Austin Healey 3000 Tri-Carb Setup & Camshafts.
This page is intended to give some help to those like myself who are interested in tuning the AH 3000 engine for road use. The information is based on my own research and findings, and neither myself nor the Austin Healey Club UK can take any responsibility for the accuracy of the information, or any consequences of it’s use.
The 3000 engine effectively appeared in four different guises relating to camshaft and carburetor specifications:
AH3000 Model Standard Engine Setup
|Model||3000 MKI 124bhp||3000 MKII 133bhp||3000 MKIIA (BJ7) 132bhp||3000 MKIII (BJ8) 148bhp|
|Camshaft timing||230 degree duration||230 degree duration||240 degree duration||252 degree duration|
|Carb setup||2 x 1.75″ HD6 (0.100″ jet)||3 x 1.5″ HS4 (0.090″ jet)||2 x 1.75″ HS6||2 x 2.0″ HD8|
|Needles||Std-CV; Weak-SQ; Rich-RD||Std-DJ; Weak-DH; Rich-DK||Std-BC; Weak-TZ; Rich-RD||Std-UH; Weak-UL; Rich-UN|
|Dashpot spring||AUC 1170, Type A-Green, 12oz||AUC 4387, Type A-Red, 4.5oz||AUC 1170, Type A-Green, 12oz||AUC 4826, Type A-Red/Green, 11.25oz|
Modified Engine: 3 x HD6 (1.75″) Carbs
The use of three HD8 2″ carbs is well documented, all three having the same needles (UH) and dashpot springs as the standard setup. However, I have not been able to locate any data for triple 1.75″ carbs. In my case, the attraction of this setup was that I already had the two standard HD6 carbs and a set of standard MKII inlet manifolds. These manifolds can be opened out from 1.5 to 1.75″ diameter but no further. Fitting triple 2″ HD8s requires larger, after-market, manifolds.
The following charts my experiments with different carburetor settings, first on an engine fitted with a BJ8 profile cam, then on my second engine with a Denis Welch DWR8 cam; details of which are given below. Both engines have a branch exhaust manifold fitted whilst the second engine also has an alluminium head and Omega forged pistons.
3 x HD6 Carbs with BJ8 camshaft (252 deg.)
|CV (MKI Std needle)||AUC 4387, Type A-Red, 4.5oz||Rich low/mid range causing plugs to foul|
|SQ (MKI weak needle)||AUC 4387, Type A-Red, 4.5oz||OK but a bit flat in the mid range|
|BC (MKII Std needle)||AUC 4387, Type A-Red, 4.5oz||OK|
|TZ (MKII weak needle)||AUC 4387, Type A-Red, 4.5oz||Very flat low/mid range|
3 x HD6 Carbs and a Denis Welch DWR8 camshaft (278 deg.) (see camshaft data below)
|BC (MKII Std needle)||AUC 4387, Type A-Red, 4.5oz||A bit rich, lumpy low range, blackish exhaust|
|BC (MKII Std needle)||AUC 1167, Type A-Yellow, 8oz*||Good, most satisfactory combination|
|SQ (MKI weak needle)||AUC 4387, Type A-Red, 4.5oz||Good, a bit lumpy low/mid range on part throttle|
|SQ (MKI weak needle)||AUC 1167, Type A-Yellow, 8oz*||Good|
|TZ (MKII weak needle)||AUC 1167, Type A-Yellow, 8oz||OK, smoother low/mid range, low power|
|RK||AUC 1167, Type A-Yellow, 8oz||Feels a bit rich, sluggish|
|TL||AUC 1167, Type A-Yellow, 8oz||OK some slight misfire at low speed part throttle. Poor when cold.|
* Using a straightened paper clip through the breather hole in the top of the dashpot top and a bit of masking tape to stop it sliding under it’s own weight, a full throttle blast indicated that the piston was reaching it’s full travel with this spring.
In conclusion, I found the BC needle to be best with the BJ8 camshaft, and the SQ needle best with the DWR8 camshaft.
The following chart below gives a comparison of the annulus area for each needle, i.e. the area between the needle and the jet, at each stage of the needle travel. The measurements are equalised at position 2 which is about the idle position. For needle data go to this Triumph site by Teglerizer Engineering
Austin Healey 3000 Camshafts:
|Denis Welch||DWR8||10.9||0.430||278||33||65||63||31||requires pocketed block & 0.15″ valve clearance|
|SC Parts||SC6614||11.48||0.452||300||50||70||75||45||Requires Webers (note as MGB Race AEH770)|