The V8 Owners Forum -

Hi,

I open this topic to have your experience of later efi HRC rods.

I had some discussions in the past with Kevin (CastelMGBV8) about how strong they are and maximum RPM you can use this rods.

I would like to have the feedback of others members.

Thanks.

With ARP bolts and Omega pistons, I run mine to 7k, buzzed to 8400 a couple of times. Nothing broken yet

Thanks,

mine will be shot peneed/ARP bolts/balanced with a tolerance of 0.5gm.

I guess it depends what kind of rpm you want to use and for how long? they will stand 6000 rpm all day long but 7000 would be pushing it if you are holding it there for a while, a buzz to 8-9000 again is fine, it more the time you are going to be holding those revs, and also the presure being forced down on the piston ie bhp? an engine making 200 bhp isnt going to have to much force on the rod, but if you double that to 400 its a lot for the rod to take.

I am building a 4.45 engine with 80mm stroke crank.

The engine is for trackday SD1 with 3.9:1 rear axle.

Engine must be able to hold 7000RPM.

Dimitri,

The only person I know who could tell you for sure is John Eales JE Developments.

He does use standard rods in some of his engines or the 1mm. longer rod that he sells for full race engines with 63mm. short stroke crank & Omega cast pistons.

He's not the greatest person for offering free advice but worth a try.

Alternatively give Ian Richardson a ring at Wildcat he loves a chat and gave me lots of advice, he should know.

Kevin.

Wotland wrote:I am building a 4.45 engine with 80mm stroke crank.

The engine is for trackday SD1 with 3.9:1 rear axle.

Engine must be able to hold 7000RPM.

Not a chance!! that will be a grenade waiting to happen! what are you doing piston wise? if you are having custom pistons made i would go for using a chevy h beam rod and milling the sides down

For the moment I found some high grade AE cast pistons to suit 80mm stroke.

I have the possibility to buy Grp A rods for a correct price.

Rods seldom fair due to power unless you are really pushing it, they fail on the stretch I.E stopping the piston hitting the head at the top of the stroke. So its more revs that kill them and the weight of the piston since its the piston its trying to stop accelerating. Big heavy forged pistons are maga bad for this for obvious reasons. I don't know what the regs were for group A but you could find they aren't much cope for what your after either. Anything group A was built to a regulation and not because it was the best available. If group A had a top RPM of 7000 then they should be fine if it was 6500 or whatever then they will probably fail. Also remember that group A pistons might have been lighter than the ones you have so again your going to have problems unless you get lighter pistons. I dont know the figures at all so this info is just so you know what your looking for and to help you choose the right parts with a bit of research. For all I know Group A rods might be perfect for the job but do the research and get rev limits and piston weights before you choose them. Maybe someone here can supply the two bits of info needed?

Not sure about this fixation to put expensive group A parts into new build engine, at best they will be old and probably abused from extensive race use.

The Volvo rocker gear is available brand new at reasonable cost, so why bother with old stuff which is probably knackered and any con rods that have done a couple of season of competitive racing are probably no better than a new set of standard rods properly prepared.

I did do a bit of research on rods and the HRC + a number indicates the metal quality and strength but the information was a bit scientific and frankly beyond me!

Kevin.

I had in the past a 3.5 Grp A engine.

Grp A rod can rev up 7200/7500RPM.

Piston weight is pretty similar.

For exemple Grp A piston without rings and wrist pin : 459gm.


4.5 pistons I have : 512gm with rings.

Rods I can have are almost news.

By the way I can have Grp A rockers very cheap. The only problem is pushrods.

Dimitri,

Nice set of pistons.

What size cups do you need for the rockers?

Kevin.

Can't you just replace the adjusters, open out the pushrod holes in the head and fit something like these:


They are guaranteed not to bend in Nascar applications

quick and dirty calculation of the G on your pistons is at 7000 rpn your in the region of around 2900 G's so that makes your extra 13 grams 37700 grams. No idea if that is acceptable or not but that's the figures. This is a stroked engine so the G goes up a lot from the original 3.5 spec as well.

If I thought to Grp A rod is because this rods which were used in Eales 4.5 Dakar engine for Range Rover Rally Raid in early 90's.
The engine delivered around 340BHP@7250RPM.

For pushrod I thought to use something like that : http://cgi.ebay.com/ebaymotors/JEGS-806 ... leQ5fParts