7A rod compatibility?

[turbo4agte]

I've been doing some research and found a thread where people were trying to get a Honda or Nissan rod into a 7A with no avail. I dont know if anyone ever thought of it, but the Mazda BP/B8 and B6 connecting rods seem like a stronger candidate.

Im not sure about anywhere else in the world, but here in the USA we have dead Protege's, Miatas, and MX3s all day in the junkyards with rods anywhere from $20-40 which OEM comes full floating pins. As well as they sell forged aftermarket rods for around $300/set.

They both share the same rod journal diameter of 48mm, and both have a 20mm piston pin diameter. The 7A rods are 132.5mm and the Mazda rods are 132.9mm, 133mm for aftermarket. The only thing thats holding me back is I haven't found the rod width spec for the Mazda or Toyota, and I could very well get a micrometer and go to the junkyard to measure them, but thought I could check here first.

Any ideas of any manuals I could find online with detailed specs like that? Anyone ever thought about those or tried them?

[jezza323]

try contacting the manufacturer of the forged rods directly. they dont usually list that in the rod specs, but they would be able to look it up

nice research btw, hope it works out for you

[Talasas]

Yeah good work on the research, I'd be interested in hearing what you can turn up. As a side note, even a slightly larger rod thickness would do fine as long as the rod caps use a nut and bolt fastener rather than the threaded rod on the 7A. That's the real weakness of the 7A rods.

[Mooro]

Haha, I did the same research and came up with the same results as you. The two candidates I came up with where the Mazda BP rods and also Nissan CA18det. I was also stuck on the rod width but I reckon it could be overcome with some machining.

I was focussing more on the Nissan rods because the CA18's a revvy engine with a similar stroke to 7a and they are tough little critters. The CA18 rods have a slightly smaller big end diameter, but length is spot on for memory. The big end diameter can be overcome with an offset grind of the crank with the added benefit of pushing the capacity up around 1.9L.

I would be really keen to hear your results with the mazda rods though, maching is expensive so if you can avoid the offset grind on the crank then the build would be much cheaper...keep us updated with how you go.

In regards to widths, as mentioned I would chase it up with the aftermarket manufacturers. Sometimes they have detailed dimensions on the web as well.

[normality78]

great find out both of you....

[turbo4agte]

Well the Mazda rods are pretty strong. People have used them in turbo 323/Protege conversions, and of course the numerous turbo Miatas. And people have run them up to 8000rpm all day. Which I think is a safe limit for the 7A anyway.

I will get a micrometer and measure them both when I get a chance and post the results. I think these would work better because you'll be able to use all OEM parts and not have to do any machining if the width is correct.

I should have the specs over the weekend.

[Mooro]

Your a legend, I'm very keen to hear the results.

[Ben Wilson]

There are also cheap(ish) aftermarket rods out there.

[Beak]

The bpt rods are pretty tough, coming from the turbo 1.8, but a cheap 'upgrade' is to fit b6t rods.

Yes, the older+smaller engine has significantly bigger+tougher rods.
It's really strange!

Just thought i'd let you know, strength-wise, b6t >> bpt.

Cheers,
Beak

[Mooro]

Yeh I have found that as well...The B6T rods are considered extremely strong for a factory rod.

From my point of view if I ever did a 7a it would be a 7age (ie no FI) with a decent rev limit so I would want to keep rotating mass down so I would stick with the BP rods.

[skiddz]

http://www.toymods.net/forums/showthread.php?t=21438

nuff sed

[turbo4agte]

Yeah, I saw that topic. But it seems he dropped the idea because he couldn't find the full specs on them. I have a shop manual because my brother happens to own a 92 323 that he's converted to turbo.

It lists the crankshaft rod journal diameter at 48mm and piston pin diameter at 20mm. I know for sure its the same there, and the length is negligible. This site below even lists a 132mm rod for $339:
http://www.importperformanceparts.ne...dsarp-all.html

Its only the side clearance that will seal the deal. As I said, I'll try to go to the junkyard and pull atleast one rod from both engines and mic them then post the results. Here is just an idea of compatible rods. I got the picture from the forum my brother frequently visits. From left to right GTR, NA/GTX, B6T:



Hopefully it will work out becuase these go for cheap and wouldn't need any machining. And besides the OEM, Toga, Belfab and Spool all sell them for $300-$400 a set in full forged billet.

[Cuzzo]

If you can find a rod which wont need alot of machining, im going to get me some.

[turbo4agte]

Well Im going to the junkard tommorow to get a 7A block. If I can find one I'll get it and pull a rod from a BP block while Im there. There are dead Kias all over here.

[Mooro]

Wow the GTR rods looks like a serious bit of kit WOuld be great for a 7agte.

The NA BP rods looks a little bit flimsy but I would be interested to see one next to a 7afe rod...I'm only looking for another 500-700rpm over the usualy 7age limit of 7,500rpm so I don't need an ultra strong rod.

Is it just me, or the angle of the phote or does the B6T rod look quite slim as the big end transitions into the rod shaft just past the rod bolts?