Ford Muscle Cars Tech Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
42 Posts
Discussion Starter #1
Hey, so I finally finished my 351C and started it up on a test stand today. But I am having yrouble withthe break-in. I have a COmp Cam Flat Tappet 275DEH, its a 2000-6000 RPM cam, Comp cam says to break it in at 2K-2.5K RPM, but I cant keep it running at that low of an RPM, it wants to run between 3-3.5K at the lowest, the faster the better...I am running an Edelbrock 750 Performer, I've played with the Idle screw and air/fuel screws all day but I cant get the RPM down there. With that said, It's entire Break-in phase has been spent between 3-5K. Does anyone know what I need to do?
 

·
Registered
Joined
·
42 Posts
Discussion Starter #3
Here's what I did with the timing...I lined up TDC, put the wires on the HEI Distr. and started the engine, then turned the Distr. until it ran smoothly. Let me say this is my first time ever building an engine...
 

·
Registered
Joined
·
235 Posts
Just rebuilt my first 351C-4V as well. Did just the same to start off. I had electric problems and left the distr loose for first few tries and like you was only able to get the best run by twisting the distr. Now that I've cured the ignition voltage it's running smooth idle and under throttle. I had some old fuel in the tank which once replaced made a big difference on idle. But yours sounds like it's running lean. Hence, vacuum leak is suspect. If that is so, a spray test will show a drop in RPMs if a manifold leak is responsible. It could be a vacuum hose leak so look around for one that's been left off. I had to make lean/rich adjustment on passenger side of Holley carb. Then tweaked on the idle setting on driver side. I'm getting closer to satisfied on the break in run but probably plenty of adjusting needed. Hope this helps.
 

·
Registered
Joined
·
42 Posts
Discussion Starter #8
Ok, I'll try that. As far as a vacuum hose leak...I plugged all the vacuum ports on the intake manifold. Is that ok? And the only hoses I have on the carb is one off the passenger valve cover going to the left side of the carb when looking from the front of the engine and the distr. One thing I just thought of was octane booster. I put half a bottle into 5 gallons of 93 oct. b/c the compression ratio is 10.5/1. Bad Idea?
 

·
Registered
Joined
·
830 Posts
if the above fails, it sounds like your cam isn't installed right, like a tooth off... put degree wheel on it and check #1 cylinder rocker movement...
 

·
Registered
Joined
·
235 Posts
Not sure mine's running tops but at idle I've got about 12" vacuum, maybe you can check that. I don't think the octane boost will have any effect. For the first three days messing with mine during breakin I left the distributor loose enough to allow adjusting on the fly. Good luck as I know it's discouraging. One or two shifts of messing with it and you'll discover the nuisance.
 

·
Registered
Joined
·
42 Posts
Discussion Starter #11
I now may have a bigger problem than the idle speed. I was messing with the timing, had it between 3-5K RPM for 10 min just adjusting the distr. and I completely let the temp gauge fall out of my scan, when I finally looked at it, it was at 240deg. I shut it down, it continued to climb to 258... then cooled off. After it cooled, it started fine, no smoke, and still had oil pressure ( 35-40 psi) should the engine be ok?
 

·
Registered
Joined
·
235 Posts
WOrrisome for sure. Bearings may be ok if it was only brief. OIl pressure is a good sign. Especially if at idle you're still good. I'd back up a bit. Take the throttle cable off the carb before your next start. I'd remove the thermostat and check it's cycling ok. You can just buy a new one for cheap. The overheat problem could be radiator. Did you do anything with it? I didn't rebuild mine but did flush it. Plus be sure it's not blocked. TO do that I back flushed it while out of car. The water pump is new right? Fan shroud installed right? I almost left a cleanliness rag in the radiator hose and stumbled onto it in double checking. If you took care of the basics above it would start looking more complicated like a blockage in the intake manifold gasket. I once had a car only overheating at idle and the only thing wrong was the radiator just not transferring heat due to rust/blockage over the years. Good luck.
 

·
Premium Member
Joined
·
2,059 Posts
When you ran it on your initial start up, you said it was idling high, how long did you run it then, and did it run hot.

Reason I ask, if it didnt run hot the first time, but did the second time while messing with the dist, you may have jacked the timing around enough to create a hot situation. So before we jump on blocked water, intakes and rads, rule out the basics. Good call on disconnecting the accelorator, and manually setting your idle, also be sure your secondaries are closed all the way as well.

New rebuilds can run hot, and not sure what cam specs you have. Couple a new eng, with a hotter cam and it will exceed the stock cooling capacity. My 68 ran cool as heck, with the mild hyd cam, rad etc, but when I bumped the cam up to a large Crower, it got hot on the cam break in, and that motor was well worn in. Just a cam change created a hot running situation.

