Engine tilt
08-17-04, 06:58 PM
#1
Engine tilt
This thread got me thinking about how much tilt is ok for the engine. https://www.rx7club.com/forum/showthread.php?t=336145
Mine is really low in back and high in front. How many degrees should it be?
Assuming the car itself is level, how many degrees should the UIM be if measured at the top where it says 3 ROTOR/sequential fuel injection? I get 3º from level. Is that normal? Isn't it supposed to be dead-level on top?
The reason I ask is because If I brought the front of the engine down a little, and up a little in the back, it would give more space between the manifold and firewall.
It's really close here.
Mine is really low in back and high in front. How many degrees should it be?
Assuming the car itself is level, how many degrees should the UIM be if measured at the top where it says 3 ROTOR/sequential fuel injection? I get 3º from level. Is that normal? Isn't it supposed to be dead-level on top?
The reason I ask is because If I brought the front of the engine down a little, and up a little in the back, it would give more space between the manifold and firewall.
It's really close here.
08-17-04, 09:18 PM
#3
I like your brass fittings on the back of the manifold. Would you possibly be able to set a level of some sort on the raised letters at the top of your UIM and tell me if it's level?
I'm not doing an FC. Here is a front view of when I was test-fitting the manifolding. Try to guess what type of car it is.
I'm not doing an FC. Here is a front view of when I was test-fitting the manifolding. Try to guess what type of car it is.
08-18-04, 07:32 PM
#5
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I'd be happy put a level on it but my engine is out being rebuilt at the moment. Won't be back for another month or so since Mazdacomp is taking their sweet *** time (2 months!) shipping parts...
08-19-04, 01:23 AM
#6
Lives on the Forum
It's dependent on your driveshaft set-up.
I think there's a rule-of-thumb on how angled you can have the engine relative to the driveshaft and rear siff.
I'll bet the old hot rod guys would know, since they deal with it all the time.
-Ted
I think there's a rule-of-thumb on how angled you can have the engine relative to the driveshaft and rear siff.
I'll bet the old hot rod guys would know, since they deal with it all the time.
-Ted
08-19-04, 12:10 PM
#7
Now that you mention it, I think there is too much downward tilt at the yoke/tranny compared to the rest of the D shaft. I'll use it as my guide. I'm also thinking about installing 1st gen springs which will lower the back a little. I'll need to raise the tranny to account for that, at least.
Since the UIM is currently 3 degrees, I'll see how everything looks as I bring it closer to 0. Thanks.
Since the UIM is currently 3 degrees, I'll see how everything looks as I bring it closer to 0. Thanks.
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08-19-04, 01:40 PM
#9
Hey, you're right. If you or anybody else can tell me how tilted your UIM is, I'll tell you what type of car it is. 
This pic shows how high everything is in the bay. The intake elbow is way too high. You can see an oil cooler behind the grill (no room for it below or anywhere else).
This pic shows how high everything is in the bay. The intake elbow is way too high. You can see an oil cooler behind the grill (no room for it below or anywhere else).
08-20-04, 12:34 AM
#10
ok, i just posted what type it is, but i want jeff to get somebody to measure for him, and since mine is still 2 months out too, i cant do it for him.
so somebody take 2 minutes and please help him out. thanks!
jeff- a 3 rotor in a 1787 lb car, thats crazy man, just crazy!!
so somebody take 2 minutes and please help him out.
thanks!jeff- a 3 rotor in a 1787 lb car, thats crazy man, just crazy!!
Last edited by paximus; 08-20-04 at 12:46 AM.
08-20-04, 04:27 AM
#11
Heh, I hope it only weighs 1787 LBS. It;s kinda funny how I can literally feel the weight difference from front to back with my floor jack. The rearend feels pretty light. The front end feels like my REPU. Of course it felt that way when it had a 13B in it. The 13B had fairly heavy components though, such as an REPU flywheel, which is rumored to be the heaviest flywheel Mazda ever made for a 13B at 33LBS (I don't know if the P plate and clutch disk were included at the time of measuring, and I forgot to measure mine when they were out), it also has the heaviest rotors at 11.5LBS ('74-'85, according to Mazdatrix' rotor weight and compression chart) vs the S5/20B rotors (9.5). Each JDM R5 side plate casting is most likely heavier than each S5/20B casting. Each rotor housing from the 13B weighs one whole pound more than the S5/20B ones. The only truely heavy part of the engine is the special 20B-only 80mm thick intermediate plate which houses a stationary gear. It weighs like 36LBS without the gear. All I have to do to offset its weight is to relocate the battery to the back.
Oh, my 13B also had a 1st gen cast iron waterpump. The 20B's heavy stock waterpump was replaced with an NA S4 (aluminum) unit. Also, the 13B's JDM (Luce?) exhaust manifold weighs about the same as the compact header for the 20B, only its weight was concentrated forward in the engine bay right at the engine, compared to the header, which is nearly twice as long as the engine, and its center of gravity is right where the bellhousing bolts to the engine (I can grab it there and it balances).
I'm fairly convinced that when I relocate the battery, the front end of my car will either break even weight-wise when directly compared to the 13B, or come pretty darn close. There is even a chance the front end will lose a little weight, but it depends largely on how much of the 20B's extra weight actually transfers to the rear suspension. I know it's fleeting to worry too much about stuff like this, especially when the stock engine was so light, but it's still very interesting.
