'74 13B rebuild and swap into a 1979 SA ?
12-13-08, 09:02 AM
#1
'74 13B rebuild and swap into a 1979 SA ?
I am tearing down a '74 13B that i bought for 75$ with 4 speed tranny and other parts ( oil cooler, starter etc. ) and depending on what i find inside of it , want to rebuild it to put in my 79 SA.
I think I will need new motor mounts and a GSL-SE oil pan but not sure what else ?
Will the '74 13B fit to my 5 speed SA tranny ?
Should I keep the Hitachi carb?
any other issues?
I think I will need new motor mounts and a GSL-SE oil pan but not sure what else ?
Will the '74 13B fit to my 5 speed SA tranny ?
Should I keep the Hitachi carb?
any other issues?
12-13-08, 09:40 AM
#2
The oil pan on your 74 13B should fit your SA. You won't even need new mounts (unless yours are trashed), might need to cut a slot into the bracket that goes from front cover to the mounts to make it fit. Also, it will bolt to your 5 speed no problem.
12-13-08, 12:59 PM
#3
GSL-SE oil pan, Tom!
Yes!
Any other issues? Yes, the flywheel. I don't like 30 pound flywheels. You can use a GSL-SE flywheel which is an improvement at 26 pounds or get a counterweight and a light steel flywheel from RB. Also get a front mount bar from RB to fit a 13B in a 12A chassis.
Should I keep the Hitachi carb?
Any other issues? Yes, the flywheel. I don't like 30 pound flywheels. You can use a GSL-SE flywheel which is an improvement at 26 pounds or get a counterweight and a light steel flywheel from RB. Also get a front mount bar from RB to fit a 13B in a 12A chassis.
12-13-08, 02:35 PM
#4
Thanks guys , I'll post some pics when I get it apart and we see what I've got ?
I've been reading your posts on the old school 13B's and hope to get your input on building a nice emissions free ( as a stock feature !!) 13B for the '79 . Make even a bit of a frankenrotor?
I've been reading your posts on the old school 13B's and hope to get your input on building a nice emissions free ( as a stock feature !!) 13B for the '79 . Make even a bit of a frankenrotor?
12-13-08, 03:06 PM
#5
The '74 Hitachi is a nice carb. It is capable of a lot of power. Its stock primary venturis are 22mm which is larger than any stock Nikki I've ever seen, at only 20mm. There are some later Hitachi carbs with 20mm venturis, and they can be fairly powerful too, but in my experience comparing stock for stock, nothing beats a '74-'76 Hitachi with 22mm venturis. I don't know of anyone who modifies Hitachis, but I can recommend a couple ways to up the performance some.
The exhaust you should get is the RB dual pipe setup because your car originally had a thermal reactor and the associated exhaust components, which you won't want to use with the 13B.
There is a guy selling a GSL-SE oil pan on the forum in the 1st gen section. You might want to grab it before somebody else does. Your stock front cover is fine.
If your engine is indeed a real '74-'75 engine, look for 3B on the casting. If it says R5 then it is actually a '76 and later engine. If R5, check for nitriding; this will narrow down the year.
Check your side plates for step wear and rust. Also check your stationary gears for tooth length and try to upgrade to the '76 and later type, as their teeth were longer for added strength. Also examine stationary bearing wear for copper. Rotor bearings are usually is better shape than stationary bearings.
Check thrust assembly components for wear. Early engines tend to wear out fast compared to '76+, which used a different material or hardening process and are a lot more durable.
Look at the rear oil pressure reg. It might be the neat adjustable type. If so, smile.
You can add a couple small washers for a boost in oil pressure for high RPM use.
IF your engine is a true 3B, it will have what I like to call '74 spec ports. They are somewhere between common streetport RB templates and '76-'85 12A size. If so, leave them alone if you want to keep using the Hitachi! That port size is freaking perfect for the street and the flow capability of the 22mm Hitachi carbs. If you port your engine, it will decrease low RPM driveability and you'll never know how nice it could have been. Seriously. A non ported 4 port 13B makes a fantastic daily driver engine if you do it right, and porting often does more harm than good.
