please help, sbc not running right

I just built a sbc 350 for my 53 gmc and it won't run worth a damn. It was bored 30 over with dish pistons, world product sportsman II heads, edelbrock performer intake with 650 edelbrock carb. The heads and cam came out of a 383 stroker motor, but showed little wear. The cam is a bullet race cam and I emailed them for the specs from what was engraved and they sent this back:

Hydraulic Cam - Lift Rule

CHS 301/301 H8
Duration @ 050 = 252/252
Lobe Lift = .300/.300
Valve Lift = .450/.450
Lobe seperation - 108

It feels like a timing issue, but I can't turn the distributor anywhere to get it to smooth out. I have swaped distributors with my really good running sbc in my hot rod along with the wires and plugs and it still runs the same. I swaped the carbs from the motors and it still runs the same. I did a compression check and it came out as follows:
1 149 psi
2 150 psi
3 130 psi
4 140 psi
5 134 psi
6 140 psi
7 134 psi
8 134 psi
this was done without warming the engine, but should at least let me know everything inside is sealing up well enough to run good. the engine stumbles, does not idle well, has a hard time getting up to rpm. Once around 2000 rpm it raps and pops really bad out the exhaust. I know this all sounds like timing, but I have moved the distributor all over the place with it running. I know I aligned the crank and cam gears properly, but I aligned them as the stock configuration. The crank gear is keyed 3 ways, should I have run it different? Please help guys, don't know what to do.

 

Dizzy off 180...?



JOE

 

Sounds like an ignition or timing problem. Maybe check and readjust the valves.

 

I'd start over with the ignition, take off the valve cover, watching #1 cylinger rockers, make sure it is at TDC of the compression stroke. Both rockers will not move while on the up stroke. Reset your ignition so the rotor is pointing at #1, line up the cap with #1 plug wire over the rotor ****on.

make sure your rockers aren't too tight - sometimes you have some too tight and they won't let the valves close causing no compression.

try to refire.

 

are you using an HEI distibutor or a coil? if its coil did you swap coils as well?

 

Valve adjustment? Is this a street engine? Seems like a lot of duration @ .050 for use on the street, I know you said it's a race cam, but. Vacuum check?

 

tried that, didn't run at all when I turned it 180

 

It's an HEI and I swaped everything including plugs and wires from the other motor

 

just turning it 180 won't change anything if your distributor is a couple teeth off.

read my first post - that is really where you need to start from .

 

but then my compression test would not have yeilded such good results, right?

 

Always look at the simple things....double and triple check your plug wires and make sure they are right for the firing order.

 

I have had issues like this when the magnetic pickup is wired backwards or the wrong rotation (chevy mag p/u in an olds). Post more details of your ignition system i.e., points, HEI, MSD, Hyfire?

 

Make sure wires are in correct firing order. Had a couple of wires swapped once and engine ran, but like ****.

 

yeah, I have done that a hundred times. I even tried the 7/4 swap on the plug wires to make sure it was not a circle track racing cam.

 

Yes...that is what I was thinking...are those #'s correct? that is a lot of duration, considering the amount of lift...
also, a lot for a low compression motor...which it sounds like you have...

 

yeah, I regret not spending another $100 for a new cam at the time I had the engine down. I got caught up in the thought of it would sound cool. Do you guys think it needs to be replaced? I thought I would get opinions here before I tear it back down. I really don't want to. This is a street engine in my truck with a 5 speed manual with 3.73 gears. What cam do you suggest?

 

Do you have vac*** advance, is it hooked up...what is happening when you get over 2000 rpm, does the motor ever straighten out, if so, at what rpm? What is your ignition system?

 

That cam still has me bugged too, only 470 lift and 252@ .050? The popping can only be ,cam installed wrong, ignition, valves too tight, BIG vacuum leak. JMO Is this thing popping out the exhaust?

 

do you have a Tach hooked up to your HEI? If you do try disconnecting the tach, I have seen some Tachs drive a HEI nuts.

 

It is popping out of the exhaust. The vacuum advance is hooked up, but I have not watched it real close. The engine never smoothes out even above 2000 rpm. It only gets worse. I don't have a tach hooked up either, I'm just estimating.

 

I would re-check valve adjustment again, other than that, cam installation. Back all valves off to zero lash and start it. It will rattle, see if it runs better. Running out of ideas,

 

I hate to admit this; so the rest of you, don't read it. I put a 327 together a few years ago using a multiple choice timing set. I lined up the keyway instead of the mark on the gear tooth. The gear tooth mark was almost invisible. That's my excuse and I'm sticking to it. The results were that the cam timing was several degrees off. It ran poorly, wouldn't respond to ignition timing changes and got hot on the exhaust side. The Comp Cams web site has a method for checking this by removing the intake manifold. If all else fails, give it a try. I ***embled 2 engines at the same time and made the mistake on one and not the other. Must have had a senior moment.

 

You should have timed it straight up that would have been the center keyway on the timming gear.

Sounds like you are running a lot of cam and heads for a low compression motor to me but it should still run.

If it crackin and poppin' and you have made damned sure its not 180 out you might check the #5 and #7 plug wires. Its common to get 'em crossed ( ask me how I know ) and it will bake it backfire to beat hell.

I would at least do the simple stuff before I tore into it.

 

I had the same problem, I took a cam out of my one engine and put it in another one but mixed up the lifters and ruined a cam lobe that would also cause that, A whiped out cam lobe would cause it to run bad and pop........

 

My engine is doing the same thing. I guess it is possible that I have made a similar mistake. Would it do this if I was supose to use a different keyway on the crank gear due to this being an odd cam? Thanks for all the help guys.

 

I'm running 9.5 to 1 compression. I thought this was a good rule of thumb for a street motor?

 

With dished pistons, it seems like the compression would be lower than that.

If you buy a vacuum gauge and use the instruction sheet that comes with it, it might help diagnose the problem.

If the headers are getting super hot near the heads (like glowing red), that's a sign that the timing is way retarded.

Is there a chance that you have a fuel pump with way too much pressure on this car, so the carb's needle and seats are leaking and fuel is gushing down the throat through the vents.

 

Flat tops with open chamber heads is close to 9.5 dished pistons are going to produce closer to 8:1 or less depending on the size of the dish.

The extra keyways are so you can advance or retard your cam timming. If you want to move your power band that is one way to do it. I run the cam in the pusher slowed down a bit (not much) I lost a little on the bottom and gained a little on the top. its a little dicey you don't just change the valve timming and fly. There are a lot of other considerations like where the piston is in relation to the valve head when the valve is open.

 

With the timing cover off, turn the engine over till the "dots" line up. At this point the camshaft dowel should be pointing at a hair past 3 o'clock, the crank key should be pointing at about 1:30. At this point the distributor rotor should be pointing at the # 6 wire segment in the cap (firing # 6). If this all good the firing order is 18436572 clockwise. Disconnect the vacuum advance and leave it off, set your total timing at 35 degrees at 3000 or less, check it at 5000 to make sure it doesn't keep climbing. HEI's are bad for that..............hope this helps

 

the machine shop I used said that these pistons along with my 64cc chambers would produce around 9.5 to 1. does this not sound right? I will have to look and see if I can find the size of the dish in the piston, but I know it is relatively small.