[PontGuy]

Now you are heading in the right direction.

I've adjusted the APT on my Lemans carb as much as 1-1/2 turns richer from where Cliff had it set and per my wideband this resulted in less than 1.0 richer cruise A/F ratio. So don't be afraid to turn it. But record the changes you make so you can always go back. FWIW After a few thousand miles and tuning to get everything optimized I ended up with APT set exactly where it started.

A bit embarrassed that I assumed the head cc numbers were correct in calculating CR. At least I wasn't alone.

So at the end of the day your setup is not all that much different than the engine in my TA with the XE 268 (except you have the nicely ported heads). My seat timing is even shorter than yours and tuning has been pretty tricky but it is running pretty good now. As mentioned I have a 10 degree vacuum can on that engine. More than that would be asking for trouble. Yes it still tends to run a bit hotter than I like, and yes the oil pressure is lower than I like when it gets over 200 deg during a long hard run in hot weather. Sound familiar?

If the engine won't crank with more than 13 deg initial and the engine wants more timing then suggest you invest in a mini-starter, or get the distributor reworked to bring in more mechanical timing. Trying to add timing with too much vacuum advance isn't the way to go.

[AdamIsAdam]

Ya know, I'm going to throw more initial timing at it. I feel it's not as quick as could be with the vacuum advance disconnected.

And today I realized it started fine with the timing advanced and only gave me any resistance when the initial timing was all the way up around 20° after I adjusted the notch plate on the vacuum advance and before I reset the initial timing.

I'm going to start again and see how good I can get it without any vacuum advance as cliff suggested this morning.

I do have a mini starter. I think the Last time I encountered hard starts my battery may not have been fully charged like it is now.

[Squidward]

Adam, I set up my timing similar to yours. I don't have as much vac advance, tho, like 17 max. Geoff from across the pond had PM'd me to help me accomplish pretty much the same thing.

I like the MVA setup that he PM'd me. It was one of the more comprehensive attempts to give me some setup instructions. Let's face it... I had little to go on, so he stepped in and gave me way more than any other advice I had received before. My car ran way better than at any other time, and it helped me understand some things. I thought he was helpful.

I'm running a 220/227 cam in a 350. It idles nice at 700 rpm. Compression is 9-something. It runs a little hot, so I am am willing to revisit my timing and tune once I get my cooling system bulletproof.

IIRC, while monitoring my truck's 5.3 LS with a bluetooth plug-in and android app, advance at cruise was something like 47*. I actually plan on plugging in again and I want to plot out some timing on that engine over various operating conditions.

If anybody has anything to offer up other than "drive it until it pings, and then back off 2 degrees", then I'm listening. What's unfortunate for those of us NOT in the know is that those that ARE in the know might risk undermining their professional livelihood. I get that.

Maybe a timing/tuning sticky thread is in order. It would be nice to have some of the experts hash out some details, like how to set optimal initial, mechanical, and vacuum advance. It would be nice to know the goods and bads of too much or too little timing, like "runs hotter", or "less power", etc.

Even things like mechanical advance: how much to add and why, because that will influence where the initial has to be for WOT. Should mechanical timing come in early or later, and why? What is the upside/downside of either? Everybody has heard of the magical 36 total init+mech, but the mystery comes in what proportions and at what rpm.

If someone wants to lay out how THEY would set up each facet of timing (init, mech, and vac) and what parameters they use for optimum determination (idle, manifold vacuum, etc.), then I'd say start a thread with your technique. And then others can offer up their technique along with their "whys".

THAT would be a gift to the community.

[AdamIsAdam]

Great idea. I think you can copy and paste just about every word you wrote into a new thread, I guess in the street section (?) and ask for replies, advice and for it to be made a sticky. I for one would appreciate it. Just ask people to keep from making it a debate about MVA vs ported vacuum advance, for example.

[Cliff R]

Tuning distributors then setting them up on an engine is pretty much like carburetor building/tuning. They must be set up exactly for the application. Sounds pretty much like an easy/blanket statement, then you have to consider that nearly every engine combination is different, and some folks have done a far better job of choosing their parts than others.

