So called normal operating temperature

[Mike T.]

Re: So called normal operating temperature

Doug - I'm unfamiliar with the brand of fan clutch you mentioned, Switzer. You did say you used the sheet of paper as a way to test the draw from the fan but curious as to how much actual resistance, or 'engagement' you're really getting from that clutch unit. I know when I've used the generic 4-Seasons or Hayden clutch units that at so-called normally seen temps on an early Corvette like 180-190 they still seem to slip a lot and a number of users have done that little 'trick' to that front spring on the face of the clutch to try to get it to lock up earlier and not wait till it hits the high side of 200*. Once you are up to temps and shut it off, when you try to spin the fan, how many revolutions does it make?

[Michael J.]

Re: So called normal operating temperature

Mike ,I don't know if there is enough proof on the over bored engines, My 63 shp and my freinds 63 300hp neither over heat. and run pretty cool. I can say that my 63shp engine has never been above 195, In bumper to bumper traffic. both wire bored one 40 over and the other 30 over.

I know others who have not experienced this, but of the 8 engines I have had (admittedly, all high performance, high compression, solid lifter types from GM, Mopar, and Ford) direct comparisons with, it has been my experience.

Edit: I would also have to add that IMO a 60 over bore is pretty big to expect no wall thin spots, many machine shops are not capable of that precision.

[Doug R.]

Re: So called normal operating temperature

Mike, to answer your comments,there is only one vacuum source on the 2818-1 carb and I have tested it during timing and idle adjustment, the carb was rebuilt less than 4 months ago.As for the switzer fan clutch it was one of two used by G.M.,it has a rectangle on the front that has "This side up" repeating it does not have the coiled spring that can be moved counter clockwise to lower engagement temp.I got it from AFC in Calif.and they assured me it is set @ 180* for engagement. Leif,I removed the 7 blade fan and installed a 5 blade just to try to return the car to the way it was meant to be.I am going to put the 7 blade back on to see what happens. Thanks to all that responded any other suggestions are gratfully accepted. Doug

[Mike T.]

Re: So called normal operating temperature

Doug - I'd be surprised if the 7-blade fan made a difference. Only going off memory here but thought that the early A/C cars that used the 7-blade fan but Chevy switched to the 5-blade version as of the 66 model year. Regarding the 2818 Holley, is yours an original or does the '-1' mean it's a later model? Reason I ask is I just did some research on an older thread on the 'other Forum' and found a reply from John Z (John Hinkley) where he mentioned the original 2818's vacuum port was full manifold vacuum but the later versions were changed to ported vacuum from that same port.

[Doug R.]

Re: So called normal operating temperature

Mike, I thought the 2818 was used on 64's and due to some mod. in 65' the carb was called 2818-1. Yes my carb is original dated 5365.

[Mike T.]

Re: So called normal operating temperature

Doug - I thought all Holleys used a 3-digit date code until the late 60's or early 70's and then when they were re-released as replacement carbs, they went to the 4-digit dating system. I have a DZ-4053 780 Holley from a '68 Z-28 and it's got the 3-digit code. I'm not sure so I'll do some checking but while I'm doing that, it would be just easier to ask you if you have a vacuum signal at idle from that one port? If so, from what I read, it's an original carb. Where I'm going with this is that manifold vacuum at idle would definitely help advance the timing and should help ease the temps. If you already do have manifold vacuum from that port, disregard my wayward theory ;-).

[Doug R.]

Re: So called normal operating temperature

Mike, I miss wrote the date code it is 535 on my carb.I think I have tested the idle vacuum while doing the things Duke told me to check, I have done so many tests and checked so many things trying to solve this issue I'm not sure,but will revisit that test. THANKS

[Mike T.]

