I met a guy with an 85 gsl and looking for a challenge I offered to help port and maybe tune his car. He recently threw in an S4 13B NA engine and mated it to a a run of the mill Holley 600. This carburator is NOT tuned for a rotary. I haven't yet seen the car so I'm just looking for initial insight. I know nothing about his intake manifold (I can only assume it's the racing beat model since how many places make such manifolds) and he's running at least a header. If he's still running a cat it'll likely be eliminated by the time I'm done with it. He had some mechanic tune it to the point where it at least idles but it is running very weak. I didn't remember to ask about the fuel pump/fpr but I'm hoping his mechanic had enough sense for that - it would be funny if it were as simple as that, doubtfull though.

My first inclination is that that's way too large a carburator for stock ports and he'll have to at least streetport it in order to run that carb on it. This is a budget build and he doesn't want to go out and buy a rotary tuned carb for the car. So assuming we perform a mild streetport on the intake (using the mazdatrix template), what size jets/airbleeds would be a good starting point to tune with? For that matter, is it possible to tune a 600 cfm carburator to run acceptably on stock ports?

Sorry, the search feature is dsiabled tonight

 

i would jet it down... if this is a budget build, a few jet changes and dyno tunes (this is hardcore tuning btw) will be tons cheaper than porting an engine. porting costs bookoos, plus after the port, you have to rebuild the engine.

 

huntersvillle isnt too far from me, check out:

https://www.rx7club.com/se-rx-7-forum-35/i77-i40-crossroads-rotary-meet-618153/


a lot of good people meet up there, and if your up to it, head to the raleigh meet, or the deals gap:

Raleigh: https://www.rx7club.com/se-rx-7-forum-35/saturdays-raleigh-nc-299706/

Deals: https://www.rx7club.com/se-rx-7-forum-35/huntsvile-deals-gap-caravan-633696/


I head to as many meetings as i can, I have been to the I40 one once and met up with a guy there after, plus, the deals gap has tons of turns (Read: RX-7 Friendly)

 

Yeah, I never thought this would be easy - hence the challenge I really wanted a chance to port an engine, and this seemed like a good opportunity to do so. Not trying to do a rebuild so much, I figured we could get by with reusing the rotor seals, bearings, ect. I told him it would be at least $250 for the minimum of a gasket set - the ghetto rebuild, I know. But if it can be tuned for a stockport I'm not going to push something he doesn't need. (not nearly as much fun that way though) As to the amount of tuning, I just wanted to get it in the ballpark, and let him finish armed with a little knowledge on how to tweak it. I guess I'm gonna have to see his setup before I know just what we have to work with here.

I wish I could make those meets. I'm going to friend's 21st bday in NY the weekend of the 20th :/. I've been wanting to make one the meets around here to meet ppl around here and all, but they always seem to happen when I'm away. Is there any word on when the next Charlotte meet is?

 

If its not a RB carb its not gonna work right unless you put a one inch spacer under the carb. Then you are going to have to install the right power valve in it, and you can only find out what the "right" one is by performing a vacuum check at idle. Get the car to idle correctly, then get a vacuum reading, then go buy a power valve for that setting. That will make the car drive well at light throttle tip in. Before you install the carb, set the throttle opening (with idle screw) to be open just far enough that it just barely exposes the transfer slots.
Go to Holley.com and read the PDF file about carbs. They walk you through how to properly set up a carb.
Another important note is you need to properly set up the float height. Its easier to do it with the floats off the carb.

 

Somebody run me over with a tank....sorry I always wanted to us that. Doc I have a Holley 600 cfm with a non-turbo S5 engine and dont have a spacer on it and it runs just fine. Whats the deal with the spacer??

 

Yeah, I was going to do a re-rebuild on my engine (streetport it, only has about 15k on it right now) with the gasket kit A,same thing you want to do. I decided against it, got a -SE 13b and half bridged 12a irons. Now I am just waiting for my 12a to pop

Charlotte meets are always 3rd saturday of the month

 

Factory Holleys are designed to run on manifolds with plenums. The RB mani has no plenum, so the "signal" produced by the engine will affect the carb differently then if it did have a plenum. More than likely it will send too strong of a signal to the carb, causing the carb to run rich. You can tune it out at idle, but at high rpm, the car will get richer as it revs up, the higher you rev, the worse it will get. Putting the spacer (open style) on there creates a "plenum" so the signal to the carb is correct.