We used to get into heated debates with several folks on this board on this topic. Most have left and some still lurk around with PM's to nearly anyone who runs a thread on this topic. Probably for the better, because I spent more time on the crapper last week than most of these folks have in total experience with these things.

Not really, but you have to remember that I do this FOR A LIVING, and have tuned thousands of different combinations at this point in my learning curve.

You are NOT going to solve the issues with all of them by simply buying a Crane adjustable vacuum advance, running really light spring tension so the timing you add it at idle doesn't fall out, then advancing the timing till the engine smooths out to find the "ideal" timing point for that engine at idle.

This topic is far more complicated than that, and anyone who does that will NEVER get thru emission testing if their car is still subject to it. I'm not saying here it doesn't work, but more times than not it's just a "crutch" to make up for a carb that's lean at idle, or engine that is a poor air pump at low rpm's.

Tuning MUST be done to both items, carb and distributor to get the best overall end result. It's nothing but a "crutch" to advance the timing clear off the scale to make up for piss-poor dynamic compression, too much overlap, LSA too tight, and carb to lean.

What I have always done, and recommended for this topic if for folks to either seek professional assistance, or spend the time and funds fine tuning the carb and distributor until you have found the very best settings for your engine.

Some engines will like, want, and require a LOT of timing at idle speed. The lower the compression, bigger the cam, and greater the squish area, the more you are going to have to lead the timing and more fuel you are going to have to add to get a clean burn at idle speed.

Other engines, with very well chosen parts, tight squish, higher compression, optimum cam timing, etc, will not want, like, require or even respond well to a lot of timing at idle speed, or anywhere else.

My own engines and most of what we build here fall into category number 2, so we do not have to get stupid with initial timing, or super-quick advance curves that get all the advance in by 1500rpm's, then have to add a bunch more via the vacuum unit to make them happy.

I've put this clip up here many times, but notice while you watch it how smooth the engine idles, smooth right off idle, and clean it is across the entire load/speed range. I run 10 degrees initial timing, 20 degree curve all in by 2800rpm's, and 10 more degrees to the VA via ported vacuum. My engine doesn't like, want, need or respond well to more timing at idle. Moving the VA over to manifold vacuum actually puts a very slight "skip" in the exhaust note, where on ported it idles smooth and steady, and the rpms barely move at all when the trans is placed in gear. Some may ask "why" at this point, as my engine has a hefty size HR cam in it with nearly .630" lift. It's about compression, very tight squish and carburetor that is tuned exactly for the engines requirements at idle speed. I'll also add here that I cool this engine with a stock 3 row Modine replacement radiator that's at least 30 years old, stock water pump, stock pulleys and stock "worn out" clutch fan. The engine doesn't even think about running hot, it actually does just the opposite, it takes nearly FOREVER to heat up, especially in cool/cold weather.

https://www.youtube.com/watch?v=6zVdoLR-VzM

Another thing I notice while we're on the subject is that more often than not, engines that fall into category #1 above tend to run hot, overheat, detonate, and REQUIRE a ton of timing to make them happy and minimize these negative attributes.

So combustion efficiency is a big player in this deal. If you find yourself having to run a lot of timing on your engine, and temps creep up in warm/hot weather, or it tends to want to run 200-230 degrees on long runs on hot days, or temps "creep" up that high at stoplights, there is a root problem.

Without exception ALL of the Pontiac engines we've had in our shop that ran hot, overheated, pinged, etc had a LOT of quench in them. We've also had a few in here that had those cheap 3 keyway timing sets installed in the +4 keyway and/or "modern" cam profiles with advanced intake closing points and tight LSA than ran extremely hot.

Quite a few years ago we worked a 400 than just ran hot no matter what we did to it. Kind of a neat story, if you don't mind a lengthy read, but it was early in my learning curve so I spent the time to figure it out.

