Thread: 3.5 - Increases in Bore and Stroke

Don't they take 3.5l out to 5l using chev rods or something like that?

Originally Posted by Vern

Don't they take 3.5l out to 5l using chev rods or something like that?

I think 4.3 was the max for a 3.5 but 5ltr for a 3.9 .

Originally Posted by garrycol

I am thinking about a project that will involve boring and stroking a 3.5 but still retain reliability - not looking for a full on high HP engine just one that will give a substantial improvement in torque and power over standard.

Note this thread is about enhancing a 3.5 block - yes a 4.0 or 4.6 would be an option but is not the subject of this thread.

So how far can 3.5 liners be bored out - or do you put new liners in. Max size??

Crankshafts - what are the options here that are cost effective - I assume suppliers are all UK rather than in Aust. Yes I know about RPI but am looking a cheaper alternatives if they exist - this is not going to be a race engine. What is the max stroke you can go to? Do you need specialist pistons and conrods or are there standard fits from other vehicles that work.

Yes I appreciate other issues with heads etc but for the moment just looking at crank, liners, pistons and conrods. The rest will come later.

Thanks

Garry

This makes sense not so much? a 4l or 4.6 block is just that, a revised 3.5

if your going to up the cubes, you still need to top hat line the 3.5 otherwise the same issues occur, quite a few options with stroking, offset ground 4.4 crank will see you out near 5l

Originally Posted by rovercare

This makes sense not so much? a 4l or 4.6 block is just that, a revised 3.5

But I do not believe a 4.6 crank will go into a 3.5 block

Originally Posted by rovercare

if your going to up the cubes, you still need to top hat line the 3.5 otherwise the same issues occur, quite a few options with stroking, offset ground 4.4 crank will see you out near 5l

i agree - if any major work is being done on a Rover engine top hatting should be on the list. Offset ground 4.4 crank? Is this a crank out of a similar engine such as a p76 or one of the Buick cousins? or a purpose built crank. I notice that in the US buick cranks are often used.

Cheers

Garry

Back in the UK I had new polished and ported heads and a new racier cam fitted to my 3.5V8i. The engine was fitted to a Discovery and the change was amazing. Still retained the old 3.5 block though. May be another way to get more power.

HTH

Ivan

You want to check the valley for thick webbing. Also the crank bearing cap surface areas.

No point screwing around with an older 3.5 block. Chances are the block will split down the valley, or you might throw the crank when the bearing caps let go.

Originally Posted by garrycol

I am thinking about a project that will involve boring and stroking a 3.5 but still retain reliability - not looking for a full on high HP engine just one that will give a substantial improvement in torque and power over standard.

Note this thread is about enhancing a 3.5 block - yes a 4.0 or 4.6 would be an option but is not the subject of this thread.

So how far can 3.5 liners be bored out - or do you put new liners in. Max size??

Crankshafts - what are the options here that are cost effective - I assume suppliers are all UK rather than in Aust. Yes I know about RPI but am looking a cheaper alternatives if they exist - this is not going to be a race engine. What is the max stroke you can go to? Do you need specialist pistons and conrods or are there standard fits from other vehicles that work.

Yes I appreciate other issues with heads etc but for the moment just looking at crank, liners, pistons and conrods. The rest will come later.

Thanks

Garry

G`day Garry ,

with you question you need to have an upper dollar figure , anything can be done with money and also a time frame for the realiability.

The factory overs are 020 and 040 aftermaket go 060 and i think even 080 but the liner would be almost nill .

There was a bloke in Adelaide that fitted wet liners & chev pistons to 3.5s used in ski boats , others have also used wet liners and aftermarket pistons , all do it for capacity and not so much reliability .

As soon as a 3.5 is bored it is more likely to have a liner move ( do a google ) but a 3.5 will only be noise with eventual gasket failure .

Stroker cranks are used and can be found , that with 020 pistons give 4.2ltr and 030 pistons give 4.3ltr approx , the pistons used are special short pistons not unlike 4.0/4.6 pistons ( other than dia ETC ) but much thicker walled and the compression surface is also much thicker ETC , they are what i consider very expensive , they are called Omega and are/were made in AU by ACL , you may have seen mention of them in the UK by specialists there .

With the same liner move that can happen of a normal 3.5 thats bored , a stroker can actually put the rings above the liner and pull it into the crankcase .

If they work a stroker is usually good for around 200k kilometers before the piston skirts start cracking .

The problem with fitting a 4.4 crank in a 3.5 block is the machining needed the 4.4 have larger mains , what rods , pistons ETC , i heard plenty of talk about doing it but never actually spoken to an owner .

If it was do-able i`d use a Terrier crank because they have larger weights than the P76 and so would pull better once rotating i`d think .

I think " Aluminum V8 " in the US do the buick 350 crank to 3.5 block , they have a site with much information on the subject if i remember right and i remember reading of Yanks importing 4.4 cranks to use but never read of a done one and coarse over there they are big on using the 300 buick heads .

If you look at the Hardcastle and Hammil books ETC they have alot of information , they should be in you local Library or gettable by them .

I`d suggest although an interesting trip to take with a 3.5 block probably a more ecomomical one may be with a 4.6 block and top hat liners fitted properly/correctly as good as the system is it won`t work if they aren`t fitted right .

People like Bradtot in WA have had good results increasing to 3.9 bore size with a 3.5 block a couple of times but it`s alot to do with who does the work and the people he used are a know factor .


Peter

Project Rangie