74 2.0 (details below)
Very gently rolling 2-lane roads. 3000-3500rpm cruise 55-65-ish MPH. Mid-90’s.

This is not a new concern but something I’ve been noticing/monitoring since I got this car 4 years ago. It’s kept at our other home where I get 5-7 day-access 4-5 times a year so it goes in fits and starts. Nothing has made a noticeable difference.

My concern is that head temps seem to skew high as confirmed by Dakota CHT gauge under #3. Pulling a gentle grade, it went to high 300’s and asking a moderate acceleration, CHT goes above 375. Touched 400 a couple of times.

Oil temps stay low 200’s (225) as confirmed by taco plate gauge and Manley dipstick thermometer and react accordingly (ie: in direct but slow relation to the CHT)

According to Jake Raby’s writings: "Engines that cruise at 375 are generally out of tune or may be misconfigured creating more heat.”

Am I making too much of this? In my head, CHT over 400 is baaaaad.

I’m going to run a snake camera around the top of the tins and check the condition of the oil cooler fins today - that’s about all I can think of at this point.

Input? What’s to tune?

Status: timing confirmed at 28 degrees. Idles at 1000 steady. 195/55’s w/speedo calibrated. All tins present and thermostat/flaps are functioning. New oil less than 200 miles ago - Driven DT50 Full-Synthetic 15w50.

Engine specs: “stock performance” rebuild by Brad Mayeur in 2010 with new, original Mahle European pistons and cylinders, Raby FI cam and lifters new German K&S bearings on a std/std crankshaft. Heads completely rebuilt, new stainless valves and new springs by Tuttle’s Parts Exchange.

Make sure all the air leaks around your tins are sealed.
Make sure you don't have mouse nests or other debris packing the tins.

Once that is done...

Try changing the timing one degree at a time and seeing if that helps, go up and down.

Confirm fuel pressure.

Zach

Will do - starting with checking tins today.

I recall reading that stock Djets/Ljets runs a little Hotter than carbs ( less tuning) I agree to check the timing and fuel pressure as Zack says.
Your oil temps sound good. Sound like they may have bumped up the compression a touch? What fuel are you using?
All setting seem to have gone out the window with the Quality of fuel each year changing. Use 28* as the base line and adjust as needed.
I changed my timing from 29 to 30* (Yesterday) and noticed an increase in CHT getting higher. NO real noticeable perfromance changes. FWIW

found it:
350-375F
These temps are standard for a STOCK engine with a stock cam at cruise speed, if it is properly tuned. Generally, if you are cruising at these speeds, as soon as you hit a hill you'll see a spike to a higher level, approaching 400F. If you experience temps of 375 in 5th gear, you may be doing the engine an injustice by keeping the tranny in 5th, hitting a hill with a shift to 4th will keep load off the engine and that reduces engine heat and increases cooling fan speed- 4th gear is a friend to stock engines.

If you see temps in the 375 neighborhood constantly you'll be having to reduce the intervals between valve adjustments to maybe 3K miles due to the extreme heat cycling the engine and valve train parts are seeing. Engines that cruise at 375 are generally out of tune or may be misconfigured creating more heat.

http://914world.com/specs/JakeRabyHeadTemps.php

@rfinegan - that's exactly the piece of "Jake info" that I was referring to as my reference for CHT temps.

Just not sure what could be "out of tune"

Just scoped under the tins and as near as I can tell it's really clean and clear. Oil cooler fins look good as well. All rubber seals are present.

Fuel - running mid-grade standard pump gas on this load. Seems to my butt dyno that I get a performance boost from "Pure Gas" no-ethanol flavor served up down the road that I frequently run but I can't recall what the temps have been.

I'll do my best to burn this tank off asap and do a refill with "the good stuff" and see what I find.

I'm thinking a small timing bump or two in the correct way might be the answer.

I'm thinking mixture at part load and fuel pressure with the Raby cam.

How is your oil pressure holding up?

I don't have a fuel pressure gauge at the moment - i'll get one in there.
oil pressure is great - warm idle at 20, cruise at 60.

Mixture: MPS is a 0280100041 but has clearly been opened as the outer screw are marked w orange paint and there is marked in sharpie: 74-762.0

You could try a thinner oil, go to a high quality 40 weight. You will get more volume and with that oil pressure you are doing fine. Remember these are oil cooled motors too. Oil doesn't help the head much but it can help a little.

Do you have an AFR? I would suspect lean mix at cruise is probably not helping. Does your 74 have a vacuum advance? Some do, some don't. If it does, disconnect it and see if that helps.

