Engine Performance suggestions

[caspianwendell]

What ignition system do you have?

Pertronix Flamethrower coil and Petronix Ignitor, Stock distributor.

I would start with compression check, and vacuum reading just to rule out the worst case first but sounds like an ignition problem to me, or vacuum leak. Do you smell raw fuel in the exhaust? Does it idle, and accelerate smooth? Is there a hesitation in the throttle?

 

[mustbrad]

My car loves timing, previous engine was 4v with huge cam after 2200 or so it took off.

 

[OpiemusRex]

There is no reason for that car to be soft at either end...provocative remark withheld.

Trying to be a good boy for Santa.

Good luck with that!

 

[mchandford]

Not a pro when it comes to the Cleveland, but isn't a low bottom end from a 4v Cleveland normal? Everyone I have "spoken to" on this forum tells me the 4v Cleveland doesn't really make any power till at least 3500 RPM. Unless you went with a stroker. Or an aftermarket dual plane intake.

I totally disagree, although I have no mechanical experience at all i do own a 351C with the 4 speed and I get all the power i need from about 1200 to 3000 and pushes you into the seat. I try to keep it under 3500 but I think that is just me being cautious. Just a thought.

 

[marks73]

On the 3rd attempt for the machine shop to get the heads right I had them taken to a different machine shop to be "checked" prior to being installed on the motor. They found the reason the was because they were using brass valve guides that didn't have the appropriate clearance and they were swelling up and pinching off the valves causing the lifters to crack. Once everything was cleaned up it had plenty of bottom end power. I am guessing the decrease in power has been gradual as I didn't even notice until a few weeks ago I tried to stretch it out at a stoplight at the bottom of an interstate and some guy in a dodge stratus was keeping up with me.

I'll try to check timing, compression and vacuum this weekend and get back with details.


Also, I can't believe its taken me this long to find a forum dedicated to the 71-73! Nice to be among friends rather than listening to everyone talk about how ugly my car is.

If your guides were indeed pinching off your valves, I believe you are going to find damage to the lobes of your. cam. That would explain a gradual loss of power as once the outer edge is damaged the lobes become reduced rather quickly.

 

[Wolverine]

FWIW, I recently put in a new distributor into my 1970 351W.

The vacuum advance and centrifugal advance were tuned for the motor, trans and rear end, torque converter.

The car has never ever run better in any regard. And I have had the car since it had 60k miles on it....and it used to run pretty good. Now it is much "sharper".

There are lots of tiny factors that add up. Make sure your advance is working as it should.

And in regards to low end, let's face it. In our pushrod engines there are sacrifices to be made REGARDLESS of the motor configuration. Better top end means a sacrifice on the low end. But, there is no lack of low end power(less, but no lack) with a 351C 4V if you have the right carb, torque converter, rear end and timing. NO LACK.