ChrisV

Let's see. When my rotary died, it was going to cost over $2500 just to rebuild teh stock 145hp, 16 second N/A 13b. If you can show me how I could have made a daily driver 400 hp rotary, in '94 (8 years ago, when I built mine) for 2 grand, then this I need to see. Especially one that would have lasted until now.

How much have any of the 10 second "daily driver" cars had spent on them to get them this way? How many have been together for 8 years?

vosko

iTrader: (4)

its your car you don't have to prove anything to me. all of the other people i've seen with conversions have cost $6000+. unless your a master fabricator with your own shop and doesn't cost anything for parts. i am impressed your car ran for 8years but there are many cars with 200k+ miles on them especially N/A. if yours failed that early it might have been from previous owner who maintained the car improperly. oh well. i'm happy your car runs now and you had no problems for 8 years

gnx7

iTrader: (10)

Plain and simple.... performance engines don't last 200K miles. A stock 13B could..... and a stock V8 probably could as well. However try to tweak 300-400hp out of both of them and the V8 will last 5-10x longer.

Performance 13B's whether they are turbo or N/A don't last long. Have deep pockets.... and be prepared for peaky HP and much lower TQ.

An LT1 with T-56 6speed and minimal mods will push any 2nd gen or 3rd gen into the 12's pretty much stock. Port the heads/intake and add a camshaft and low 11's shouldn't be a problem.

ChrisV- your car is was a prime example of a conversion done right!

I think Turbo'd V6's are better than V8's though.

GNX7

I hope to be in the 10's in the springtime this year. For under $10K total with entirely rebuilt driveline and overall nice driver.

I know that rotaries on the East Coast are more popular than here on the West Coast.... but I have yet to see a street car rotary run 10's. I have seen a handful of high 11's with bolt ons and stock 13B's. Built turbo'd 13B's here are very rare.

Felix Wankel

I agree with that totally.

Dyre

Here the **** we go again....

god damnit----

rx7_ragtop

You would be surprised at how many there are. Not many in the US though... lots in PR and OZ.

Quote:

Due to the light weight of the converted RX7s, 11s are easy on N/A small blocks of around 400 hp, and are easily daily driveable as the engines are so understressed. 10s can be had with nitrous and still retain the driveability, or run a 500 hp supercharged version without nitrous and have the same result... A supercharged version of around 600 hp should hit 9s. A car tuned to run 10s can also still be tuned to handle good (due to the light weight of teh V8 and teh total engine setback in teh chassis), though faster than that and weight transfer issues to allow accelleration start to encroach on handling setups, regardless of car or engine choice.

This is misleading. V8 engines are NOT light... nor do they sit FURTHER back in the chassis than a rotary.

Quote:

The rear ends are surprisingly strong internally. It's the mounting ears that are weak in this application (it's not a drag car, and this is an issue even for built rotary cars at these speeds). You can weld them up for strength however, if you want to retain the IRS.

This is a pretty good point. Also, at the point where you break axles, stronger ones are available... but they still use the stock ends that attach to the differential, so there is the weak link. (other than the mounting ears mentioned above... which wheel hop is more damaging to than just straight power.)

Quote:

In the end, this will cost less for the power than the rotary version, and at the same power levels, be more reliable. But, rest assured, it will still not be cheap (not as cheap as an 11 second V8 7 would be)

This too is misleading. EVERY example I have seen has cost MORE than a comparable rotary. Let's see your parts and price list. I am open to being wrong... but PROVE it.

Brad

rx7_ragtop

You know... I notice a thread in the 3rd gen forum... at about the same time... with the same sort of topic... by the same NEW USER. Go somewhere else if you want to troll.