With that in mind I need to ask why you want to upgrade to a 13B in the first place. For more torque? Better driveability?
The exhaust you should get is the RB dual pipe setup because your car originally had a thermal reactor and the associated exhaust components, which you won't want to use with the 13B.
There is a guy selling a GSL-SE oil pan on the forum in the 1st gen section. You might want to grab it before somebody else does. Your stock front cover is fine.
If your engine is indeed a real '74-'75 engine, look for 3B on the casting. If it says R5 then it is actually a '76 and later engine. If R5, check for nitriding; this will narrow down the year.
Check your side plates for step wear and rust. Also check your stationary gears for tooth length and try to upgrade to the '76 and later type, as their teeth were longer for added strength. Also examine stationary bearing wear for copper. Rotor bearings are usually is better shape than stationary bearings.
Check thrust assembly components for wear. Early engines tend to wear out fast compared to '76+, which used a different material or hardening process and are a lot more durable.
Look at the rear oil pressure reg. It might be the neat adjustable type. If so, smile.
You can add a couple small washers for a boost in oil pressure for high RPM use.IF your engine is a true 3B, it will have what I like to call '74 spec ports. They are somewhere between common streetport RB templates and '76-'85 12A size. If so, leave them alone if you want to keep using the Hitachi! That port size is freaking perfect for the street and the flow capability of the 22mm Hitachi carbs. If you port your engine, it will decrease low RPM driveability and you'll never know how nice it could have been. Seriously. A non ported 4 port 13B makes a fantastic daily driver engine if you do it right, and porting often does more harm than good.
With that in mind I need to ask why you want to upgrade to a 13B in the first place. For more torque? Better driveability?
12-14-08, 01:23 PM
#6
Thanks jeff ,very uselful.
Nice to hear the Hitachi carb is a good keeper for the rebuild plan . Initially , the 13B purchase was just to use the engine to practice on as it will be my first engine rebuild . My '79 SA has very bad oil control rings and smokes bad. It has 186,000 km (120000 miles) and needs a rebuild. The dilemma is I would like to leave the 79 12A stock , but also want more performance ( obvious contradiction) . What appeals to me is removing the stock 79 engine and putting a rebuilt '74 13B in it with no emmissions stuff as it was designed in '74 . All I really want is a little more punch than the 100HP 12A. 125-150 HP would be nice and I'm hopin the 13B project with a RB exhaust woill do that
I was wondering about your exhaust porting to T2 specs I've seen you did and wondered how that turned out ???. Sounds like the stock intake ports are fine and carb jetting . Any other suggestions ?
Electronic ignition is an option too I guess
Nice to hear the Hitachi carb is a good keeper for the rebuild plan . Initially , the 13B purchase was just to use the engine to practice on as it will be my first engine rebuild . My '79 SA has very bad oil control rings and smokes bad. It has 186,000 km (120000 miles) and needs a rebuild. The dilemma is I would like to leave the 79 12A stock , but also want more performance ( obvious contradiction) . What appeals to me is removing the stock 79 engine and putting a rebuilt '74 13B in it with no emmissions stuff as it was designed in '74 . All I really want is a little more punch than the 100HP 12A. 125-150 HP would be nice and I'm hopin the 13B project with a RB exhaust woill do that
I was wondering about your exhaust porting to T2 specs I've seen you did and wondered how that turned out ???. Sounds like the stock intake ports are fine and carb jetting . Any other suggestions ?
Electronic ignition is an option too I guess
12-14-08, 04:04 PM
#7
Don't port the exhaust ports to T2 spec. I wish I didn't. The '74-'75 exhaust port sleeves are too small I later found out.
