I finally got the new engine in and running. It's pretty quick, but not quite as fast as it seems it should be, so I'm thinink maybe I should advance the timing a little more. You can see the exact specs for the engine in my sig, also, here's the cam specs

Duration at .006 Lift: Intake 308° Exhaust 318° Centerlines
Duration at .050 Lift: Intake 234° Exhaust 244° Lobe Separation: 112°
Lift at cam: Intake .325 Exhaust .340 Intake Centerline: 107°
Lift at valve: Intake .488 Exhaust .510
Timing at .050 lift: Open Close
Intake 10° BTDC 44° ABDC
Exhaust 59° BBDC 5° ATDC

I know I should be setting the timing as per lars' instructions, but I don't have an adjustable timing light right now, it is on the way though. So for now, what should I set the initial timing to? I have it at about 12* right now, could I go more or no? Also, what else should I check out that might be robbing me of power. Don't get me wrong, it does have pretty good power, but it just doesnt seem like it's all there. Thanks guys

 

What is you fuel mixture like? How do the plugs look? You probably need to dial in the carburetor. How about the advance curve, is it all in at 3000 rpm? You could probably go another 2 degrees on the initial timing. Are you certain the timing marks are reading correctly? Are the secondaries opening? Also, how many miles are on it? Things will free up as you put on more miles.

 

I usually don't use a timing light. Put the grade of gas you expect to use in, advance the timing and drive it. If it pings-retard, if it doesn't-advance till it does then retard till it doesn't.
:cheers:

 

The solution is sitting in your garage, waiting to be installed. Too much cam for the stock converter and probably the gear too. Once you finish, I think you'll find that your car has been transformed.

 

burners: they are mechanical secondaries, so I don't think that's the problem. What should I be looking for when inspecting the plugs? Also, I have the edelbrock performer carb, the two mixture screws are right at the front of the carb, will turning them in lean or richen my mixtures, which way leans it, and which way richens it?

gerry72: Sorry, I haven't changed my sig yet, I did install all the items listed in my sig, except the 3.70's.





[Modified by TravMsns, 9:04 PM 6/6/2002]

 

TTT, any other thoughts?

 

Greetings,

Turning the screws clockwise richens it, counterclockwise makes it lean. I'm running mine 6 turns clockwise from the screw seat...that's where mine seems to run the best, but of course every engine is different! My timing is 14 degrees with a Comp Cams 280 Magnum cam.

Good luck!

 

The plugs should look clean or have a slight coloration. If they are black you know it's running rich. Set you idle mixture using a vacuum gage. Adjust the idle mixture screws (evenly between the two sides) to get the highest vacuum reading.

 

Are you sure about that?
That would mean the screws are left handed, which I doubt!

It's USUALLY clockwise is LEANER because you're closeing off the jet.
But maybe I've been working on hollies too much :crazy:

:crazy:

 

stock ignition?

 

drives61: it's the distibutor that came with the engine when I bought it. It looks to be a stock HEI though. I'm considering getting the aftermarket 4 pin module that goes in the the HEI that's made by MSD. Think that'll help, what are some other options for the ignition?

Jason and 427V8: which is it? clockwise for leaner or clockwise for richer?

Also, anyone else who could give me a quick walk through on how to adjust the mixtures with a vacuum guage, I would really appreciate it. Where to I hook up the vacuum guage? How do I start? Overall, how do I do this? Thanks alot guys!

 

to set carb see my article: http://community.webtv.net/MATTGRU/AFtesting

try bypassing resistor wire, run 12v to coil as a test; gap plugs .030"

 

I advanced the timing a little more, it's reading 16*. It seems to run a little better, but is this too much advance? I haven't test driven it yet, but did a few revs up to 4000 and it doesn ping. Is it ok to have it advanced this far?

 

It's not gonna ping without a load on it. It may not re-start when hot though. You're gonna have to drive it (warm) to find out.

