• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

BJ8-BT7 Tri-carb Conversion?

Share this page

6

62BT7

Senior Member
Country flag
Offline
Forum Members: Howdy, I'm a new member, an owner of a recently acquired '62 AH 3000 Mk. II. I have a project in mind and have looked online for the answer; also inquired of the local AH club to no avail. Here's the issue: The owner(s?) past at some point installed a later version BJ8 engine (29KR, etc.) into my car. The car runs great on the stock BJ8 carbs, but I'd like to take a run at installing the original tri-carb set up. Yes, I've heard it's a relatively tricky assembly, harder to tune, etc. Call me crazy...but I'd like to give it a go. I have the complete set-up in boxes in the garage (E-bay purchase) and have pored over diagrams and photos of the assembly, linkage, etc. I'm comfortable I can do it mechanically, but the missing link for me is the tri-carb>BJ8 rejetting. I've seen a web post on rejetting a triple BJ7 set up (HD6?) to a BJ8 cam but nothing on a triple HS4 carb set up to a BJ8 block & cam. To throw a bit more on the bonfire: I live in Denver at 5000' altitude. Does anyone have ANY info on the rejetting issue? Any other tips would be greatly appreciated. Many thanks in advance.
 
Sounds like your already to go here. Why not just install them and worry about the tuning afterwards? If your asking has anyone else done this before I'm sorry I can't help you there.
Good Luck.
 
You might consider sending them off to Joe Cortino or another reputable carb rebuilder. I had good luck rebuilding my twins a few years back. Not hard, just need a clean area, good light and patience. Once on the car tuning them is not that difficult and once set, don't change them. Remember 90% of SU problems are electrical (timing).

If you need assurance about your kit being complete call Bill Bolton. He should have any missing bits. Alternatively get a hold or Roger Moment there in Colorado, he is a very very saavy cat on these cars. Rumor is Roger accepts bribes.
 
I agree with the others. Do the install and mess with the fiddly stuff afterwards, that’s assuming they are in good working order. Just food for thought…there is a reason why BMC switched back to a dual carb setup, but reason probably doesn't figure into the equation. Whatever your plans you will find a wealth of knowledge on this forum and many helpful people. Best of luck with your Healey.
 
Actually the reason was entirely logical - Healey got feedback that the tri-carb set up was to difficult to maintain....
 
Scott: Thanks very much. I've seen this article before a few months ago, it's part of my growing conversion library. Although I suspect there's probably a near perfect jet for the conversion I plan, there's obviously little chance anyone would have the exact same set of variables as my situation (altitude, slightly modified distributor curve, a future aluminum head install, etc) Still, it was worth asking if anyone had jetting info on the basic tricarb>BJ8 conversion. The article you've attached just reinforces that the stock MK II jet/spring set-up probably will be OK (e.g. in the article it was the best with a BJ8 cam and 3 HD6's) and it'll probably fire up with the 3 HS4's I'll use. Finding that elusive best jet combo will no doubt be like finding a needle in a haystack...ha! Couldn't resist! Thanks again.
 
I haven’t paid for the full version of this program, but WinSU seems pretty cool. It doesn’t cover my Mikuni carbs but it may help with what you want. You can download a trial version to see how it works before you take the plunge.
 
Back
Top