Re: So called normal operating temperature

Doug - Well, that 3-digit date code would indicate an original #2818 which means you should be seeing full manifold vacuum from that one port. That's good. From the sounds of it, you've done a lot of testing and so far, nothing seems to leap off the page as being the cause of your overheating. The reason I asked earlier about how quickly it came up to temp and how recent the rebuild occurred was due to wondering if there was some sort of head gasket leak that would have combustion gases finding their way into your cooling system but that doesn't seem to be the case either. How do the plugs look, are they bright white or showing a bit of color? I realize it's a bit of a stretch but at this point, even with optimized A/F mixture screw settings, but in your conversation with Duke, was there any talk about richening up the idle fuel supply?

[Jim T.]

Re: So called normal operating temperature

I have a 65' 327/365,I would like to ask the forum what they consider to be hot weather operating temps.,both cruising and city speeds? My car runs around 190* hi-way, and heats up to 220-230*in town. At idle it will kiss the mark for 240*.I just want know if this is par for the course or abnormal. Thanks Doug

Doug when I bought my new 1970 I learned the importance of vacuum advance in the second week of ownership. Being a summer day I was using the air conditioning and got out of the 70 leaving it running with the air on. This 70 has a solenoid that controls vacuum from the carb to the distributor vacuum advance. The distributor was not getting any benefits of vacuum to the vacuum advance unit. At operating temp vacuum advance operation was not permitted until the automatic transmission shifted into third gear. Sitting at idle my 70's engine temp increased high enough that a head mounted thermostat sent a signal to the solenoid that controls vacuum that allowed the vacuum from the carb to operate the vacuum advance. What got my attention to what had just happened was the increase in engine RPM while standing by my new 70. This experience led me to read my owners manual to learn how the solenoid operates that controls vacuum. From the learned knowledge I then bought a length of vacuum hose and hooked up my distributor's vacuum advance unit directly to the carbs full time vacuum source. Still using full time vacuum 44 years later. Doing this I could drive in city stop and go traffic in downtown Dallas in July with the air on and never experienced any over heating. Reason for my post is the temps you posted about your temps in your 65 in town and at idle. My city driving gas mileage also increased with full time vacuum. A lot of information has been posted on this board about the advantage of using a vacuum advance unit that functions with high performance engines that do not produce high vacuum readings.

[Duke W.]

Re: So called normal operating temperature

The timing now is in spec with initial timing @13* and WOT timing @ 39*.I have adjusted the the Idle vac screws per the shop manual procedure.Here's what I have, I installed a new repro. switzer fan clutch.

At what RPM is the centrifugal all in? You said the engine had a lot of incorrect parts. The spark advance map needs to be very close to OE with all centifugal in at about 2350 and a functioning 236 16/B28 replacement VAC that is connected to a full time manifold vacuum source, so total idle advance should be in the range of 28-34 degrees (sum of initial plus full vacuum advance plus a couple degrees centrifugal since is starts at 700) at about 900 RPM/10" manifold vacuum with the 30-30 cam.

Most current replacement fan clutches are "tuned" for 195 degree thermostats, so they tighten at a higher radiator exit air temperature than originals from the pre-emission control era that were tuned for 180 degree thermostats.

Duke

[Kenneth B.]

Re: So called normal operating temperature

[QUOTE=Duke Williams (22045);712268Most current replacement fan clutches are "tuned" for 195 degree thermostats, so they tighten at a higher radiator exit air temperature than originals from the pre-emission control era that were tuned for 180 degree thermostats.Duke[/QUOTE] BINGO. IMHO I think this is 75% of overheating problems.

[Doug R.]

Re: So called normal operating temperature

Thanks for the info. , I am in the garage now looking my engine over and noticed I have a 3/8" gap at the top of my radiator between the rad. support in the front and 3/8" in the back between the shroud and the rad. the sides also have some gap. The raditor bracket seems to be holding the radiator in the middle of the opening so nothing is rubbing. Could this be a problem by not directing enough air through the radiator?

[Leif A.]

