels really good.

60 psi was with a standard compression gauge, carb was @ idle , just cranking it over, doubt the battery was totally up to snuff but it gave me an idea. all 6 faces reporting same psi.

runs like hell, pulls good, but doubt my fuel pump is going to keep up, @ only 42 gph but so far no starving I have seen, just a rear float that I keep needing to take lower and lower and still it fills the bowl up to the top. mech secondaries work fine, I can feel it in the pedal tension as well. will have to make some timing marks on the pulley to fine tune leading/trailing.

YES some proper instrumentation is in order for this car. hope to add all the usual suspects soon as well as a good wideband setup.

is it too overkill to use a rear view backup camera to monitor the fuel bowls in real time?

I can see a clutch job in the near future.....

taking the header and downpipe off to properly merge the tubes and install a chambered muffler in place of the cheap glass pack presilencer.

thank you all for your input, it's greatly appreciated.