SBC 302 is in, running!, Needs some tuning, any suggestions? Options

[marks914]

Got the 305 out and put the 302 in, runs pretty well.
I am running an edelbrock 600,
Hydraulic roller cam .56 lift 236/236 duration.

I am in the process of tuning it right now. I have HEI vacuum advance hooked up to the timed port on the carb.

The engine has some lope to it, when I advance the distributor to smooth out the idle, it purrs like a kitten and no spark knock. The problem is when I advance the ignition timing this far, it is difficult for the starter to turn over the engine.

Here is what I am going to try, please tell me if this makes sense:
I was going to put the vacuum advance on the manifold vacuum port, thus giving more advance at idle, I do not think this would affect the initial start up advance, making the starter able to turn the motor over when hot.

here are some pics

Thanks

Mark

PS, the car is a bit quicker now, the power comes on at 3000 RPMs, so it is very driveable around town with the power where it needs to be.

[marks914]

Hooked up the vacuum gauge and I have 7hg" at idle.

I looked in my Edelbrock manual tonight and for long duration cams it reccomended:
1. placing the distributor vacuum adance on the manifold side OR
2. changing the step-up spring to a lighter one.

I tried the manifold vacuum, and it idles much better, no noticable difference in drivability, it still smoked the tires at a 30 mph roll.

I am going to see if someone locally has an Edelbrock jet "kit" with the various rods and springs. The bad thing about jegs and summit is you can't get hot rod parts locally anymore, not even here in Detroit.

Mark

This post has been edited by marks914: May 31 2007, 09:35 PM

[byndbad914]

Hey Mike - I am going to just kinda reinforce a couple statements already made so you have a clear idea of how to set the car up:

1. Get rid of that air cleaner as they do have a tendency to burn a car down with a backfire thru the carb and the filter does breakup after time and suck into the carb.

2. You have Edelbrock RPM heads IIRC. So, my guess is at your altitude you probably want 32-34 degrees total mechanical timing at 3000rpm and higher. So, get a dial back light or somehow mark 32 and 34 degrees on the balancer and set the timing with the vac advance disconnected, holding rpm around 3K. Then, for shits and giggles (tho' essentially irrelevant) you can see where the timing is at your idle rpm. Reconnect the vac advance to vacuum if you want to but frankly I have never ran a vacuum advance on a hot engine. I just set total timing mechanically and run from there. I would personally not even use the vac advance, but that is a matter of personal taste.

3. Get a gear reduction starter and you will never have a starting issue. I tried the stock 914 starter with my 11:1 motor and smoked it! I think it sorta turned the engine over twice and then threw in the towel (IMG:style_emoticons/default/biggrin.gif) So I got a "mini" starter and I can crank the motor until I get oil pressure with the dry sump before firing, so it spins it pretty well.

I have ran 20 deg of mechanical advance in most of my hot street engines I built, set the timing at 32-38 degrees (depends on engine and altitude, etc etc) and then base timing was somewhere in the 12-18deg range and run reduction starters. That setup will snap off the line and run great on the street, no vacuum adv of course, and kicks ass.

The long rod dwell you will have with the 302 will also affect the amount of total timing you will want. Safe is 32-34 total probably, but I used to run my long rod 302 Ford back in the day at 36 on the street at sea level in SoCal and around 40-41deg at the dragstrip in Palmdale at altitude!! Best times were at that much timing, so trust me, timing is very engine dependent and altitude, etc etc etc.
Best of luck,
Tim

[marks914]

Its runnimg better.
I changed to lighter step up springs and the a/f mixture at idle is better, it was running overly rich with the low vacuum. That helped, Also the manifold vacuum with 6 deg of vac advance at idle also hepled. Just about there, I will hook up a timing light sunday to check where I am at. I will probably get some ligher mechanical advance springs as well, right now my mech. advance kicks in at 1500 RPMS.
Withthe cam I am running, the lope is just going to be the nature of the beast, with 110 deg lobe seperation, that is just the way it is, I just want to try to keep my decklid from vibrating at idle.

as for driveability, its really nice. Not too much torque down low, the power comes on once the revs come up, it actually drives like a porsche now! I think ehat even though i am running some serious HP, withthe flat power curve, the tranny should stay alive.

As to the starter, on SBCs, if you advance the ignition timing too much the starter will have a difficult time turning the engine over. I am running the big IMI gear reduction starter.

Mark

[JPB]

Them valve covers are sick Okay, I want a SBC now:beer1:

[marks914]

Got it idling decent finally.
I got an accel advance kit thet has a very light spring, 10 deg. advance at 900 rpms. The car likes 18 deg at idle. This worked out well, set the initial at 8 deg BTDC for easy starting when hot, when idling at 900 RPMS I am at 18 BTDC for the smoother idle. This adds up to 32 deg total advance, plus additional vacuum advance if I need it, which I can adjust quickly.
The new 302 is dangerous now, I got into it a bit yesterday, I hope I don't break anything. I am hoping the CVs will act as a "fuse" to protect my tranny, which I already have a decent amount of money into.
Now I have some surging bet 1700-2200 RMP at light throttle, I think I am going to richen the mixture up a bit, that should help.
Thanks for all your help

Mark

[messix]

