CHT seems high - oil normal? Options

[gereed75]

I am very curious about the basis of this statement - “Retard would send the heat to the oil rather than the head though”. Maybe I can learn something

The things that control cylinder head temps (assuming adequate/constant cooling air flow) are mixture and timing.

The one thing we are missing on engines without O2 sensors or EGT gauges is info about AFR. EGT will peak at around 13.5 :1 AFR IIRC. When running rich of this peak, which you should be under load, richer mixture will cool the temps and more advance will create higher combustion chamber pressures and heat the head.

I know nothing about the tricks to effect mixture on L jet or the various vacuum arrangements on 914s that effect timing, but if you follow those precepts regarding mixture and timing, you can tune down the CHTs.

Seems that you are very close as CHTs peaking around 375 would have to be considered really really good.

[914_teener]

Next up:
-picture/confirmation as to where the advance hose is routed on the other end.
-checking vacuum on MPS.
-checking the vacuum cans on the dizzy - how?

For the vac cells.

Pull the cap on the dizzy....disconnect the hoses and pull enough vac to make the breaker plate move. If it won't hold vac...it's toast.

For the MPS: About 12 HG static and let it sit for a while...5 min or so with no leakdown.


Yep...see where the hose goes and check Jeff's website.

[emerygt350]

That's just an old saying. Seems right from my personal experience though. Retard it enough and you will make your exhaust manifolds change to bright interesting colors as well...

I think we are playing with a D-jet.

[emerygt350]

Next up:
-picture/confirmation as to where the advance hose is routed on the other end.
-checking vacuum on MPS.
-checking the vacuum cans on the dizzy - how?

For the vac cells.

Pull the cap on the dizzy....disconnect the hoses and pull enough vac to make the breaker plate move. If it won't hold vac...it's toast.

For the MPS: About 12 HG static and let it sit for a while...5 min or so with no leakdown.


Yep...see where the hose goes and check Jeff's website.

Very carefully check those diagrams. Many out there do not have the correct routing. Jeff's should be good though.

[FlacaProductions]

Waiting for the vac tester to show up at FLAPS despite it showing IN STOCK online...grrrr. that slowed me down an hour....

Meanwhile:
The one vac line currently on the dizzy can DOES lead just as Jeff's diagrams show, to the rear of the throttle body. So - that's correct. Connections are tight.

And confirming no decal valve.

[FlacaProductions]

Seems that you are very close as CHTs peaking around 375 would have to be considered really really good.

It just seems that it shoots up too fast, too easily.
I should be able to put my foot in it on flat ground and not go right to approaching 400....

[emerygt350]

I don't know how mine will behave going forward (just turned it into a 2056), but my original 2.0 would climb pretty fast (that's why the CHT is so nice to have). If I were doing 70 on a warm day on the interstate it would sit around 350, dropping to 320 without load and climbing to 375 when pushing it climbing hills/passing etc. That is 5th gear though. I would say that at Watkins Glen, pedal to the floor, top speed, pushing the car so hard for 2 days I melted the tires, the temperature never passed 360. That was always in 4th gear at the most.

It really can be fan speed dependent.

[914_teener]

Waiting for the vac tester to show up at FLAPS despite it showing IN STOCK online...grrrr. that slowed me down an hour....

Meanwhile:
The one vac line currently on the dizzy can DOES lead just as Jeff's diagrams show, to the rear of the throttle body. So - that's correct. Connections are tight.

And confirming no decal valve.

First things first. Make sure all is working...then run what the engine is designed for.

You should run a decel valve with D-jet. Find a good one and install it.

[FlacaProductions]

Vacuum test update:
MPS - no issue holding @12 for 5 minutes without loss.

Top distributer vacuum canister nipple that operates without a hose connected DOES HOLD 15 for 10 minutes.

Side/firewall-facing nipple with advance hose normally plugged to vacuum on the throttle body DOES NOT HOLD 15 FOR 5 MINUTES - DROPS TO 10 and will keep declining...

So.....?

[914_teener]

Vacuum test update:
MPS - no issue holding @12 for 5 minutes without loss.