@emerygt350 No AFR although I'm familiar with them coming from the 944 Turbo world. AFR paves the way for tuning via MPS adjustment - correct?

Just switched to the DT50 from VR1 after reading others experience with lowering temps.

How do I tell if I have a vacuum advance? I have two nipples on the advance can - one has a hose (that I disconnect and plug when timing) and the other (on top) is open and without hose.

TPS have anything to do with mix at cruise?

You didn't say what CR Brad set the heads at. Really critical to know. Hopefully around 8.5:1 or so IIRC.

Check the FP first...you can get one at HF along with the vaccum gauge there. Cheap.

Then...should should check the part load mixture and the only way to check that is underload...from the sound of it without checking the other stuff assuming it's good...going lean. You can get the Innovate wide band with the clip for a bung or tail pipe to check the mixture under part throttle.

Check everything else first though before you start messing with the MPS.

Edit: You can go to a dyno...but $ and have a wide band with you. Might be worth it just to find out without buying the equipment.

So just read this....really important to have the right hoses going to those two cans AND that they don't leak.

One is for spark retard and and the other is vac advance. Vac advance hose is ported vaccum and retard daiphram is manifold vaccum. REALLY important that these don't leak and function properly otherwise your timing will be off.

Ask me how I know. I found mine leaked and was doing the same thing...running hot but running ok. So ditched the stock dizzy for 123...no more issues.

This is the pressure I have seen on my gauge too ( T4 OIL PUMP) CURENT BUILD Looks Good to me

Getting yourself a 123 is a great way to eliminate lots of gremlins. Can't recommend enough. 74 (late I believe) kept the retard and lost the advance. Since your idle is a little high, I suspect something might be up. Your throttle will have 1 port facing the rear of the car or 2 small ports on opposite sides. One is giving you 'manifold' vacuum (the rear facing), the other is just above the butterfly. That is the one that only pulls vacuum at cruise and is the advance. A late 74 should only have the manifold vacuum and that should be going to the ... Inside? can. Can't remember now. Others will know.

@914_teener - Correct - CR is unknown to me. I can check with brad but it was done under previous ownership (actually one before that....)
Will be working on checking fuel pressure asap.

To be clear: I am NOT messing with MPS.

I would like to see what the mixture is so the Innovate suggestion might need to happen.

I’ll give a rundown on what my dizzy/hose connections are but a 123 may be a good option.

@emerygt350 - late ’74 - yes.

Bingo!
I’ll read the rest of the thread
But even a stock MPS is too lean with todays fuels.
Richen the fuel. Verify with AFR
And I bet your head temps drop

I know you don't want to mess with the MPS

But maybe you could borrow another one from someone with a similar engine just to try it out.

Or have someone test yours with a LCR to see where it IS set.

ok - lots to things to work on here - i really appreciate the input.
I only have thru Saturday on this trip and it's not just a 914 trip but I'll get started.
@Olympic_914 - I'm not against messing with the MPS if it'll help or is "the answer" - I'm mechanical but with a fairly limited tool resource.

First thing is fuel pressure - ideally, i'd find a way to T off the fuel rail port.

Just throwing in the ring some echoing comments, these are all good points that have been made. Pardon any redundancy.

In order, the three best things that have helped tune the engine (IMHO) for me.

1. By far, the 123 distributor. I had the stock 205A that I messed with, adding Pertronix, lubing, etc., but was never able to get it right. Close, but adding the 123 was totally game changing. I was very hesitant to spend the $$ but it was well worth it.

2. AFR gauge. Yes, it’s easier to make air/fuel adjustments with Ljet (I never had the pleasure of messing with an MPS) but it’s obviously doable. Getting that mixture right is so important on air cooled stuff.

3. CHT gauge. I like being able to keep an eye on what’s going on. Do my best to keep temps under 375°, no guessing involved. Mount the sensor under the #3 plug. Dakota digital gauge is great. Make sure all tins/seals/grommets are as they should be.

Fuels today do suck, I can’t get non ethanol here.

I do have a fuel pressure gauge, but again, once it’s good, it’s not really necessary.

I now run regular gas, no pinging, with very satisfactory performance.

Hope that helps.

@Porschef - Thanks for this.
I'm taking all-comers - unfortunately, I only have 914-time in short bursts.

123 - I've added a pertronix in the last year and it smoothed out the idle but nothing earth-shaking. Glad I did it though - no points going forward at least.

AFR - yup. I think in the long run, this happens.

CHT - yup. I have a dakota and it's been the indicator that has lead me to this point. I'm sure it saved me since the oil temps look good.