It was a fresh 400 engine build, stock cast pistons way below the deck, 6X heads, and Ultradyne cam from Butler. This engine ran quite well, but just too hot, and the longer you ran it the hotter it would climb (sound familiar?). After doing ALL the basic carb and distributor tuning, trying MVA and all amount of timing everyplace we moved on to deeper issues. First, we installed a 4 row Desert Cooler, didn't help much. Upgraded to a 7 blade fan and HD clutch. Then we upgraded the 67 timing cover/waterpump to the later design with different pulleys to speed up the water pump.

After all those changes we were able to pull the temps from 230 plus down to about 190-210 on long runs. I still wasn't satisfied with the results, feeling that we more or less "crutched" the situation and didn't address the "root" cause.

Anyhow, just for the heck of it I removed the timing cover and retarded the camshaft 4 degrees. Not sure to this day why I did that, but we were nicely rewarded with an engine that ran too cool, took nearly forever to heat up, and didn't even think about going past 180 degrees for any reason!!!!

Wow, all that money and time spent and the entire time it was a combination of too much quench and cam timing. I didn't know at that time that the quench was a big player in the deal, but did figure that out a few years later on another 400 with similar issues.

Anyhow, I'm not sure if a tuning section would really be all that helpful here, the basics of this deal aren't all that overly complicated, but the combinations of parts folks come up with continue to amaze me, and with all the good information out there on engine building, and tuning, etc. If I can offer advice here, it's best to take steps early in the game to come up with a more favorable outcome. Building an engine and doing things during the rebuild to improve efficiency pays big benefits later on, rather than to throw a bunch of parts together then find out it idles poorly, runs hot, overheats and you have to go thru all sorts of hoops to correct all the issues......FWIW......Cliff

[PontGuy]

Just one more thought from me (at least here).

One thing not discussed is what the actual mechanical advance curve looks like and how well it "fits" the engine setup. I worked with SunTuned to optimize the points distributor for my Lemans engine and the attached shows the difference in the original curve and where we ended up. The engine hated the original curve and there was no amount of base timing adjustment that could make it run really right. The curve that we ended up with is actually more aggressive than the target that we were aiming at but it turned out to be just about perfect for the engine- given the lazy cam lobes, 9.5:1 CR, etc. I set the initial at 10-12 deg and it manages 14 deg vacuum advance on top of this without any problems. The engine runs cool here in hot Georgia summers with just a 15+ year old 4-core stock replacement radiator, and never any pinging anywhere.

I don't think the curve has anything to do with your surging problem, but its always worth recording mechanical advance values at different RPMs to see what you are working with at least to make sure it is reasonable.

A sticky might be useful for the basic tuning process and guidelines for a "typical" stockish Pontiac engine, but agree with Cliff that it might result in a lot of opinions and opposing views once you get past that. I just don't think there is a magic formula that covers all of the various combos that we are working on, many of them far from optimum. Case in point- I tried a similar curve and base timing on my TA engine when I first started tuning, and with the XE cam it wasn't close to right.

[AdamIsAdam]

Thanks, Pont,
I did post my curve (to some extent) in prior post. It's about:
12-14° initial.
~20° around 1,800,
34-36° all in around 2,800.

These are approximates as I've been tweaking it.

[Cliff R]

Here's part of an email to Adam, but it fits well here since we've pretty much turned this into a tuning thread:

"The order of tuning goes like this.

First find total timing, drag strip, dyno, seat of the pants, etc, without detonation.

Then find the initial timing the engine likes the best. If it likes 36 total and 16 initial, then a 20 degree mechanical curve is required. If it likes 36 total with 12 initial, then a 24 degree curve will be required, etc.

Tune the idle mixture screws with each test of initial timing to find out where they need to be, and make sure to do some fully heat soaked cranking tests to make sure it’s not “bucking” the starter.

Next add in vacuum timing (I use and prefer ported for most set-ups) and do some light throttle cruising and fine tuning the APT if/as needed for best results.

