how long do people own jensens?

[Basil McKinley]

The easiest way to calculate your compression ratio is to use a compression ratio calculator e.g. one from Diamond Pistons:
http://www.diamondracing.net/tools/" onclick="window.open(this.href);return false;

Regards,
Basil
p.s. you can always do it from 1st principles if you want to exercise your mathematical skills. It is the total volume at BDC divided by the total volume at TDC.

[Grant]

The easiest way to calculate your compression ratio is to use a compression ratio calculator e.g. one from Diamond Pistons:
http://www.diamondracing.net/tools/" onclick="window.open(this.href);return false;

Regards,
Basil
p.s. you can always do it from 1st principles if you want to exercise your mathematical skills. It is the total volume at BDC divided by the total volume at TDC.

Basil.. he can't work it out unless he knows how far down the bores the piston tops sit @ TDC... the only way he find that measurement is if the heads are off... or have missed something in Gary's reply/listing?

[Grant]

Hi Grant
The first mod I made was to get rid of the original exhaust system and put in headers - that freed up the engine so it could be "blipped" easily i.e. it could get rid of the build-up of spent gases. Probably gave an eager 20hp immediately and better fuel consumption. Cruising on German autobahns I average 18/19 mpg at 85-90 constant and still do with the bigger cam + carb now on.
Next I changed to alloy heads and replaced my original Carter for the same Edelbrock model ( something like 1406 I think).
At the same time I installed an Edelbrock intake manifold. Next I added a set of Harland Sharp roller rockers and custom pushrods.
We were doing OK with bhp then at about 320 on the rolling road - so I put in an a CompCams Xtreme Energy cam and an 800 cfm Carb and took it back to Peter Baldwin's rolling road and we got 337bhp at 5200RPM.

After our track laps at Le Mans Classic last year we seemed to be running on 7 the 6 then 7 pots all the way home. I decided to take things apart bit by bit and after confirming all was well with my plugs and leads we took the dizzy out and as we broke that apart noticed a tiny pin in the bottom. That pin of course is meant to hold all together so it was moving about on the timing parameters - put the pin back in an d straight onto all 8 pots. However I thought after 42 years or so she should have a new dizzy and talking to someone at Demon Tweaks he mentioned the relatively new electronic model, slightly smaller but "billet" made (actually a beautiful piece of engineering on its roller bearings) that works with the MSD 6al digital ignition system.

A couple of weeks ago I had the rocker covers off and renewed the zero lash + 1/2 turn spec for the roller rockers and I am currently running about a degree or so miss-aligned on timing so it's taking about 6 spins to start her and she's a bit rough below 1500rpm. The original start advance was 20 degrees but at present it's about 24/26 so I need to have a chum on the strobe light to get it properly adjusted again.

Below are the actual model numbers:

Jensen Interceptor III 1972
Chrysler 383 cu.in. / 6,276cc

Edelbrock Performer (60189) RPM Alloy Heads: 88cc combustion chamber, 210cc intake ports & 70cc exhaust ports

Edelbrock Performer (2186) intake manifold Standard deck, dual plane

Edelbrock Thunder (1813) AVS Carb
4-barrel, 800cfm, electric choke

CompCams Xtreme Energy Cam/Lifters
21-222-
Basic Operating Range 1,300-5,600 RPM
Hydraulic, flat tappet, Lift: .462/.470';
Duration: 218/224

Harland Sharp S70015K needle-bearing, single shaft-mount, Roller Rockers
Needle bearings, 1.5:1 ratio

Delta Headers:
Stainless Steel 2.25 inch pipes with “H” cross-over connection pipe

MSD Digital Ignition 6AL plus MSD 8545 Pro-Billet Distributor

337bhp @ 5200-RPM at rear wheels when measured on a rolling road

Are you planning on upgrading your engine?

all the best
Chris

Hello Gary ... thank you so much for your in-depth reply .. really interesting... and it is pushing out really good horse power for what is noted in the book @ 8.7:1 being a "G" series engine.. but those figures as quoted by Chrysler were normally/can be way out.. but whichever it sounds like you have got it about right... sad about the lumpyness under 1500rpm though really something you don't want in a Jensen and even more any Auto trans car. I am always interested in engine performance work and have built a 440 for my other MK2, but my "G" series performs really well as standard and untouched within the engine and I don't plan to upgrade it as yet apart from adding a 4 speed manual to it but not this summer as I am using this one, but I am so happy with how it pulls and didn't think I would as it is a "G" series engine and thought it would be sluggish with that sort of compression, ... I am a firm lover of the alloy heads though and prob will add them too in the winter when I go manual with it.. and then anything my follow .. what is the advatage of the roller rockers and custom pushrods then Gary? I guess you are stating that the roller rockers are adjustable then if you were adjusting them for "0" lash Gary?.. I never did check the cam centre line timing when I built my 440 engine though mentined below >>
The 440 I built I used 440 source alloy heads, a 69 road runner cam which is the same as an "E" series cam and lightend and balanced the engine, it is around 9.5:1 comp, it also has a set of S/steel headers, I am going to add a mapable ignition system to it too... this has a 5 speed manual box attached to it, but am just doing some other stuff to the car prior to fitting the engine and box back in, here is a pic of the engine >>
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Always interested in engine work Gary and many thanks for sharing
With my kind regards
Grant

[Basil McKinley]

Hi Grant,

Basil.. he can't work it out unless he knows how far down the bores the piston tops sit @ TDC... the only way he find that measurement is if the heads are off... or have missed something in Gary's reply/listing?

Yes, you need that information if you want to calculate your exact compression ratio even if it is a stock engine since it seems that there was a wide machining tolerance on the block deck height. There are other inputs you also need to know including the bore and compressed thickness of the particular head gaskets you used. You would also have to cc your heads if you want to get it as accurate as possible,

Regards,
Basil

[Pymmie]

Had my Mk3 7 years today ...

Been a roller coaster with long periods of restoration

and promises that were never kept.

Have I regretted buying it? Never

Puts a huge smile on my face every time I turn the key.

John P

[Grant]

Had my Mk3 7 years today ...

Been a roller coaster with long periods of restoration

and promises that were never kept.

Have I regretted buying it? Never

Puts a huge smile on my face every time I turn the key.

John P

It looks beautiful John, really beautiful

[ernie100]

I have had my MKII for three-and-a-half years. The original owner had it for 35 years until his death!

May I ask what is the colour of your car?...very nice

[Grant]

I have had my MKII for three-and-a-half years. The original owner had it for 35 years until his death!

May I ask what is the colour of your car?...very nice

It's Blue David

[Robinson D]

I had it restored to the original Crystal Blue.

[felixkk]

The C-V8 and the 541 since 2012. The previous owners had owned the cars for 35-40 years, including the FF. Only the C-V8 has been on the road continuously for its entire life, the others had been stored away awaiting restoration or fixing.

[Mathias]

Since 2006!!

[ernie100]

I had it restored to the original Crystal Blue.

Thanks...a lovely colour....its on my list currently ranking as favourite re rebuild colour....

[ernie100]

May I ask what is the colour of your car?...very nice

It's Blue David

Ok Grant is that Blue as in the music , as in the emotion or as in naughty (films)....