Hey Guys
Could someone please tell me what is involved in fitting Chev 350 Main bearings to a mk4 3.5lt. I have been told that 2 sets are required. Are the Chev journals the same size as Jaguar, ie would .020" undersize Jag be the same as .020 Chev. Does the block need modification? Do the bearing shells need modification?
What is the general opinion as to the better way - Chev or the Vanguard/Leyland truck method.?
We’ve pu t Chev mains in several engines from SS1 to MK IV
Yu do need twosetsas the chev has only 5 mains, But then next car you only need one set
There is a bit of modding
Tunnel bore and the rear chev main is like an SS and incorporates the rear thrusts, but while tunnel boring this can be machined An original crank will need t o be clean d in a tank crack tested, checked for true, balanced, Nitrided etc
The rear of the crank needs a little bit of work to match this. But while all this is happening you can change the flywheel bolts from 4 x 3/8"BSF to 6 x 7/16"UNF for modern proper flywheel bolts
The Chev main s are narrower but that doesn’t matter , they’ll take more HP than the pushrod engine can deliver. And replacements will be easily available for hundreds of years.
Things to remember… SS/ mK IVbearings were white metal faced and the crank material suited that. When they changed tocopper lead post was[ <MK VII] they changed the crank material
so if you run copper lead against a MK IV/ SS crank it needs tobe Nitrided { Unless you are using a new Auscrank.
BUT… the big end bearings you buy are for MK VII onwards and copper lead but the mains being sold at a kings ransom for MK VI?Ss are white metal and in any case the thrusts are white metal faced. And you need to have uniformity of bearing materials
Considering the power a 350 chev is made to take and modern oils they should literally last forever.
And your MK IV originally had alloy rods. The alloy rod is nature’s natural predator of the MK IV block
mK Vs had steel rods which were a bit heavier and later jag got heavier culminating in XJ rods which are very heavy and have no oil feed.
So you need to find as light a set of rods as possible to avoid vibration. Hence the invention of te Auscrank crankshaft. 1 2 counter weights and good for over 6000 rpm. Not that 6000 is needed but it means that it is extremely smooth running
So instead of rushing to get a 5 speed box so the engine will bemrore “relaxed 'at freeway cruising speed conside rthe arithmetic…
with a 4 .27 diff the MK IV revs at a bit over 3000. 2/3 of it’s max revs
But with and Auscrank the bit over 3000 is half the max revs
So with my saloon at 60 mph on the freeway… it’s not silent. not with all that wind noise and the noise of 550x 18” tyres. It’s never going to be as quiet as a Corolla etc
But in the test we did, we eliminated the engine noise by simply putting it into neutral and coasting at 60 mph. And there was no change to the noise level
And wear is not an issue these days and if petrol consumption is a worry, you can’t afford a MK IV
Thanks very much Ed - a thorough reply. I think all the modification needed to fit Chev is more than I really want to do. Hopefully this is the last time I will be stripping the engine so the ready availability of Chev perhaps becomes irrelevant. Think I will pay the King’s ransom and get Jaguar bearings which with modern oils should outlast the years I have left. So - with new pistons, new bearings, ground cam and your new cam followers the beast should sound pretty sweet.
Regards Mike.