This part of the testing may take several tanks of fuel once you get close, but you can nail down the very best performance and fuel economy with this part of the testing.

At this point you have a choice as to add it initial timing via the VA with manifold vacuum for more timing at idle. This may help with some set-ups, typically those with not enough compression for the cam choice (low vacuum at idle), but is seldom if ever needed on an engine with a well chosen CID/compression/cam combo."

The reason we find total timing first, is that we do NOT want to damage the engine moving the distributor around trying to find initial timing. Detonation will destroy the best prepared shortblock, so we want to find the ideal total timing at full load before we start tuning the mechanical and VA.

The only part of tuning that leaves us with is how quickly the timing curve comes in and at what rpm it reaches full advance. Most engines don't want or need ALL the timing in right off idle, but to this day I continue to see folks installing "kits" that get total timing in really early. In almost all cases, the curves as so quick and springs so light that some of the timing is actually in at idle speed, which makes idle tuning difficult, if not near impossible, and for auto trans cars this causes a HUGE drop in engine rpms when the trans is placed in gear (sound familiar?).........Cliff

[72LuxuryLeMansLa.]

Great information Cliff. If anybody is interested in a good method for finding best total timing and timing in general, go to pages 114 and 115 in Jim Hand's book. I don't have a scanner so I can't post it, sorry.

[gtofreek]

Originally Posted by 72LuxuryLeMansLa.

Great information Cliff. If anybody is interested in a good method for finding best total timing and timing in general, go to pages 114 and 115 in Jim Hand's book. I don't have a scanner so I can't post it, sorry.

Plus it's copyright material!

[AdamIsAdam]

This is an interesting video on setting timing, starting with total mechanical timing:

https://youtu.be/wifTHbb06_I

I'm going to start again from scratch. I'm at a car show and on the drive here the temps were close to 210°. But with the current setup, it did run nicely, especially cold.

[AdamIsAdam]

Thank you all so much for your help and time on this thread. 2,300+ views and 150+ posts! I finally started a new thread on tuning to pick up where this one left off. PLEASE go over to here because I really need advice.
http://forums.maxperformanceinc.com/...21#post5404221

I have it running well but at 210* water temps!!! Surge is gone, timing adjusted. etc. Please see the other thread for updated details.

I'm going to copy Cliff's and a few other tuning tips over to that thread.

Thanks!

[AdamIsAdam]

Originally Posted by PontGuy

Just one more thought from me (at least here).

One thing not discussed is what the actual mechanical advance curve looks like and how well it "fits" the engine setup. I worked with SunTuned to optimize the points distributor for my Lemans engine and the attached shows the difference in the original curve and where we ended up. The engine hated the original curve and there was no amount of base timing adjustment that could make it run really right. The curve that we ended up with is actually more aggressive than the target that we were aiming at but it turned out to be just about perfect for the engine- given the lazy cam lobes, 9.5:1 CR, etc. I set the initial at 10-12 deg and it manages 14 deg vacuum advance on top of this without any problems. The engine runs cool here in hot Georgia summers with just a 15+ year old 4-core stock replacement radiator, and never any pinging anywhere.

I don't think the curve has anything to do with your surging problem, but its always worth recording mechanical advance values at different RPMs to see what you are working with at least to make sure it is reasonable.

A sticky might be useful for the basic tuning process and guidelines for a "typical" stockish Pontiac engine, but agree with Cliff that it might result in a lot of opinions and opposing views once you get past that. I just don't think there is a magic formula that covers all of the various combos that we are working on, many of them far from optimum. Case in point- I tried a similar curve and base timing on my TA engine when I first started tuning, and with the XE cam it wasn't close to right.

OK, I'm back at this game. This time better prepared:

PontGuy,

Your chart is interesting, so I recreated it as best I could, and added my own curve to it.

My timing curve looks like this:
RPM Added Advance in Degrees (vacuum disconnected)
750 0
1000 ?
1500 8
2000 15
2500 16
3000 19
3500 19

How does one know what the curve should look like for an engine?

