3.9 rods

Speedball1 · Post by **Speedball1** » Fri Mar 23, 2007 10:17 pm

Hi this is my first post here. I am currently rebuilding a 3.9 for my trials L/R. Two of the big ends picked up and have damaged the rods. The engine was originally a 3.5 from an SD1 but has been bored out to 3.9 prior to my ownership. The pistons look fairly new and are AE items. Everyone keeps telling me that 3.5 and 3.9 conrods are the same but this is not what I am seeing on the bench. The gudgeon pins on the pistons that are in the engine have a diameter of 23.8mm while standard 3.5 and 3.9 rods take a 22.2 mm pin. The rods in the engine correctly fit the crank. Does anyone have a clue where the rods/pistons are from and where I can get new rods?

ian.stewart · Post by **ian.stewart** » Fri Mar 23, 2007 10:28 pm

I beleive both Real Steel and Rimmer bros do reconditioned standard rods, Ask for HRC injection rods, about the best of the common bunch, other than GrpA rods and then Metro6R4, and possibly XR220s

Wtth the pin size increase I wonder if you have Chevy 327 rods

Post by **katanaman** » Fri Mar 23, 2007 10:32 pm

the small ends might have been bored out to take different pistons although not 4.0 4.6 pistons as the hole is too small and they wouldn't work anyway. It seems like a lot to machine out though. 3.9 and 3.5 rods are the same by the way, I think 4.2 rods are the same as well.

Speedball1 · Post by **Speedball1** » Fri Mar 23, 2007 10:45 pm

Problem is I just bought a new set of rods and pistons from DJE. The rods fit the bores but the 'standard' sized pistons actually seem oversized. I don't want to have to rebore. I really want to find a rod that will fit the crank and my existing AE pistons. The existing pistons fit the bores but have odd pin sizes. The rods that broke in all other respects look like the standard ones

katanaman I also am in Edinburgh

Speedball1 · Post by **Speedball1** » Fri Mar 23, 2007 10:46 pm

should have said the rods fit the crank - doh

Post by **katanaman** » Fri Mar 23, 2007 11:53 pm

oh wait a minute if this is an early converted 3.5 it might not be using 3.9 pistons as they didn't exist at the time. The bore was slightly smaller than what we know now as the standard 3.9 and obviously the pistons were different. If this is the case you should be able to either bore it out to standard 3.9 or get the rods taken out to fit. None of the off the shelf parts are going to work for you.

Post by **katanaman** » Sat Mar 24, 2007 12:06 am

I have searched through my stuff and found the original non factory 3.9. It was done by JE engineering and had a bore size of 93.5mm first oversize was 94.04mm which is now standard size so you can re-bore. These used omega pistons which fitted the standard rods but other conversions were done with different pistons so probably wont. Have a measure and see what your bore size is and we can take it from there.

Just noticed you said your in Edinburgh too so extra welcome to you

What area are you in? There is a few of is in here from in or around Edinburgh.

Speedball1 · Post by **Speedball1** » Sat Mar 24, 2007 8:04 am

I have measured the bores and they are indeed 93.5/93.6mm! I have rehoned the bores and don't think they need taken out further if only I can sort out the rods and pistons.

The rods in my old 3.5 (also broken) have the part # HRC1037 SDF 45

The existing rods in my '3.9' have the part # 602393 STSDF86. These fit the Rover crank but have the over sized gudgeon pin at 23.8mm. I take back any bad thoughts I was having about DJE - the pistons they have sent may be correct after all.

The '3.9' pistons that are in the engine are AE. The skirt on one side has the codes 1B85 PATENTED AE and on the other side 413 with arrows pointing in on either side of the number. A second code of G1 19299 is the listed slightly lower!?!

By the way I am in Liberton on the south side - thanks for the welcome:)

Post by **katanaman** » Sat Mar 24, 2007 11:53 am

Ok so you do have a very early conversion. I don't think you have rover rods either so your going to have to look at other engine alternatives such as Ian's idea of them being chevy 327 rods. I honestly cant help you with that as I know squat about alternatives like that.
I cant help but think since you already have new standard pistons and rods boring it out if nothing else is going to be your easiest rout. At least it can be done if you get stuck with the rods but hopefully someone else can chip in with what rods you need to get. If you get stuck and need a good machine shop I can give you a number for a local shop in the west of Edinburgh.

Speedball1 · Post by **Speedball1** » Sat Mar 24, 2007 2:58 pm

I have just checked my old 3.5 block - it is goosed where it threw a rod so time for the bin. I have also looked at the '3.9' rods in more detail. It looks very likely that the little end bushes have been bored out to accommodate the larger pin of the very non standard early 3.9 pistons. I am thinking now that I might just get to other 3.5 rods reamed out to suit.

By machine shop on the west side of town did you mean East of Scotland Engineering? They are due to close in the next two weeks. Where about are you in town? Do you fancy taking a butchers at my stuff?

Post by **katanaman** » Sat Mar 24, 2007 10:33 pm

Yes it was East of Scotland I was on about, I didn't know they were shutting down. That's a bummer as they were a really good shop and I trusted them unlike George Browns down Leith. Looks like its time to find a new machine shop

.

I am just along the road from the Western hospital. I don't mind having a look at your stuff at all. I will PM you my number and we can arrange a meet.

Speedball1 · Post by **Speedball1** » Sat Mar 24, 2007 11:19 pm

To add insult to injury Pistons and Components at Drumbrae have also gone bust about 3 months ago - will we still be able to make anything in ten years? Throw away societies..............

Post by **katanaman** » Sat Mar 24, 2007 11:23 pm

Speedball1 wrote:To add insult to injury Pistons and Components at Drumbrae have also gone bust about 3 months ago - will we still be able to make anything in ten years? Throw away societies..............

That doesn't surprise me, last time I checked he wanted £600 for a set of rover pistons. When I told him the proper price he was stunned and said "no wonder I haven't sold any". He also wanted £135 for a set of mains shells which I also declined

Speedball1 · Post by **Speedball1** » Sat Mar 24, 2007 11:54 pm

I'll need to move fast to get East of Scotland to oversize my rods before they close. Off to bed to sleep it off. Just taken the dogs out for a short walk - can hardly make progress in a straight line

Speedball1 · Post by **Speedball1** » Thu Mar 29, 2007 9:17 pm

I have finally tracked down John Eales as being the man that built my engine in the first place. He has put me in touch with Chesman Motorsports in Coventry (02476 689665) who did the re-machining of the conrods at that time. They are happy to do me a couple of replacement rods and at a very reasonable price.

East of Scotland finish up tomorrow and they couldn't find anyone else in the Edinburgh area that was happy to do the Job. The bloke Dave at EoS is setting up on his own but I am less than convinced in his ability. Hopefully that will be me - many thanks to one and all. Katanaman - I did try you last Sunday but got no reply. If you fancy a gander at the weekend I should be in most of Sat. I will send you my mobile by private message.

Cheers
Phil

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