Hi all,

I'd previously enquired on the HOT 704cc engine build thread about a problem I've encountered with my similar specification engine build. I had some very helpful replies, but I didn't want to completely hijack the thread with my own issues, so thought I'd start one afresh.

I'm building a 704cc engine based around a D'Angelo kit and 126 crankcase, but using some of my original 500L ancillaries and a Dellorto FZD carb. When it came to setting the up the valvetrain, Tom (The Hobbler) very kindly provided me with an article on correctly calculating the geometry of the rockers and therefore the necessary pushrod length. As a result, I know that I need my original 500 pushrods to be shortened by 2mm each (tip to tip). This doesn't sound like a lot, but it's enough that without doing so, there is no valve clearance and the whole setup is wrong/inefficient.

I've removed the tips from each of my pushrods (using heat and crowbars either side of each tip) and was expecting that to be the hard part of the exercise, before taking the rods to be machined at a local engineering shop. Having removed the tips however, it appears that the (aluminium?) pushrods have a very shallow hardened insert at each end, which would presumably also need to be removed before the rods themselves can be machined. I've attached some photos to illustrate what the rods and tips look like after doing so.




At this point I'm wondering what's the best approach to achieve the correct pushrod length- the insert at the end of each rod is only 1.5mm at each end and I can't see a way of removing this. I think my options are therefore as follows;
1. I could grind each insert down 1mm and then replace the pushrod tips, but this might compromise the integrity of the insert beneath each tip and after a bit of use the inserts could wear away completely and throw out all my clearances again.
2. I could obtain some chome-moly rod of close to the correct size/length, then have this machined down to the correct dimension for the tips to be refitted.
3. I could commission some custom pushrods, but can only find a company in the states who would do this.
Any advice or recommendations as to the best way forward?

The best person to answer this question is Ian (Bleeding Knuckles)--he has done this job on his own engine.

Any advice or recommendations as to the best way forward?[/QUOTE]

Hi MacF, I have seen your pushrods before, but never in the flesh. I believe that they are an earlier design that has been superseded. I would council that you simply obtain replacements of the later 500/126 type. The design of the later type is much easier to work on (as stated in my other thread) and is the same used in both of my engines. You can find second hand parts on Ebay (Lp-Garage) for the sum of £8 each, I can confirm that the chap selling them is very good. Or you can go the whole hog and buy new with prices ranging from €8.60/9.90 to £19.95 each . You may be able to use yours, but given that the design is so different the machining required may ruin them. If you need any more help - ask.
Ian.

Ian,

Thank you very much for your response and suggestion. Sorry, I had missed the reference to the later type of pushrod in your thread. I will endeavour to source some of the later pushrods and then have them modified. Nothing's ever easy when modifying engines, is it?!

Lori

Ian mentioned "LP Garage" as a source of 2nd-hand pushrods. I have dealt with Lucasz Reszczynski (the owner of the garage) on a great number of occasions. Deal directly with Lucasz and you might find it a bit cheaper than going on line. If you want to use my name as a reference, feel free to do so--Tom Montagu.I have no qualms suggesting Lucasz as a supplier of parts--nice guy to deal with.

£27.20 including postage if interested.

Mcflozza said:

Ian,

Thank you very much for your response and suggestion. Sorry, I had missed the reference to the later type of pushrod in your thread. I will endeavour to source some of the later pushrods and then have them modified. Nothing's ever easy when modifying engines, is it?!

Lori

Click to expand...

Hi Lori, sorry for the MacF reference I don't mean to be rude
when you get to the machine shop get them to check the original length of the pushrods - they should be about 235mm, prior to them parting off the excess tubing remind the operator to be gentle and aware of the internal tail fitted to the steel end piece I would recheck your measurements for the rocker angle With The New Type of Rod to make sure of the final length. All of my rods were cut at the bottom end ONLY - thus ensuring that the top fitting for the rocker adjuster remains as at manufacture, and NO the modding road can be a rocky one at any time.
Ian.

Toshi 975 said:

£27.20 including postage if interested.

Click to expand...

Thanks Toshi, that’ll do nicely! I’ll DM you my details.
Lori

Bleeding Knuckles said:

Hi Lori, sorry for the MacF reference I don't mean to be rude
when you get to the machine shop get them to check the original length of the pushrods - they should be about 235mm, prior to them parting off the excess tubing remind the operator to be gentle and aware of the internal tail fitted to the steel end piece I would recheck your measurements for the rocker angle With The New Type of Rod to make sure of the final length. All of my rods were cut at the bottom end ONLY - thus ensuring that the top fitting for the rocker adjuster remains as at manufacture, and NO the modding road can be a rocky one at any time.
Ian.

Click to expand...

Thanks for the tips Ian, I’ll be sure to follow that advice. I think that I’ll need to remove the tips myself- I’m hoping that a bit of heat, a tight grip and a bit of twisting will do the job.

Mcflozza said:

Thanks Toshi, that’ll do nicely! I’ll DM you my details.
Lori

Click to expand...

Push rods are on their way

Hi all,

126 rods safely received from Dave today and, surprisingly, were already the perfect length to get my valve geometry right! These rods appear to be about 2mm shorter than the 500 rods, at 233mm tip to tip and no shortening was required. As a result, they’re now installed and the geometry as well as the valve clearances are correct.

So it’s now on to the next challenge that this restoration cares to present me with!

Thanks all for your help.
Lori