Re: So called normal operating temperature

Thanks for the info. , I am in the garage now looking my engine over and noticed I have a 3/8" gap at the top of my radiator between the rad. support in the front and 3/8" in the back between the shroud and the rad. the sides also have some gap. The raditor bracket seems to be holding the radiator in the middle of the opening so nothing is rubbing. Could this be a problem by not directing enough air through the radiator?

Doug,Do you have all these parts:-Dr REBUILD's Corvette Parts - MODEL ------------------ ------------------- Part # A 63-65 327 Fan Shroud Lower Seal Die cut thick textured surface sheet rubber with the correct asymmetrical pattern. Beware the brand X seal with bogus material and an incorrect symmetrical pattern. Attaches with 5-7 staples. Dr. Rebuild's Corvette66-67 327 or 427 Air Dam with Air Conditioning Please do not confuse this part with the bogus FLAT thick sheet that must be folded into an impossible curve. Ours has the curve vulcanized right into the part as original & will maintain it's shape. Authentic in absolutely every detail because we had it re-manufactured by the General's original supplier. COOL TIP SEE BELOW Part # 66-67 327 or 427 Air Dam with Air Conditioning 1274506 COOL TIP The above 66-67 air dam can be installed on any 63-67 that is RUNNING HOT and will help direct air flow through the radiator. Installation only takes a couple of minutes without any tools or modifications to you Vette. If you enter shows where originality is judged, it can be removed without a trace in minutes. - Dr REBUILD's Corvette Parts ----------- - MODEL -------------- --------------- Part # 66-67 AC 327 Lower Radiator Seal Die cut thick Black sponge rubber notched to clear the lower support brackets. Glue to the radiator support with Black weatherstrip adhesive. 1274207 I know a couple of these parts are listed for the '66-'67 models but they may work on your car as well. Without these on my '67 L79 she overheats badly.Others will chime in as to whether these may help or not...anything to help seal the radiator, radiator support and shroud area to keep as much air coming thru the radiator will help...IMHO.

[Doug R.]

Re: So called normal operating temperature

Leif, thanks for the info. I am going to explore your idea of more seals aroud my radiator. Doug

[Domenic T.]

Re: So called normal operating temperature

I will chime in on what Lief said. I remember these seals when I was a line mechanic back then. When installing a radiator or schrod they were in the box with a WARNING. It said they MUST be installed to assure proper cooling.

DOM

Doug,Do you have all these parts:-Dr REBUILD's Corvette Parts - MODEL ------------------ ------------------- Part # A 63-65 327 Fan Shroud Lower Seal Die cut thick textured surface sheet rubber with the correct asymmetrical pattern. Beware the brand X seal with bogus material and an incorrect symmetrical pattern. Attaches with 5-7 staples. Dr. Rebuild's Corvette66-67 327 or 427 Air Dam with Air Conditioning Please do not confuse this part with the bogus FLAT thick sheet that must be folded into an impossible curve. Ours has the curve vulcanized right into the part as original & will maintain it's shape. Authentic in absolutely every detail because we had it re-manufactured by the General's original supplier. COOL TIP SEE BELOW Part # 66-67 327 or 427 Air Dam with Air Conditioning 1274506 COOL TIP The above 66-67 air dam can be installed on any 63-67 that is RUNNING HOT and will help direct air flow through the radiator. Installation only takes a couple of minutes without any tools or modifications to you Vette. If you enter shows where originality is judged, it can be removed without a trace in minutes. - Dr REBUILD's Corvette Parts ----------- - MODEL -------------- --------------- Part # 66-67 AC 327 Lower Radiator Seal Die cut thick Black sponge rubber notched to clear the lower support brackets. Glue to the radiator support with Black weatherstrip adhesive. 1274207 I know a couple of these parts are listed for the '66-'67 models but they may work on your car as well. Without these on my '67 L79 she overheats badly.Others will chime in as to whether these may help or not...anything to help seal the radiator, radiator support and shroud area to keep as much air coming thru the radiator will help...IMHO.