I dont think you have hurt this one, I have seen engines get a lot higher and run fine, including the 68 above.

I dont think you have hurt the motor, do a cheap test, pull the cap off the rad, take off your belt and fan off (if your running a stock or flex fan). Loop your belt back over the water pump pully and then hand hold it loosley on a drill chuck and turn the drill/pump slow and faster to see how it flows. You can rig an old pully to a bolt and chuck that up to make it easier, but its a decent test to see how much water is moving (be sure to set the drill direction in the right way).

I am betting you have a carb or intake gasket leaking, creating the vacuum problem or you have your Dist in a tooth off.

When it is running btwn 2 and 5K RPM, is it smooth or rough?

Good luck.
 

·
Registered
Joined
·
42 Posts
Discussion Starter #15
It's been getting hot since the first time it fired up. Not right away, but after 5 min or so it gets to 210. In the beginning it didnt get too hot because I didnt keep it running for sustained periods due to adjusting the timing. It seems to cool off when I momentarily get the engine to 5K RPM. It does run smoothly at 3K. I am going to try using a timing gun in a few min and set it to 12. I am also going to unhook the dist. vacuum from the carb... I will mess around with some of the ideas you guys have given me. I'll get back to you all this evening with how it went.
 

·
Premium Member
Joined
·
2,059 Posts
Do you have a blower fan set up in front of the Rad? 3-5 K is a lot if you dont have airflow over the radiator.

Most dyno shops set up fans to keep the cars cool, give that a try - also a garden sprayer with water on the rad will keep the temp down. Maybe just a new engine, not a lot of air/cooling issue.

Good luck
 

·
Registered
Joined
·
42 Posts
Discussion Starter #17
I didnt get to fire it up today. I have the fan on the engine and 2 blowing on the radiator. On the stand the radiator was below the top of the block i.e. the thermostat, today I adjusted the radiator to where the upper inlet on the radiator is above the thermostat. Hopefully that will help the flow of the coolant because before there was air above the radiator inlet...? I also, bought a 160 deg thermostat to replace the 180 deg to help start the cooling process before it gets too hot
 

·
Registered
Joined
·
42 Posts
Discussion Starter #18 (Edited)
Got it! I raised the radiator to where the inlet (top hose) is above the thermostat housing, and I used a 160 deg thermostat instead of the 180. Also, got a new radiator cap (16psi). And the temp is great. It ran between 170 and 190 for 30 min straight on the stand.

Timing. I disconnected the ported vacuum and capped off the vacuum on the dist., set idle to 1500 RPM and set the advance to 12. Then ran it at 2.5K for 30 min for a proper break-in. Was 1500 RPM idle too high to set the advance to 12 b/c I am still having trouble getting it much lower?

Note- When I installed the distr., the harmonic balancer was at TDC, I had to turn the inside of the distr. Counter-Clockwise a bit, inorder to get the distr. to sit down on the driveshaft, could that be causing this problem with the idle speed. It runs great at 3K and above...
 

·
Premium Member
Joined
·
2,059 Posts
I just put my thumb over the #1 plug hole and turn the engine until it hits the comp, gets a good hiss. You can put your #1 wire/dist posit anywhere you want, just mark it on your intake etc, but yes you have to twist the dist back a bit so when it falls in it will spin and settle on the #1 posit.

Good on ya, never considered the hose being above the thermostat. Are you running a high volume water pump, if so those require a special thermostat, so they say.
Got it! I raised the radiator to where the inlet (top hose) is above the thermostat housing, and I used a 160 deg thermostat instead of the 180. Also, got a new radiator cap (16psi). And the temp is great. It ran between 170 and 190 for 30 min straight on the stand.

Timing. I disconnected the ported vacuum and capped off the vacuum on the dist., set idle to 1500 RPM and set the advance to 12. Then ran it at 2.5K for 30 min for a proper break-in. Was 1500 RPM idle too high to set the advance to 12 b/c I am still having trouble getting it much lower?

Note- When I installed the distr., the harmonic balancer was at TDC, I had to turn the inside of the distr. Counter-Clockwise a bit, inorder to get the distr. to sit down on the driveshaft, could that be causing this problem with the idle speed. It runs great at 3K and above...
 

·
Registered
Joined
·
42 Posts
Discussion Starter #20
Yeah, High volume water pump, but I'm not running a high volume thermostat. Tried to find one, but couldnt.

Is 12" advance correct/ok for 1500 RPM?
 
1 - 20 of 22 Posts
Top