Charlie's Echo/Madam Mayhem - glacial Bedford RL project

[Tamber]

There's about 12mm between the top of the top ring land, and the piston CROWN.

But wait!
...it isn't as easy as just making the rods longer. But I'll get to that shortly.

Started measuring the bores this evening. Didn't get far with that. Getting wacky results that might be down to sloppiness in my measuring technique (I'm using snap-gauges and an outside mic, for now), and measured an average 98.62mm by 98.75mm at the top of cylinder 1 underneath the wear ridge when the widest new bore spec is 98.44mm and maximum wear spec (+0.010in) for that would be 98.69mm.

Hmmmmmmm. The investigations will continue.

Anyway! Back on to the rod-length thing... As I was getting changed out of my overalls after giving up on measuring the bores, I was pondering how much I'd have to have the piston stick up out of the block to get the appropriate compression ratio, and a sudden realisation hit me. I didn't consider changing the rods earlier, because there is nowhere for the piston to go. So that's why I was noodling over pistons instead.



Oh well.

[legend]

ahh, ok, in that case is there anything in the piston catalogues that's anywhere close? American V8 stuff probably has lots of stuff in a similar bore, and lots of info online

[dodgerover]

I can't see the picture but how do they deck the block in that case?

[Tamber]

Mar 19, 2020 23:44:35 GMT legend said:

ahh, ok, in that case is there anything in the piston catalogues that's anywhere close? American V8 stuff probably has lots of stuff in a similar bore, and lots of info online

Some very brief searching tells me that there's a good amount of Chevy stuff with a 3.875in bore (Makes sense, there's family connections at play, if you squint real hard.) so even if that doesn't give me the direct result I want, there could well be something close enough to make work. More investigation required.

Mar 19, 2020 23:56:46 GMT dodgerover said:

I can't see the picture but how do they deck the block in that case?

I really have no idea. I can't see it working in the slightest! But, this engine does seem to be a bit of a hodgepodge, so maybe there's a combination that does let you do that.

[legend]

A full set of chevy V8 pistons were cheaper than 4 off 73mm A series ones many moons ago,

[Tamber]

Mm, having had the time to start digging into piston catalogues rather than briefly flipping through google results, it appears that the "3.875in" results for the Chevy stuff is actually the stroke, not the bore. Ah, so close, yet so far.

No matter, the search will continue.

(And the moral of the story here: The computer will find things that roughly match what you searched for, but it is not smart enough to understand what you really mean; just that it found a page that had "piston", "bore", and "3.875" on it.)

[Frankenhealey]

Burt Munro cast his own pistons using beach sand for the mould boxes, Can't be too hard! Just sayin'

[johnthesparky]

Mar 24, 2020 22:06:16 GMT Frankenhealey said:

Burt Munro cast his own pistons using beach sand for the mould boxes, Can't be too hard! Just sayin'

Watched that again with the kids the other night. You need to quench them in your water butt too

[legend]

Some duff info?
www.corvetteactioncenter.com/tech/knowledgebase/article/small-block-and-big-block-engine-bore-and-stroke-chart-283.html

everything from 3.6" to 4.4" off the shelf

[Tamber]

Yeah, looks like I saw too many numbers and got confused. Seems like it's the 283 that shares the same 3.875 bore with the RL, but further digging is making it look less and less promising.

RL gudgeon pin is 1.000" dia; the 283's is 0.927"; the RL pistons have a compression height in the region of 70mm... And, by my calculations, I'd need to add a ~5mm dome on top of that to get to where I want. If my calculations are correct, and the engine is what I think it is; which is something I am less and less confident about the more I think about it.

Bearing in mind, I was under the impression that it's a 6.1:1 engine with an early head based on having the casting number for the early head; but further reading in the manual is casting more doubts over that. (The devil is in the details.) Might just have to set aside the thoughts of a bump in compression for the time being, and leave it as an exercise for the future. (And, of course, as others have mentioned I *could* always add compression dynamically...)