You can port them a little as they tend to be as restrictive as US-spec 12A rotor housings. I've had good results, on a 12A I ported to '74 spec size, by only porting the exhaust ports up 2mm and wider by 2mm on each side for a total of 4mm wider like a T2, but not as tall). I didn't touch the bottom or 'opening' port timing. What this 2mm treatment does is delays the exhaust port closing slightly and allows more flow thanks to increased width without disturbing the original overlap by very much. The low end torque wasn't damaged much and the high end power was increased. I also installed an RB dual pipe exhaust and a light steel flywheel. Because it was a 12A and inherantly has less low end than any 13B with the same porting, your low end will be 'damaged' less and your high end potential should be even greater. Granted the heavy '74 rotors weigh more than the '83-'85 rotors in the 12A I ported, but the increased driveability due to the better torque will more than make up for it... as long as you get a light aftermarket flywheel like the light steel, but not as light as aluminum (that's my problem right now with an S4 rotating assembly in a set of GSL-SE rotor housings and Y plates and it's too light in the low end for decent daily driving - light steel or the stock 24 pound FC flywheel would be two choices for me, which I'll need to make in about a month when I pull it to drop into my bro's car). You must not use the 30 pound stock flywheel if you can help it.
Yes the stock jetting is fine at 106 primary and 140 secondary. You don't want to go any *bigger. If you have access to some small drillbits, solder and a coupe of nickel plated 60 slow air bleeds from a Nikki, I can tell you how to mess with your Hitachi's air bleeds after your engine is broken in and needs more fuel up to a higher RPM. You don't need to worry about this right now. In other words you don't want to rev it until it's broken in, so the stock (low RPM) air bleeds are fine for now.
*RB recommends dropping the primary jets down to 105 for more power and better fuel economy as they tend to be jetted rich from the factory, but since you will want to port the exhaust slightly anyway and go with a direct fire electronic ignition upgrade, you can keep the 106 jets and they should work fine for you. The secondaries are perfect at 140 believe it or not. Of course you mileage will vary.
I got a set of 105s and tried them - I didn't really notice a difference so far. My next chance to test them will be in a fresh rebuilt 4 port 13B consisting of Y plates ported to '74 spec and '74-'75 rotor housings with STOCK exhaust ports sitting in an MG midget conversion project. The exhaust will be sinmgle pipe straight through 2" RB pipe and Rotary Engineering glasspack headed by a short unequal length header. The intake manifold is a reverse runner from a '76 Cosmo but the carb is a true '74 Hitachi with 105 pri/ 140 sec and smaller than stock air bleeds for high RPM use. Removed secondary actuator spring. Electronic ignition with DLIDFIS (direct fire upgrade). I've had it running with my REPU's old '74ish engine (missing chrome and a wrong NO intermediate plate and it was still pretty powerful). I haven't gotten it running with the new engine yet because I had to put it on hold for other projects, but I'll get around to it eventually. The exhaust has to be redone and the brakes are gone. Maybe we can get our two '74 engine projects running simultaneously?
You can port them a little as they tend to be as restrictive as US-spec 12A rotor housings. I've had good results, on a 12A I ported to '74 spec size, by only porting the exhaust ports up 2mm and wider by 2mm on each side for a total of 4mm wider like a T2, but not as tall). I didn't touch the bottom or 'opening' port timing. What this 2mm treatment does is delays the exhaust port closing slightly and allows more flow thanks to increased width without disturbing the original overlap by very much. The low end torque wasn't damaged much and the high end power was increased. I also installed an RB dual pipe exhaust and a light steel flywheel. Because it was a 12A and inherantly has less low end than any 13B with the same porting, your low end will be 'damaged' less and your high end potential should be even greater. Granted the heavy '74 rotors weigh more than the '83-'85 rotors in the 12A I ported, but the increased driveability due to the better torque will more than make up for it... as long as you get a light aftermarket flywheel like the light steel, but not as light as aluminum (that's my problem right now with an S4 rotating assembly in a set of GSL-SE rotor housings and Y plates and it's too light in the low end for decent daily driving - light steel or the stock 24 pound FC flywheel would be two choices for me, which I'll need to make in about a month when I pull it to drop into my bro's car). You must not use the 30 pound stock flywheel if you can help it.
