This Is One Red Hot 1965 Mousemotor

[Joe C.]

Yes, this 327/365 runs real strong, thinks it's a ratmotor, and is not even "broken in " yet. It's got about 3 hours run time prior to rolling, and the odometer now reads 24 miles since the restoration.
Some of you might remember the threads, "Idle To Overheat", and "Thar She Blows" a couple months back, in which we discussed the possible ways of addressing this mouse's elevated temperature during prolonged periods of idling. I would like to keep you folks informed of the latest, and provide some food for thought for the likes of Duke, John H., Clem, and others who have contributed to the above discussions.
Here is what we have as of 10/7/02:

Ambient @ 78*F.
Fired engine cold- idled 45 min.- shutdown
Temp gauge at mark midway between 180 and 240 (calculated at 213 based on non linearity of gauge), which is actually 218, as measured with IR at thermostat housing. Needle was still slowly climbing at shutdown.

1. New DeWitts, belts, hoses, water pump. All "correct", numbers, etc., etc.
2. Rebuilt (by a "good man" most of us know) original fan clutch
3. 50/50 Zerex/H2O
3. 13# cap., correct from John Pir---
4. 6 qts Castrol 10W-40 motor oil
5. Bore is .020 over--journals are .010 under
6. 461 heads were cc'd, pocket ported, bowls opened, exhaust valve unshrouded
7. Engine built using all parts "as new", including domed pistons, 30-30 cam.
8. Actual CR calculated as 10.5 min. to 10.7max. (based on variances in chamber volume).
9. 236 vacuum can
10. Idle (hot) @ 900 RPM
11. Idle vacuum meas @ 15 in-hg --- needle very steady
12. Idle mixture screws backed out from 3/4 turn, to 1 1/2 turn (spec).
13. Static timing @ 10 BTDC.
14. Static + vac. advance @ idle meas. @ 27 BTDC.
15. Exhaust manifold temp., meas. with IR, at confluence of 2 center ports:525*F.
16. Heat riser approx. 1/2 open at idle. Spring is like a limp d--k, and blows open with any increase in exhaust pressure.

Still, the temp. continues to slowly climb if I let the beast idle for an extended period.

Can any of you with midyear smallblocks, claim that you can idle your motor INDEFINATELY without boilover! If such is the case, then I would very much appreciate your feedback. I am fairly certain that my engine/cooling system is operating within design parameters, and would appreciate any empirical evidence to the contrary.

Joe

[Duke W.]

Re: This Is One Red Hot 1965 Mousemotor

Everything sounds good. The total idle timing and manifold temp are in the optimum range. The only thing that suprises me is that it pulls 15" at 900, but that's not likely contributing to high temps.

How about the fan? It should offer much more resistance to turning by hand when the temp is over 210 than ambient. Also, if you rev it up to 2500 when hot, you should feel more air flow coming off the fan than when the engine is cold.

Duke

[Joe C.]

Re: This Is One Red Hot 1965 Mousemotor

Duke:

I haven't measured the cylinder pressure, but I will assume it is AOK - maybe I did a decent job lapping in the valve seats, which will account for the good, steady idle vacuum reading. Maybe I am wrong, but I recall that most engines with mild overlap cams pulled about 17-18 in-hg @ idle, so 15 doesn't sound unreasonable with a fairly radical cam, like the 30-30.

As for the fan (correct 5 blade unit 17 1/8 dia, etc., etc.), and clutch (fresh rebuild by Mr. O,, smallblock flange-to-flange dimension), what more can I say. Radiator is uniformly hot to the touch, with no tactile evidence of temp. variation.

I would certainly like to hear from any owners of midyear smallblock Corvettes, in their "correct" configuration, who can idle their engines indefinately without experiencing an overtemp condition. And, if the temp does stabilize, then what is the (indicated) value.

Joe

[Duke W.]

Re: This Is One Red Hot 1965 Mousemotor

I'm fresh out of suggestions for your overheating issue, but the idle vacuum still intrigues me. Solid lifter SHP cams typically deliver about 10-12" idle vacuum if set up ideally as yours is with full vacuum advance at idle and total idle timing in the range of 25-30 degrees. I think John Hinckley has reported 10" @ 900 with his '69 Z-28, which also has the 30-30 cam, and he and replaced the OEM vacuum emission inspired vacuum can with the 8" can from the mid-sixties SHP/FI engines.

The Duntov and LT-1 cams have less effective overlap, so they will pull about 12". The L-79 with less effective overlap that the Duntov or LT-1 will pull about 14" at 800. Not that it has anything to do with your overheating issue, but with 15" @ 900 I have to question if you have the 30-30 cam.

Duke

[Everett Ogilvie]

Re: This Is One Red Hot 1965 Mousemotor

So, does it puke when you shut it off? In other words, is it really hot, or does it just look hot (on the gauge)? I just recently came across a Chev service bulletin from early '66, in which the factory recommedation is to install a new, differently calibrated, temp gauge. This policy was due to customer's complaints about perception that the cars were running hot. The recalibrated gauge simply changed how the gauge "looked" to the customers... this factory service bulletin is quite interesting reading.

[Clem Z.]

