1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

4 port 13b crapped holley need some help

Old 04-12-19, 02:43 PM
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NJ 4 port 13b crapped holley need some help

First and foremost id like to thank any and everybit of info i can get, especailly Going over the MANY Holley threads.It was amazing and pretty much answered most of my questions and thought me much. I purchased this 4 port 13b(looks like 77/78 13b) and it basically had holly mani headers and muffler with a generic Holley 4160. both exhaust and intake ports on the engine look ported in comparison to the other 13b from my rx4. I have all the gaskets to rebuild this carb, I know if I want to change jets on my secondary I have to change my plate to a metering block from Holley PART# 34-13. I know if i don't want the stumble while turning ill need to change to center pivot float bowls and jet extension on both sides and perform a whole host of mod that ill deal with down the line I just need some help at starting. now the carb has a red(kind of cover in crap might be pink ill verify tonight)Accelerator pump cam with a 30cc diaphragm. I have pictures of everything to make my questions as precise as possible. i understand every engine is diffrent and theres no magic settings as everything has to be adjusted to that specific engine and elevation. im just looking for a good starting ground.

1: would my primary jets be a good starting point for this setup its currently at 58? I've seen many posts referencing 60+. but since my carbs body is from a 450cfm would this jetting be precise enough?
2. thinking of replacing my 2ndary(
major crack through it) with the conversion, so what would be a good starting point for 2ndary jets?? (...the plate on it now has the following numbers: stamped 9 at the middle, 34r-9716B there's a 7 stamped above the 6)
3. im looking at 400- 550 + on doing all of these mods, would something like holly 0-82651SA just be a better starting point as is it has everything i mentioned doing to this carb and is around 450ish new locally idk used but i fear 650cfm on might make the tuning illrelevant seeing as its huuuuge lol compared to my 450cfm holley. not sure jetting so far down is possible.





holly cast numbers are(see picture) : 9776
3457
which leads me to believe its:

CFM 450
Model 4160
Primary Main Jet 58
Primary Power Valve 8.5
Primary Pump Nozzle Size 31
Secondaries Mechanical
Throttle Bore 1.5
Part Number 0-9776

i have verified that the prim jet is 58, power valve is 8.5 and the secondary plate has a major crack through it

seller pics

seller pics 2

seller pics 3

seller pics 4

seller pics 5
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Old 04-12-19, 02:44 PM
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primary jets 1

primary jets 2

casting number
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Old 04-12-19, 02:45 PM
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Old 04-12-19, 02:52 PM
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Man, if you are going to spend that much money I would consider a different carb, maybe an Edlebrock which I've heard works pretty well with a rotary or a modified nikki.
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Old 04-12-19, 09:39 PM
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Tom,
I just did this on a RB 465 for my 12A, and hope to get it installed and adjusted this weekend. Basically converted the 4160 to a vac secondary 4150, with extended jets and new-style vent whistles to control slosh. Where do you live? I need a choke to start in the winter, otherwise I'd get their 390 HP.

For the 12A carb RB uses 49 or 50 primary jets, and blocks off the PV. I got mine used w/ 55 jets and it was waaayyyyy too lean on my stock 12A with header. I put 59's in the primary with a 9.5 PV, and 69's on the secondaries (no sec PV). PV transitions from cruise to full-enrichment before the secondaries come in (Edelbrock metering rods serve the same purpose). Rule of thumb is to pick a PV that is marked 1/2 of your idle vacuum. My vac is 19, so 9.5 PV is a good starting point. I will install tomorrow (hopefully) and adjust jetting from there.

Measure the runner openings on your manifold and compare to the bores of your carb. I have been running an Edelbrock AVS II 500cfm and the secondaries are larger than my manifold ports. Even without the electric choke I still need a spacer or else the secondary butterflies contact the manifold. Otherwise the Eddy is a nice, good looking, easy to tune carb. But this Holley 465 port-matches my intake about perfect, so I'm giving it another shot.