I've measured the bores with some concerningly accurate tools (albeit wielded by a concerningly inaccurate tool), and come up with figures for the bore diameters that show wear that isn't altogether terrible. Wear limit, per the EMER, is 0.010"; which works out as an overall bore measurement of 98.653mm (3.884in) at the tightest grade. Largest measurement I've got was 98.51mm (3.878in); there's a smidge of ovality and a pinch of taper... but I think I may well be good to just get another set of rings, give the bores a quick hone, and call it good for the time being.

Perhaps I've been overthinking this. I can always save the hot-rodding portion for later down the line, maybe get a set of fresh liners, bearings, etc to stash away for a future full rebuild; and just see how it pulls as it is. Certainly seemed sprightly enough in low-gear, with 4 pistons' worth of stuck rings and a stuck valve; and I've definitely got enough on my plate


This under/over-thinking brought to you by Gin.

[glenanderson]

Personally, I’d rebuild it stock for the time being. The psychological benefit of having it running will help you get through the rest of the work to make it roadworthy. Pick up the bits to build a more potent engine as and when they fall on your lap cheaply rather than have to find them now and pay through the nose.

[glenanderson]

Another possibility worth investigating, if you simply fix the existing engine for the time being, is to look at straight six Chevrolet engines, because I'm sure they're from the same family. It might open up a whole load of off the shelf solutions in a package that will suit the nature of the beast.

I'm assuming a diesel conversion isn't on the cards?

[Tamber]

As far as I understand it, they're of the same family but not directly related. There's a definite resemblance on the outside, though.

Diesel conversion not on the cards, no.

[kevins]

I'd stick with stock as well, you could always supercharge it at a later date.

[legend]

if you have the head off you can measure the chambers and calc the compression ratio,

[Tamber]

Apr 12, 2020 19:23:16 GMT legend said:

if you have the head off you can measure the chambers and calc the compression ratio,

Already did! And I got 120cc, which appears to work out to having a CR of 7.4:1, which certainly isn't what I'm expecting. I really do need to go double-check things just to confirm what reality I'm operating with. (Would help if I'd not already pulled all the pistons out, but hey, I can sling one back in again quickly enough.)

Who knows, there's always the possibility that there's another engine change that occurred in a range later than my manual covers, and I'm operating on faulty assumptions from the start!

[Tamber]

Well, sanity check done. I started with very little of it, and I still have very little left. Also, the other measurements appear to be what I was expecting, so the engine does appear to be somewhere a little north of 7:1 comp (possibly nearer 7.5, depending on the head-gasket thickness). Nice!

Since then, I have... ...mostly just painted the bumper. Well, the weather was nice up until about 1 this afternoon, so why not. Shown here after the black stripes were done, but before I masked it off to start on the yellow.


I've also been noodling over how to mount that front towing hitch (Probably something similar to how it was before, but less wonky), and the winch that I may or may not fit (Below -- and slightly behind -- the front bumper, with drop-brackets from the chassis, I think.)

Furthermore, I removed a gaping hole in the roof where there used to be a wiper spindle, and put back a neat hole that fits a wiper spindle.




Welds on the back still need tidying up, but since that whole cavity behind that upper 'dash' section needs serious attention, I just slapped it with paint for now.

Flush with success from that, I went to free up the other spindle to try have a matching pair. And snapped the spindle shaft trying to turn it.
Okay, I'll have to make a new shaft, just need to get the remains of the seized old one out...

...and then I managed to snap the cast mazak outer, trying to drift the remains of the shaft out. Marvellous. Some minor engineering drawing done to come up with a replacement, but it seems perfectly feasible with a lathe.

In better news, more of my EFI conversion pieces have arrived. Idle air valve (A VW part), and now ignition coil-pack (for a Vauxhall Omega V6), to be added to the pile.

[greencarfritz]

This is the best thing ever, do keep us updated with it all! Thanks!

[generallee]

Pretty much what Mr Fritz said ^^^^

[a30racer]

I have really enjoyed reading your thread on the old Bedford. An inspiration to those who moan about how cold your garage is, when you're slaving away outside.
A great effort so far and hope you have sufficient momentum / enthusiasm to get the old war-horse gracing the highways again.