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74 J series 440 looking to improve MPG, heads off.

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by johnw » Wed Mar 07, 2018 11:51 pm

We have a stock 440, with 902 heads, stock flat top pistons, and the carb replace with an Edelbrock. The old Thermoquad is in the boot and would need a rebuild. There is an adapter plate under the Edelbrock. We would like to run on European 95 0ctane fuel.

The car has done about 68K miles, and there is a very slight but still noticeable dishing of the tappet faces. Original flat top pistons (with two nick marks on each top facing forward). Bores and bottom end look good. Still has the original silentglide Nylon timing gear (only lost a couple of teeth), which we are replacing with a Cloyes double roller.

My first thought was to switch to Source 440 heads, as a valve job in Switzerland might cost as much on the old 902 heads (which may have cracks in the seats, we will check when our new valve spring compressor arrives), and should allow us to run higher compression if we pick the right CC volume on the new heads. I had also thought about an SP spec cam to go with higher CR, the aim would be to get closer to the superior SP fuel economy, however bedding in a cam with flat top tappets these days seems problematic given the oil situation mentioned in other threads. We don't want to get too radical with FI, roller rocker conversions, etc.

So the question is, will the Source 440 heads allow us to up the compression and perhaps improve fuel consumption using a stock '74 cam?
What CC volume shoud we look at on the alloy heads given stock pistons?
Are we better off sticking with a stock cam or is there something that would optimise economy, that we could bed in easily with modern oils?
Do we HAVE to go to roller rockers if we swap the cam these days? We are not after performance unless it comes almost for free.
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by Grant » Thu Mar 08, 2018 1:05 am

Hiya JohnImage.. there isn't such a thing as Stock 440 really in that they were all the same C.RImage.. some were high compression and some weren't.. if it is an early one ie 1972 there is more chance it will be high Comp.. but if it a late one 74/75 it probably won't be.. anything in between those years you just don't know.. so you are best to measure how far down from the deck the piston tops are and work it out from there with CC volume etc.. there are calculators to do it on the net Image
The 440 source heads are a no brainier in my opinion when you start having valve guides and new stainless valves etc with some engineering work etc.. the 440 source heads are out of the box and on for around 1K.. they will up the compression about half a point ie if you are on 9:1 with those 902's they will give you 9.5:1 but you can add all that into your C.R ratio calc
With regards to a cam get to the spec of a 69 Plymouth RoadRunner and they're are great for all the low down torque :P these were used in the "E" series 383's and the early magnum 440's (the early high comp ones and the Sp's from I can work out.. but I can't confirm thatImage but I believe they were)
If you do go for the Alloy 440 Source heads make sure you get single valve springs as opposed to the double springs and you won't have any issues with bedding in that cam as long as you use the correct oil for bedding them in.. high in Zinc I think it is.. a cam superlube oil is a must.. have a read about it.. most important :wink: ... there we go then :lol: Image.. GrantImage
John Edit.. I just re-read and saw you said it was a 74 J series.. I didn't see that bit.. it is probably (but you need to check with piston top height) as stock if it is the original engine 8.2:1 C.R as stock :? .. Wack a set of pistons in it they are cheap enough and get it up to 9.5:1 Image.. You'll then be able to do Half Hour in 20 minutes Image
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by Chris_R » Thu Mar 08, 2018 5:49 pm

John, as far as I know the stock 440 was designed to run on lower octane fuel than we have in Europe so should have no problem running on 95 Octane.
As far as economy goes also have a look for the threads from Philip Lochner from South Africa, he has done a lot of work on EFI and on the Thermoquad and has accumulated a lot of useful data regarding set up of both.
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by Steve Payne » Fri Mar 09, 2018 3:06 am

John

If you want to improve your economy you should look at EFI, there are systems on the market now for about £700. Increasing the compression ratio with new pistons will help but I would also look at the valve gear. As much as 25% of the engines power is used to drive the valve gear so roller followers ( no need to bed them in) and roller rockers will reduce this.

Modern EFI systems will tune them selves to a degree as long as your cam is not to wild. With a wide band lambda sensor you can set the car at its optimum on cruise.

The other thing to consider is gearing, in standard form an Interceptor crusies on a motorway at about 2700rpm but with an overdrive this can be reduced down to under 2000rpm so aiding economy and with a lock up torque convertor this will also aid economy.

With all the above modifications you can get about 20mpg out of an Interceptor if driven carefully on the motorway. One of the benefits of this on long journeys your range is increased between fuel stops to well over 300 miles.

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by johnw » Sat Mar 10, 2018 7:39 am

Some really good input there, covering the whole car, thanks everyone.

Just focussing on optimising the heads and cam for now, assuming highway cruising:

For the SP to hit 16 mpg standard, and given that a wide band lambda sensor lets you manually set your Thermoquad to deliver the perfect mixture, as good as injection when cruising, the compression ratio and cam must be the factors that give the SP better fuel economy.
Am I missing something else? Different air intake from SP air filter is one difference, but I don't see that as really significant when cruising.

