[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!

[Cliff R]

Adam, tune the carb and distributor for best idle quality, off idle smoothness, throttle response, and drivability in the "normal" driving range.

If the carb is lean or timing insufficient you will notice loss of power, "flat" on light throttle acceleration, and even some "bucking", kicking, or you just have to apply to much pedal to make things happen. It other words the engine will let you know when it isn't happy.

Once you are happy with how the engine performs, fuel economy is good, and no lag or lacking power anyplace, etc, and you still think it's running a bit hotter than it should, attack that as a separate issue.

We NEVER under any circumstances want to "wash" the engine with too much fuel to "crutch" a hot running condition. Even the big 455 should delivery decent fuel economy. Yours should end up in the 12-15mpg range, depending on city/highway, fuel quality, wind speed/direction, driving style, etc when doing the testing.....IMHO.....Cliff

[jonmachota78]

you might try a 180 deg thermostat. The 160 stat you are using doesn't stand a chance of maintaining a steady engine temp and the wide range of temps you are seeing only make tuning more difficult. A 180 deg stat will narrow the range of engine temps you are see and simplify your tuning efforts. The 180 stat will not make you car run hotter. It will keep it between 185-200 rather than 165-200 like is happening now. It will raise the floor but the ceiling won't change.

[AdamIsAdam]

except that once warmed up the lowest temps I see now are 180. It never goes below there. (and I did verify the new T-state in a pot of boiling water. It was quicker acting than the old 160 I removed)

[PontGuy]

Cliff beat me to the punch. For gas milage to be that bad the Holley must have been running pig rich on the primaries. Probably good for cooling things down but not so good for the engine (or the cost to operate it!)

[Cliff R]

+2, 3, 4, 5 and 6!!!

"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."

7.8 MPG average is ABSOLUTLY UNACCPEPTABLE. It tells me that something in the mix is WAY off someplace. It's often a combination of things, but I can tell you or anyone else reading this for certain, a stout 455 with iron heads, around 10 to 1 compression, and well chosen camshaft will just about double that number for fuel economy when correctly tuned.

I've had half a dozen engines in my Ventura since the late 1980's, from 406cid to 468, and gear ratios from 2.73 to 3.73, and ALL of them got over 12mpg's, and the 406 with 2.73 gears just under 20 mpg's.

Even the current 455 is very thrifty on fuel. It uses no more fuel for "normal" driving than the last 455 did. I checked the last engine for fuel economy several times, and it would EASILY make 180 miles per tank (about 14.0-14.4 gallons), and I've had a few tanks in the 200-230mile range when there was considerable highway driving involved, and the operator had enough willpower to stay out of the secondaries (seldom happens).

Even the big Holley carbs I've ran and tested, and the POS Edelbrock AFB clone would muster 160 miles per tank, which is closer to 11mpg.

Adam, I would NOT under any circumstances put the Holley back in service in it current state of tune, it is "washing" the engine for sure consuming that much fuel, running cooler or not......FWIW......Cliff

[AdamIsAdam]

Cliff, no worries about the Holley, it's long gone

One change I made is that I used to run 100 octane, either straight in or mixed 50% (more or less, depending on when I got to the pump). And yes, at nearly $10/gallon, that was a lot! Then you pointed out to me that if I'm not pinging, I'd likely go slower with higher octane. So I stopped putting that octane in. Maybe that has something to do with my temps rising? That's what someone else suggested. It's worth a try checking, now that I'm logging my data more carefully.

Speaking of data, I checked the dates on some of my pictures and it looks like my temp issue actually started before I installed the Qjet, even before I changed intake manifolds (I ran the Holley on the new intake for about a month). I know it definitely got much worse when the Qjet went on last November, but the problem was clearly lurking before. So I must have a few things going on as you said before, Cliff.

[72LuxuryLeMansLa.]

Originally Posted by AdamIsAdam

Cliff, no worries about the Holley, it's long gone

One change I made is that I used to run 100 octane, either straight in or mixed 50% (more or less, depending on when I got to the pump). And yes, at nearly $10/gallon, that was a lot! Then you pointed out to me that if I'm not pinging, I'd likely go slower with higher octane. So I stopped putting that octane in. Maybe that has something to do with my temps rising? That's what someone else suggested. It's worth a try checking, now that I'm logging my data more carefully.

Speaking of data, I checked the dates on some of my pictures and it looks like my temp issue actually started before I installed the Qjet, even before I changed intake manifolds (I ran the Holley on the new intake for about a month). I know it definitely got much worse when the Qjet went on last November, but the problem was clearly lurking before. So I must have a few things going on as you said before, Cliff.

Adam,

What radiator are you running? More importantly how old is it and when was it last PROFESSIONALLY cleaned? A little scale goes a long ways in reducing cooling capacity!

The other question I have is about driving conditions. You state that the real issue shows up after highway driving and disappears once you get off the highway, correct? If it stays cool even in city traffic jams but gets warmer on the highway that is a hint. Under 40mph the fan/fans are in charge, but at highway speeds air feed from the front of the car, ie air dams, grills and such are in charge. Have you mounted a new cooler for the engine or transmission in front of the radiator?