Brad

rao

I don't understand why people have to argue about this. Nobody is forcing anybody to make a V-8 or V-6 swap. I am doing mine because it is cheap and is a fun project. I'll let you know how it works when it is done, which should be pretty soon

RX-7 GT

v8's in 7's fucken A

ChrisV

I suggest you weigh a 13B turbo, with turbo and intercooler plumbing, and then weigh an N/A Ford 302. The Ford weighs 420 lbs, the 13B non turbo weighs 325, and 360 with the turbo plumbing. That means the cast iron head 302 weighs merely 40 lbs more than the turbo 13b. Add aluminum heads and the Ford and 13B turbo weight the same. YOU are being misleading.

With the engine fully behind the axle centerline, any driveline weight is carried evenly between the axles. Period. This is not misleading, it's bassic chassis science. I never SAID it sat further back, merely that it sat FULLY behind. Meaning, the car is NOT made nose heavy.

I built the mounts myself, and have the plans on my website. They cost me $20. You want to buy a premade one, from Grannys or Philly Fabrication, it will cost $350 for the same thing. I built the car myself. You can't do that, it costs for labor. Just because you see a couple people PAYING someone else to build their car does NOT mean that the conversion is expensive if you do it yourself. I know of a couple more people who have built from my plans, and saved thousands. Hell, even I spent too much, by spending a grand on the engine and trans, as a Ford 5.0 engine trans combo can be had for under $500 these days. But if you want, you can spend $4000 on a crate LS1. That doesn't mean that's what it costs to put a V8 in. It only means they spent that much. Mine was a used engine from a drag car, with over $3500 worth of work done to it. But if you look around, you can duplicate it for the same price. You want to spend more, it's your perogative, but you've lost the cost benefit of the swap. Had it cost ME more to do than rebuild the rotary, I wouldn't have done it.

One of the guys on V8RX7.com built a Ford powered 2nd gen for under $2k including the dead RX7 to start with. Another one spent $14k and still has a beat up stock looking RX7. HE would have been better served building up a rotary.

My list:
used 400 hp drag Ford engine and AOD: $1000 (and was able to make $100/month payments to the guy, too which is what allowed me to do this on a $7/hr job)
mounts: $20
driveshaft mods $70
Griffin radiatior $300
electric fan: $85
GM 1 wire alternator: $85
hoses and wiring: $100 (upper and lower hose, charging relay, sending units)
exhaust: $400 (MAC equal length shorty headers, on sale, dual 2 chamber flowmasters, also on sale, fitment at local exhaust shop)
Mazda automatic shifter assy: $15 (used)
B&M shifter cable: $45

$2120 for a 400 hp engine swap. My cost was going to be $2500 for a stock 145 hp 13B rebuild. Hmmmm. Do you honestly think that the end result could have been duplicated by a rotary for the cost? Now OR then?

LUV94RX7

iTrader: (3)

Only thing I don't like about the forum is the immaturity of some of the members.

Someday they'll grow up.

Ken

rx7_ragtop

Got it right the first time. Multiple posts like this look like trolling. What do you suppose would happen if we went on the Syclone/Typhoon forum and posted about a 13BT swap into that truck? Perhaps MULTIPLE posts, one in the Typhoon section, one in the Syclone section?

rx7_ragtop

Oh... so you are comparing aftermarket to stock huh? Also comparing a stripped 302 to a 13BT with all accessories. Let's try to get it right:

Add the exhaust manifolds for the 302- how much do those hunks of cast iron weigh? About 35 lbs each, right? (you're comparing to a stock TII with cast-iron exhaust manifold... when lighter tubular ones are readily available...) Also the DRY 13b is about 290 lbs... that's what you are comparing to for the 302, so let's keep it even.

Aluminum head motor and meet the price you listed below? Yeah, right. The heads cost that much by themselves.

What about the cast-iron intake manifold, on any but the late fuel-injected motors... which raise the cost AND complexity by having to wire up the computer.

I have seen swaps that weigh the same... compared to a stock TII with all the power accessories, etc... but they didn't have A/C, power steering, or anything else under the hood (like emissions control stuff.)

Either compare with BOTH stripped or BOTH fully equipped. The V8 comes in about 100 lbs heavier, or slightly higher. More for a SBC instead of a Ford... and 90% of that is on the front wheels.

