BJ7 Engine Rebuilding

[JMACENGINESHOP]

I am a British engine rebuilder, but I have not rebuilt a BJ7 before. I am building it for an enthusiast I have worked with before on another project that is now on the road. He just purchased an AH 3000 he is going to restore to former glory. We are gathering information before starting in on the engine. Here is a list of the things I want to know from the outset: (realize I know my way around engines, just not this particular engine.)

What are the weaknesses of the BJ7 motor I will want to address?
What are some things I will want to improve on to make this engine more reliable and to last longer? I already know I will want to improve the rear seal, for instance.
What has been done to the BJ7 motors, with success, to boost HP and performance?

The owner likes HP but wants to keep it drivable and fun on the road. He will not be racing this engine but while we are rebuilding it, we want fix core problems it has and at the same time add some pep to it's step. He will not want to go crazy on the money spent, but he knows he will have to spend extra to get what he wants. In other words, he wants to keep the extra expenditures practical, not extravagant.

 

[DerekJ]

I don’t think there are any weaknesses as such. These 3 litre engines are slow revving, long strokes and are pretty much indestructible if properly maintained. The fly wheel is very heavy and you can remove 6 or 8 lbs without affecting the smooth running. I would then replace the cam with a Denis Welch fast road version, or one with a similar profile. The carbs can handle that upgrade so no need to go to 2 inch HD8s. If you want more grunt than that then choose the Denis Welch Rally Cam which is still very driveable at low revs. HD8s would then be a good upgrade, or for show it’s Triple Weber’s, but that’s over carbing it for road use.

 

[Legal Bill]

Is it already apart? Will you use stock pistons or overbore it? Will you deck the head? If so, by how much? You can rebuild it to 3000 MK III specs and gain power and keep it very smooth. You would then want HD8 2 inch carbs and manifold. The stock exhaust manifold is a big impediment to power. The Dennis Welch performance manifolds make a big difference. While it is out of the car, have the radiator recore’d unless it has been replaced recently. Buy a Texas Cooler fan from Moss while you are at it. I always send out my engine parts to be balanced before reassembling. It doesn’t cost much and results in a smoother engine and less wear on the internals. Make sure the oil pump is perfect or buy a new, high quality replacement. Buy a new rocker shaft and Re bush the old rockers. This is an area where you can not only lose performance but also oil pressure.

 

[JMACENGINESHOP]

I don’t think there are any weaknesses as such. These 3 litre engines are slow revving, long strokes and are pretty much indestructible if properly maintained. The fly wheel is very heavy and you can remove 6 or 8 lbs without affecting the smooth running. I would then replace the cam with a Denis Welch fast road version, or one with a similar profile. The carbs can handle that upgrade so no need to go to 2 inch HD8s. If you want more grunt than that then choose the Denis Welch Rally Cam which is still very driveable at low revs. HD8s would then be a good upgrade, or for show it’s Triple Weber’s, but that’s over carbing it for road use.

Thanks for the replies!
Derek. I've been on Denis Welch's website; they've got a lot of great stuff. It looks like going to Fast Road is pretty costly. What about compression? Is there anything to gain there?

Bill, no, I've not got the engine yet. The owner is going to ship it to me in the next couple of weeks. We are gathering information on what we should do to it. As Derek mentioned, I know these are heavy, slow revving engines. That said, I know there are enthusiasts out there that have done things to improve on that. My machine shop will do what I tell him to do. That's the rub. I don't know what to tell him to do to the head, block, etc. I always aim for a like new engine but with performance upgrades. It will get bored for new pistons, the crank will be turned to the next undersize, the rotating assembly will be balanced; those are done to all my engines. I don't have a manual for this car so I don't have any specs to look at. I can usually download one online, but haven't found one for free yet (LOL, I'm cheap, ok I said it). The owner is supposedly going to supply the engine and spec pages from a manual. That said, I would like to find information like "if you shave .xxx off the head you will increase the compression to x.x:1, by changing to a certain cam profile will add this or that. It makes sense to lighten things up where I can, like the lighter flywheel that Derek suggested. There is not much that can be done to quicken a long stroke engine except lighter rods and pistons. Denis Welch would like to sell me a steel crank, "H" beam steel rods, Omega forged pistons, aluminum rear plate, with the various extras to the tune of $8500. That is just the bottom end. That would be nice but not financially tolerable. I usually go through the rocker assembly and will take your advice on the new shaft and rebushing the rockers. I always go with a new oil pump, good oil supply is the lifeblood of the engine.
I would like a practical list of what you would do to this engine to improve it. I am told it has a BJ8 head. I'm assuming that is a positive upgrade. If changing from the stock exhaust manifold is a good upgrade, that is very doable. If a carb change is necessary to improve the available power curve we can definitely look into that.
I've been reading about the cooling problems this engine has. I will pass along your radiator and cooling fan suggestions. I can see that happening. If we can see tangible benefit that outweighs the cost, it will probably happen. Adding bling isn't on the list.

