A question to those familiar with 20b's. I'm not asking CAN this be done. I'm asking who has done it?

I am looking to install a n/a high compression 13b into my first gen. For the last couple of weeks I have been tossing around the idea of a high compression n/a 20b.
By high compression I mean the 89-91 n/a rotors.

Mounting the engine off of the front cover all'a first gen style (setting it back in the frame) and then using a T-56 tranny (I've read in a couple places that they are shorter than the Rx-7's tranny's) to place the shifter in the stock position. This would help maintain a much better balance than hanging the motor over the front axel line.

I have a reasonable grip on the amount of fabrication that is going to be involved in this project. I am looking to gather the advice of individuals that are well versed in the ways of the three rotor. I welcome input of all kinds, but the majority of my questions revolve around the engine assembly and the tranny selection.

Is the motor as simple as swapping the rotors??? Will the front cover from a first gen support the weight AND the tourqe of the three rotor?? Should I use the FD rotor housings for the cooling benifits and better coating on the inside surface?

Is the tranny as simple as have a bellhousing adaptor made? Mabey using one from a T-5? Would I be better off trying to fit an SA shifter housing on to a Turbo 2 tranny to make the stock shifter location?

Thanks in advance!
Ryan

 

Good luck mating a T-56 to any Mazda rotary. Not saying it can't be done, but we're talking big bucks. Figure maybe $500-1000 for an adapter and $3000 or so for the transmission, since the OE transmissions used in Vipers and F-bodies are useless for swapping. They don't use bellhousings the way normal trannies do, they have a kind of half-bellhousing. Aftermarket T56s have "standard" bellhousings. There are adapters on the market to mate a Ford T5 transmission to the rotary (cost: about $500 or so) and they make an aftermarket T56 for Mustangs to replace the T5. However if you read the fine print, this transmission is not made with the Ford T5 transmission pattern, it uses the old Toploader pattern and requires switching to a pre-82 bellhousing, so the "Mustang T56" won't bolt up to a Mazda-to-T5 adapter.

You can't put an SA shifter housing on a T2, since SA's do not have shifter housings, the shifter is integral with the tailhousing instead of seaparte like '81-up transmissions.

I also don't think it would be wise to hang a 20B by the front cover. It's probably been done, but JEEZ... the front cover is awful thin aluminum, and the 20B is definitely not a light engine. It would probably work, but I don't know how wise it'd be, you know?

I do agree with you, though, that it'd be a much better idea to shove the engine rearward as far as possible.

 

So is the only difference between the aftermarktet T-56 and the T-5 the mounting pattern of the bell housing or are the dimensions of the "stuff" different? Input shaft length? Loaction of the input shaft in relation to the front of the transmission?

The real question could a T-5 adaptor plate be "adjusted" to fitt the T-56?

Not trying to argue here, just being objective. What do the cars running 10's use (IE Steve's) to mount the motor to the chasis. I know he is using a 13b, but it's pulling the damn wheels off of the ground. The combined tourqe of the n/a 20b along with it's increased wheight couldn't possibly generate a force equal to that. Could it??

Ryan

 

I doubt you'll pull your front wheels of the ground, if that was your question. I'd recommend against using the '74-'85 front cover mount because in my opinion, it's only good for up to around 200HP or so, and I've seen some cracked ones. The oil pan also will not bolt to it because the 20B has a squared front and the older rotaries had three angles or facets. The T2 also has a squared front, but that doesn't help you. Anyway, you ought to look into K2RD mounts and see if you could fabricate something that will allow the 20B to mount to your subframe/frame rails like near where the steering box is bolted to. It ought to be strong enough down there. Your oil pan will have to clear the centerlink anyway. Yes, try to move the engine as far back as possible without stepping on the starter when you floor it!

 

Like I said, it'd probably work. I'm more worried about the effects of, say, slamming over a big bump and 500+ pounds of 20B are banging down hard against that thin casting.

I am not near my handbook, unfortunately, have to get back to you on the specifics. B-W makes about six or seven different aftermarket T56s. There are differences between the models. They make T56s with Chevy trans-to-bellhousing patterns, Ford Toploader trans-to-bellhousing patterns, Mopar... different imput/output splines, trans mount placement, etc.

I'm sure SOMETHING could be worked out, but as it stands right now it appears there is nothing close to plug-and-play. I don't have a scanner, but maybe I can get a good pic of the sheet with my digital camera and throw it up here. Anyone want that? (Do I even have to ask?)

 

The motor mounting and the transmission issues aside, would there be any suprises in putting the motor together with the N/A rotors? Would the 20b counter weights work with the n/a rotors?

Ryan

 

the 89+ rotors are all the same wieght.

mike

 

500+lbs?? I thought the long block without the turbos weighed around 375-390 lbs and the turbos don't weigh 200lbs.

 

the entire engine wieghs that much, but the 89+ engine rotors are a little over 9lbs each.

mike

 

Are the rotor seals different between the 20b and the N/A FC?

What size injectors?

Which fuel computer? I will be using a distributor so ignition control is not a feature I am looking for. I was thinking one of the Haltech fuel only's, but would like the simplicity of SDS. Plus I think the hand held controlers are cool

Ryan

 

are you looking to find a tranny for your n/a 20b? if so is a n/a 20b gonna put down that much trq that you would need to upgrade it? am i just confused by this whole topic? can smeone educate me and put me on track.

luigi

 

no, 550cc
and what ever you want....

mike

 

i don't see any NA 20b needing much more thatn a T2 tranny... Now, I know the current all motor class leader is an NA 20b in an FB... he's running low 10s consistentely.... Something to look at is grannies speed shop. they are the evil people that swap V8s into rx7s... but they have a bolt in rearend, and now they are starting to offer conversions for the other way (sorta). i believe they are making some rotary adapters to Domestic tranny stuff, but nothing as fancy as the T-56

 

A T2 tranny would be more than enough for htis motor. But I am looking at mounting the motor of off the front cover which would put the t2 shifter where my power window controls are!!

 

Well the simple solution is to move the power window controls etc to the front and have a reverse cantilevered shifter like an old Cobra.

Or you could do something like Dietstop Racing did to their R-100 with a 13B sitting in the passenger footwell, make a linkage and a second shift lever.

 

peejay, I started calling the second shift lever with all its associated parts a 'dog leg'. I read it somewhere (probably in that same thread). Is that the proper term?

 

Kurgan
are they offering rears for rx7, is that what you are saying? if so is that for all generations?

luigi

 

which thread?

 

I think it was in the thread with the R100 you mentioned.