Last edited by Maxwedge; 04-13-19 at 08:53 AM. Reason: Re-read title.
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Old 04-13-19, 09:59 PM
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Tom,
I did a little research on that carb of yours. As you probably know it's made specifically for dual carb tunnel ram setups on V8's. The 450 size sounds good for your motor, but the fuel delivery on the secondary opening will give you problems.
There's no secondary pump, and no vac pot to time the secondary opening. The tunnel ram manifolds have an open plenum at the top, and these carbs rely on a large pumpshot and squirt nozzle on the primary to mix with the secondary air inside the open plenum, before blasting down the runners. Point being, on a RB type manifold there's no shared plenum space to mix in, so the primaries will be too rich and the secondaries too lean (for a moment). Perhaps the mix will mix together in the chamber, but I think you'll have to experiment with a large open spacer between the carb and manifold. I like the mods you speak of but the nature of your carb doesn't seem suited to an individual-runner manifold.

Also, here's a recent thread by serf2 on jetting an early 4-port 13B. Hope it helps -
https://www.rx7club.com/1st-generati...-info-1134204/


This is your carb and it's intended purpose.

Last edited by Maxwedge; 04-13-19 at 10:16 PM.
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Old 04-15-19, 10:07 AM
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Originally Posted by Maxwedge View Post
For the 12A carb RB uses 49 or 50 primary jets, and blocks off the PV. I got mine used w/ 55 jets and it was waaayyyyy too lean on my stock 12A with header. I put 59's in the primary with a 9.5 PV, and 69's on the secondaries (no sec PV). PV transitions from cruise to full-enrichment before the secondaries come in (Edelbrock metering rods serve the same purpose). Rule of thumb is to pick a PV that is marked 1/2 of your idle vacuum. My vac is 19, so 9.5 PV is a good starting point. I will install tomorrow (hopefully) and adjust jetting from there.
Scratch that. I blocked the Power Valve and went with a more conservative 58/59 jetting. Overall it runs really nice, reving smoothly up through the buzzer and seemlessly into the secondaries. Not as much initial power as with my Edelbrock, so i think I need to either go up a jet size or possibly a 50cc accelerator diaphragm (?). the Edelbrock took off best on the biggest pump shot. Only issue was once it got good and warm I started getting warm-start problems. The secondary bowl felt hot to the touch, and it was only about 70F outside. Time to look at heat shields.



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Old 04-16-19, 01:59 AM
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shield is not a bad idea.... always end up making one... best thing to do is make a large out side air intake. intake manifold gets heat soaked pretty quick good to use a insulator between the carb....this is the one i use . https://www.jegs.com/i/SCE+Gaskets/8...UaAuf5EALw_wcB
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Old 04-17-19, 08:02 AM
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You need a shield. It should be designed to bolt to the top two bolts of the header or bottom bolts of the intake and extend out perpendicular to the engine covering the headers as much as possible. This will help keep the whole carb and intake much cooler. RB has one but its easy to fab your own.

Intake Manifold/Header Heat Shield for RX7 1975-1985 - Racing Beat
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Old 04-17-19, 08:17 AM
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Thanks for the tips guys. RB Heat Shield, 1/4" pheonolic spacer and remaining parts to hook up A/F monitor should arrive by the weekend. Wife and son are away Fri till Sun, so I have nothing to do except wrench!
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Old 04-17-19, 04:25 PM
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i've tried two brands pheonolic spacer . warped both of them.. maybe because i'm boosting and makin more heat.. the one i mentioned is soft and hav plastic spacers only 4 corners of the gasket where the bolts are used
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Old 04-21-19, 07:55 AM
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What ever happened to OP Tom--? ???

Well my Holley is running great. I spent the day with a portable A/F meter on the tail pipe, running and adjusting both my Eddy and my Holley, improving both. I wasnt shooting for any particular A/F ratio. Just seeing where the car liked it.