[AdamIsAdam]

My radiator came with the car. It looks like a generic brand. Oh, and during a nice highway drive it still hit highway temps.

Her is what I have, which is how u bought it...

[Cliff R]

You may be able to cure the heating up issues simply by installing a heavy duty thermostatic clutch fan. They pull a BUTT LOAD more air than any electric fan set-up.

Even on my 455 which doesn't even think about heating past 180 for any reason in any weather didn't like the electric fan set-up much. It did OK, but it kept killing my battery if I used it to keep the engine cool on hot summer days at the track. I went back to a HD clutch fan and never looked back. I can cool the big 455 with a stock Modine 3 core radiator that's over 25 years old at this point.

I'd also put that cam on the endangered species list. 276 degrees seat timing isn't nearly enough for a 455 Pontiac engine at 10 to 1 compression, especially ground on a 110LSA with the ICL down at 106. It's better used serving a 400 engine build about 9 to 1 compression, if one goes that direction at all.....IMHO and FWIW.......Cliff

[AdamIsAdam]

Yes, I may look into the clutch fan. And yes, I know this cam isn't ideal for this engine. Remember, I didn't put it in there.

Corrected picture from last post:

[PontGuy]

Looking at the pic Adam that electric fan setup looks very restrictive for highway driving. A factory clutch fan with a proper shroud might even get you to 180 down the highway just like Cliff's car!

Just for the record, both of my cars also have factory shrouds and clutch fans. The Lemans tends to run around 190 down the highway in warm weather. The T/A gets up to 200 but it has an A/C condenser and massive trans cooler in front of the radiator, and the timing is pulled back because it still has the XE cam. I put an aluminum radiator in it to help keep the temp down but kept the original to try when I get around to putting a proper cam in it and get the timing set right.

One thing you guys don't have to worry about living up north is the hot summers here. Temps typically are in the high 90's mid summer, but then again its not much fun driving these cars in that sort of heat. They just stay in the garage when it gets near 100.

[Cliff R]

For sure the cam isn't helping you anyplace. I've tuned enough Pontiac engines using those cams to know to avoid them completely. Typically they want more fuel and less timing, telling me that the short seat timing events aren't making things more efficient, at least pound for pound compared to more ideal choices.

I try to stay off the subject, because I quickly get called the Comp XE "cam basher", but I really only mention these things to help folks make more educated decisions and to get a better end result all the way around.

For absolutely sure 455 cid and a solid 10 to 1 compression needs more cam than 276 degrees seat timing to make optimum power on pump fuel, and to effectively manage pump fuel with "normal" fuel and timing curves. When the cam is too small, and intake closing too early/LSA too tight, one will often run into many of the issues that you are here, which include running hotter than it should be, just to mention one of them......Cliff

[AdamIsAdam]

Good food for thought. It's on my list... to change the cam which would be an excellent time to change the electric to a clutch fan. Hmm. Would I be able to use my existing radiator or is it not the right size? I guess I'll waddle on over to the cooling section and see what fan and shroud options there are.

Thanks for all the feedback. And Cliff, I still have your recommendations as to which cam to go with for when I'm ready. don't think that was a waste of time by any means.

Thanks.
Adam

[Cliff R]

The size of the radiator certainly becomes less important when the basics of engine operation aren't dumping a TON of heat into the jacket water.

I'm found out that having a successful engine build starts with the basics, which include optimum quench, compression, cam choice, intake valve closing point (where you put the cam), carb/distributor tuning, to name a few.

For sure all of these engines need an efficient cooling system. I've never really seen any negatives from too much radiator, but I have seen folks install HUGE radiators to combat fundamental issues and still end up with a pretty hot running engine.

With my current engine I see negatives every Fall and thru the colder months, it just runs WAY too cool/cold, and refuses to heat up the coolant in what I would call "normal" conditions.

My last two engines have been like this, they just take FOREVER to reach operating temperature, unless it's 90-100 degree days, and even then count on a solid 15-20 minutes of running time before it gets past 160 degrees, even with a 180 stat in it.......Cliff

[AdamIsAdam]

Originally Posted by Cliff R

My last two engines have been like this, they just take FOREVER to reach operating temperature, unless it's 90-100 degree days, and even then count on a solid 15-20 minutes of running time before it gets past 160 degrees, even with a 180 stat in it.......Cliff

There are many people who hate you for this sentence, ya know!

[PontGuy]

Yeah Cliff is good at pointing out what is possible, not necessarily what us amateurs should expect. Sort of like watching pro golfers pound out 340 yard drives. (When I play a bunch I average around 270 yards off the tee, and that's about where my Pontiac expertise is on the relative scale.)

Its really been interesting having two cars with engines that are set up very similar except for the cam. It takes my Lemans a good little while to come up to temperature with the long seat duration cam- seems like forever in cool weather. The T/A is up to temperature in a matter of a few minutes with the XE (and necessary retarded timing.) But at least the T/A heater works quickly during the winter.