Frustrated! No power.

[drsam]

I'll start with a description of my car. 66 coupe with 306 ,GT40p heads with I believe trick flow springs, 1.6 rockers, trick flow hydraulic lifters , trick flow stage 1 roller cam, edelbrock 500 cfm carb, Weiand stealth intake, flamethrower distributor, performance automatic trans with 2600 stall and 3,55 gears. Car starts fine and runs ok but its got no get up and go! Ive checked everywhere for vacuum leaks. Timing initial is 16 and 38 at 3000 rpm. Pulled plugs and other than a bit black seem ok. Tried to check compression but with these heads, its nearly impossible to do, no room! Any ideas?

 

[7991LXnSHO]

Is the secondary side opening? If throttle response is good at part throttle, but does not get up and go under full throttle, that’s one guess.
My first thought was ignition timing. Are you sure TDC is really at the 0 mark?

 

[dennis112]

My first thought was ignition timing. Are you sure TDC is really at the 0 mark?

Adding to this: Was the cam properly degreed after determining true TDC? Just zeroing the timing gears isn't an accurate installation.

 

[drsam]

Well, this was my first build. I followed instructions but prob need to go back through this? Fairly certain TDC is at 0 mark. Secondaries do open on carb.

Can you refer me to source to properly degree the cam?

 

[Mr.Vegasmax]

Does the engine have any misses? What do the plugs look like, does it idle smooth? Are you using a good timing light? Does the distributor advance,you can confirm with timing light. If all this checks out pull front timing cover and double check, the timing marks, if bolt tight and dowel in place and the confirm timing mark is right. You can find a youtube video if not sure how to confirm the timing mark on balancer. I bet you'll find the problem. Also check distributor gear as well. Car should run pretty well if everything right. Good Luck you'll get it.

 

[drsam]

Does not sound like missing at idle, only when trying to accelerate. Plugs were a little black, not bad though. Distributor does advance. I checked timing again last night. With vacuum advanced hose off and port plugged, it is set at 16 idling. It runs better around 20 though which is higher than usual I understand. Increasing RPMS to 3000 its 36-38 range. Will go over 40 if cont to increase rpm, should it do that? Distributor gear is new ARP.

 

[7991LXnSHO]

That sounds like too much initial timing, and overall advance.
Your carb, cam and compression ratio can vary this, but the efi versions have 10 (to 14 max) degrees initial timing, and 32-36 sounds like a more reasonable total timing.
As far as it running better at 20 deg without the vac diaphragm connected, remember the canister adds advance, so you’ll be looking at 8–14 extra degrees of timing on top of the initial 20 at idle and light loads. That’s going to rattle and do bad things under any load.
Back it off and verify your timing marks and harmonic balancer with a piston stop and careful hand turning of the engine.

 

[Mcmahst]

So, it’s missing as you accelerate? Is it bad like the engine shakes when it misses? Since you can’t do a compression check, I would find a shop to check the AF ratio. Black plugs are a typical sign of a rich mixture, but a 500 CFM isn’t too big of a carb, so getting that sorted might solve the off idle missing. The miss is trying to tell you something.

 

[7991LXnSHO]

If your carb was a Holley, I’d tell you to check the power valve, set screws and definitely the float levels. I have not played with an Edelbrock, the float levels and set screws are still on my suspected list.
Then make sure you have no vac leaks. They can mess with a carb or EFI running right.
I think that’s plenty of common things to check on then please and report back on with results.

 

[drsam]

No the engine does not shake . I rebuilt carb not long ago when it wasn't idling well, fixed that part. Made sure the float valve was set correctly.

 

[Mr.Vegasmax]

Lifter preload set right? Looks like time to confirm the cam timing is right. What RPM does it idle? Did you buy a good timing set? Does it have multi key ways? Just keep eliminating stuff till you find it. Take it by someone you know and trust that can listen and he might notice something different. A thought carb gasket, sound simple but....it happens might look at it closely making sure it seals .

 

[MustangIIMatt]

If your carb was a Holley, I’d tell you to check the power valve, set screws and definitely the float levels. I have not played with an Edelbrock, the float levels and set screws are still on my suspected list.
Then make sure you have no vac leaks. They can mess with a carb or EFI running right.
I think that’s plenty of common things to check on then please and report back on with results.