Top distributer vacuum canister nipple that operates without a hose connected DOES HOLD 15 for 10 minutes.

Side/firewall-facing nipple with advance hose normally plugged to vacuum on the throttle body DOES NOT HOLD 15 FOR 5 MINUTES - DROPS TO 10 and will keep declining...

So.....?

Case of diminishing returns. You can fret around trying to find a new vac cell. Or get a 123 for d-jet and be done. Since you know now that the advance on part load is off...could be the problem, but after you get the dizzy straightened out I'd still check the AFM.

One thing for sure...you need to run the decel valve so unfortunately you are gonna have to open up your wallet a little. With the engine you have and set up.....it's worth it.


For the benefit of the forum from Brad Anders website and operational theory of the stock D-jet dizzy for the advance and retard vac cells:


Vacuum Retard - Idle Condition
For reduced exhaust emissions, the timing at idle is retarded by several degress, lowering HC and Nox levels. The timing is retarded by using a vacuum cell attached to the side of the distributor that is connected to a port on the throttle body. The port is positioned below the throttle plate, where there is a strong vacuum when the plate is closed at idle. The extent of the vaccum retard is on the order of 8 to 12 degrees for 1973 2.0L engines, and 8.5 to 12.5 degrees for 1974 and newer 2.0L engines. The retard vacuum cell is a unit in combination with the advance vaccum cell described below, and the unit is designed so that if vacuum is present at both the retard and advance ports simultaneously, the vacuum advance dominates and the vacuum retard is inactive. Both the retard and advance cells use a single arm connected to the points plate, which moves the position of the points plate either to the retard or advance side, depending on which cell is active.

Vacuum Advance - Part-load Condition
The air-fuel mixture under part-load conditions is leaner (due to a leaner part-load mixture and additional mixing of the air-fuel mixture with residual combustion gasses in the cylinder) and burns more slowly and needs more time to combust, requiring additional timing advancement. Like the vacuum retard system, the vaccum advance system uses a vacuum cell connected to a port on the throttle body. In this case, the port is positioned right at the edge of the closed throttle plate, so that under idle conditons, there is no vaccum present. However, when the plate is opened a few degrees (like under part-load conditions), vacuum is exposed to the port and the vacuum cell is activated. The extent of vaccum advance is on the order of 6 to 8 degrees for the 1973 2.0L engine, and 5.5 to 7 degrees for the 1974 2.0L engine.

[FlacaProductions]

OK. I hate things that are unresolved and this certainly seems to be (at least) the main issue that needs to be addressed.

I think a 123 should be in my future and I'll add the decel valve while I'm at it.

Thank you for the vacuum info - there's a lot out there and this is a very helpful slice.

[emerygt350]

Yes, good advice. I bet you might find a decel around here. Any conversion means no use for it. Although I would add, your motor does not, and never had, a vacuum advance. You can see the port is sealed on your TB.

The 123 is a great addition. No damage done, you can put the original dizzy on a shelf for the next person if they want it original.

In the meantime, just plug the TB port for the retard and disconnect it. It isn't doing anything anyway. It's a vacuum leak and that is all.

[914_teener]

Ok....to the OP, while the port might not be there if it's a 74 TB doesn't mean you shouldn't have it. I'd recommend a TB if interested for fun's sake and driveability sake.

Just becuase in 74 it was a change was made...doesn't mean it was better. While you
you are sourcing the Decel valve I'd recommend a TB with ported vaccum for a 2.0.

The last copy and Distributor post from Brand Anders site:

As the model years of the 914 progressed, emission restrictions became more stringent. Later cars (75-76) had additional systems added to combat emissions, such as an air pump and exhaust gas recirculation (EGR). But one other change was made that is not noticed by many owners, which is that on the later cars, the vacuum advance port from the throttle body was attached to a hose that was capped off, and not connected to the vacuum advance cell of the distributor. Why? Because while vacuum advance improved engine throttle response under part-load conditions, it also increased HC and NOx emissions, limiting the ability to meet emissions requirements. Furthermore, since there was no change in the vaccum cell unit used on these later cars, the vacuum retard remained active long after the throttle was opened, because no vacuum was ever present in the advance cell. This had the additional effect of causing even worse off-idle response.



