Pete's Place

I have a 427 390hp which was just rebuilt and not yet installed in the car. I ahve it ste up on a test stand with radiator for the car hooked up to it and have had it started. When setting the intial timing it labors when running at 4*btdc with vac adv unhooked, but if I move it to 10* or 12* btdc it smoothes out. What should it be set at? The shop that did the machine work and where I got my parts got what they called an RV cam for it, I didn't want want anything big for it. Also when I run it, it heats up right away to 218* I haven't let it run but mabey 4 of 5 minuets. I have read some of the suggestions for running hot but those are all when it's in the car, and I don't to install it to I'm sure it's right. Any thoughts would be appreciated.

Avispa

Sounds like you need to change the amount of mechanical advance available so that you can have static timing at 10 to 12 deg. BTDC at idle and 36-38 degrees BTDC timing at full mechanical advance. There are bushing and advance limiter kits available to do this.

As for the heat problem, if you're running just the radiator with no shroud on the test stand, your fan may not be pulling enough air through the radiator to adequately cool the motor.

And for weirdest of the weird, I had a problem with my big block running on the hot side (210+) even on moderately warm days and the radiator "puking" when I shut it off. I changed the 160 degree thermostat to a 180 and both problems went away completely. You might try a 180 degree thermostat if you're not already running one.

Pete's Place

So let me see if I have this right, with the engine running at an idle and the advance hose on the dist. the timing should be 10 to 12 deg. and 36 to 38 deg. at full advance when line is hooked back up.
I have a 185 thermostat in it now.

Bluestripe67

Did the machine shop install a "roller lifter" cam? If not you must have the engine running at 1700-2000rpm for 30 min to properly break in a flat tappet cam. Letting it run at very low rpm/short time doesn't allow the oil to be splashed up on the cam lobes. It can damage the cam and that equals $$. I hope this is not the case. Dennis

mikem350

To add to above..sometimes there is air in the system (at the heads where the sender is) and it will read high till the thermo opens, letting air out and water in.

If on a test stand run a garden hose into lower hose and dump out thru the upper hose..keep the upper hose higher than the intake so all the cavities stay full

Timing is VERY important to keep from too much heat being absorbed by the block/heads!! Run your 10-12 initial and full time vac adv!! Make sure the mech adv is kicking in too This is a common mistake at break in!!

Should be a screaming torque monster w the RV cam
Once its in the car you may have to back off the initial to avoid detonation, but np!! Trial and error there

shemp

ask me how I know. Shemp.

Avispa

Sorry for the lack of clarity in my answer. The timing figures mentioned are with the vacuum advance disconnected. As others have pointed out, the vacuum advance should be connected to a source of full manifold vacuum and not ported vacuum (why it's referred to as "timed", I have no idea), "ported" vacuum being the carb vacuum fitting that has no vacuum until the throttle is opened slightly.

66BlkBB

With the RV cam in the engine it will be a stump puller but you won't see any benefit to mileage or horsepower. I know as I did the same install when I first built my engine. I ran it for a year or so and then pulled it out. I went to a bigger than stock 390 cam and I didn't look back. Hated the RV unit as the most RPM I could get was about
4200. Wanted more than that when I kicked it down.

midyearvette

i don't get some of these engine builders using those cams
i bet i have swapped out 4 or 5 of the same thing over the last decade and you are exactly right on how they perform...oh well....

maybe the op should take heed now......

Jakes64

Can't believe no one has mentioned Lars yet. Send him an email and get his tech articles. They are all very good reading.

"How to Install your Chevy Distributor"
"How to Set Your Timing"
"Vacuum Advance Control Units"

Anyone interested in the articles can send Lars an e-mail request at V8FastCars@msn.com or search the archives.

65silververt

http://www.corvette-restoration.com/...ine_Timing.pdf