(Graph with Adam's curve added)


I'm back at this game as I said. This time I've got a log book and better data. Plus, I upgraded my wiring to the starter to 0ga wires so cranking is not a problem any more up to 20* or more.

I used the methods outlined both by Cliff and in Rocky's book. Without the vacuum advance connected, I raised initial timing to as high as I could go so that when driving at WOT, I started to get clear pinging. I immediately let off the gas and set timing down 2*. Kept test driving and determined that the car likes 16* initial timing. It starts fine there when hot and runs great!

I adjusted the idle speeds as needed to keep it around 850.

I drove at 3,000 RPM without any surging.

TEMPS DROPPED AS I WAS DOING ALL THIS from 210 down to about 185 while idling in the driveway between drives.

I then added the vacuum advance, it idles great using MVA (I tried ported too), low end drive-ability is terrific. I have 12* of MVA at idle and that's the lowest I can get from my Crane adjustable unit. With it connected, I get surging at 3,000 RPM, but not at 2,600.

So I took another new OEM vacuum advance can that has a very light Hg requirement (well below 10") and I welded in material to limit travel at .12" as per Cliff's suggestion. This should be 10* of crank timing added. I will install this next and test for surging at 3,000 RPM.

The car is running great, however, after about 20 minutes of steady highway driving, the temp will still creep up to about 205, and it will come back down at idle to about 195. If I don't go on the highway, the temps seem a little lower.

It was very cool out this weekend, so as I drove on the highway, I turned off my electric fan and the temps went from 205 up to 210. Turning the fan on HI brought the temps back down to 205, so the fan is not limiting flow at 65 MPG as someone suggested to check.

I have adjusted the APT slightly, but am not done doing that. I guess the carb could be running a bit lean at cruise causing temps to inch upward.

I'll report back once I install the new vacuum advance unit and reset timing. Then I'll adjust APT as well.

Thoughts? Suggestions?

As a reminder for those who don't recall or have the time to read the history, the cooling system kept the car in the 185-190 range on hot days (MUCH lower on cool days) before I changed the carb, intake and timing, so I'm not rushing to change the cooling fan just yet until I'm sure this is not a tuning issue. I have a spring in the lower radiator hose also.

Thoughts?

[PontGuy]

Great to see you back at it.

Just to recap, you still have the XE274 cam and the C/R is somewhere around 9.3:1? Did you cc the head and confirm C/R while you had it off? (Forgot details of that whole story.)

Pretty good re-creation of my chart considering all you had is a .jpg shot of it to start with. You even managed to cut off the scaling at the bottom just like I did. I can email you my Excel file

Your curve looks reasonable and 35 deg all in with no pinging sounds good to me. And no surging with the vacuum advance disconnected is a good sign. Interested to hear whether the new vacuum can eliminates the surging and helps cool it off a bit when on the highway. And there's nothing wrong with opening up the APT a bit especially since it is easily reversible. My bet is that your Holley ran a bunch richer than the Q-jet and as discussed earlier adding some fuel could help. Personally, the only time I experienced real surging was with a stick car having a spreadbore dp Holley that was jetted very lean on the primaries.

For reference my Lemans 455 runs best around 36 deg all-in with 14 deg vacuum advance, so 50 deg max total cruising on the highway at 3000 RPM down to 36 pulling hills. Very close to where you are heading with yours. The best I can get on my T/A 455 is 30 all-in with 10 deg vacuum advance, so 40 deg total cruising on the highway at 3000 RPM down to 30 pulling hills. (They both have the same size rear tires and gear ratio, and that puts them around 75 MPH.) The biggest difference between my two engines is the cam. If the weather holds out I might take the T/A to the track tomorrow night to see how it really compares to the Lemans.

[AdamIsAdam]

Originally Posted by PontGuy

Great to see you back at it.

Just to recap, you still have the XE274 cam and the C/R is somewhere around 9.3:1? Did you cc the head and confirm C/R while you had it off? (Forgot details of that whole story.)