Quote:

With the engine fully behind the axle centerline, any driveline weight is carried evenly between the axles. Period. This is not misleading, it's bassic chassis science. I never SAID it sat further back, merely that it sat FULLY behind. Meaning, the car is NOT made nose heavy.

You don't seem to have a very firm grasp of this chassis science, or you would understand that just being "behind the centerline" does NOT distribute the weight evenly. Try this, to prove it to yourself: Take a ruler or similar flat stick (like a paint stirrer stick.) Fill a 32oz glass with your favorite beverage. place it 1" from one end of the stick, and lift the stick by both ends. Is the weight evenly distributed? NO! Now enjoy your beverage while you ponder this. The closer it is to the center, the more even the weight distribution. A V8 actually sits in about the same location as the 13B, but is slightly longer, and shifts the weight slightly forward, in addition to weighing more, which also shifts the weight slightly foreward. You end up adding almost 100 lbs to the front wheels, and virtually nothing to the rear.

Another negative impact on the handling is that about 40% of the weight of a 13B is BELOW the centerline of the eccentric shaft. (think crankshaft.) A V8 engine has a MUCH higher center of gravity- the weight sits higher in the chassis, causing more tendacy for body roll and less stability in cornering.


You're comparing a fresh rebuilt 13B to a used motor. Try a J-spec 13BT for $699... add a single 3" exhaust, a home-built (hey, you can fabricate stuff, right?) FCD for about $10, a cone intake, and bigger secondary injectors from a junkyard GSL-SE. About $250 added to the $699, and you should have about 250 RWHP with a LOT less hassle, and still be reliable. IF you want to compare to "built" V8 motors, then it's only fair to use a modded 13B. About 2 grand for a street port, $1200 for a Haltech, and $1000 for a big turbo. This is very close to BDC's setup, and he puts 425hp to the wheels with a few additional VERY LOW COST tricks. (like homemade air-to-water intercooler using the stock core...) You could duplicate his setup for $5000 EASILY if you did the work yourself, as you are evidently willing to do. That's 425 RELIABLE, DAILY DRIVEN hp for the last 3 years.

Quote:

One of the guys on V8RX7.com built a Ford powered 2nd gen for under $2k including the dead RX7 to start with. Another one spent $14k and still has a beat up stock looking RX7. HE would have been better served building up a rotary.

You are right, he would have.

Quote:

My list:
used 400 hp drag Ford engine and AOD: $1000 (and was able to make $100/month payments to the guy, too which is what allowed me to do this on a $7/hr job)
mounts: $20
driveshaft mods $70
Griffin radiatior $300
electric fan: $85
GM 1 wire alternator: $85
hoses and wiring: $100 (upper and lower hose, charging relay, sending units)
exhaust: $400 (MAC equal length shorty headers, on sale, dual 2 chamber flowmasters, also on sale, fitment at local exhaust shop)
Mazda automatic shifter assy: $15 (used)
B&M shifter cable: $45

$2120 for a 400 hp engine swap. My cost was going to be $2500 for a stock 145 hp 13B rebuild. Hmmmm. Do you honestly think that the end result could have been duplicated by a rotary for the cost? Now OR then?

No... but I think it COULD be done for well under $5k... and do YOU honestly think you could go out, THIS WEEK, and duplicate it? I don't think so either. I bet YOU would have to spend over $5k to do it as well... in fact, I bet the engine alone would cost you that much to duplicate. You're comparing a "once in a lifetime" deal on used parts to a newly-built rotary, and using it to "preach" the cost-effectiveness of a V8 swap with numbers that we both know are not realistic. If you want to compare used costs, fine... compare average used cost to average used cost... if you want to compare new, that's ok too. Just don't try to compare a "deal" on a used V8 to an average or even slightly high new cost on a rebuilt rotary... it's misleading, and makes you look dishonest.

vosko

iTrader: (4)

well put rx7_ragtop. i didn't feel like arguing anymore

Blue Goose

I really don't feel like getting into a pissing match right now, but FYI, you can usually find motors like that pretty cheap if you are willing to put 1-2 weeks into looking for it...hell, I have 2 extra SBC's in my driveway because someone decided to give my little bro a 350 to replace the 305 in his camaro...plus he included the cost for headers, so don't penalize him with the weight of stock exhaust...also, you can get a griffin radiator for $180 (I just did) and get headers and exhaust cheaper than that...not that I am going to argue the weight distribution side of this...