Was it the compression ratio, simply the sweet spot and Jensen hit it right on the nail economy wise as well?
Is the cam more or less not a big factor for highway cruising?

What I have gathered now is that we can fit the Source 440 heads, and this will likely up the compression ratio from 8.2 to 8.7 compared to stock 902 heads. That seems to be a nice simple unobtrusive move in the right direction.

For the wideband Lamda sensor, where abouts do people normally fit those on the downpipe? Half way along on the more or less vertical section where the downpipe joins the manifold? Is pointing forwards best?
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by Steve Payne » Sun Mar 11, 2018 7:22 pm

John

I have a few theories why the claimed fuel consumption is so good. The main one is probably the low CFM middle carb the engine runs on while in cruise situations, high airflow will atomise the fuel better. These SP engines we running 10.3 compression ratio so that would help but you have to remember they were running them on 5 Star fuel and even Super Unleaded wont match that for knock resistance so you will be retarding the advance to keep your engine intact so fuel consumption will suffer.

I also think that the manufacturers were exagerating, it was common practice in those days to do this. I remember a friend of my dad bought an SD1 Rover 3500 and it was claimed that it would average over 30mpg :shock: , the best he ever achived was mid 20's and he had driven it like a saint to achieve that..

As far as placing a wide band lambda you want it as close as possible within reason if it is used as a control mechanism but do remember they are sensitive to heat extremes so if you are running lean at cruise it will destroy it in a few thousand miles. If you are only only using a sensor for setting up it can go in the tailpipe, an Innovate LM1 with a tailpipe adaptor will be a good investment.

Just putting a new set of heads in my view wont give you what you are trying to achieve, new pistons with Moly rings will be a wise investment but who ever does the machining will need to be very careful they are not to tight or loose or they will be a waist. The sweet spot for moder fuel is mid 9's comression.

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by bkbridges » Sun Mar 11, 2018 8:22 pm

John,
If you leave the stock pistons, your best bet is to go with a set of closed chamber cast iron "915" heads for both performance and economy. You can then use an RV style cam (low overlap) to help further. They should eliminate any pre ignition problems as well. I enjoyed 9272 when it was in that configuration with its stock thermoquad, but eventually the bottom end wore out (@98Kmiles) Putting aluminum heads on the low compression 74 motor will actually reduce performance/economy from my experience. The real stumbling point on the low compression 440 is...the low compression. The combustion chamber is effectively down in the cylinder (about .100" deep) and does not promote efficient combustion, just lower NOX emissions. It makes the motor very hard to tune for performance and efficiency. The six pack motors had higher compression, allowing more efficient burning of the fuel, but could not be made to meet the emissions requirements of the day.
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by Philip Lochner » Mon Mar 12, 2018 10:20 am

johnw wrote:The old Thermoquad is in the boot and would need a rebuild.

...the aim would be to get closer to the superior SP fuel economy,

...and perhaps improve fuel consumption using a stock '74 cam?

...or is there something that would optimise economy, ...



Optimisation of my old cars (not performance) is "my thing"....

I have:
1) Fitted EFI to my Jensen 440 (see my signature);
2) Upgraded the engine from low compression to high compression (calculated to be around 10.9:1...);
3) Fitted a GM 4L60e (Electronically controlled) ;

If fuel economy is your top requirement, the best route (by far) is an overdrive transmission. All engine improvements will only yield incremental improvements, but an overdrive top gear will yield substantial economy gains (open road only, where top gear comes into play).
Best regards
Philip
Mk3 7.2 #128/8120 Jan 73 http://tinyurl.com/hsjucm5
Mk3 7.2 #2240.9677 May '74 modified:
Fuel injected: http://tinyurl.com/qyrx93f
GM 4L60e 4-sp transmission: http://tinyurl.com/qxlwk95
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by Steve Payne » Mon Mar 12, 2018 12:02 pm

Philip Lochner wrote:
johnw wrote:
If fuel economy is your top requirement, the best route (by far) is an overdrive transmission. All engine improvements will only yield incremental improvements, but an overdrive top gear will yield substantial economy gains (open road only, where top gear comes into play).


As Philip says, this is the best way but a word of warning. You would think with an engine as big as ours a huge overdrive would be the way, go too high and you will never use it. As I previoulsy said mine is doing 1800rpm at 70mph and if the revs were any lower long gradients would be impossible even at motorway speeds as you are below the torque curve.