View: https://youtu.be/1WNpdy9-zdE


Edelbrock carbs are that easy to deal with.

For the engine configuration, I'd actually recommend an Edelbrock 1406 (600cfm with electric choke). 500cfm is just a tad small. (That might be the first time I've ever recommended a bigger carburetor to someone on this site!).

That said, the 500cfm will run that engine all day if tuned correctly, but it may run out of breath on the top end.

 

[Mr.Vegasmax]

Please define your first statement in your initial post:"Car starts fine and runs ok but its got no get up and go!"
Does it accelerate normally? Like a daily drive from stop to say 75 at a normal drive rate with no stumbling or missing? What happens at 45mph when you floor it to passing gear? Stumbles or what? Is the power non existent at every rpm? No back fires or a stumble then takes off? Have you set the carb with a vacuum gauge or just by ear? Things to check another thing your coil or electronic box maybe the problem as well. This car should be fun around town driving it. Keep us all posted. Black plugs indicate running rich not lean.

 

[7991LXnSHO]

View: https://youtu.be/1WNpdy9-zdE


Edelbrock carbs are that easy to deal with.

For the engine configuration, I'd actually recommend an Edelbrock 1406 (600cfm with electric choke). 500cfm is just a tad small. (That might be the first time I've ever recommended a bigger carburetor to someone on this site!).

That said, the 500cfm will run that engine all day if tuned correctly, but it may run out of breath on the top end.

Agreed that this 306 will run fine on a 500 CFM vac secondary, as it will on a 600 CFM.

@drsam
@MustangIIMatt is a pro. (I’ve been around the block enough times to own it, but not BS about what I do not know about.)

Carburetor CFM Calculator - Find Recommended Carburetor Size

Find the recommended carburetor size for your engine using the carburetor CFM calculator, plus see the formula for finding the idea carb CFM.

www.inchcalculator.com

If the 306 is spun to 600 rpm with an optimistic 90% VE, it’s only going to use 478.13 CFM. If it is being spun faster than this, I expect more than the carb is going to need upgraded to not
Please review posts 7, 9 and 12 and let us know the results. And don’t break a knuckle!

 

[drsam]

Please define your first statement in your initial post:"Car starts fine and runs ok but its got no get up and go!"
Does it accelerate normally? Like a daily drive from stop to say 75 at a normal drive rate with no stumbling or missing? What happens at 45mph when you floor it to passing gear? Stumbles or what? Is the power non existent at every rpm? No back fires or a stumble then takes off? Have you set the carb with a vacuum gauge or just by ear? Things to check another thing your coil or electronic box maybe the problem as well. This car should be fun around town driving it. Keep us all posted. Black plugs indicate running rich not lean.

Power is non existent at every rpm. No backfires. Yes if try to take off quick, it stumbles . If going 45 and floor it, kicks down to 2nd for a second then right back to third, no power. Set carb as far as idle by edelbrock instructions. I think plugs got that way trying to get it to idle?

 

[drsam]

Thanks for all the suggestions. Havent had time to work on it anymore. Will keep you posted.

 

[Mcmahst]

A car that runs but has no power and stumbles usually has a carb problem. There are several things in the carb that could be causing, but not getting fuel is the likely culprit. Either not getting into the carb or can’t get out. It’s not too big of a carb. Good luck, I’m sure it’s going to come to you.

 

[drsam]

So like I said, its been a while since I've worked on it much. I found TDC on compression stroke with a piston stop and marking on harmonic balance is correct at zero. I rebuilt the carb earlier in spring when it wasnt idling right which helped that issue. I checked temp at each collecting tube as it comes from head and found cylinders 1,6 and 7 to be dramatically cooler than the rest. Changed all spark plugs just to make sure and when changing made sure each were firing. I think my next step is to check the preload on lifters. I've watched a few videos on this like I did prior to installation. None of them are setting the preload on engines that are installed and there seems to be alot of different answers on how to do this with hydraulic lifters?

 

[Mcmahst]

If three cylinders are cooler than the rest, I suspect either lifter issues, like you do, or worse. Can you post all of the cylinders temp? Also, if that’s the issue, a compression test should show significantly lower. Hope it turns out to just be a few bad lifters.

 

[drsam]

Tried to check compression, very tight on drivers side , esp cylinder 7,8 with the gt 40 p heads. No luck