ChrisV

No, I'm telling you what it friggin' COST me to build. I HAD X number of dollars to spend. You want to spend my money for me, you come over here and EARN it. I could not build a new or used rotary with anywhere near that power output with the money I had at the time. PERIOD. Yet high power used V8s in that price range were and ARE all over. SBC have been in production since '55 and SBFs since '61. It's cheap and easy to get them. Just because you won't believe that doesn't make it untrue. If you want, a $1200 rebuilt, 300hp warrantied SBC is a phone call away at ANY major city, and most minor ones. One time deal? Not hardly.

You or I could go out right now, grab an Autotrader or "Buy& Sell" (which is the want ad version) and find a built up domestic engine for the same cost. People do it all the time. Unlike used rotaries, they are CONSIDERABLY more reliable, or at least the chances of getting a reliable one are MUCH better. I've DONE the "used rotary" route before. But the days of the $300 12A rebuild are long gone. It's called supply and demand. Supply is way down and demand is way up for the rotary. And used ones are simply not a good bargain. Hell, that was my FIRST choice.

No, I'm comparing stock to stock AND cost to cost. AND also comparing V8 to rotary at desired power output levels. YOU said "V8s aren't light" which is what I was responding to. Please pay attention. We're not talking your big block Cougar. 400hp from a streetable rotary is a turbo. 400 hp from a V8 is N/A. So at a given power level you have to compare turbo rotary weight to N/A V8 weight! It's pretty simple, even for someone like you. AND you don't HAVE the option of reducing the weight of your turbo engine any more, while I do. At the power levels we are talking, and for similar money, I can have a lighter engine using the V8 than you can using the rotary, at that power output! It messes with the cost a bit, as the aluminum heads add almost a grand (though we are still talking a lower overall dollar figure at the same power levels), but it DOES show that the V8 isn't automatically going to add weight, which is the original thrust of your argument. Or are you backpedalling again?

Now, I never compared the 13B with ALL accessories, merely the bits necessary for X power output. Anyone who does the conversions doesn't change the weight of A/C or alternator so that would be a wash (although, if they removed the A/C, then as far as the CAR is concerned, the weight drops). I also never mentioned exhaust manifolds on either engine. YOU are the only one to do that.

In my car's case, it didn't have A/C or power steering, so I CAN compare what it's chassis has to deal with to a chassis that still has to deal with the weight of A/C and power steering pump. And with one that still has it's batttery in front. Your assumption is that after the conversion the car HAS to weigh more in the nose than stock. And that assumption is wrong. it MIGHT weigh more, but it MIGHT (and in my case, did) weigh less than it did stock. And that's the bottom line.

I'm not misleading anyone. This is what it cost, and how it ended up. PERIOD.

You have NO issues with a stock TII, right? You'd NEVER accuse one of being a nose heavy pig, right? Yet you assume that a V8 conversion wil AUTOMATICALLY become a nose heavy pig, and that is demonstrably untrue. Becasue even IF a V8 engine weighs a bit more than a bare non-turbo rotary, it can STLL weigh less than a stock turbo engine with AC, and as far as the chassis is concerned, weight reduction is weight reduction, no matter how it's achieved! Yes, even with a rotary, you can remove the A/C, yes you can move the battery. But if you want a streetable 400 hp, you can't remove the turbo or intercooler, so that weight HAS to be factored in.