Re: This Is One Red Hot 1965 Mousemotor

if the max temp comes down once you start down the road i would say there is nothing wrong but if it does not cool down once under way i would pressureize the water system to 10/12 # and see if it holds pressure for several hours. do this when the engine is cold and if it goes down you have a leak somewhere,either into engine internally or on the suction side of the water system.

[Everett Ogilvie]

Question about your heat riser valve

Your comment about the heat riser valve seems odd to me. It is only half open at idle (with hot engine)? Forget about the fact that if you rev it the valve opens - the valve should be fully open at idle with the engine at full temp. In fact, it should be fully open even when you shut off the engine. On my cars when I want to check the valve operation, I push it by hand with a cold engine to check for free movement over the whole range, and that it returns to the closed position. Then with the engine up to temp, I push on it with a tool to verify that it is open all the way. It seems that if yours closes a bit at idle, the spring is too strong, or something.

How much this might contribute to higher temp at idle, I don't know, but it isn't helping cool things down... You could always install a spacer temporarily to see if it makes even a slight difference.

[Wayne K.]

Re: Question about your heat riser valve

Everett,

I have a 67 L-79 and my heat riser works just as you described. This summer I was in bumper to bumper traffic that hardly moved for about a half hour on a humid 90 degree day and my temp gauge went up to between 200 and 210 and returned to 190 after moving out. I have a 180 thermostat and car usually runs between 180 and 195 depending on use. I also might add that I have a copper relplacement radiator that was in the car when I bought it which I plan to replace at some point with a correct one but it won't be because I'm overheating. I think you might be right about the heat riser adding to the problem it not working properly

[Duke W.]

Re: Question about your heat riser valve

I missed the part about the heat riser. As Everett said, it should be closed when cold, but open all the way with finger pressure and be full open when the engine is warmed up, including idle.

Heat riser valves are problamatic. The themostatic springs appear to lose their calibration over the years due to themal cycling. If you only drive in mild weather I would suggest wiring it open. I replaced mine with a FI spacer, as I just got tired of dealing with it, and it rots the RH exhaust system even if it functions properly.

Duke

[Peter L.]

Re: This Is One Red Hot 1965 Mousemotor

Joe - Everett mentioned the Technical Service Bulletin (DR #774) issued Nov 23, 1965. Basically with the '65 temperature gauge as quoted from the TSB "This positions the gauge needle close to the "HOT" position even though the coolant temperature is within safe operating limits (indicated by no coolant loss)." So, I'm not clear from your posting if it's been established that there is coolant loss. Please clarify. Thanks, Pete

[Bill W.]

Re: This Is One Red Hot 1965 Mousemotor

What happens if you put a heavy duty house fan in front of the raditor when running to simulate driving? I remember the dealers I worked at having a suction device that would suck gasses out of the radiator at hot idle to check for exhaust gasses heating the water.this can be caused by a cracked head or blown head gasket.Bill

[Terry M.]

Re: This Is One Red Hot 1965 Mousemotor *TL*

I have seen test strips that test the coolant for combustion gasses. I would think a good radiator shop would have them.
If one has a gas analyzer (doesn't everyone), just holding the test probe over radiator opening (same probe one would put in the exhaust pipe to test emissions) will give one a HC reading if combustion gasses are present.

[Joe C.]

TO ANSWER MOST OF YOUR QUESTIONS

Thanks to all for your interest and suggestions. This is, after all, similar to one of those "Brain Buster" games found in some newspapers.

Duke: Camshaft is Federal Mogul "Sealed Power" PN "CS-118R" Lash:.030-.030:Lobe Centers: 110-118 : Cam Lift .323-.323 ; Valve Lift: .485-.485 ; SAE Duration: 295-295.
I teed into the vac line to the advance can to obtain readings. It is possible that my vac gauge is giving false readings. Will check and let you know.

Everett: Yes, it did boil over once while checking, but I won't let it get to that point again. I had previously tied the heat riser open, but it made no difference. My valve is new, and to be more exact, was more like 3/4 open, rather than 1/2 open.

Terry/Bill: I don't think I have an exhaust leak into the coolant, but I will check. It would be great if I can find those test strips.

Peter: I have calibrated the temp gauge by adding a trimmer resistor in series to indicate 180 at a measured 180. All other gauge readings on either side of 180 are within 5 degrees, with the variation increasing to 20 degrees at both extremes of the gauge. All temps were measured at the thermostat housing, using an IR located within 2 inches of the target.

Clem: Temp immediately stabilizes at 180 once the car is rolling.

[Clem Z.]

Re: TO ANSWER MOST OF YOUR QUESTIONS

if the temp comes down after moving i would think you have a fan or fan shroud problem and 20 min. idle is a long time. the fan blade should be 1/2 inside the shroud and 1/2 outside the shroud,in other words the end if the shroud should split the fan blade to work properly. make sure the shroud has a good seal to the rad or it will just pull air thru the path of least resistance.

[Duke W.]

Re: TO ANSWER MOST OF YOUR QUESTIONS

Yes, that's the F-M 30-30 replacement cam, and to the best of my knowledge it conforms 100 percent to the GM specs.

You might want to borrow another vacuum gage and test to see if you get a consistent reading. Maybe Jon Hinckley can chime in with his idle vacuum on his '69 Z-28, but I recall him reporting about 10"@900 with a 8" can connected directly to manifold vacuum.

Duke