• 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

Port and polish BJ8

Share this page

S

SteveHall64Healey

Jedi Trainee
Offline
Has anyone had any experience with a port and polish on a BJ8? Specifically, I am looking to understand the observed performance improvement and what carb and/or needle changes were needed.
steve
 
I don't think there's a lot out there that will provide the info you're looking for, unless you can get some of the racers to give up their secrets. Perhaps your best source is some of the period articles that were published. Go to John Sims's website: https://healey6.com/technical.htm and look under "Competition". There are a few articles there describing period mods like polishing and the correct carb needles.
 
Al those years of porting, port matching and polishing..decades even...and someone figured out a certain amount of port mismatch and port roughness actually improved performance by keeping the mix...mixed.
Dead smooth, they figured out fuel started dropping out of the mix.
Go figure.
 
Heres what I did and its real easy .
Get your new intake manifold gasket and snuggly bolt it to the intake manifold with nuts and bolts in its correct location . DONT CRUSH IT...
Take you favorite die grinder and bit and open up the ports to the same size as the holes in the gasket and carefully look at the way the port goes and smooth away any rough spots .
Now I know all you experts and race heads are gonna tell me I don't have a clue and its not flow balanced blah blah blah ...... But it worked ...more power and had to just dial in more fuel to get the plugs that nice tan colour again as she ran too lean . More air you need more fuel .
Now if your going full bore race performance then yes you need more precision but if you just want to go with more air more fuel more power equation then I can say Yes It Works .
 
Healey Nut said:
Heres what I did and its real easy .
Get your new intake manifold gasket and snuggly bolt it to the intake manifold with nuts and bolts in its correct location . DONT CRUSH IT...
Take you favorite die grinder and bit and open up the ports to the same size as the holes in the gasket and carefully look at the way the port goes and smooth away any rough spots .
Now I know all you experts and race heads are gonna tell me I don't have a clue and its not flow balanced blah blah blah ...... But it worked ...more power and had to just dial in more fuel to get the plugs that nice tan colour again as she ran too lean . More air you need more fuel .
Now if your going full bore race performance then yes you need more precision but if you just want to go with more air more fuel more power equation then I can say Yes It Works .
Click to expand...

How is smoothness through the rev range? Did you just dial in more fuel or also change the needle?
steve
 
Steve, what Healey Nut is describing is a simple port match. Is this all you are doing to the engine? Is it otherwise stock? It would be hard to predict what changes to the carbs are required or possible without knowing more. If that is all you are doing, I'd probably tune it with the stock needles and then go up one needle size to a richer midrange and see how it compares. You would not need different carbs to take advantage of a simple port match.

Please be sure to match the gasket to the head and then compare the gasket to the manifolds before you start grinding anything. You want to make sure the gasket openings are already the same size and shape as the openings on the head before you start grinding the manifolds. If not, all you have done is matched the openings in the manifold to a gasket and fuel air mixture will run into the same restriction about 30 thousandths of in inch later when it hits the openings in the head. Often you have to cut away on both sides of the gasket.
 
No needle changes , just re dialed in the mixture to compensate for the extra air the engine needed . She runs smooth right through the rev range .

The carbs were fresh rebuilds from Apple Hydraulics so were already balanced . I just had to re tweak the mixture .
 
Getting your carbs dialed in always make your engine run better. But, if you really want to make a difference, replace your exhaust manifold with headers. Otherwise, all of those other little tweaks are pretty much useless in making more power.
 
What exhaust system works best with headers--'big bore,' stock, etc. (not interested in side exhaust ... I spend 400+ miles in my BJ8 at times)?
 
Thanks for the links, Bill. I'll keep these in mind come overhaul time.

Any effects from not having an exhaust manifold in contact with the intake manifold to heat the incoming charge ('American-style' fixed-choke carbs use coolant circulated through the base of the carb to prevent icing)?
 
Bob, sorry if I created the impression that I have these parts. I went completely stock with the exception of the oversized pistons and light milling of the head, both of which were needed due to wear. I did consider building the car with some light engine mods, but decided against it. I would have purchased the headers and exhaust (or whatever the equivalent exhaust was at the time) if I had gone that route. I would have lightly reshaped the combustion chambers, opened and matched the intake and exhaust ports and milled the head to get to 9 to 1 compression.
 
DerekJ said:
Dennis Welch claim they tested a BJ8 before and after they installed headers and the difference was 8 bhp.
Click to expand...
I wonder if they did that to the air-cleaner that they claim an increase of 6 bhp for the BJ8's?
 

Attachments

  • DSC02490.JPG
    DSC02490.JPG
    138.9 KB · Views: 120
  • DSC02491.JPG
    DSC02491.JPG
    144 KB · Views: 111
Back
Top