No, again, it's YOU that knows little. My car got set up on the corner weight scales at Fordahl Motorsports. My friend Greg and I have been setting up road race and autocross cars for decades. What have YOU been doing with your time? The weight distribution went from 51/49 f/r to 49/51 f/r. Measured. No matter what you want to argue, that was the numbers. (To be honest, I was surprised, too). Total weight, 2720 lbs. You have assumption and a bit of book learnin'. I have practical experience over decades AND a bunch of book learnin', too: Engineer to Win, Tune to Win, Prepare to Win, Race Car Aerodynamics, Chassis Engineering/Chassis Design, Building & Tuning for High Performance Handling, How to Make Your Car Handle. I've built SCCA national champions. You? My car was considerably more balanced and much faster on the autocross course than before the conversion. And other than the front swaybar, I didn't change anything in the suspension during the conversion from what the race setup had been before the rotary died.

Do you know what weight transfer is, and weight jacking using spring rates and alignment? Probably not.

40% of the rotary weight is below the eccentric shaft, but the eccentic shaft is in the middle, not the bottom. meaning the weight in the chassis is STILL carried starting at a point just above the crossmember. The engine doesn't sit lower in the chassis than the V8. And where do the turbo and intercooler sit? Up top? Right. Where does the battery sit? Forward and up high. Now what happens when it's moved to the well behind the passenger seat?

The rotary sits farther forward than the V8 does: the bellhousing of the trans is farther back than the rotarys. the rotary uses a LARGE front oil cooler, which the V8 didn't. That removed forward weight, too. Weight previously carried ahead of the axle. You obviously don't know how the weight is carried in your own car...

I DID want to build one up. But look at your figure. $5k is WAAAAY out of my budget at the time. As I've said before, you want me to spend more than I did, you come and earn the money for me, too. If I were to build another RX7, it WOULD be a TII (Although a turbo RX3 would be my first choice, as I still have a soft spot for my old RX3s...). But I can afford that kind of thing these days. Hell, the reason I was playing with RX2s and RX3s back in the day was precisely because they were cheap to build. $1200 was a whole car WITH a heavily ported 12A and Racing Beat intake and exhaust. Good for high 13s back in the early '80s, which was insane fast then. By '93, however, a 6 port 13B Turbo was an insanely expensive engine to build up. Add to that the FACT that in '93, there was no such thing as Apex seals that would last at 400hp on the street. In '93, Mazda itself was having a hard time keeping 250hp cars together.

Lastly, these aren't 1 of 36 original Ferrari 250 GT0s. These are dime a dozen secretarymobile 2nd gen RX7s. I don't see you going around spending your money saving every dead one around, or stopping them from going to the crusher. The cars simply aren't worth doing that for (rest assured, if a real 250 GTO was headed for the crusher, people would step up!). If I have one and my engine dies, I don't see you stepping up to hand me the money to fix it to YOUR standards. The cars aren't worth that to the automotive community at large OR even to the RX7 community. If you're not paying me to rebuild it, you abrogate all right to complain about how it gets rebuilt.

jimlab

Great post Chris, couldn't have said it better myself.

Icemark

Chris,

Great that you actually posted some numbers on the scales, although I am of course still skeptical of the balance being retained. You started with a strippy sport 2600lb car didn't you?

Retained all the interior and exterior.

Removed the engine/trans

And added a SBC and Turbo-Hydromatic?

No oil cooler, no AC, No PS, No tranny cooler?

and it only weighs 100lbs more?

and can it pass emmissions? I am figuring no.

And it is perfectly streetable so that your wife or girlfriend can hop in a take it down to the mall if she had too? Again I am doubtful.

Or was your intention to design a car that just went fast?

The V8 conversion would not be practical for me. Too expensive (at least $2500 to $4500 if I understand you and others correctly) as well as I don't need nor want 300 hp well alone 400. A nice T2 motor with minor tuning to 250 is fine and still passes emmissions (a requirement in CA). But then also I am at the age where I don't need to prove my car is faster than everyone else anymore. And I can do a tuned, rebuilt 13BT for under $2000.

But I am glad that someone is actually posting some scale numbers!

Felix Wankel

His car ran a Ford 302/AOD combo. A bit lighter than a SBC.