 

[Bob_Spidell]

I had my BJ8 engine rebuilt by a local speed shop a few years ago. The engine had approx. 210K miles on it so I was certain the crankshaft would need to be ground, but my mechanic said it was still new spec and only needed polishing (I'd already bought undersized bearings--I sold them).

There were two types of oil pumps used with the 3L engine: earlier cars had a rotary vane type, and later cars, probably including BJ7s, had a gear type (the gears were made of sintered iron). The rotary vane type is recommended for road cars, the gear type for racers (DWM sells both). The gear type (presumably) moves more oil, but the gear type offers less resistance (I bought the gear type). I'm not clear on the details--the knowledgeable will correct me--but, at some point I believe an extra tooth was added to the pump drive shaft to lessen the load on the cam and shaft gears and the pump due to excessive wear (of the gears). With getting a new cam and pump you'll probably want to get a new shaft. 20PSI at hot idle is considered excellent pressure.

Running hot is a never-ending issue. The consensus seems to be that inadequate airflow through the engine compartment is the main culprit, and blocking the airflow around the radiator can help. Usually, the cars--both my BN2 and BJ8 behave exactly the same in most criteria--will be OK at speed then will heat up at idle. Certainly a radiator reconditioning and, preferably, a more efficient core is called-for (sometimes called 'Excel'). Higher flow fans help a little, maybe an aluminium rad would too, but it's something most of us have learned to live with. The racers often install side vents, some have cleverly hidden vents in the wheel wells. My BN2 is a 100M so has the 'louvred bonnet,' but still heats up at idle.

The quality of aftermarket parts is sometimes suspect. There is one brand--County--that many would say to avoid--esp. their water pumps--but some have had OK results for pistons. Aftermarket water pumps are iffy, but there's a guy in Canada that rebuilds BJ8 water pumps and sells kits. BJ7s and early BJ8s came with 3/8" pulleys and belts and later BJ8s used 1/2". AFAIK, the only difference is the pulleys, but I won't swear to it. I have DWM fast road cam--with tappets; they sell both as a kit--pistons and oil pump and am happy with them. Forged pistons are overkill for a road car, but I didn't want to worry.

Adding a rear main seal is hit-or-miss; some see little-to-no improvement in oil loss, some have better luck. We installed one on our BN2, and I think it increased sump pressure (compression is very high on all 4). I have a PCV setup on my BJ8, with no seal, and it only loses a few drips after a long run; I'm looking into installing one on my BN2.

I don't know about other British cars, but the throttle linkage in a Big Healey is a Rube Goldberg contraption (some have gone to a cable setup). There is a specific setup/adjustment sequence in the manual, needed to get the most out of the induction system. Tell the owner to have a good look at his throttle cross-shaft on the scuttle; the bushings are almost certainly shot if original, introducing slop in the arrangement. New, aftermarket teflon replacements are ideal.

It's a flat tappet cam, so proper break-in is critical. My builder did mine on a stand, and replaced my Pertronix electronic points with mechanical points so he could time it to start on the first crank (and forgot to re-time it when he put the Pertronix back in--engine ran like crap when I got it back in the car, until I checked timing). Break-in oil is a good idea for the first 500 miles or so.

 

[Legal Bill]

Thanks for the replies!
Derek. I've been on Denis Welch's website; they've got a lot of great stuff. It looks like going to Fast Road is pretty costly. What about compression? Is there anything to gain there?

Bill, no, I've not got the engine yet. The owner is going to ship it to me in the next couple of weeks. We are gathering information on what we should do to it. As Derek mentioned, I know these are heavy, slow revving engines. That said, I know there are enthusiasts out there that have done things to improve on that. My machine shop will do what I tell him to do. That's the rub. I don't know what to tell him to do to the head, block, etc. I always aim for a like new engine but with performance upgrades. It will get bored for new pistons, the crank will be turned to the next undersize, the rotating assembly will be balanced; those are done to all my engines. I don't have a manual for this car so I don't have any specs to look at. I can usually download one online, but haven't found one for free yet (LOL, I'm cheap, ok I said it). The owner is supposedly going to supply the engine and spec pages from a manual. That said, I would like to find information like "if you shave .xxx off the head you will increase the compression to x.x:1, by changing to a certain cam profile will add this or that. It makes sense to lighten things up where I can, like the lighter flywheel that Derek suggested. There is not much that can be done to quicken a long stroke engine except lighter rods and pistons. Denis Welch would like to sell me a steel crank, "H" beam steel rods, Omega forged pistons, aluminum rear plate, with the various extras to the tune of $8500. That is just the bottom end. That would be nice but not financially tolerable. I usually go through the rocker assembly and will take your advice on the new shaft and rebushing the rockers. I always go with a new oil pump, good oil supply is the lifeblood of the engine.
I would like a practical list of what you would do to this engine to improve it. I am told it has a BJ8 head. I'm assuming that is a positive upgrade. If changing from the stock exhaust manifold is a good upgrade, that is very doable. If a carb change is necessary to improve the available power curve we can definitely look into that.
I've been reading about the cooling problems this engine has. I will pass along your radiator and cooling fan suggestions. I can see that happening. If we can see tangible benefit that outweighs the cost, it will probably happen. Adding bling isn't on the list.

