1500 top-end rebuild

[tosoutherncars]

Hi all,

I posted in the Spridget section, but since it's a Spitfire engine I thought this might be of interest over here...

I blew my head gasket (between pistons 3 and 4) on Friday (rather spectacularly - car lost all power, compression measured at 150 / 150 / 20 / 20.) I'm refreshing things as I R&R. Here's the list...

- Head milled .100" to raise compression ratio (it's the low-comp NA head, used with dished pistons)
- mild homebrew port job (intake runners only, Dremel and sandpaper cartridges)
- Valves cleaned and lapped
- Viton valve stem seals installed (on both intake and exhaust)
- new water pump
- mechanical fan delete (inefficient, heavy, broken clutch currently ziptied together)
- electric fan with automatic controller
- Payen head gasket and all ancilliary gaskets
- 165 deg. thermostat


FWIW, the Payen gasket set looks MUCH better than the one I took out (Felpro, maybe?) It is rubberized, has copper o-rings around each water jacket hole, and the siamesed rings (for the later, recessed blocks) are attached to each other (1&2, 3&4). The cheaper HG had four seperate rings, and of course it blew out between 3 and 4 where there is no 'meat' to the gasket.

Hopefully I can get it back on the road in a week, we'll see how long the machine shop takes. Funny story, I told them I wanted "a tenth of an inch" off. "That's too much, you mean ten thou" said the owner. "No, really... a tenth" said I. Had to show them the low-comp head before they would agree to do it.

My sorta-local Moss distributor (Pièces Robert in Montreal) was able to supply a controller / relay for the electric fan (ebay). A little pricey ($45) but it came with an inductive pickup that sits between the rad fins. I would be interested to know if I could use the temp sensor that is already installed in the rad... do these work on resistance? If I put them in boiling water and measured resistance across both of them, would similar readings mean I could use the stock sensor?

Pics... starting the porting.

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/headporting007.jpg

New electric fan

https://i10.photobucket.com/albums/a126/tosoutherncars/Midget/June23003.jpg

 

[AltaKnight]

Funny story, I told them I wanted "a tenth of an inch" off. "That's too much, you mean ten thou" said the owner. "No, really... a tenth" said I. Had to show them the low-comp head before they would agree to do it.

I also had 100 thou machined off my TR6 head recently, that raised the CR to about 9.00:1 roughly.
My machine shop (who know LBC's) didn't want to take that much off either, had to sign my life away to get them to do it, but it worked perfectly.

 

[tosoutherncars]

Graham, what difference did you see, as far as the driving experience?

 

[AltaKnight]

Still working on that Duncan.
I also installed a TH5 cam from BPNW at the same time, c/w lifters and shorter push rods.
I've only got just over 400 miles on it since and haven't got over 3500 rpm yet though I'm getting close to opening it up now.
Initial impressions are very good on the "get up and go" aspect now that I've corrected the valve timing (my fault), it doesn't ping or run-on but it is lumpy on the idle (I think that's the cam), it's very smooth from 1200rpm up. I may have problems with the carb bypass valves at idle.
Another week or two and I can really open it up.

 

[tosoutherncars]

Question...

My 1500 has about 85k miles on it. Bores look in very good shape, thrust washers just done a few hundred miles ago. Compression was 150 across the first two cylinders, even with the valves at .015 and the HG blown between 3 and 4.

While the head is off for machining, engine still in the car... should I be thinking about doing anything else to the bottom end? Rings, lower end bearings? Or should I leave well enough alone? I don't want to be off the road for more than about a week, two at the max.

Thx,
Duncan

 

[AltaKnight]

Most definately yes. If not already done and everything is in good shape then do the following;

New rings
New main bearings
New rod bearings
Thrust washers, oh, you've done them already

When I checked the bearings on my car at 50K miles the babitt metal was half gone showing plenty of underlying bronze metal. The journals were perfect and checking with a micrometer showed no perceptable wear; the oil pressure really came up after that.

When you change the rings, check the pistons for wear (see manual for tolerances) make sure you check/adjust the ring end gaps in the bore before installing them on the piston.

All these are reasonably easy to do with the engine in place, although you will have to stay at it to get it all done in a week (assuming you have and need your day job!)

 

[tosoutherncars]

Shoot, I was afraid you were going to say that...

1) Is a place like NAPA likely to have the rings & bearings?

2) I'm guessing the rings are easier to do with the head off? Never done any bottom-end work before.

TIA,
Duncan

 

[70herald]

Uhm with 150 PSI, your rings are in good condition. you are just asking for ex$pen$ive troubles by pulling out the pistons. Since the bores are in good condition, and the engine was running well, prior to the gasket failing I wouldn't even consider pulling the pistons. If you do, you will also need to re-hone the cylinders so that the new rings seat properly. You will also need to get special top rings which are cut so that they don't hit the ridge which develops at the top of the bore. Normal rings WILL break if there is any ridge at the top of the cylinder.

