Chubrolet three fiddy powerd Jaagggssss?? Why??

OK, the cool XJS advertised on CL in another thread got me thinking. Honestly why are there so many Chevy powered Jags out there? Yes I know people claim, justifiably in many cases, that they are unreliable, but doing an engine swap does seem like the nuclear option to me.

The engines themselves are pretty reliable, it’s the eclectics I see people complain about most. So you have a car that’s not running right. You can either:

a) Spend 10-20 hours at a garage or at home diagnosing it and fixing it for the hourly rate plus parts

OR

b) Spend what? 40-50-60 hours having the old engine and trans pulled. Buying a Chevy engine and trans, buying a fitting kit, installing it, wiring it, getting fuel to it, paying for a new driveshaft, paying for a new exhaust, paying for a new radiator, paying for hoses, troubleshooting it to get it running right etc. etc..

How is that ever, honestly a better bet. Now, if the goal is to build a hit rod with 500+ hp I get it, but most out there seem to be replacing engines as DD’s.

I honestly don’t see how this is/was a better option. Heck if people were having issues with the fuel injection it must have been cheaper, especially with the straight six’s to convert back to carbs as the parts are available off the shelf from old 60’s jags.

Yeah but it's option 'a' every couple of weeks, whereas option 'b' is once.

RossD wrote: Yeah but it's option 'a' every couple of weeks, whereas option 'b' is once.

Not sure I agree, but then what about my option c. Fit carbs to the Jag engine. That has to be better???

I was told it's normally the trans that causes the switch. Jag trans let's go and the 350 swap is cheaper than trans rebuild of jag unit.

It's like LSx'ing an RX. You get all the power, better economy and easy to find parts with it with no discernable downside. Hate on it all you want, I'd take a V8 powered Jag any day over a stock one.

Isn't the Jag unit just a TH400?

www.jagsthatrun.com

Bobzilla wrote: It's like LSx'ing an RX. You get all the power, better economy and easy to find parts with it with no discernable downside. Hate on it all you want, I'd take a V8 powered Jag any day over a stock one.

I'm not hating on it, it's an honest trying to understand question. I do see a difference though. With an LSx Rx7 you are quite often doubling the power right off the bat. That's worth it in the end. I'm not convinced you're going to get a massive increase in fuel econ with a carb V8 to make it worth it, and I still stand by my original Q, isn't it cheaper to fix what's there correctly, or at worst swap to carbs than do a whole power train swap? Also parts can't be that hard to find. Jag used the same in line 6 from 1949 - 1992. That's a long run of cars and parts. You want a cheap easy way to 500hp in a Jag, then Chevy swap all the way, I still don't get the DD thing.

Well, if a 350 powered Jag bugs you, then hold onto your spot of tea carefully for this...

This was mine, many years ago. IIRC, it was a '67 2+2 (could have been a different year, but pretty sure it was '67). 302 Ford powered, with a C4 trans. Yes, those are ghost flames on the hood. Jag purists used to shoot daggers at me with their eyes. But everyone else would give me thumbs up, take pictures, ask questions. It got as much attention as my Viper, Cobra, etc... And man was it a wild ride. It could smoke the crap out of the tires at will. It had the prince of darkness electrical gremlins, but I learned to live with them.

EvanB wrote: Isn't the Jag unit just a TH400?

On teh V12 cars, yes, on the I6 cars, no.

And while the basic XJ engine is a fine unit, the emission controlled ones do tend to drop valve tappets guides causing all sorts of internal problems. This happens due to the catalytic converters being up near the heads, causing them to heat up and expand, allowing the tappet guides to come out. This can send shrapnel all around inside the engine.

Doing the Chevy swap gets a better trans, a more reliable engine, a better starter a better alternator, more power and less weight. A win-win all around. On the V12 cars, there are a lot more issues than that, so doing the Chevy swap really makes a lot of sense.

Chris_V wrote: And while the basic XJ engine is a fine unit, the emission controlled ones do tend to drop valve tappets guides causing all sorts of internal problems. This happens due to the catalytic converters being up near the heads, causing them to heat up and expand, allowing the tappet guides to come out. This can send shrapnel all around inside the engine.