 

You can set total timing without an adjustable timing light. Measure the circumference of the balancer, divide that figure by 10, put a mark that distance from the TDC mark. Rev the engine until it stops advancing, align the new mark with 0º and you'll be at 36º total. Be sure to disconnect and plug the vacuum advance. Also be sure to rev it until all advance is in as many distributors don't reach total advance until past 4,000 rpm. How much power your engine will make depends a lot on having optimum total timing.

I didn't know that Edelbrock made a mechanical secondary carb. Are you sure they're not vacuum? The idle adjustment screws only affect the mixture at idle and shouldn't have any effect on performance above idle rpm.

 

How can I tell whether it's vacuum secondaries? I'm pretty sure that it's mechanical because there's an arm on the side of the carb opposite the throttle linkage, and when I get to 3/4 throttle, the arm starts to push on some linkage on that side and the secondaries start to open. If I push the carb to WOT even when the engine is not running, the secondaries DO open up. That's why I thought it was mechanical secondaries. Am I correct? I've checked edelbrock's site and Jegs and summit and they don't say whether its' vacuum or mechanical secondaries. It's and eldebrock performer 750 cfm, model #1407.

Anyway, it seems that all I have to do is fine tune the carb a little bit and set the timing correctly, which will probably involve recurving the distributor. It is really that much of a difference to run the car up to 2500 or 3000 and set the timing? I've read all the explanations as to why it is better, but how will this affect my initial timing? Is there really that much of a noticable difference to set it at 2500?

For the carb tuning, I would really appreciate it if anyone could chime in as to how to set the idle mixtures. Just a quick step by step process. Where do I hook the vacuum guage? Where do I start the screws? Does screwing the screws in richen or lean the mixture?

If the idle mixture screws only affect the car at idle, how do I actually tune the carb for off idle performance? those are the only two adjustment screws on the carb. Is this done with new jets and rods?

Thanks alot to everyone who has helped me so far. I'm learning so much.

 

The 1407 has vacuum secondaries. You don't want to set your timing at 2500, 3000, or whatever unless that's where your advance is all in. With the timing light hooked up, watch the mark as you increase rpm. When the mark stops moving, make note of the rpm and set your timing. As already posted, many distributors don't reach total advance until past 4,000 rpm. If you set it before you've reach total, more advance will continue to be added at rpms above that and you'll have too much.

The relationship between total and initial is static and depends upon how much centrifugal the distributor adds as rpm increases. If your distributor adds a total of 20º and you set total at 36º, you will have 16º initial. Once that you know how much your particular distributor adds, you can set your timing at initial and know how much total it will result in. The key is knowing how much advance the distributor adds. Recurving the dist to bring in more timing sooner and also adjust the amount of advance that the distributor can result in being able to set total timing for best power while having optimum timing from idle to total.

Different engines make the most power with a certain amount of advance and some are more particular than others. One combinaton may make it's best power at 32º while another combo might do best at 38º. You see 36º total recommended frequently, not because it's optimum for all engines but because it's usually close to optimum for most and isn't likely to cause damage. Too little or too much advance can hurt power and can also cause serious damage to your engine. The mistake a lot of guys make is to increase initial without knowing how much total they're winding up with. It may feel stronger on the bottom end but they may losing serious hp at high rpm. What's the point of spending money for more power only to give up a bunch of it because of something that's free?

 

I have a similar set-up to yours and had some initial difficulty getting it to run right. I ended up running with 18* initial timing and with the 20 or so degrees in the HEI`s mechanical advance giving 38* total it ran fine, I think I used a light and a medium spring on the weights. I also bought a recalibration kit for the carb and rejetted for a little bit richer than the setting it came with and used a vacum gage to set it up.

One thing you should be aware of is that the RPM cam only gets going at 3000+ rpm below that I found it to be poor. You have to rev it hard to get it working, it is as someone has already said a lot of cam for your rear gears, once you get a few revs on it it will scream. I have to say I got fed up with it very quickly and replaced it with a COMP Cam which will give up a bit of horsepower but hopefully restore some drivability.

See my 81 go http://www.smartgroups.com/vault/cor...he%20dragstrip