If you want to do some more work, then what you should do are the main bearings and the big end bearings. The 1500 engine is rather hard on these bearings do to the long stroke and the weight of the crank, particularly since the balancing work done at the factory was not exactly great. (The 1300 crank I pulled out of my old engine looked like it was balanced with an angle grinder)

In general, if you want to ensure long engine life, you should swap the main / big end and thrust bearings about every 30,000 miles on these engines and you will never have a problem.

As for the thermostat, yes it works on resistance, but as for using it to switch on the fan, it seems like more trouble than it was worth. A year or so ago, someone here was trying to design a circuit to do exactly that, and eventually gave up.

The only question I have is why the gasket blew in the first place?

 

[tosoutherncars]

The only question I have is why the gasket blew in the first place?

Good question! Well, the head was last off about 1200 miles ago, when an intake valve broke. It was torqued down initially, but never retorqued. It was also a discount brand, not nearly as solid as the Payen that is replacing it.

The head didn't seem warped (measuring corner to corner with a straitedge) but it will be even straighter after the machining it's currently undergoing.

Running temps seemed fine, no overheating.

I do drive it fairly hard, though... :wink:

Thanks for the comments, 70herald. I really don't relish the thought of pulling the pistons and doing rings right now, so I might just do lower end bearings. I'm happy to hear that you think that's reasonable.

-D

 

[tosoutherncars]

Should be done today, the shop tells me... Woo hoo!! High compression, here I come.

 

[Mark Jones]

I'm a little late answering here but for main and connecting bearings, Christian Hollum in Lachine still has Vandervel bearings in many sizes for the 1500 engine. Chrstian Hollum

 

[tosoutherncars]

Darn, wish I'd known that when I went to pick up my parts in MTL last weekend! I'll definitely give them a call, once I know whether my main bearings are standard. Thanks for the tip, Mark!

 

[aeronca65t]

......I'll definitely give them a call, once I know whether my main bearings are standard. Thanks for the tip, Mark!

Is the engine out of the car?

If it isn't (and you don't intend to pull it out) it's impossible to replace main bearings.

For what it's worth, the main bearings in my 1500 racer have about 60 hard hours on them and they're still OK. That's probably like 100,000 miles on a street car.

The wear on main bearings is far less than the wear on rod bearings (assuming reasonably regular oil changes).

I swap out my rod bearings and thrust washers on my 1500 every 20 to 25 hours and the rod bearings always show considerable wear. For sure, I'd swap them (and it's good you already have the thrust washers done).

The rings are sort of a toss up. Your head milling will put a slight bit more strain on them (higher comp), so it's not a bad idea to change them (I would). It just requires the confidence to give it a try. The pistons *must* come out throught the top, so yes, with the head off is the right time to do it.

If you decide to do the rings, put a new one in the bore (without piston) and check the "end-gap". This can be done with a feeler gauge and is a reasonably good way to see if the bores are decent (but it would be best to measure them with an inside micrometer too).

Be sure to get piston grooves clean and mark the "front" of pistons before removing them so you don't reinstall backwards.

I find that I can get parts for my Brit cars from AutoZone and NAPA almost as easily as from Moss.

 

[Mark Jones]

I did a bottom-end rebuild on my Spitfire 6 years ago. I have no idea how many miles are on the engine, but it had a bit of tapping at higher rpms. Compression was good so I left the cylinders and head alone, that was about 15,000 miles ago.

One thing to check is the thrustwashers by pushing hte crank back and forth to see if the thrustwashers are worn or not.

 

[tosoutherncars]

Nial, do you typically hone the bore as you're doing rings (in the car?) Or just clean?

So, if I'm feeling brave...

- drop the oil pan

- disconnect the con rod bolt

- push piston / conrod out top of engine

- insert ring in bore, measure end gap

- R&R piston rings, reinsert piston in bore

- intall new con rod bearings

- reinsert con rod bolt (cannot be reused?)

- repeat x3

Do I have that about right? (I'll get out the shop manual when I get home.)

 

[startech47]

Make sure you torque the rod, main, and head fasteners to the correct value and in the correct pattern.

 

[tosoutherncars]

Absolutely... torque wrench at the ready.

 

[Fishplate]

Is the engine out of the car?

If it isn't (and you don't intend to pull it out) it's impossible to replace main bearings.

Huh? I've done it on a '76 Spitfire 1500...it was a piece of cake. Kind of hard on an air-cooled VW, but that's another story...

 

[70herald]

If it isn't (and you don't intend to pull it out) it's impossible to replace main bearings.

Nial
Is there something on the frame of the MG which makes it impossible to get the oil pan off? As long as the pan comes off, the mains can be replaced, without pulling the crank. Easier with the engine out, but doable.

 

[startech47]

You can't remove the crank with the engine in the car, but you should be able to replace the main bearings. You will need to loosen all main bearing bolts and remove one cap at a time. They make a tool or you can make it out of a cotter pin. It looks like a t-nail. You insert it into the oil hole in the main journal and rotate the crank shaft by hand to remove and replace the upper main bearing shell. Make sure you plasti-gauge the clearances after the bearing replacement.