Unless the customer lives in an area where he can easily buy high octane fuel (like a LOT higher than 93) I would not go for higher compression, beyond whatever the results are from oversized pistons and decking the head enough to get it perfectly flat. I find it is tough enough to time out the knock and run-on with oversized pistons and a modest deck job.
The BJ-8 cam with 2” carbs and bigger pistons and 6-10K off the deck will easily surpass 150 hp. Add a good exhaust manifold and you should be between 165 and 170 HP. I don’t know how different the BJ8 cam is from a road grind cam. I would give Welch a call and ask them about it. You can buy a Healey manual (Bentley) for short money. Charge the client for it and give it to him with the engine. He’ll need it!!

 

[Bob_Spidell]

IIRC, all DWM cams except the DWM1 ('road') require a relief ground into the head. Also, DWM, and others, sell an upgraded timing chain tensioner ('stock' aftermarket have been known to come apart). It's one thing that I wish I'd put in my engine. Both my BN2 and BJ8 engines suffer from run-on ('dieseling'); higher compression would likely make that worse, lighter flywheels might help.

 

[John Turney]

The DWM cams, except the DMW1 require reliefs machined in the block. I would stick to the DWM1. DWM's cams come with better lifters/tappets than stock and are recommended.

The new rocker shaft should be nitrided / Tuftrided to reduce wear. Wear on that shaft is a weak point.

The earlier, vane-type oil pumps produce more flow, but are weaker. That's why they were changed. Agree to avoid County brand. A friend bought one of their oil pumps and the clearances on it were worse than on his old pump. The oil pump drive is the same shaft as the distributor drive.

Agree that lightening the flywheel is probably the best mod to make the engine seem more powerful, although it really isn't.

I did get a BJ8 intake manifold and HD8 SUs. The BJ8 did make more power than the BJ7, because of the cam and bigger carbs. Triple Webers are for racing and looks only. SUs seem to be better at part throttle.

The oil feed passage to the head passes close to a water passage. Some people have found corrosion between the two, so it should be checked.

The recommendations from DWM are good for racing, but useless on a road car.

 

[Bob_Spidell]

DWM also offers 'bucket' lifters (probably not a big upgrade for a road engine, though).

 

[JMACENGINESHOP]

You guys are coming through bigtime! This is awesome information! When I formulate a plan with the owner, I'll come back and run our plan by you again to see if you concur or can add information.

Thank you, thank you, thank you!

 

[DerekJ]

I agree lightening the flywheel doesn’t increase power per se but it does increase responsiveness so you get up to max power more quickly. This is why F1 cars don‘t have flywheels.

Its easy to spend a lot of money very quickly, that’s why it’s important to decide what it is you want and how much you have to spend. You cannot add 50 BHp without spending a lot. Also the original bhp numbers are overstated, a stock BJ8 engine does not produce 150bhp.

The biggest addition to power will come from an upgraded cam shaft. Forget fancy stuff like steel crankshafts, aluminium backplates and radiators etc. Tubular exhaust manifold is worth about 5 bhp

 

[JMACENGINESHOP]

Yeah, the steel crank and rods are off the table; too costly. We might do the aluminum flywheel as a way to lighten the rotating assembly and make it a hair quicker which is like cutting the tail off a hippo. I'm still waiting on the spec pages from the manual so I don't know what compression ratio this engine had from the factory. Compression is often an easy way to squeak more HP, but if this engine already has 9:1 compression I will need to find the HP elsewhere. If it was 8:1 I might be able to find a little HP in increasing the compression. But from what Legal Bill said about knock and run-on, I will have to think that through carefully. Some of things are all relative to other components of the system; like if I change the cam, I will need to increase the flow to the head from the manifold and carbs as well. I think it already has the BJ8 head, if I add the BJ8 cam profile and 2" carbs I may have what I want or as much as my client can afford. Basically, all I'm doing is making a BJ7 into a BJ8.

I agree 100% on how quickly we can spend money. My client knows he will have to spend a little more but we don't want that part to balloon on us. Spending more money doesn't always translate into more HP. I am trying to gain enough information that we don't spend money on things that don't gain us much or hurt our desired outcome.

