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13B 6 port on Carb, Performance secrets?

Any type of technical questions or info

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13B 6 port on Carb, Performance secrets?

#1 Post by Super Deluxe » Thu Feb 16, 2017 8:50 am

I have a stock S4 13B 6 port in my RX3 using an adapter plate and Hitachi 4 barrel carb and performance is non existent:
Image
Image

Secondaries are manualised and work OK (a bit of a jerk when they come in) but the engine makes no power.
It runs perfectly, revs out fine and is very easy to drive around town on the primaries.
I had a weber on the same engine in a different car and it wasn't much different.

Is there a secret with the timing with these things?
Thanks
Ian



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Re: 13B 6 port on Carb, Performance secrets?

#2 Post by bumpstart » Thu Feb 16, 2017 12:09 pm

you have a RESI 6p from 83-85 / it has a particularly small primary port and the aux port timing is not as late as the s4/5 versions

it also has the heavy rotors so wont quite rev the same

taking away the aux staging with 4 barrel or weber conversions gives it a flat spot down low . . usually you mate this motor with a 4.4 rear to keep the engine spinning above 4 K rpm on up changes and out of its flat spot /

the motor, given a good carb will make power past 7K rpm. when others have fallen off

timing is usually about 5-10 BTDC at idle to 25 BTDC at 4 k and zero vac
this info generic for all 3 versions of 13b 6 port .. a s5 would max a few degrees shorter ( about 23 BTDC )


myself have seen 180 out of weber fed 6 p /. the stock carb will run out a bit less without fuelling mods

recently one popped up with a 220 dyno plot. though how much it is exaggerated by moving the weather station temp probe mid run, i dont know . or which mods to the engine
( for example if i rebuild i will use a turbo centreplate in s4 6 ports , and the RESI i will use a Y or R plate )


for a stock carb.. there is some improvements in fitting longer studs, and stacking up phelonic spacers and cross port mods , but retaining a ( moddified ) vac secondary arrangement
( which holds out secondaries till vacuum drops away and therefore control secondary staging better and maximises the low down TQ )

thats all im going to give you .. there is absolute volumes of this stuff all over the net
ive typed it all out many times myself and recently been trolled for it all . if you find help lacking you can blame the idiot whom was one before you


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Re: 13B 6 port on Carb, Performance secrets?

#3 Post by bumpstart » Thu Feb 16, 2017 12:29 pm

PS .. more pics of carb, and the bung front plate under the dizzy

because--

6 p adapters from the past are all ( that i have seen ) for 13b carb and manifold ( hitachi )

turbo motor adapters are for nikki carb/ 12a manifold

6p RESI engines have no overhead ACV.. ( same as s4 turbo ) .. s4 6 port do have overhead ACV

as such.. there is a problem here.. it appears you have a nikki carb . and definitely do not have overhead ACV


so either you have a RESI block.. and it has a turbo adapter forced over the 6 P inlet ,, with a nikki carb

as such the port matching needs to be confirmed,,
as in this combo ( 4 port inlet, 6 port motor ) will be `gutless, have seen this bodge many times



or you have a s4 turbo block ( apparent if under the dizzy there is a bung fitted aftermarket into the turbo oil feed gallery )
with a turbo adapter.. and a nikki carb


looking at the font and unable to see if it has a re-bunged turbo oil feed im guessing its a RESI engine , with turbo adapter , and it needs to come off and be port matched to 6 P


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Re: 13B 6 port on Carb, Performance secrets?

#4 Post by bumpstart » Thu Feb 16, 2017 1:00 pm

http://i.imgur.com/4EQH8h7.jpg" onclick="window.open(this.href);return false;

http://i.imgur.com/tbpsohx.jpg" onclick="window.open(this.href);return false;

http://i.imgur.com/GviGsee.jpg" onclick="window.open(this.href);return false;
capiche?

it is getting exceeding difficult to post pictures now.. this forum has limits far to low for any current phone pic, and imgur decides to crop my photos at will and i havent got all day to fuck around


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Re: 13B 6 port on Carb, Performance secrets?

#5 Post by KYPREO » Thu Feb 16, 2017 3:01 pm

Bumpstart, if you have an Android phone, download an app from Google Play called "Quick Image Resizer". It reduces images by a fixed percentage in an easy step. Reduce it to 20-30%. Attach the reduced image to your post. Done. Probably easier than uploaded to Imgur and remote linking too and the image is permanently on AusRotary this way.


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Re: 13B 6 port on Carb, Performance secrets?

#6 Post by Super Deluxe » Thu Feb 16, 2017 4:11 pm

Pics of motor going in:
Image
Image

I'll get a few pics of carb tonight.



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Re: 13B 6 port on Carb, Performance secrets?

#7 Post by bumpstart » Fri Feb 17, 2017 12:34 am

RESI engine .. has the horizontal ACV.

2 hole inspection plate

and the oil injectors are lower, on the ridge
whilst FC-FD housings have them up almost on the lump for the bolt casting above

engine mount lump on middle plate between the exhausts ..

the other give away is the front plate to water pump
( FC and FD have a third hole tapped into the gasket line for a long bolt right through pump into plate for the alt bracket location )


cant tell what the carb is till you show pics of float bowl glass or accel pump

since you had the manifold off. was it ported to 6P?


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Re: 13B 6 port on Carb, Performance secrets?

#8 Post by Super Deluxe » Fri Feb 17, 2017 10:21 am

Float bowl glass is round, so definately Hitachi 13B, and I'm pretty sure the adapter plate is the same as in your second pic above, ie 13b 6Pt to early 13b. Although it might be worth pulling it off to check as I have two of these engines in cars (1 not yet running) and my memory is not as good as it was.



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Re: 13B 6 port on Carb, Performance secrets?

#9 Post by bumpstart » Fri Feb 17, 2017 11:18 pm

if carb is hitachi then it will follow that you have the correct 6 p adapter . back in early nineties i ran almost the same combo ( with a 4..44 ) and used the nikki carb on two phelonic spacers
( a nikki one on top of the hitachi one. , studs moved to suit and the phelonic spacers port matched to each other )
in my rx2 while my mate ran the same ( with hitachi and later a holley ) in his rx4 ( on a 3.9 , 13b diff )

i ran rings around him . how much is the diff, and how much was carb, you would have to guess
but i ran mine with a cut spring stretched back out and it ran great . while hitachi lacked power , and the holley was shithouse everywhere

later i supercharged that engine ( wray ) and also ran it dual SU and weber . .. weber woke it up ( well so did the S/C )


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Re: 13B 6 port on Carb, Performance secrets?

#10 Post by brown hornet » Wed Feb 22, 2017 8:48 pm

I had a 13b 6 port in my last rx7.

initially I had a nikki with double spacers, machined venturis and mechanical secondaries, I thought it went well.

then I put on a weber, went better... had plenty of torque and another 500 rpm than the nikki..

bolted on a turbo and it was awesome.. its in Sydney these days...

not sure why yours seems gutless, I loved mine, plenty of torque an revved well..


My RX7's - ..
The new one - not so stock anymore S3 - http://ausrotary.com/viewtopic.php?f=21&t=223532" onclick="window.open(this.href);return false;
The old one - DIY 13b 6 port turbo - http://ausrotary.com/viewtopic.php?f=21 ... &start=100" onclick="window.open(this.href);return false;

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