Pretty good re-creation of my chart considering all you had is a .jpg shot of it to start with. You even managed to cut off the scaling at the bottom just like I did. I can email you my Excel file

Your curve looks reasonable and 35 deg all in with no pinging sounds good to me. And no surging with the vacuum advance disconnected is a good sign. Interested to hear whether the new vacuum can eliminates the surging and helps cool it off a bit when on the highway. And there's nothing wrong with opening up the APT a bit especially since it is easily reversible. My bet is that your Holley ran a bunch richer than the Q-jet and as discussed earlier adding some fuel could help. Personally, the only time I experienced real surging was with a stick car having a spreadbore dp Holley that was jetted very lean on the primaries.

For reference my Lemans 455 runs best around 36 deg all-in with 14 deg vacuum advance, so 50 deg max total cruising on the highway at 3000 RPM down to 36 pulling hills. Very close to where you are heading with yours. The best I can get on my T/A 455 is 30 all-in with 10 deg vacuum advance, so 40 deg total cruising on the highway at 3000 RPM down to 30 pulling hills. (They both have the same size rear tires and gear ratio, and that puts them around 75 MPH.) The biggest difference between my two engines is the cam. If the weather holds out I might take the T/A to the track tomorrow night to see how it really compares to the Lemans.

YES, please email me the excel file. I struggle with pivot tables as you can see. LOL I'll PM you my email address.


Yes, I still have the XE274 cam with new 1.65 rockers.
My CR is actually 10.01.
My heads CC is 75.

My Holley initially was running lean at WOT according to the dyno session when I first got the car so I went up 2 jet sizes on both sides of the carb. Not sure about part throttle A/F. So maybe it was running richer than the Qjet is now. I suspect that to be the case also because the Qjet was running better on very hot, humid days this summer.

Many say 10* of vacuum advance is not enough, but all I know is that there is no surge at 3,000 RPM without any vacuum advance and surge with it at 12* added.

But here's the one thing that's bugging me now: when I had 12* vacuum advance added this weekend, the temps were still creeping up during highway only. You think that's all because it's cruising lean?

I know I can add a lot of fuel with the APT at part throttle because Cliff said my need jets are tapered (I think I said that correctly.).

[PontGuy]

I am hardly an expert here- more of an experienced hobbiest. But I've learned a lot after installing A/F meters in my cars. After swapping carbs, playing with jets, etc. I've come to realize that street engines are more forgiving than you might think. Small changes to jetting can have a big impact on A/F readings without a huge impact on drivability, but I have to think that combustion efficiency is affected.

Sounds like part throttle (not into the secondaries) was the concern, so not sure I would have gone up on jet sizes on both sides of the Holley. But that's water under the bridge now. 10 degrees vacuum advance is not a lot, but given your C/R that may be what you need.

As you well know getting temps down is all about combustion efficiency and ability of the cooling system to remove heat. In theory running lean at part throttle could be contributing. Only way to tell for sure is to richen it up some with the APT and keep testing.

Pivot tables... not hardly an expert at those either. But I do know how to make pretty graphs

[AdamIsAdam]

UPDATE: I installed my modified vacuum advance unit. It's P/N VC1849/AR19. It begins advancing at 4-6" of Hg and is all in by 7-10" providing 12* of distributor timing (24* crank timing). So I had the travel limited by welding in metal. Total travel is .12" which provides 10* of advance at the crank, exactly as Cliff said it would. And it works as promised.

Results: Still with 15* of initial timing and now +10* of vacuum advance added, the cold start-up and cold driving was wonderful. Driving was all around excellent. There was a SLIGHT surge felt at a steady 3,000 RPM which I'll come back to. So on to APT and temps:

But... (you knew this wasn't going to end so fast)...

I'm still running at higher temps than I used to with the Holley. Around town on a lovely, 75* fall day, it idles at 180* and goes to about 185 (MAYBE 190) around town. But after a long steady highway drive, it settles in at about 200*. Once up at that temp, it'll only go back down to 185* or so if I'm idling for a long time.

