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Series 1 XJ6 (SWB) Jaguar Modifications

Cylinder Head:

1.  Series 3 head has 1-7/8's inch valves in it vs. the Series 1 head with 1-1/2 in valves. The series 3 head with the larger valves is known to be a 20 HP "bolt on" upgrade.

2. Tulip shaped intake and exhaust valves from Rob Beere Racing. I'm not sure what the hp boost could be from these valves but it's in there some where.

3. Up-rated spring from Rob Beere racing. Up-rated "Fast Street" valve springs were add to this head to generate a "monster" head for this Series 1 XJ6 Jag.   

4. The head was is a fully "flowed" series 3 head, with "matched" intake, and exhaust. "Flowing the head" means that extra metal has been removed from the inside of the "chambers" so that the combustible gas, and vapors have less obstructions in their path on their way to the cylinder. This removal of obstructive metal from the intake manifold normally results in an increase in horse power. 

NOTE: The work done on the intake, head, and exhaust has been calculated to have increased the "flow" (in CFM, Cubic Feet per Minuet) by approximately 75 CFM.  

5. The head was shaved to generate aprox. 10-1 compression.  Normal compression on an series 2 or series 3 - XJ6 is 7.8-1 for standard. Actually in the Series 1 XJ6, 8-1 compression was considered low compression, and the block had (has) an "L" stamped in the back of the block (by the transmission) that signifies the 8-1 compression ratio. The reason 8-1 was considered LOW only because in the Series 1 XJ6 normal (or standard) compression was 9-1. The block in MY Series 1 XJ6 had "standard" compression and was already 9-1. I bumped it to 10-1.  


1.I removed the twin Stromsburg's carburetors, and installed a Triple  2 inch S.U. (HD8'S) set up  with 2.75 inch tall high flow K&N air filters.  Carbs were re-jetted to accommodate the increase in flow (aprox 75 CFM) that was achieved from the porting of the head. 

2. This engine develops almost 23 inches of vacuum. Standard vacuum on a Jag  is aprox 18-20 inches of mercury. The amount of vacuum is a direct relation to the ability of the head to "flow", and so vacuum is also indicative of developed HP.


1. The stock cylinder bores were simply honed, and the original Series 1 piston, and stock rings were installed. 

2. The crank shaft was turned 20 over, and  balanced to zero (0) deviation at 10,000 RPM.  Pistons, and rods were balanced as well.


1. Up-rated bushings, 1 inch front sway bar, (7/8th's rear sway bar to be installed)                                                                                                       

2. I installed 17 inch alloy rims, with 245/40/17 PS2 Pilot sport rear wheels, and 235/45/17 Pilot sport A/S front tires. 

3. Up-rated 7/8th inch rear sway bar has been installed

Cooling system:

1. The 1971, OEM radiator was replaced with the Installation of Alloy radiator (16 fins per inch) capable of cooling up to 500 HP.                              

2. A 3,700 CFM thermostatically controlled electric cooling fan was adapted and installed .               

Horse power, and torque numbers:

I haven't been to the Dyno yet but I'm of the impression that the car develops around 275-290 HP.