I can get non-ethanol here so that's going to be the requirement going forward. This tank is 10% ethanol which can't be helping but no pinging.

Off to NAPA to figure outa fuel pressure setup.

Plug your fuel pressure gage into the Cold start injector. It is not in use in the warm weather and no T fittings needed.

Yup. Did just that @rfinegan - right on 30psi.
A bit more than stock sooooo - leave it?
Bumping timing next.

Lots of people run at 30 psi...leave it there for now

Bumped the timing from 28 to 30 and it seems to like it.
Noticeably lower temps - feels snappier but I think there's more room for improvement. I'll bump to 31 or 32 and see what it says but I have to call it progress.

I agree with Brant as well. Do that stuff first.

Get that vacuum gauge and test the vacuum cans for leakage on your dizzy and report back.

@914_teener and @brant - I follow.
Going to be a longer-term (probably winter) project in order to have the window to get the AFR installed as well as a bung welded in.

And then "richen the fuel" - this means via MPS tuning with the AFR - correct? No other way to mess with mixture.

Vacuum gauge - on it next for both dizzy cans and MPS

Test the vaccum cans first. I've got a gauge if you need to borrow it.

30 psi with djet should be plenty for that displacement. Think that cam has some overlap but no a lot.

Don't touch the MPS until you've done that. Do what Brant suggests first and if you need a vacuum gauge I've got one.

@914_teener - I appreciate the offer but I'm with the 914 in SE Indiana.
Getting the Mityvac later today.

Yeah, only touch the mps once you are sure about what is going on.

If that's the bar....it'll NEVER happen!

Yeah, true.

A couple of pics of my distributer advance can and associated hoses.

TOP of can - this one has always been open/without a hose:
Click to view attachment

Firewall side of can - this is the one I disconnect and plug when setting timing:
Click to view attachment

TB/Plenum - this red plug has always been present:
Click to view attachment

Where is that vacuum hose headed? Does it go to the tb or the plenum? I can see from the picture your car does not have advance, only retard on the timing.

Pretty sure the inside can is the retard. That hose coming off of it should go to the back side of the TB.

And just FYI, from the factory they would dangle a hose off the unused advance can. No idea why.

I believe on a 74 that little plugged nozel would head to the decel valve. They really switched those things up between 73 and 74. Same with the PCV.Click to view attachment

Here is the 73 version. The place where your plugged nozel is located is a large diameter version heading to a t which goes to the pcv valve and a small hose that heads to the decel.

On the TB you can see the plugged advance on the right (123 dizzy and I don't use it) and the plugged retard port on the left (same there, I don't use it).

Ok...couple of things I see:

1. Looks like you have a dual diaphragm on your dizzy.

2. The advance hose is plugged to somewhere....probably and hopefully ported vacuum on the throttle body. Ported vacuum is on the atmosphere side and not the plenum side of the TB. Check Jeff's diagram on his website.

3. In one of the pictures...it shows a plug on the plenum which probably at one time went to the other side of the can...hopefully the retard side. If not needed...don't plug the nipple on the can, so in this case leave it.

The dual "nippled" or dual diaphragm can...if it doesn't leak always has to have vacuum for the dizzy to provide the correct amount of timing advance. Technically you don't need it (advance/retard)....being that when at low rpm...where manifold vacuum is high...provides a little less time for combustion sake...so hence the rumor it is not needed since we live in a different time( pun intended). HOWEVER this will change the dynamic curve somewhat and that MIGHT be your problem since that is how it's engineered since it is a dual acting vacuum cell..but check the vacuum cell first..if one side leaks..the whole cell is bad.


If it leaks...on static timing to spec....it will idle too high and most people just adjust the air bleed or idle mixture to take care of it. Ask me now I know...wait...don't ask me I'm telling you it will. So while you think statically it's timed right at idle and idles perf at 800 rpm...that won't be the case through the RPM and different loads conditions...like cruising. So check that first.

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?

Just pop the vacuum pump on there and see if they hold 15 or so. It does appear your decel valve is gone, not a big deal, just hard on the mps. If it is there it may not be hooked up correctly.

I suggest pulling the distributor cap and watching the rotor move while you do it. Watch to see how easily it returns after you release the vacuum. The mechanism often gets gummy and starts to stick over the years. Retard would send the heat to the oil rather than the head though.

A issue that can happen with gummy weights is you pull the retard vacuum line (and plug it of course), and the rotor does not return, you set your timing and you have now set it more advanced than you thought when the weights finally spring back.

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.

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.

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.

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

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.

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....

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.

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.

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.