See, this finally makes sense. I grew up in the UK where we didn't even get unleaded petrol until 1992 and leaded wasn't phased out completely until 2000. So the cars I grew up with never had cats on them so didn't have those issues, they were dead reliable.

It's probably worth considering that Jag engine parts are going to be a lot more expensive and hard to find than parts for a ubiquitous 'Murkin V8.

Klayfish wrote: Well, if a 350 powered Jag bugs you,

Aaggh, I never said they bugged me, I just didn't understand the need.

Very cool car BTW

Adrian_Thompson wrote:

RossD wrote: Yeah but it's option 'a' every couple of weeks, whereas option 'b' is once.

Not sure I agree, but then what about my option c. Fit carbs to the Jag engine. That has to be better???

Now, there's option D- re-fitting the car with a modern FI. Heck, if I could find an Jag sedan with a super solid engine, but with horrible electronics, I would very much consider a re-wire job.

It's really not that hard, if you have wire to do it.

And an MS powered Jag I6 can't be that hard.

If there are core mechanical problems that are end results of other problems, that's a different story. Grenading engines are good reasons for engine swaps.

GameboyRMH wrote: It's probably worth considering that Jag engine parts are going to be a lot more expensive and hard to find than parts for a ubiquitous 'Murkin V8.

Yes, but....

So you can't go to your local parts place and get stuff, but the interenet is a wonderful thing. Knowing availabilty of Alfa parts, I can't imagine getting similar support for Jag parts is that undeard of.

Jag with a 4.8 V8 or a 4.2 I6 sounds like a good idea

GameboyRMH wrote: It's probably worth considering that Jag engine parts are going to be a lot more expensive and hard to find than parts for a ubiquitous 'Murkin V8.

That's another part of it. For example, the Lucas starters go bad, and there are no new ones left. All the ones you can get for the cars are rebuilts, and some have been around the rebuilt cycle a few times, so it's hard to find a good one. I'm not even sure you can still get the Bosch gear reduction starter replacement anymore, which is what I used on my Series III XJ6.

Same holds true for alternators.

But even after the engine swap, what's to prevent the passenger side window from falling out at the next stoplight?

I get the impression (from watching one or two episodes of Top Gear) that Brits have similar biases on cars just like we do, but I think objectively speaking; British cars have heart and beautiful design, but the engines, transmissions, and electronics are complete crap.

I think its that reason that I would consider the jag swap. For me, I can buy a jag over here for cheap if it doesn't run (which 90% of the time it won't :) Then I can refresh one of the 350s I have sitting out back for $150, buy a junkyard TH350 and do a $20 fluid and filter change, use some scrap steel for mounts and drop it in on the weekend. That's an extremely simplified interpretation, but even if it cost me $1000 to do the swap, that will likely pay for itself in two years time on just parts alone that would need to be dumped into the Jag engine/management

There are two 4.2 on the floor of my shop right now. They weigh around 700lbs fully dressed. I am completely baffled as to how they do it, but they are staggeringly heavy.

Honestly a 'merican V8 swap would be the first step in improving handling.

Lighter, more reliable, better power increase options, better fuel economy, manuals can easily be added, simple swap, bolt in kit availablity, nice V8 sounds, starts when you turn the key.

What was the question?

I borrowed one for 2 weeks last time I was in Oz, it was a nice cruiser and started every day.

For people who enjoy midnight mechanical mayhem, who enjoy cutting and welding for fun and profit, and who have fifty years' worth of accumulated SBC paraphernalia scattered about their shop,garage, and/or yard, shoehorning SBC's into anything with roughly four wheels makes some sense.

Me? I like the idea of Jag engines in Jags. And Fords in Fords. But,I do understand the swappers' view.

Almost without exception Chevy engines make everything better

EvanB wrote: Isn't the Jag unit just a TH400?

Only on the V-12s.

I want a V-12 jag in the worst way. It makes me sad when I see an XJS or XJ-12 converted to Chevy power, the I6 cars, not so much.

It's done because the days of finding someone that can work on an in-line Jaguar engine are pretty much gone. Any boob can work on a chivvy.