To stroke or not to stroke?

[JayTheBarbarian]

Obviously, I know the answer will be biased on a strokers forum, but these are my concerns:

I have an '87 Wrangler with the 4.2 L engine. I was thinking about putting in a Howell TBI, but if I'm getting to the point where I need to rebuild the 4.2 anyway, I started thinking about swapping in a 4.0 with FI, and then I started reading about what can be done if you have both a 4.0 and a 4.2 handy, which is what brought me here. I've been lurking all over the forums for a while, but haven't seen answers to these -- apologies if I missed them.

First off, if I do anything to increase the HP, can the rebuilt Peugeot BA-10/5 handle that? If I remember correctly the engine put out something like ~110 HP when it was brand new. If I just rebuild the 4.2, I should be back to that and have no problems. If I swap in a 4.0, I should already be going up to ~190 HP. If I do one of the 4.0/4.2 combination builds, it seems like I'd be theoretically going up to ~250 HP. More than doubling the HP going into a transmission that everyone says sucks in the first place doesn't seem like it would be a good idea.

And, maybe more importantly, if I can't legally put in a high-flow cat (have to get my Jeep smogged every two years in Ca), would I get any benefit at all from making a 4.5 or 4.6 out of a 4.0/4.2 combination build?

Thanks in advance for your input/help!

[IH 392]

The OE style cat will flow enough if you're not holding it against the rev limiter.
The stroker engines will pass emissions if tuned correctly.

[Cheromaniac]

If you're intent on keeping the weak Peugeot BA 10/5 transmission, just rebuild your 4.2. The BA 10/5 only had a short production run because it was notoriously unreliable and was fitted to the 87-89 YJ (4.2) plus the 87-89 XJ (Renix 4.0). Thereafter, Chrysler replaced it with the strong and reliable Japanese made AX15.
If I was in your shoes, I'd try to find a good used AX15 5-speed transmission and build a 4.0L based EFI stroker using the crank from the 4.2.
Strokers should have no problems passing emissions. An eBay header with a 2.5" exhaust system plus a high flow cat will get the job done nicely and produce a deep, sporty growl.