timing question
 

Hi folks,

Asked this question in my engine rebuild thread (71 GMC 3500 longhorn), but am getting no response. I have the initial timing set to 14 deg BTDC. It's been running pretty good but, difficult start after warm. I want to get it right. My driving range is 5000-6000 feet above sea level and manufacture setting is 8 deg BTDC so I added 6 degrees to set. This is what I've always thought was right. What do you guys think?

Engine is 454 from an 83 dually truck all smog crap removed and bored .030 over, flat top pistons installed. Cam is 292 int./302 exh. duration (advertised) with matching lifters and springs, edelbrock 7809 double roller timing set and edelbrock performer rpm manifold 7161 non-egr oval port. 1406 600 cfm edelbrock carb, oval port heads rebuilt from the original 402.

Thanks in advance,

:gmc2:

-Dan

Re: timing question
 

The hard start after being warm is very often caused by that edelbrock carb. What fuel pump are you using? The edelbrock carb needs low incoming fuel pressure. Also, the carb could be getting hot and causing a slight boil issue. A thick gasket, or carb spacer can fix that issue.

I'm running a sbc and while in El Paso, I never had carb issues. I moved back to California and rebuilt my top end and had nothing but issues with hard starts and carb boil..... until I got the correct fuel pump and thick gasket. Now the carb is smooth as can be.

Re: timing question
 

I thought you said you had it at 14 and it started good!
I assume you proved your timing tab/balancer when you had it apart.
If not you should.
Stock timing for a 454 with stock peanut port heads is likely 8 degrees. Now you've changed it with the 396 heads, and your timing changes too.
Usually mechanical timing doesn't start until 850 rpm, so getting the idle as low as possible to set it is needed.
And your elevation does effect your max timing. You can run more initial.
What are you using for a timing light?
What do you mean by hard starting? Do you mean slow cranking or just doesn't fire up right away.

Re: timing question
 

I know the above poster says the timing on the later 454 is like 8 degrees. When I have had big block trucks[I rebuild wrecks]and I have had several I would bump the timing up on them[unplug the timing plug on the injected ones]it would seem as though a whole 'nother engine had been added. The simple timing increase really would wake the slumbering beast.
Now with your issue, Do you have headers? Lots of times with them the starter gets heat soak and needs a remote solenoid added to cure that problem. When it is hot have you tried backing the timing just a touch to see if it does fire right up?

Re: timing question
 

Geezer, It colds starts excellent, but after I run it hot and restart, it cranks a bit and I have to hold the throttle open to start. I'm using a sunpro inductive timing light. Can you tell me what effect the oval port heads from the 396(402) will have on timing? When it was apart, I had it on TDC on #1 and the tab was at 0. Also, I have the idle set at 600-650 for timing.

Lefty, I'm using the stock fuel pump.

Hugger, I am using headers, but since I switched the starter to a mini torque starter, cranking over isn't a problem.

Thanks guys,

Dan

Re: timing question
 

If it's not cranking hard (slowly) then it's not too much timing.
Try bumping the initial up until it cranks hard and then pull it back 2 degrees.
Head change could alter the compression depending on the difference in chamber volume.
Sounds like you have a slight carb percolation or flooding situation.
Also watch fuel pressure. Eddy's don't like more than 5 psi. Also you need to run your float levels a bit lower at elevation. Less air pressure lets the fuel rise slightly higher.
You might need a heat plate if you don't have one.

Re: timing question
 

Thanks Geezer,

I advanced the timing until it started cranking hard, then turned it back 2 degrees. Timing turned out to be much more advanced than I thought it would using this method. 18-20 BTDC (tab stops at 16). Seemed to run pretty good on my test drive.I'm going to get a spacer for the carb and see if that solves the heat issue. The fuel pump does not have a return on it like my 73 so maybe there's too much pressure. I'm driving it to work tomorrow 35 miles each way so we'll get a good test on the performance.

I'll give an update tomorrow.

:gmc2:

Dan

Re: timing question
 

Make sure you listen closely for low speed detonation. It'll sound like a rock in your hubcap. Usually if you back off on the loud pedal quickly.
When you make your new fuel line use 5/16 inch tubing. That helps in the possible fuel pressure problem.

Re: timing question
 

Well, too late. I already bought 12 feet of 3/8 stainless steel fuel line. Working with hydraulics, line size limits volume but retains the same pressure. At least that"s what I always understood. Can't I get a pressure limiter?

Definitely need a carb spacer. Fuel in the carb seems to heat up as it sits, but it acts like after I run all the hot fuel out it runs fine. What type spacer do you guys suggest? I've seen mixed reviews.

Re: timing question
 

You're exactly right. For the purposes of 1 size of fuel line, size does not reduce pressure, only volume. Yes, you can get a pressure regulator. Phenolic 4 hole spacers, and the edelbrock "thick" 4 hole gaskets work the best for reducing heat in the carb. Steer clear of aluminum spacers for that purpose.

Re: timing question
 

Keep in mind, that our country now runs gas with an unknown amount of alcohol in it. The boiling of the fuel is more prevelant with the alcohol mix and when you add a change in altitude, that assists in the boiling of fuel. I had issues with my engine in good ole Kansas and had to put a 1" spacer under the carb to stop the transition of heat from the intake to the carb bowls. I also added an edelbrock fuel pump with a change of the plate on the bottom to allow me to get a return line to the fuel tank, to keep from boiling the fuel in the pump. Yes it is also susceptable to heat.

Re: timing question
 

Sounds like a fun beast .

The phenolic spacer will do you best .

Re: timing question
 

I have ordered the spacer kit. More to come...

Re: timing question
 

I removed the existing 5/16 line from the tank with 3/8 steel line (still mounted on the rail but not used for some reason, probably a quick fix to install an electric fuel pump), ran steel line from the pump to the in line filter, elevating the fuel line away from the block.
http://pic20.picturetrail.com/VOL122.../411347237.jpg
The existing 5/16 line was connected to a disconnected in line electric fuel pump....
http://pic20.picturetrail.com/VOL122.../411347236.jpg
I'm sure that didn't restrict the flow!
The line out of the main tank under the truck was cracked at the clamp so I replaced it also.

Fuel supply should be all good now! Just waiting on that spacer I ordered.

:gmc2:

Re: timing question
 

Hey geezer, sent you a PM, just in case you don't check them(like me) I'm asking how far to adjust my floats at 5200-6000 feet for that 1406 edelbrock.

Also everyone, the spacer worked fine for the heat issue. I have also added ceramic 115 degree angle accel plug wires to combat the heat generated by my headers that was burning up my old wires.

Changed the oil at 600 miles to castrol GTX full synthetic with copper additive. Leaning out the carb that came set from edelbrock for sea level with new jets and metering rods. Things are going good!

some pics:
new spacer http://pic20.picturetrail.com/VOL122.../411531675.jpg
redneck washer reservoir http://pic20.picturetrail.com/VOL122.../411531674.jpg
http://pic20.picturetrail.com/VOL122.../411531673.jpg
ceramic plug wires http://pic20.picturetrail.com/VOL122.../411531672.jpg