 

[Legal Bill]

Austin Healey 100-6 and 3000 Workshop Manual | eBay

Find many great new & used options and get the best deals for Austin Healey 100-6 and 3000 Workshop Manual at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[twas_brillig]

Jere: suggest to your client that he join this site, and that he & you should spend a few minutes reading through these two threads:

> Restoration: What Would You Have Done Differently? <

> Tasteful upgrades for a BJ7 <

They are generic to the whole car, but contain some specific comments regards the engine & accessories. Whilst (Yay! I speak British as well as Canadian/American!) looking for the above, I ran across the following on cooling. They are just examples, but one contains a link to a very good article

> Electric Fan vs. Texas Cooler <

> New water pumps on the market <

A couple of suggestions for items to think about:
- don't throw anything out! There's the possibility that the worn out item you're replacing is better than the aftermarket replacement (oil and water pumps, as an example)
- consider getting hardened seats for the head if it doesn't have them already
-oil pressure is limited by a 'bullet' and spring in the side of the block. I'm suspicious that our engine has some wear at the metal to metal interface, and it might benefit during a distant future rebuild from having the faces ground/polished/lapped/whatever to provide a good seal
- get the radiator triple cored. I like the reliability of having an original radiator that can be repaired vs. installing an aluminium one.
- use Water Wetter in the cooling system
- make sure that your client understands that flat- tappet engines have specific engine oil needs

I don't consider our BJ7 at all powerful, but it does gather speed majestically. Good fortune to you and your client

 

[dougie]

Yeah, the steel crank and rods are off the table; too costly. We might do the aluminum flywheel as a way to lighten the rotating assembly and make it a hair quicker which is like cutting the tail off a hippo. I'm still waiting on the spec pages from the manual so I don't know what compression ratio this engine had from the factory. Compression is often an easy way to squeak more HP, but if this engine already has 9:1 compression I will need to find the HP elsewhere. If it was 8:1 I might be able to find a little HP in increasing the compression. But from what Legal Bill said about knock and run-on, I will have to think that through carefully. Some of things are all relative to other components of the system; like if I change the cam, I will need to increase the flow to the head from the manifold and carbs as well. I think it already has the BJ8 head, if I add the BJ8 cam profile and 2" carbs I may have what I want or as much as my client can afford. Basically, all I'm doing is making a BJ7 into a BJ8.

I agree 100% on how quickly we can spend money. My client knows he will have to spend a little more but we don't want that part to balloon on us. Spending more money doesn't always translate into more HP. I am trying to gain enough information that we don't spend money on things that don't gain us much or hurt our desired outcome.

Hello Jere -

I moved away for DWM motor parts years ago due to the expense and suspect build quality. I've been using US high quality Comp Performance Chevy LS valves & heavy duty beehive springs in all my race motors for years. It just takes an easily made spacers to accommodate the additional length. You'll gain all the power you'll need for a street performance Healey 6-cylinder with a BJ8 cam and a proper ported head. I ran my first performance street/track motor with a BJ8 cam & twin SU HD8's, proper ported and and valve train. It made made 200 hp at the wheels and was very streetable, although a loud for the neighborhood.....

 

[Legal Bill]

Dougie, I’m just wondering if you decked that head and cc’d the combustion chambers and if so, are you willing to share the numbers you used?

 

[bob hughes]

Often missed in a rebuild is the oil way that runs up through the block and feeds into the cylinder head for the rocker shaft.
after a length of time these things can start leaking as they pass through the water jacket and they can get severly corroded.
Kits can be purchased from most of the usual suspects. I actually got mine from SC Parts and Bill Rawles installed it for me, as he had the equipment to do it with. You don't want to be dealing with that sort of a problem after a rebuild.



Bob

 

[dcarlg]

Very good advice so far.
For improved reliability I would add:

1. Gapless second rings on pistons.
2. Pertronix ignition.
3. Lucas Sports or Pertronix Flamethrower coil.
4. Gear reduction starter motor.
5. Alternator.
6. Proper bellows-type thermostat.

Good luck with your project.
The support in this forum is incredible.


Douglas Glesmann


Disclaimers:
I'm not a mechanic.
I'm not an engineer.
Sample size of 1 Healey, but I've learned a lot working on it since 1976.

 

[dougie]

Dougie, I’m just wondering if you decked that head and cc’d the combustion chambers and if so, are you willing to share the numbers you used?

The iron head pictured is one of my older units it was just very lightly decked to clean-up any uneven areas. Its at 50cc, and I ran it at 9.5:1 compression with small domed pistons. I'm running a totally different combination on my full racers motors.

 

[Legal Bill]

The iron head pictured is one of my older units it was just very lightly decked to clean-up any uneven areas. Its at 50cc, and I ran it at 9.5:1 compression with small domed pistons. I'm running a totally different combination on my full racers motors.

Thanks. Do you recall what grade gas you ran on with that engine?