The Eddy got better but couldn't compete with the smoothness of the Holley. I can't feel the secondaries come in at all it's so smooth, it just goes faster faster. I have a 1/4" pheonolic spacer under it and it helped a lot. The RB heatshield should be here Tuesday.

Current jetting is 56/59 but I'm going to try 60 in the secondaries today. The AF leans way out at high rpms and it scares me a little. It idles around 12.5 -13, cruises happily between 13.5-14.5, but hi-rpm WOT puts me in 16-18 territory. It's very strong there, but piston knowledge has me spooked by those numbers.

Yes, I know it's a rotary, not piston engine.

I'm going one step richer on secondaries and if it loses power I'll switch back. For a car that has seen 10 miles a week since I bought it last October, I ran through 2 tanks of gas last night, smiling all the way.
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Old 04-21-19, 11:55 AM
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Wow, glad to see the Holley is doing well. I've got an Eddy and a boost prepped Holley I'll be letting go of soon (the Holley is listed on the forum already). I was wondering how your setup will run if you achieve closer to 11 at WOT on either carb. Seeing anything leaner than 13 worries me because that is when you are wanting the most fuel. Did the Eddy do the lean thing at WOT as well?
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Old 04-21-19, 12:06 PM
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I don't remember now, but it stumbled and bogged, that is what I remember. Going to stiffer step-up springs helped, as did adjusting the AVS to come in later. I could probably get it to work but the Holley just responded better to adjustments. I'm still an Edelbrock guy, but the car is running great right now with the Holley.

Yeah high teens for the A/F ratio actually feels great, but scares me. I'm headed home now to change the oil in my Subie and change jets in the RX. Then get cleaned up for Easter dinner.

Happy Easter guys!
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Old 04-21-19, 12:11 PM
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My Eddy is a Performer series with the weighted donkey door and it can sometimes open and close in sustained WOT (just needs some steel drilled out of it a little at a time to lighten it up). I've not tried the AVS style so I can't comment on that but the Performer Eddy did seem to drive smooth with only the common glitch when you slow down and turn, like the Holley has. I'm surprised your Eddy has given you so much trouble.
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Old 04-21-19, 01:54 PM
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I have to get a shower and go to my in laws, but here's the carb timeline-
*Bought car with tired Nikki. Barely drove.
*Ordered a Nikki rebuild kit, then saw a used RB Holley/manifold for sale. Bought it.
*Holley ran WAAAYYYY too lean (see my avatar pic)
*Rebuilt Nikki. Stripped emissions bits and did Sterling Accel. Pump mod. Ran better, but I was NOT impressed.
*Put on Eddy AVS 500 and it ran AWESOME on primaries, but bogged on secondaries. Adjusted sec jets up and down, but couldn't find the happy place.
*Did a few rebuilds on the Holley, eventually converting to 4150 style bowls with jet and vent extensions (to counter cornering issues). Got an A/F meter to help tune, and it's running like a freaking scud missile.
*Changed back-and-forth between H and E this weekend. Worked on tuning both with the A/F meter, and the Holley just got better So much faster with minor tweeks. I had it on the turnpike last night and I can accelerate and pass people from a steady 80mph. ****, last week it could barely hit 60.

I may go back to the Eddy and try again, but the Holley is a "true" square bore with 4 barrels that all match the RB intake. The Eddies' secondaries are much bigger than the RB runners, and I keep wondering if that is a stumbling block.

I'm actually looking at Holley 390's now, but I need to pay off all the other work I've done to this point.

Bottom line, right now, is that it's running like Flo-Jo on crack and molly. I'm the happiest I've been since buying the car. and I'm gonna go eat Easter dinner.

Braaaaaaaaaaaaaaaaaaaap, Braaaaaaaaaaaaaaaaaaaaaap, Braaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaap, POP, Braaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaap
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Old 04-21-19, 05:36 PM
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Congrats. You're making me want to keep my boost prepped Holley now...
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