upgrading Toyota engine

You can replace it with a 675 Mack engine. However, it will be very hard to replace the 4 cyl engine with either engine.

You can do it. But it is not recommended. You're going to have a very hard time of it.

Jeff

Thanks for the reply, Jeff. Why is it going to be so hard? They are both Toyota engines and both were used in the same truck chassis.

The engine may not properly fit with the transmission (different bolt pattern), the electronics all have to be replaced, the engine would have to be mounted differently, there may not be motor mounts in the right places, the transmission might not be an appropriate model for the engine.

In general, going from a 4 cyl to a 6 cyl or other way is usually hard. Going from a 4 cyl to a 4 cyl or a 6cyl to a 6 cyl can be pretty simple, if it essentially the same block with a different bore or stroke, like the old Chevy 289, 305, 327 and 350 - essentially the same block and heads - the engine were easy to switch.

This page might interest you.

Jeff,

Thanks for the additional information and for the link.. It is helpful and gives me some promising new ideas.

Regards, Chris

The quest for "More Power!" is universal.

If you live in a Smog State (CA or NY) consider what will happen at the next biennial check before you make any big changes - you might turn your Motorhome into a big planter when they see the modifications that don't meet the regulations and the state refuses to issue a smog certificate and tags...

That said, an engine swap can always be done, but with EFI and emissions systems it's a royal pain in the ass to do it right, to where they'll approve of the swap with their official blessing (and your tags). The emissions have to meet or exceed the chassis year specs, so no swapping in older dirtier motors.

You will basically need a parts donor vehicle with ALL the necessary bits from the replacement engine that have to all be transferred to your chassis - the computers, the wiring harnesses, the smog plumbing and bits, engine mounts and brackets... Big expensive job, and success is not guaranteed when you start something like that.

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Thanks for the advice, Bruce. I wasn't aware that anyone had to approve of it. I live in Florida where we don't even have inspections anymore.

Regards, Chris t

You can do the engine swap with no concerns if there are no biennial smog checks in Florida - but if you ever move to a state that does them, you'll have to sell the motorhome in Florida. (Or another unregulated state.) There are exemptions issued for cars that can't meet the rules, but few and deliberately hard to obtain - California AFAIK has a few hundred a year, and they are snapped up literally in minutes at the beginning of each year.

You have to document the engine change with Florida, even if they don't have to "approve" it they still need to know about it. Give the DMV copies of the bill of sale for the engine and/or parts donor vehicle - you create a paper trail for the engine swap just in case there are questions later. There's usually a way for the state to enter the swapped engine's block serial number in the database instead of the original engine SN, change the cylinders and displacement entries, etc.

If a cop ever gets suspicious and inspects the vehicle, and the engine details (V-6) don't match the paperwork (I-4) they might think you stole the engine or the vehicle. If you are traveling and all the receipts you need to establish provenance are at home...

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In California, I believe there is a limit on how many years they go back. Do you know how many it is? When I blueprinted my 72 Ford 390 the smog guy told me is passed *current* requirements (91). If memory serves, it was exempt the following year.

Thanks for the advice, Bruce.

Regards, Chris