Engine run 1st time for me, now issues

[yoshi]

Finally got my engine (sbc350 1977) started today. I have some issues that I'm not sure if related. 1st off the engine gets hot real quick even with fan running & an external industrial fan used for removing welding fumes in confined spaces. We checked the thermostat, pulled it out while still quite hot & it was open & slowly closed while cooling down. It could be as simple as the radiator blocked. Also there is low vacuum pressure about 5 bar. We believe a new mild cam has been fitted. It's a little lumpier than a standard engine would run. What would cause a low vacuum reading?

[nvrdone]

Check your timing. If timing is off it will cause low vacuum and hot running

[yossarian19]

Originally Posted by nvrdone

Check your timing. If timing is off it will cause low vacuum and hot running

Yep.

[Speedbumpauto]

No offense, but I think the heater bypass idea is bad info. Chevy trucks like ours were offered without a heater from the factory. Did they have hot spots? I don't think the designer/engineers would have allowed that or at least if it seemed to be a problem, they wouldn't have allowed the same design to be used for 40 years. I have built and/or seen hundreds or even thousands of open street rods and T buckets without heaters that have small block Chevys and I've never witnessed this problem or the fix shown. I'm open to new thinking but I'd like to see a little proof.

[geezer#99]

Originally Posted by Speedbumpauto

No offense, but I think the heater bypass idea is bad info. Chevy trucks like ours were offered without a heater from the factory. Did they have hot spots? I don't think the designer/engineers would have allowed that or at least if it seemed to be a problem, they wouldn't have allowed the same design to be used for 40 years. I have built and/or seen hundreds or even thousands of open street rods and T buckets without heaters that have small block Chevys and I've never witnessed this problem or the fix shown. I'm open to new thinking but I'd like to see a little proof.

All the factory heater delete vehicles I've encountered had some sort of bypass.
However like you I've seen many street rods without any bypass, but at the same time heard lots of complaints about running hotter than expected.
I've tried running them that way but with a bypass they ran cooler.

[Speedbumpauto]

As to the original overheating question, I just can't see the bypass or lack thereof, being a problem as the T stat is (hopefully) fully open, directing as much hot coolant as it's design allows to the radiator. In this situation, I can't see where a bypass located in the front of the manifold where the T stat opening is can help at all. As a matter of question, seems it could hurt as it is only directing heated coolant back to the water pump without the advantage of going through a heat exchanger. IMO, Yoshi needs to look in another direction to solve his heating problem.

[57chevyman]

I have the same engine . I thought it was running hot, but turned out that the temp gauge wasn't grounded properly. ( I have an aftermarket temp gauge ). Just want to make sure the engine is definitely running hot before fixing it!

[xaircav]

Originally Posted by 57chevyman

I have the same engine . I thought it was running hot, but turned out that the temp gauge wasn't grounded properly. ( I have an aftermarket temp gauge ). Just want to make sure the engine is definitely running hot before fixing it!

Same thing happened to me with my Omega Kustom gauges. Omega tech told me to add a resistor to the sending unit wire and all was well. The other guys who mentioned timing are correct. If you have a replacement balancer or timing cover the marks may not be accurate.

[mr48chev]

Running hot HOW?

What temp reading did you have?

Was it puking coolant?

Or did it just feel too hot to the touch?

Some setups are prone to getting air pockets in the engine as Orrie suggested and the rest of his suggestions are well worth following.

Check the timing with a timing light to make sure it is correct. Late timing will cause the engine to overheat. I ran into that big time on my 51 Merc with an Olds 350 in it after we did a points change just before a road trip and didn't put the timing light on it as it started great and sounded great.

If you are running an electric gauge make sure that it is accurate. My buddy"s Model A roadster with a 350 in it would show 265 degrees on the gauge but he was able to pull the radiator cap off without spewing any steam or hot water. The actual Temp in the top of the radiator was right at the rating of the thermostat in the engine when checked with a probe type thermometer.

