• Hi Guest! Being a Paying Supporter is NOT a requirement to participate at BCF. However, subscribing will help ensure we can continue to serve the LBC community for years to come. If you enjoy BCF and find our forum a useful resource...Please consider supporting us by **Upgrading**
    (PS: Subscribers don't see this banner)
Tips
Tips

1500 top-end rebuild

tosoutherncars

Jedi Knight
Offline
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

Jedi Knight
Offline
tosoutherncars said:
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.
 

AltaKnight

Jedi Knight
Offline
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.
 
OP
tosoutherncars

tosoutherncars

Jedi Knight
Offline
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

Jedi Knight
Offline
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!)
 
OP
tosoutherncars

tosoutherncars

Jedi Knight
Offline
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

Luke Skywalker
Country flag
Offline
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?
 
OP
tosoutherncars

tosoutherncars

Jedi Knight
Offline
70herald said:
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. :smile:

-D
 
OP
tosoutherncars

tosoutherncars

Jedi Knight
Offline
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

Great Pumpkin
Offline
tosoutherncars said:
......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

Jedi Warrior
Offline
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.
 
OP
tosoutherncars

tosoutherncars

Jedi Knight
Offline
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.)
 

70herald

Luke Skywalker
Country flag
Offline
aeronca65t said:
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

Jedi Knight
Offline
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.
 
Similar threads
Thread starter Title Forum Replies Date
tosoutherncars 1500 top end refresh Spridgets 4
Morris 9:1 flat top 1500 pistons Spridgets 0
D Spitfire Top replacement recommendations for a Spit 1500??? Triumph 9
Thor Does the coil mount on top of pedal box on 1500? Spridgets 2
G 79 Midget 1500 overheating Spridgets 2
G General MG Leaking Fuel on twin HS4's 1500 MG Midget MG 5
I Spitfire Triumph Spitfire 1500 refuses to awake after 10 year hibernation Triumph 5
I Spitfire spitfire 1500 refuses to awake after 10 years Triumph 2
M Spitfire 1500 LH Door Triumph Classifieds 0
M 1976 Spitfire 1500 (RHD) Triumph Classifieds 2
B COMPLETE DROP-IN Rebuilt 1975/6 MG Midget 1500 engine PLUS rebuilt Spitfire Overdrive trans NEVER INSTALLED Spridgets Classified 0
R Spitfire Spitfire 1500 Triumph 3
B MGA Solution! 1600 harness in a 1500 MG 1
S For Sale Mg t-series crankshaft tb tc td tf 1250 1500 MG Classifieds 0
R Spitfire 1500 gearbox question Triumph 1
R 1500 gearbox question Spridgets 0
A Spitfire Need help with 1980 Spitfire 1500 Triumph 5
A 76 Midget 1500 Oil filter Spridgets 6
M Wanted Twin carb manifold for 1500 Midget or spitfire Spridgets Classified 3
M Rocker feed kit for 1500 from Victoria British Spridgets 0
G For Sale TR2 TR3 TR3A TR3B Unrestored Hardtop with Window, New Hardware kit and Seals $1500 Triumph Classifieds 2
sparkydave 1500 battery cable colors Spridgets 1
GS67 1500 Operating Temperature Spridgets 2
doc50 Nash Metro w/MGA 1500 discrepancy... Other British Cars 2
doc50 Metro 1500 Has Slack Timing Chain? Other British Cars 20
B 1500 head studs Spridgets 3
DrEntropy For Sale MGA intake manifold [1500] MG Classifieds 0
busybrit For Sale 1960 MGA 1500 Restoration Project for sale. MG Classifieds 2
sparkydave 1500 clutch master Spridgets 4
Steve P. 1500 radiator in an earlier 1275 cross flow Midget? Spridgets 2
P Pristine MG TF 1500 Spotted 0
aseriesspares Spitfire What Gearbox are you using. Spitfire / Midget 1500 Triumph 2
aseriesspares What Gearbox are you using. Midget 1500 Spridgets 5
T Putting a Spitfire 1500 into a 1972 Midget Spridgets 6
AN5Sprite T-Series 1955 TF 1500 For Sale This Spring MG 3
JPSmit 1500 slave cylinder question Spridgets 0
bigjones Vacuum advance on a 1500 Spridgets 13
Rut 1500 gas pedal for sale Spridgets 7
dklawson Spitfire Spitfire 1500 Block Decking Following Boring ??? Triumph 4
dklawson Spitfire Spitfire 1500 - Front Pulley Nut Removal? Triumph 2
DanLewis Two midgets available: '79 is free [no engine, trans], running '77 $1500 [NFI] Spridgets 1
DanLewis 1500 cc MG Midget Radiator in a Bugeye??? Spridgets 5
Editor_Reid T-Series Original Price in US Dollars for an MG TF 1500 MG 4
B 1500 Exhaust Spridgets 10
F Spitfire Spitfire 1500 Mechanical Fuel Pump & Spacer Triumph 6
T Spitfire Oil Filter 1500 Triumph 1
bthompson A quick 1500 fix for when you go for reverse and rip off your shift lever! Spridgets 4
B Spitfire Advice on swapping to J Type OD with 1500 engine in 69 Spitfire Triumph 13
R reason for it said 1500 has cooling [run to hot] problems? Spridgets 18
J 1500 mg midget fuel issue Spridgets 2

Similar threads

Top