4.6 crank,??????

ian.stewart · Post by **ian.stewart** » Mon Jan 21, 2008 4:24 pm

Just working over my options for next year,

and after a short conversation with a offroader around the corner, He has a 4.6 crank that needs a regrind, as it was cheaper for him to replace the crank, its surplus to requirments, now the thoughts are heading towards a 4.6+ engne for the cortina,
Has anyone got the dimensions to offset grind the crank to get the max CC from the extra stroke, and what the capacity would be using a 3.9 bore, 93.5??
And the next question would be, HOW STRONG is it when undercut bt the required amount, will it go to 7k???? with the right rods, there must be a few people who have gone down this route,

Ian

kiwicar · Post by **kiwicar** » Mon Jan 21, 2008 6:00 pm

What big end diamiter are you planning? standard rover 3.9 or somthing a little more exotic?
http://cgi.ebay.com/ebaymotors/NASCAR-L ... enameZWDVW
I think this covers it using standard 3.9 rods http://www.aluminumv8.com/tech/increasedisplacement.htm
If you keep the 4.6 mains then it would retain meat between the mains and big ends, as for spinning it to 7k, with a chunky bottom end brace to keep it all stable and stop the block flexing then I would think a cast crank should handle it pretty well, some one on here had a nice one (are you using a cross bolted block ?)
I would think it would be worth having the crank shot peaned to avoid cracks starting.
Sorry If I am teaching my granny to suck eggs.
Best regards
Mike

kiwicar · Post by **kiwicar** » Mon Jan 21, 2008 7:03 pm

Hi
with 3.9 rods should get you 3.375 inch stroke, with 93.5 bore that gets you 4,709cc.
With the exotic rods (I think they are honda acura journal size) you end up about 3.5" stroke, though if the crank needs a grind, I guess it does as it is being replaced and it takes off .01" so work on 3.49" getting to a total of 4.869cc.
Could be quite torquey

Mike

Post by **Coops** » Mon Jan 21, 2008 7:08 pm

Bugger you Mr Stewart,
i'm never going to catch you at this rate,

sounds an interesting setup your working on,
dont forget to pay me a visit in the 13's bracket some when

HairbearTE · Post by **HairbearTE** » Mon Jan 21, 2008 7:11 pm

Ian I think that if the crank needs a grind anyway the most you can really expect would be an extra 2-3mm using a 2" rod journal size. A 3mm increase in stroke would give you about 4.7-4.8 depending on your overbore. I don't know what piston rod combo would work with that but you might have to shave the pistons a bit if you're using all rover parts. You can get near to 5ltr if you go to honda journal size of 1.89" and these size rods are available with chevy pins cheaply enought from Eagle but you will then be forced into using either chevy 305 pistons (requires slight overbore) or custom jobs (say goodbye to a grand or so). If you can figure out a combo of stock rover parts that'll work with a slight stroke of the crank and 2" journals then that is probably the best £/hp you are gonna get.

ian.stewart · Post by **ian.stewart** » Tue Jan 22, 2008 6:00 am

Ive got a set of early Chevy Steel rods allready to fit the Small journal size of the non X bolt crank, they are only a few thou longer than the rods I have allready, and I will see how much meat I have on my omegas. Honda rods, they must already be of a substantal rods cos Honda Vtec engines rev way past 8k

Wotland · Post by **Wotland** » Tue Jan 22, 2008 10:27 am

4.6 crank can be stroked to 3.4'' stroke without problem. But it is not cheap +/-300GBP.

Here an short thread about rod/piston combo with 3.4 stroke (self as buick 300 crank) :

Post by **Rossco** » Tue Jan 22, 2008 6:23 pm

I've done this.

You have to watch the piston to couterweight clearance. You'll probably find you need 4.85" rods to clear sufficiently.

ihatesissycars · Post by **ihatesissycars** » Tue Jan 22, 2008 9:28 pm

Just so you know I have a 4.0 crank, rods and pistons you can HAVE if they're any use to you.

Or to anyone else that wants to come and get them. . . .

CastleMGBV8 · Post by **CastleMGBV8** » Wed Jan 23, 2008 4:53 pm

Ian,

V8 Tuner do a set of pistons which work with 3.9 rods for a 4.8 engine for £250.00 including rings.

He does not state the stroke on his web site but I assume it;s 86mm give him a ring and check the required stroke as this would make for a cheap 4.8 engine if you already have the 3.9 rods and can get the crank offset ground at reasonable cost.

Kevin.