Also I've seen way too many guys with old rigs with newer engines panic when the gauge gets up to 185 or 190 when a newer engine is just up to operating temp because the reading seems "way high" to them.

[yoshi]

1949 chevy 3100 truck: 1st run-Our 49 3100 chevy truck: http://youtu.be/S4oyeQrtClA
2nd run-
http://youtu.be/bb4hjT5sBx8 its also breathing

[OrrieG]

Make sure you do not have an air bubble in the radiator or cooling system too. "lumpier" could be a vacuum leak, not big cam. It takes a pretty radical cam to reduce the vacuum that much.

Make sure all the fittings, hose to booster, trans, etc. are not leaking. Check the carb for uncapped ports and good gasket seal. I would also play with the timing as suggested, in the old days the vacuum gauge was used to set timing. Since it appears to be holding steady in the video probably not valve adjustment, etc.

[yoshi]

Yeah I believe some cams are that radical the booster needs a vacuum tank. Valve adjustment was the 1st thing he did before we ran the engine. He thinks that the timing could be 1 tooth out

[yoshi]

Can I check cam timing with engine in place? I'm thinking of removing rad & flushing through.What's the best way to not get air trapped when refilling cooling system?

[Speedbumpauto]

Remove the heater hose or plug from the intake manifold and fill until the coolant reaches the fitting. Replace the hose/plug and continue filling until full. Don't believe the engine would run or idle that well IF it was a tooth off. Don't think that can be your problem. Sounds lazy, like retarded timing. One thing you can check is TDC #1 with the timing pointer. It's the most important thing where timing is concerned. Make sure the external timing light info you get is accurate.

[yoshi]

Hired hand with me had the timing gun setting it up, temp was 220*

[_Ogre]

yoshi how are you checking the temperature?
our trucks don't have temp readings on them just h and c on the gauges
try an ir thermometer right at the thermostat housing

[yoshi]

We used a hand held digital laser thermometer

[OrrieG]

In the open radiator reading the fluid temp or shooting at the block radiator? I would hook up a known accurate gauge and check it, I'd bet the external engine metal temp is reading hotter than the fluid. I run mine out of the head behind #1 plug which reads 10-15 degrees hotter than the intake maniford water jacket port. Sitting at 220 would not panic me, I have driven SBC across Arizona and Texas at the temperature for hours with no problems. With 50% coolant the boiling temp goes up to about 235-240 when the system is sealed and pressurized.

[yoshi]

Ok so if I check the cap & it's a low number I'll replace that, I'm gonna move the fan to the inside of the rad & pull the air through. I'll check everything else. I'll check out all the vapour hoses for leaks & I'll check that plug No.1 is at TDC & where the marker is. 'm not sure when that'll be so be patient. What would cause the heavy breathing?

[Highsider]

My TF with a mild 350, stock brass radiator, 190 thermostat, manual-activated electric fan (so off), if I am moving I get an indicated (SW) temp reading of 190.

Based on Orrie, last spring I stopped worrying when the gauge went up to near 220, when slowing down for traffic. Then I would turn on the fan.

Good luck yoshi. I enjoy your posts.

[yoshi]

Thanks highsider, didn't know anything about these 3100's & sbc's but I'm learning, thanks to these guys

[geezer#99]

I can't be sure in your pics but it doesn't look like you have a heater core hooked up or a bypass from the intake back to the pump.
Without either you'll keep running hot.
Here's a link on tdc.
You can make a piston stop from an old sparkplug too.
http://www.crankshaftcoalition.com/w...op_dead_center

[yoshi]

No heater, where 's this bypass hose go, from water pump to? Thanks

[geezer#99]

From intake to water pump.
There's a discussion in this thread plus some pics on post #82.
http://67-72chevytrucks.com/vboard/s...=649618&page=4

[yoshi]

Ah i see thanks, 3/8 npt both ends?