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by johnw » Mon Mar 12, 2018 12:35 pm

OK, So putting all this together: The pistons top out 3.8mm below the deck height, so a bit worse than .1" (2.54mm) Bruce! I had 915 heads on the '67 FF I was driving in the 90s, they were great on leaded. Apparently 78cc chambers. The 902 heads would be about 88cc volume for open chamber, I guess but that is irrelevant. However the alloy heads cost as much as an unleaded valve job and some used 915 heads. The 440 Source Stealth Alloy heads are 80cc nominal and fortunately a closed chamber design with a quench area, and a thick deck that allows some milling! Now I have the deck clearance figure, and assuming a 1.2mm felpro gasket, 4.5" bore. Then the CR goes from 8.7:1 to 9.3:1 with the Stealth heads. The 915 heads would take it to 9.42 (assuming 78.5cc volume), which might well be about right? Assuming that you could take 1mm off the Stealth heads, that would take the CR to 10.1:1. Instead, switching the gasket to a 0.5mm Mopar shim gasket would see 9.9:1 CR, without skimming the heads. Wow!

So Mopar shim gaskets, plus Copper Coat, anyone tried that with alloy heads? Some on the net say no but they have not tried it, and one or two people that have seem to have had good results! Another question, is there a European equivalent to copper coat?

Right now, the heads are off so that is the main focus! Philip it has been interesting reading your input in blogs, youtube, etc. I am wondering if upping the diff ratio would help instead of an overdrive? I had a '68 Mk1 FF (no 73) and the factory had worked on the motor and kept the low stall (non A/C) torque convertor of the Mk1, and fitted Mk2 diffs front and rear, which worked brilliantly together, although I never bothered about gas mileage back then and don't have a clue what it was like. I am wondering if the cars would take higher still diff ratios? Probably not, especially as the friend I am building this for lives in Switzerland, so there might be a few hills.
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by Philip Lochner » Mon Mar 12, 2018 1:16 pm

johnw wrote:I am wondering if upping the diff ratio would help instead of an overdrive?


AFAIK, the only options we have on the Interceptor is 2.88 vs 3.07. My '74 has the 3.07 diff and my '73 has the 2.88. At our speed limit (75mph / 120km/h) the difference is only 200rpm. Hardly worth the money and effort making a change.

The REAL win with an overdrive transmission is not even the improved economy. It is the fantastic, relaxed, calm nature of the drive. And make no mistake, this benefit does NOT only come in at highway speeds!!! My transmission shifts into 4th at 50km/h (31mph) and then it pulls hard - steam train like - to 70km/h (44mph) where the torque convertor locks up, and then it just pulls relentlessly to the speed of my choice. (and all this happens at 1400m AMSL where barometric pressure is 85kpa. At sea level (101kpa) its even more impressive!!)

It must be said though that my cam was chosen to offer lots of low end torque. With a racing cam, that offers performance high up the rev range, the experience may not be the same as mine.
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Mk3 7.2 #128/8120 Jan 73 http://tinyurl.com/hsjucm5
Mk3 7.2 #2240.9677 May '74 modified:
Fuel injected: http://tinyurl.com/qyrx93f
GM 4L60e 4-sp transmission: http://tinyurl.com/qxlwk95
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by johnw » Mon Mar 12, 2018 4:38 pm

The friend I am helping with this car doesn't have a clue what it is like to drive or be a passenger in a Jensen. :D :D :D
He seems to think it is just a cool looking old car, and he is not bothered about performance at all. 8)
I am wondering if 9.3:1 CR and the stock cam will be enough to get him fully addicted.

I'm just waiting for that moment: "I'm going to have to test the kickdown now and make sure that the 727 holds low gears properly." :D :D :D

Transmission swaps and overdrive will have to wait for now. I just want some heads back on the car. A steering rack leak is next.
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by Hangtowner » Mon Mar 12, 2018 6:06 pm

The April 2018 issue of Mopar Action has a pretty good article on installing 440 Source Stealth heads onto a 1971 383 Road Runner(8.5 CR) without doing anything else except a aluminum intake manifold and water pump housing. They explain the cross over pretty well. I will have to wait for another month to find out how it runs.
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by Philip Lochner » Mon Mar 12, 2018 6:23 pm

johnw wrote:The friend I am helping with this car doesn't have a clue what it is like to drive or be a passenger in a Jensen. :D :D :D
He seems to think it is just a cool looking old car, and he is not bothered about performance at all. 8)


In that case a bog standard 440 with low compression and lame cam should do fine. He is unlikely to ever even explore full throttle. No need to waste his money on fancy heads.
Best regards
Philip
Mk3 7.2 #128/8120 Jan 73 http://tinyurl.com/hsjucm5
Mk3 7.2 #2240.9677 May '74 modified:
Fuel injected: http://tinyurl.com/qyrx93f
GM 4L60e 4-sp transmission: http://tinyurl.com/qxlwk95
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by Steve Payne » Mon Mar 12, 2018 6:38 pm

Philip Lochner wrote:
In that case a bog standard 440 with low compression and lame cam should do fine. He is unlikely to ever even explore full throttle. No need to waste his money on fancy heads.


Exactly, depending on what else he drives the torque of a correctly tuned engine with a gearbox in good condition will probably impress him. Even something as simple as a worn convertor can make a car feel sluggish.

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