So I adjusted the APT screw CCW. I started with 1/2 turn, then a full turn, and the surge was diminishing. I went one more 1/2 turn for 1.5 turns CCW total from the 2.5 that Cliff set it at when he built it. The surge subsided further, but it's ever so slightly detectable. I'd be fine with the car if the temps weren't still 200* on the highway.

To me I think I still need less vacuum timing, since the surge is gone when no vacuum advance is connected. But the temp situation really has me annoyed.

As a reminder, I have a new 160* high flow, tested t-stat, a Ford Taurus electric 2 speed fan that's automatically on at about 170, and I run Evan's Waterless coolant that doesn't boil until 375*. Oh, and I have a home made wire/spring inside the lower radiator hose. I have a new one from Ames that I can install when I get around to draining the system again. The hoses are in excellent shape. The water pump I believe is the right type but I didn't pull it apart to check and clearance it because the car ran cooler with the Holley.

Thoughts? Next steps? Timing? A/F issue? cooling system issue? What next?

[78w72]

this is a long thread so i may have missed it if it was mentioned before... but if the car runs ok at idle & around town & only gets to ~200 on the highway, i dont really see that as a problem. you are far from "overheating" & no damage is being done to the engine. i say enjoy the car. in some aspects the 200* is good as far as engine wear & usually MPG. pontiac used a 195 t-stat originally. i agree its nice to stay at 180* 100% of the time but maybe your combo of parts & settings just wont do that with the new carb? or put the old carb back on if you cant live with the temps. IMO a carb change (if its set within reason for the engine) shouldn't require you to change or improve your existing cooling system that worked fine with a different carb.

best of luck figureing it out, everything i know of has been mentioned here, im stumped.

[PontGuy]

I just re-read the thread and it sounds to me that you are close. Not many of these engines are going to run much under 200 deg at sustained 3000 RPM highway driving unless it is cool out. It is getting into fall now so you are running out of time to test hot weather driving this year, but I would be interested to hear if it stays about the same when up in the 80's. Both of mine run 190-200 on the highway whether it is 75 or 85 deg out. Idle oil pressure drops into the teens when I first get off the highway but then recover to normal pretty quickly. No harm, no foul.

I just re-read the whole thread and came across this, referring to the switch from the Holley to the q-jet.

The one thing I can say is that my MPG nearly doubled so far

Is this really true? Exactly what sort of milage were you getting then compared to now?

[AdamIsAdam]

Originally Posted by PontGuy

I just re-read the thread and it sounds to me that you are close. Not many of these engines are going to run much under 200 deg at sustained 3000 RPM highway driving unless it is cool out. It is getting into fall now so you are running out of time to test hot weather driving this year, but I would be interested to hear if it stays about the same when up in the 80's. Both of mine run 190-200 on the highway whether it is 75 or 85 deg out. Idle oil pressure drops into the teens when I first get off the highway but then recover to normal pretty quickly. No harm, no foul.

I just re-read the whole thread and came across this, referring to the switch from the Holley to the q-jet.



Is this really true? Exactly what sort of milage were you getting then compared to now?

My higher temps seem to be the same regardless of outside temps. Yesterday it was mid 70's and there was no change. So time will tell. It just bugs me since I didn't run this hot before.

I may just have to tune it as best as possible, then do some other routine tricks to combat the temps. I guess the two big ones being the clearance on the water pump and maybe changing over from electric to 7 blade HD fan.

As for MPG, over the last year, I've been seeing around 6.1-8.1 under most driving conditions, excluding trips where I did a lot of tuning and idling in that tank of gas, so I'd say the average was around 7.8 before. On the only tank of gas that I've run post-Qjet and post valve job that excludes tuning work, I got 12.1. Clearly I can get on the skinny pedal more and easily get the MPG down back into single digits, but before I almost always stayed around 7-8, so it's better. Plus, now that I have a choke and a Qjet, it starts up and runs nicely cold, which will become more important soon enough as the calendar moves ahead!