Yes the stock jetting is fine at 106 primary and 140 secondary. You don't want to go any *bigger. If you have access to some small drillbits, solder and a coupe of nickel plated 60 slow air bleeds from a Nikki, I can tell you how to mess with your Hitachi's air bleeds after your engine is broken in and needs more fuel up to a higher RPM. You don't need to worry about this right now. In other words you don't want to rev it until it's broken in, so the stock (low RPM) air bleeds are fine for now.
*RB recommends dropping the primary jets down to 105 for more power and better fuel economy as they tend to be jetted rich from the factory, but since you will want to port the exhaust slightly anyway and go with a direct fire electronic ignition upgrade, you can keep the 106 jets and they should work fine for you. The secondaries are perfect at 140 believe it or not. Of course you mileage will vary.
I got a set of 105s and tried them - I didn't really notice a difference so far. My next chance to test them will be in a fresh rebuilt 4 port 13B consisting of Y plates ported to '74 spec and '74-'75 rotor housings with STOCK exhaust ports sitting in an MG midget conversion project. The exhaust will be sinmgle pipe straight through 2" RB pipe and Rotary Engineering glasspack headed by a short unequal length header. The intake manifold is a reverse runner from a '76 Cosmo but the carb is a true '74 Hitachi with 105 pri/ 140 sec and smaller than stock air bleeds for high RPM use. Removed secondary actuator spring. Electronic ignition with DLIDFIS (direct fire upgrade). I've had it running with my REPU's old '74ish engine (missing chrome and a wrong NO intermediate plate and it was still pretty powerful). I haven't gotten it running with the new engine yet because I had to put it on hold for other projects, but I'll get around to it eventually. The exhaust has to be redone and the brakes are gone. Maybe we can get our two '74 engine projects running simultaneously?
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12-14-08, 05:14 PM
#8
When I originally did my REPU I purchased a GSL-se pan and a supposedly REPU pan and they both looked pretty much identical to me except with the REPU pan it had the pieces that basically amounted to a broken up pan brace. Maybe somebody sold me something that wasn't what they said it was 
Oh well.
Oh well.
12-14-08, 06:49 PM
#9
If it makes any difference, the engine came from a RX-4 wagon but I don't know the mileage .
Jeff, any idea what approximate HP the stock '74 with exhaust port widening , RB header and electonic dizzy would make?? I like the flywheel idea , but that only makes the HP more available I guess . Will a S4 or S5 13B flywheel work ?
Also , will the 79 airsnorkel on the Nikki mount on the hitachi ? I'd like to keep that look the same in the engine bay if possible.
Jeff, any idea what approximate HP the stock '74 with exhaust port widening , RB header and electonic dizzy would make?? I like the flywheel idea , but that only makes the HP more available I guess . Will a S4 or S5 13B flywheel work ?
Also , will the 79 airsnorkel on the Nikki mount on the hitachi ? I'd like to keep that look the same in the engine bay if possible.
12-14-08, 06:51 PM
#10
When I originally did my REPU I purchased a GSL-se pan and a supposedly REPU pan and they both looked pretty much identical to me except with the REPU pan it had the pieces that basically amounted to a broken up pan brace. Maybe somebody sold me something that wasn't what they said it was Oh well.
Oh well.
12-14-08, 08:55 PM
#11
Tom, yeah you probably got the wrong pan. But yes a GSL-SE pan fits fine. I prefer the slightly higher oil capacity of the REPU pans myself.
ourxseven, it might make some difference where the engine came from. Can you confirm that it has 3B castings or R5 castings? Any way to take some pictures? I'd also like to see the carb to try to visually confirm what year (and therefore what jets etc) it is.
A stock '74 REPU engine, complete with all emissions, makes 110BHP at 6000RPM and 117 torque at 3500RPM. I'd think that with electronic ignition, better yet with direct fire, and a free flow exhasut system with widened ports could make 125 to 135HP easily while keeping the torque. It doesn't look like much, but it's so smooth and full of torque that it will feel like a lot more.