It is clear from this discussion that this is a complex system and that for proper operation, all components must be functioning properly. Below is a list of items that should be checked to make sure that the advance systems are working properly.

[emerygt350]

Yes, I was an advance supporter too for exactly those reasons (the cool balancing act between the two parts of the can particularly) but after a/b ing the driveability using a 123 with advance, without, with retard, without, I have found the digital distributor doesn't need advance (as many others have found as well). I will keep trying it (all I have to do is put the hose back on) to see how it affects the 2056 with much higher compression, but I am not expecting much. I have found zero difference with part throttle tip in etc. I rarely stick my neck out like this, but with a 123, advance just isn't necessary. The same company that brought you the crazy retard advance dizzy also decided it wasn't necessary in 74. Did it help a 74 if you switched to a 73 TB with advance? Not sure. I haven't seen anyone add it or talk about adding it to a 74-76. Advance on the 2.0 was a 1 year thing.

[FlacaProductions]

OK - how do I determine which decel part number is the one for me: 039133551?
I think I'll need a stacked elbow as well and the proper additional hoses.

Do I need to be the ringleader for another 123 group buy?! (IMG:style_emoticons/default/biggrin.gif)

(and a serious thank-you to everyone offering up the input and advice - I know it takes time to read in and then formulate a response - I appreciate it!)

[emerygt350]

You shouldn't need a t for a late 74 I believe. Your plenum looks like it is for a passive PCV system. That is where the pcv goes into the air box and there is no valve on the oil filler box. The small plugged nozel goes to the decel, and the big nozel next to it goes there as well. The third port on the decel goes to the air box. I wish Jeff would chime in though. In his diagram for late 74 it has an active pcv with valve and the t. The t needs a big port on the plenum

[emerygt350]

Here is mine, but it's a 73. Probably the same.



0280160108

227 below that number

[FlacaProductions]

Thanks for this - there are two different model numbers on ebay (0280160108 and 0280160124 for example) at the moment - I'll do some research but may also start a new thread on decel valves....

[emerygt350]

Soo.... some very interesting things in my 2056 build related to this. Basic background. Stock 2.0, 96mm pistons, flat tops, new sleaves, cleaned up the heads and new guides. Didn't crack the case. Cleaned all the crap off the engine. 8.4:1 compression ratio. Didn't touch the dizzy or any settings on the fuel injection.

My car used to run pretty cool. As described earlier.

the 2056 Ran really warm, just as Brian described for his 2.0 in fact.

I put the advance hose back on (123dizzy) and ch temperatures at cruise fell considerably. 20 degrees I estimate. Put about 4 degrees advance into it and performance suffer and temps were no different. Pulled it back about 2 degrees and performance peaked and the temp was more consistently low during hard acceleration. Still higher than before but my bad rings and leaking valve guides were not making for a fine tuned engine. Just goes to show you always have to keep an open mind. I really thought advance meant heat but I suspect with much higher compression on the 'new' engine things changed. Efficiency and all that...

[Porschef]

Soo.... some very interesting things in my 2056 build related to this. Basic background. Stock 2.0, 96mm pistons, flat tops, new sleaves, cleaned up the heads and new guides. Didn't crack the case. Cleaned all the crap off the engine. 8.4:1 compression ratio. Didn't touch the dizzy or any settings on the fuel injection.

My car used to run pretty cool. As described earlier.

the 2056 Ran really warm, just as Brian described for his 2.0 in fact.

I put the advance hose back on (123dizzy) and ch temperatures at cruise fell considerably. 20 degrees I estimate. Put about 4 degrees advance into it and performance suffer and temps were no different. Pulled it back about 2 degrees and performance peaked and the temp was more consistently low during hard acceleration. Still higher than before but my bad rings and leaking valve guides were not making for a fine tuned engine. Just goes to show you always have to keep an open mind. I really thought advance meant heat but I suspect with much higher compression on the 'new' engine things changed. Efficiency and all that...

This is very interesting. 20° is a decent temp reduction. Would you mind sharing the advance curve? Just for posterity, whatever that is.

Thanks