LD28 3.1 engine build

[madkaw]

3 hours ago, jonbill said:

that's interesting, how far down were they? 

.025

[jonbill]

6 hours ago, madkaw said:

.025

quite a bit more than you'd expect to make up in a skim then.  weird. 

[madkaw]

6 hours ago, jonbill said:

quite a bit more than you'd expect to make up in a skim then.  weird. 

From my research you have a zone you need to stay in or stay out of . Maybe this engine is based on the latter . I was surprised to see it myself . Running a 38cc head to get 10.75:1 . It runs good and haven’t blown it up yet! 

[jonbill]

I took the old engine out at the weekend to take the head off and get the Kameari twin idler setup off and on the new engine. 

This week the head is being drilled for M12 bolts and the timing cover finished. 

I've also been measuring up and making lower engine mounts. It's more complicated than I imagined, since the mount faces on the cross member are at an angle and 15mm shorter mounts will lower the engine more than that I think - and the engine brackets end up hitting the mounts below their mid point, so I think I'll have to do something to correct that, maybe. 

Anyway, I hope to assemble the engine next weekend.

 

 

[jonbill]

Oh, and I've done some measuring up of the XTD RB26 flywheel and clutch in comparison to my std flywheel and ACT clutch in the current engine. 

The current clutch collar is 24mm tall, and the XTD setup is 5.5mm taller than the ACT setup, so I'll be going with an 18mm clutch collar, which I *think* is the standard collar for S13/S14 FS5W71C gearboxes. 

 

 

[jonbill]

Engine is assembled. Next step, trial fit in the engine bay and figure out the engine mounts. 

[jonbill]

I've made my engine mounts and the engine sits in the engine bay under my strut brace. 

the engine is sitting about 15mm lower than standard. 

 

I think that means that the gearbox tail will be higher now, having pivoted about the gearbox mount, changing the driveshaft angles.

Which I assume is undesirable, so I'm trying to work out how much to lower the gearbox to correct it. 

Do I want to lower it enough to position the gearbox output/driveshaft front joint at the standard level, or do I want to lower it a bit more, to keep the angle with the rear driveshaft joint as close to standard as possible?

i.e. do I lower the gearbox to be on the dashed line, or on the dotted line?

https://docs.google.com/drawings/d/1a1wM6wG2ZG1w3WTNqj22jJPKzhEA00ezUdC-XjMPnTs/edit?usp=sharing

 

[jonbill]

I had to grind the inside of the bell housing some to get the clutch to clear. I'd read that about the XTD RB flywheel and clutch some time ago and forgot so that cost a few hours. 

Next problem: with the taller block, the exhaust fouls the bottom of the bellhousing. More grinder work. 

[grannyknot]

On 5/29/2021 at 5:11 AM, jonbill said:

i.e. do I lower the gearbox to be on the dashed line, or on the dotted line?

You want the lowest total angle so the dashed line but remember you can also tilt the diff down a couple of degrees as well with shims.  Try to align the trans and the diff so they are as close to parallel as possible, the driveshaft angle will split the difference.

[jonbill]

51 minutes ago, grannyknot said:

You want the lowest total angle so the dashed line but remember you can also tilt the diff down a couple of degrees as well with shims.  Try to align the trans and the diff so they are as close to parallel as possible, the driveshaft angle will split the difference.

thanks, that makes sense. But, how would I shim the front of the diff to get it lower? surely a shim would raise it? 

[madkaw]

4 hours ago, jonbill said:

thanks, that makes sense. But, how would I shim the front of the diff to get it lower? surely a shim would raise it? 

If you had a GM mount hanging the diff you could shim it - down

[madkaw]

Wait until you hear that chain tensioner :-0

[jonbill]

5 hours ago, madkaw said:

If you had a GM mount hanging the diff you could shim it - down

Thats a thought. I have an RT mount as a snubber, so would only need to add the GM bit. I understand it lowers the diff a bit by default. 

[jonbill]

5 hours ago, madkaw said:

Wait until you hear that chain tensioner :-0

what should I expect? I'm using the Kameari twin idler, so I'm not expecting trouble

[grannyknot]

23 hours ago, jonbill said:

thanks, that makes sense. But, how would I shim the front of the diff to get it lower? surely a shim would raise it? 

Sorry, I assume everyone has an RT mount for the diff. and as Madkaw suggests, it is possible.  I modified the front diff xmember so I could drop the front of the diff 3/4" and then stacked some washers under the snubber.

The pics below were in the mock up stage but you get the idea.

 

[madkaw]

16 hours ago, jonbill said:

Thats a thought. I have an RT mount as a snubber, so would only need to add the GM bit. I understand it lowers the diff a bit by default. 

A bit - but the urethane mount can be shaped as you need . I have it as part of my diff sandwich by using the stock mount below and GM above 

[madkaw]

16 hours ago, jonbill said:

what should I expect? I'm using the Kameari twin idler, so I'm not expecting trouble

More visceral -ness 

[calZ]

A whole lot of whirrrrrrrrr

[AydinZ71]

I’d love if someone could explain the purpose or advantage of the twin idler. I think it’s cool as hell. If it doesn’t serve a functional purpose though, I don’t think I would get it for the race engine. That noise indicates it is adding friction/resistance to the engine but I’m sure there is an up side! Does it keep the chain from fking up at high rpm? 

[jonbill]

3 hours ago, AydinZ71 said:

I’d love if someone could explain the purpose or advantage of the twin idler. I think it’s cool as hell. If it doesn’t serve a functional purpose though, I don’t think I would get it for the race engine. That noise indicates it is adding friction/resistance to the engine but I’m sure there is an up side! Does it keep the chain from fking up at high rpm? 

There's a lonf thread on here about it somewhere. I think the main points is it controls the chain at high RPM and especially when the engine is decelerating - the standard setup lets it go baggy on the tight side, changing timing. 

Also its dead handy for taking up extra slack after you skim the head and  also it doesn't try to fall out when you take the head off. 

I'm not sure about it sucking energy to make that noise. It really is just two idler gears with little resistance. Maybe something to do with the oil spray from it.