S4 and S5 have completely different counterweights cast-in. Your only choices are GSL-SE, your stock (heavy) flywheel, or get a rear counterweight and a light steel flywheel. You will also need to get a clutch disc and pressure plate. You have two choices here: 215mm or 225mm.
ourxseven, it might make some difference where the engine came from. Can you confirm that it has 3B castings or R5 castings? Any way to take some pictures? I'd also like to see the carb to try to visually confirm what year (and therefore what jets etc) it is.
A stock '74 REPU engine, complete with all emissions, makes 110BHP at 6000RPM and 117 torque at 3500RPM. I'd think that with electronic ignition, better yet with direct fire, and a free flow exhasut system with widened ports could make 125 to 135HP easily while keeping the torque. It doesn't look like much, but it's so smooth and full of torque that it will feel like a lot more.
S4 and S5 have completely different counterweights cast-in. Your only choices are GSL-SE, your stock (heavy) flywheel, or get a rear counterweight and a light steel flywheel. You will also need to get a clutch disc and pressure plate. You have two choices here: 215mm or 225mm.
12-15-08, 07:19 AM
#12
I will take some pics as soon as I can. The engine is at a friends garage waiting for me to work on it . haven't had time to get started yet and its ridiculous cold here this week (-44 with the wind chill). Maybe on the weekend. His garage is heated
I know the housings have the older "MAZDA" lettering if that helps . Where is the casting lettering ?
Here is a link to my '79 the engine may go into
https://www.rx7club.com/showthread.p...dition+project
I know the housings have the older "MAZDA" lettering if that helps . Where is the casting lettering ?
Here is a link to my '79 the engine may go into
https://www.rx7club.com/showthread.p...dition+project
12-15-08, 04:30 PM
#14
I found someone local with some GSL LE engine parts .
Anything else I useful I should grab other than the oil pan and fly wheel ( what does it weigh)?
Would the electronic ignition swap over to the '74? ............... Water pump ?
Anything else I useful I should grab other than the oil pan and fly wheel ( what does it weigh)?
Would the electronic ignition swap over to the '74? ............... Water pump ?
Last edited by ourxseven; 12-15-08 at 04:39 PM.
01-05-09, 10:18 AM
#20
Heres a few more of just getting the peripherals off and a look inside that carb .... ugghh , . Like the rest of the block , pretty dirty
The MAZDA automobiles is there and the 3B casting on the intermediate plate next to the oil filler neck and on the end plate . Looks like a true 3B
I have cleaned up the exterior and removed the flywheel, pulley and front cover but don't have the pics down loaded yet . Both the flywheel and pulley came off no problem with and impact wrench. Next job is to get to the internals and see what shape those housings are in .
The MAZDA automobiles is there and the 3B casting on the intermediate plate next to the oil filler neck and on the end plate . Looks like a true 3B
I have cleaned up the exterior and removed the flywheel, pulley and front cover but don't have the pics down loaded yet . Both the flywheel and pulley came off no problem with and impact wrench. Next job is to get to the internals and see what shape those housings are in .
01-05-09, 12:42 PM
#21
heres just a few more pics .... the intake manifold exposed and some marks I made on the pulley and distributor for the timing . Not sure if this was necessary but did it anyway
the outside intake ports look pretty ugly , not sure if that is a sign of things to come ?
the outside intake ports look pretty ugly , not sure if that is a sign of things to come ?
01-19-09, 09:21 AM
#24
Well I finally got the time to open it up and see the internals .
Looks pretty good to me as a first look. I am going to get everything cleaned up better next weekend and then check the tolerances. The pics below are of the front housing . No chrome chipping evident in this one and no broken apex or scarring.
Looks pretty good to me as a first look. I am going to get everything cleaned up better next weekend and then check the tolerances. The pics below are of the front housing . No chrome chipping evident in this one and no broken apex or scarring.
01-19-09, 09:26 AM
#25
The front rotor is carboned bad and rusty on one side . I guess one of the front housing coolant seals was bad and has been rusting away while sitting in storage . Don't know if this can be saved ??? the gear side looks OK at first glance . No scoring of the rotor apparent and all seals and springs were intact