Since I'm using a front cover motor mount from... oops, almost gave it away, I was able to keep the front of the engine at the same spot while having the 20B's extra 16cm (6 5/16") of length go rearward. The only thing that hangs off the front of the engine beyond the motormount is the waterpump which will help to offset the weight of the air oil cooler I added to replace the beehive I was using temporarily on the 13B.
Oh, I almost forgot to mention that the 20B's UIM and LIM weigh the same as a stock 13B intake manifold with ACV and carb. I think the 20B TB weighs just about the same as a stock REPU air cleaner assembly (there is a charcoal canister under the lid and a rubber snorkle, which makes it a lot heavier as a unit than an FB air cleaner).
Man, so many things are lighter or breaking even and helping to offset the extra rotor and housing that I don't feel bad about not building a really light 13B for this car anymore.
Hey paximus, thanks for not spilling the beans. j9fd3s said it's supposed to be level on top in a JC Cosmo, but I really need to know how it sits in an FC or FD. It only takes two minutes.
It;s kinda funny how I can literally feel the weight difference from front to back with my floor jack. The rearend feels pretty light. The front end feels like my REPU. Of course it felt that way when it had a 13B in it. The 13B had fairly heavy components though, such as an REPU flywheel, which is rumored to be the heaviest flywheel Mazda ever made for a 13B at 33LBS (I don't know if the P plate and clutch disk were included at the time of measuring, and I forgot to measure mine when they were out), it also has the heaviest rotors at 11.5LBS ('74-'85, according to Mazdatrix' rotor weight and compression chart) vs the S5/20B rotors (9.5). Each JDM R5 side plate casting is most likely heavier than each S5/20B casting. Each rotor housing from the 13B weighs one whole pound more than the S5/20B ones. The only truely heavy part of the engine is the special 20B-only 80mm thick intermediate plate which houses a stationary gear. It weighs like 36LBS without the gear. All I have to do to offset its weight is to relocate the battery to the back.Oh, my 13B also had a 1st gen cast iron waterpump. The 20B's heavy stock waterpump was replaced with an NA S4 (aluminum) unit. Also, the 13B's JDM (Luce?) exhaust manifold weighs about the same as the compact header for the 20B, only its weight was concentrated forward in the engine bay right at the engine, compared to the header, which is nearly twice as long as the engine, and its center of gravity is right where the bellhousing bolts to the engine (I can grab it there and it balances).
I'm fairly convinced that when I relocate the battery, the front end of my car will either break even weight-wise when directly compared to the 13B, or come pretty darn close. There is even a chance the front end will lose a little weight, but it depends largely on how much of the 20B's extra weight actually transfers to the rear suspension. I know it's fleeting to worry too much about stuff like this, especially when the stock engine was so light, but it's still very interesting.
Since I'm using a front cover motor mount from... oops, almost gave it away, I was able to keep the front of the engine at the same spot while having the 20B's extra 16cm (6 5/16") of length go rearward. The only thing that hangs off the front of the engine beyond the motormount is the waterpump which will help to offset the weight of the air oil cooler I added to replace the beehive I was using temporarily on the 13B.
Oh, I almost forgot to mention that the 20B's UIM and LIM weigh the same as a stock 13B intake manifold with ACV and carb. I think the 20B TB weighs just about the same as a stock REPU air cleaner assembly (there is a charcoal canister under the lid and a rubber snorkle, which makes it a lot heavier as a unit than an FB air cleaner).
Man, so many things are lighter or breaking even and helping to offset the extra rotor and housing that I don't feel bad about not building a really light 13B for this car anymore.
Hey paximus, thanks for not spilling the beans. j9fd3s said it's supposed to be level on top in a JC Cosmo, but I really need to know how it sits in an FC or FD. It only takes two minutes.
09-13-04, 12:09 AM
#19
I don't know.
I've actually tried to photograph it before. The flash reflecting off the metal part always causes everything else to get really dim. All you see is the metal part. It's installed in the engine, which is in a garage, which has less than adequate lighting. Maybe when the engine is running outside I'll be able to get a daytime shot without the flash.
I may eventually go with ECU controlled ignition, but having it mimic what the dizzy does is pretty tall order due to the requirement for late leading sparks. None of that single leading spark lameness for me.
I've actually tried to photograph it before. The flash reflecting off the metal part always causes everything else to get really dim. All you see is the metal part. It's installed in the engine, which is in a garage, which has less than adequate lighting. Maybe when the engine is running outside I'll be able to get a daytime shot without the flash.
I may eventually go with ECU controlled ignition, but having it mimic what the dizzy does is pretty tall order due to the requirement for late leading sparks. None of that single leading spark lameness for me.
Last edited by Jeff20B; 09-13-04 at 12:12 AM.
09-13-04, 06:57 AM
#20
20B N/A Wide Body FC3S
Your engine tilt will be dependent on the car you put it in and which driveline you’re running... When you accelerate or launch the car everything flexes and you want the entire drive line to be as in line as possible when under power. If not then the U joints, output shaft, drive shaft and diff yolk/pinion gear can take abuse or break... It will mostly depend on which rear diff you are running and how it moves/twists in its mounts...
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