Got it idling decent finally.
I got an accel advance kit thet has a very light spring, 10 deg. advance at 900 rpms. The car likes 18 deg at idle. This worked out well, set the initial at 8 deg BTDC for easy starting when hot, when idling at 900 RPMS I am at 18 BTDC for the smoother idle. This adds up to 32 deg total advance, plus additional vacuum advance if I need it, which I can adjust quickly.
The new 302 is dangerous now, I got into it a bit yesterday, I hope I don't break anything. I am hoping the CVs will act as a "fuse" to protect my tranny, which I already have a decent amount of money into.
Now I have some surging bet 1700-2200 RMP at light throttle, I think I am going to richen the mixture up a bit, that should help.
Thanks for all your help

Mark

part thottle surging is a pain, you can kinda fool it by playing with the fuel pressure. you hav a regulator right? go up or down a pound and see how part throttle reacts. you might work out with that and just readjust the idle mixture.

[Dr. Roger]

Hey fantastic! Congratulations. Those 302's ARE dangerous! LOL

I also have that part throttle surge thing going on.
I thought it might be an ignition or carburetion thing.

Fuel pressure??? Hmmmm....

I might play with that. =)

More Pics!

[messix]

it's another way to lean or richen the set up on the carb.

pressure up puts more fuel on top of the main jets. this makes it easier for the air bleeds to pull fuel into the discharge venturies.

pressure down does the opposite.

think syphon.

you could also try a 1" open carb spacer under the carb to give more plenum volume. this would buffer the intake pulses that tend to starve cylinders on dual plane intakes chevy is one of the worst , 4-7 swaps are debatable solutions.

[new cams to swap the firing order of cynlinders 4 and 7]

[marks914]

Its definately running lean. I drove it to work today at 3100 rmps 85-90ish MPH and I pulled a couple of plugs at lunch, it was running way lean in the mid range/light throttle.
I gingerly drove the car home and I will be getting my calibration kit tomorrow. I was trying to make it to our "wild wheels at work" car show, but I would rather leave the car at home and wait to re-jet the carb.

As to the spacer, my intake is a performer RPM which is a semi-high rise dual plane, should take care of any pulsing. Once I richen up the mid range, it should be OK

I hae been running 5.5 PSI of fuel pressure, as reccomended by Edelbrock.
Mark

[LarryR]

Sweet! I am now inspired to continue my project. Thanks.

[messix]

Its definately running lean. I drove it to work today at 3100 rmps 85-90ish MPH and I pulled a couple of plugs at lunch, it was running way lean in the mid range/light throttle.
I gingerly drove the car home and I will be getting my calibration kit tomorrow. I was trying to make it to our "wild wheels at work" car show, but I would rather leave the car at home and wait to re-jet the carb.

As to the spacer, my intake is a performer RPM which is a semi-high rise dual plane, should take care of any pulsing. Once I richen up the mid range, it should be OK

I hae been running 5.5 PSI of fuel pressure, as reccomended by Edelbrock.
Mark

i wouldn't go any higher on fuel pressure at 5.5 psi.

[marks914]

Well I have had it running pretty well for about 1000 miles now.
Here is what I did:
set timing at 18 deg inital, 37 total with an accell curve kit on the med. setting
Went 1.5 stages richer on the carb
fattened up the idle to get rid of the surging. It idles a bit rich, but runs great
Adjusted the shot for more fuel on the accelerator pump and the off idle stumble is gone.
The car runs great, its definately more like a Porsche to drive now, nothing like the sound of zinging a V8 up to 7K
The only thing I would do differently is backing off on the cam a little.
Mark

[jimkelly]

don't use that foam air filter - darn - that is what i just put on mine to replace my tiny 5 inch round air cleaner - guess 5 inch is going back on.

http://www.914world.com/bbs2/index.php?aut...ach&id=7973

[marks914]

The foam air cleaner has been on my car for 5 yeras, no problem, I just change the element every 3 years

Mark

[dakotaewing]

Mark -
What pistons are you running? Could you give a part # please ? I am using the TRW 2210's
And what cc heads are you running? I just want to compare notes... I would hate to finish mine and end up with a dog because I was not running enough compression...

Thanks -

Thom

[marks914]

Mark -
What pistons are you running? Could you give a part # please ? I am using the TRW 2210's
And what cc heads are you running? I just want to compare notes... I would hate to finish mine and end up with a dog because I was not running enough compression...

Thanks -

Thom

Tom,
Here are the specs:
1970 High nickel block .030 over
SRP fored -6cc domed pistons 10.1:1 CR
Edelbrock 60899 Performer heads 64cc
Comp Cam custom grind hyd roller cam .560 lift 230/230 duration
Comp cam roller lifters, springs, roller rockers
1178 crank
Pink rods

The pistons are here:
http://store.summitracing.com/partdetail.a...mp;autoview=sku
They are called out as 10.4:1but by the time the dome is radiused, it comes out to about 10.1:1

The heads are 64cc and cleaned up a bit:
http://store.summitracing.com/partdetail.a...mp;autoview=sku

Mark

[dakotaewing]

Thanks Mark -
My heads are rated at -18cc Dome, so with the larger 76cc heads I should be running about 2 cc less compression than what you currently have...
I was also going to use a smaller cam than what you are currently running -
If you were to change cams, do you have something in mind that is smaller ?

Thanks again -

Thom