Performance Upgrades

[Money_Pit]

I've decided to give the stock engine with HD6 carbs a little bit of a power boost. Without going to radicle (I'll regrind the existing crank to BJ8 specs) what would you suggest for other performance upgrades? Go HD8 carbs or go all the way with Weber tri carbs?


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[Dave Russell]

I think that Weber tri carbs are an expensive overkill for a street engine & kind of hard to get jetted & sized right. Note that the Healey tri carbs used -6 carbs not -8's. Two HD8's should be more than enough. Building it to BJ8 specs should do a pretty fair job.
D

 

[Money_Pit]

Dave

I think your right. I don't think for the cost you really get that much more out of the webers. I've got a spare 1957 2 port engine thats just been torn down and cleaned. About the only thing of use is the block. Me thinks I should just do a build up on that and save the BJ7 in tact!

 

[Dave Russell]

BJ7 Upgrades
There are a number of things you can do to increase power & reliability:
I have no idea how extensive/expensive you wish to go on this project.

A Pertronix ignition & coil is a good start.

The reground cam must be used with new or reconditioned lifters. The lifters must be all checked for a hardness of RC50 to RC55. The cam & lifters should be coated with a good cam assembly lube & cam breakin procedures followed. New cam chain & sprockets should be used. Installed cam timing should be checked against specs with a degree wheel & dial indicator. While you are at it, verify the TDC marking on the front pulley. There are ways to correct timing errors if found. Valve springs must be up to spec & the keepers & retainers in top condition. If in doubt, replace them.

If oil pressure is not presently around 30 hot idle & 50 running, either the oil pump is worn, or crank & cam bearings may be too loose. If the pressure is unknown, check the oil pump clearances & bearing clearances against spec.

Cylinders should be rebored if the bores are not perfectly round & with no taper. The cylinders should be bored to fit each individual piston. Not all pistons in a set may be exactly the same. If not reboring, the cylinders should still be honed with a surface finish that is compatible with the rings you are using. Not all rings use the same cylinder finish. Cylinder bore condition & piston & ring fit will probably make the single biggest difference in power. The Deves style (gapless) rings seem to work very well.

Rocker arms & the shaft are frequently worn & they can be reconditioned if not perfect. Otherwise they will flood the valve stems with excessive oil which is drawn into the combustion chambers. Oil in the combustion process noticeably lowers the effective octane rating of fuels.

The head & block mating surfaces should be perfectly flat within .002" & corrected if they are not. Manifolds & mating head surfaces should be flat within .005". You can run a large heavy, stiff, flat file over the surfaces to easily see any low spots. Low spots can be measured with a straight edge & feeler gages. I would use new cylinder head studs, washers, & nuts.

Valve guide to valve stem clearances & valve seating must be perfect. So called three angle valve jobs can make a noticeable improvement. Valve guides can be machined for much improved stem seals.

Note that most of this involves perfect fitting of stock parts. We are talking semi blueprinting here which can make 20% difference in power over an engine that is just stuck together with some hope that everything is correct. Even with the same go fast goodies. It can also make a large difference in how long the engine lasts.

As previously noted, two HD8 carbs will provide more than enough air for the engine. The stock exhaust system is pretty good but a set of good headers will help a bit.

It would be good to have the crank & rods Magnafluxed to verify that nothing is about to break.

You can check a newly built engine with a cylinder leak down tester. A well built engine should measure no more than three percent leakage even with no break in except for the 20 minute cam break in run.

Have fun,
D

 

[JamesWilson]

I might add to Dave's list:

1) Aluminium rear engine plate and Oil Seal Kit.
2) Lightened flywheel.
3) Upgrade to BJ8 Clutch & Pressure Plate.
4) Tubular exhaust manifold.
5) Spin-on Oil Filter (not really a performance enhancement)
6) The moving parts could all be balanced.

 

[Money_Pit]

Thanks Dave and James

By the time I have all the work finished off that you mention I will indeed be living up to my handle! Suggestions on suppliers?

 

[vette]

Hi Money, My Bj7 engine was built by the P.O. , it is really a sweat running engine. It has HD8 carbs and a reground cam that i have been told was intended for ralling. So I really don't know its profile. But the engine is quick reving. Smoothe off idle response, and quick wind-up. there have been two down sides to this engine set up for my type usage. Firstly, it has been difficult to keep it idling much below 1000 rpms. I initially had to settle for about 900 after complete warm-up in the summer time. early this summer i did a complete tune-up (valve adjustments and all) and started playing with different initial timing adjustments. i now have it set about 3 degrees retarted from where it was at when I brought it home 3 years ago. This and readjusting my carbs has allowed me to get the idle to stay at about 600 maybe 700rpms. but with this adjustment the engine is alittle sluggish at midrange. And even in lugging it down in high gear to the 15mph range, which I usually don't do, it does not like that too much, yet I,ve read that a stock engine readily can handle that with no complaints. If I put the timing back up about 3 degrees and accept the 900 to 1000 rpm idle speed, then this engine really screams. Winds up to 5000 rpms and more with ease. but my wife and I just go for rides, and my CDl drivers license can't stand a ticket, so this engine is much more than I need. Anyway HD8's and a Cam make a big difference. /ubbthreads/images/graemlins/cheers.gif

 

[Money_Pit]

Thanks Vette

Sounds like you've got a pretty hot cam in your BJ7. I'm hoping with the setup I decide on I won't run into that but one never knows? I'm trying to get some prices on the build up from some British Suppliers. I've checked prices against a Big U.S. supplier and from what I can tell I'm better off getting it from the Brits. I'm going to leave my BJ7 engine which is a good runner in tact and use a 1957 C series for the build up. I'll have to change heads and rebore the block but I think it's the best way to go! /ubbthreads/images/graemlins/canpatriot.GIF /ubbthreads/images/graemlins/patriot.gif /ubbthreads/images/graemlins/england.gif

 

[DerekJ]

Money Pit

I suppose you know that the 1957 engine is not the same design as the 3000 so there is some risk in boring it out to 2920 cc due to the position of the water channels. There have been threads on this subject before. It has been done by several people without apparent problems - however others say its risky and caution against it.

 

[zblu]

Had mine resleeved with 21'st century barrels inserted so as to feel better!

 

[anthony7777]

jameswilson,of the 6-very good suggestions you mentioned on 'performance upgrades',#3 "upgrade to bj8 clutch and pressure plate",do you know if this would be a direct replacement change?,or would there be a need for additional modifications?i.e.throw out bearing,fork,machining etc,?thanks much.anthony7777 1963 bj7 3000 M.K.II /ubbthreads/images/graemlins/cheers.gif

 

[Money_Pit]

Thanks Derek

After talking with my machinist it's back to plan "A" and the build up on the BJ7 motor! Any one looking for a 1957 C series 2 port engine?

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