Lethargic big block - what to check first?

[dhardison]

My 454 took me over 3500 miles on the Power Tour without incident, but it's WAY down on power. The engine is just lethargic, I don't know any other way to describe it. It's slow to rev and starts to pop/spit above 5000rpm (6000rpm redline). Otherwise it idles and runs smooth.

I'm wondering if you guys can suggest what to check first. I normally run the timing at 36 degrees advanced, but for the Tour I ran it at 20 degrees. Surprisingly there was no difference (i.e. decrease) in power from 36 to 20. I'm thinking about checking compression, maybe a different timing light, etc. Any suggestions??

Thanks,
Dan

[dhardison]

No suggestions????

[NovaPwr]

Dan, I would just yank it out of there, throw it on a cradle and I will drive right over to get it out of your way. lol. Good time to install the 572. Just run a quick compression test. My old 427 was always hard on plugs. I liked that old motor. When it got lazy you just ran the valves, adjusted both sets of points and threw in new plugs and zowee, ran like a new one. But, that was a long time ago. Good luck with it.
Dave

[dhardison]

Thanks Dave, but I think I'll hold on to it for now. lol

The last time I can remember it really running good was at Bowling Green a few years back. Since then I've done mostly cruises/shows and two Power Tours (i.e. no racing) and it's slowly become more lethargic. The only changes since Bowling Green were new plugs and running the valves a few times. I have a Pertronix, so no points to adjust. I dunno, maybe she's just tired....

It was running way rich during the '06 Power Tour (as you can probably attest by following me out of Harrisburg) and mileage was down 2mpg over the '05 Tour.

Dan

[Matt@RFR]

If it's carbureted, disassemble the carburetor and clean it all up. Maybe that will help, and if you have good gaskets in it allready, it'll be free.

[TonyHuntimer]

...from experience I don't hope to re-visit. If you have not done so, you should pop the valve covers off and inspect the valvetrain. I had some valve retainers fail, the locks pulled through, a piston had a fight with a valve. Nobody wins in a fight like this.

For two weeks before it let loose I had been slowly loosing power. I could not explain the power loss until it was too late. I happened from two errors... cheaping out on a rebuild and not replacing the old stock retainers and over-revving the engine without a load. Free revving is REALLY bad for and engine. It sounds cool to spectators while cruising in Reno but it's not good for your engine. Everyone was young and dumb at one time. :)

The problem retainers are not common, but worth a look. I wish I had taken 30 minutes to take a peak under the valve covers.

My $.02,
Tony Huntimer
RaceHome.com

[dhardison]

Thanks Tony, I actually did check under the valve covers and luckily everything was ok. I forgot to update the thread with the actual cause which was a worn out distributor assembly. The mechanical advance assy wasn't always advancing properly. I replaced everything with a new billet electronic distributor and hi-output coil and now everything is back to normal. Thanks for everyone's input!

[Madspeed]

This is a lesson in that you allways check the basics first
Fuel air spark and compression are all needed to make a gasoline engine run
gasoline engines dont want to burn fuel at 100 lbs compression or less

Always start simple =) spark pplugs can tell you a lot =) and a compression test while they are out tells you more. Oh and while your doing it make a logbook

Glad you figured it out and it was a simple fix =)

[67speedfreak]

Did you degree the cam shaft when you installed it?
Could be cam timing.
What cam , intake, heads and carb are you running?

[camcojb]

Did you degree the cam shaft when you installed it?
Could be cam timing.
What cam , intake, heads and carb are you running?

He figured it out a couple posts above yours..... that's what you get for not reading every response! :lmao: Just kidding, here's his solution:

"Thanks Tony, I actually did check under the valve covers and luckily everything was ok. I forgot to update the thread with the actual cause which was a worn out distributor assembly. The mechanical advance assy wasn't always advancing properly. I replaced everything with a new billet electronic distributor and hi-output coil and now everything is back to normal. Thanks for everyone's input!"

[67speedfreak]

Cool so it was a timing issue.:hand:



He figured it out a couple posts above yours..... that's what you get for not reading every response! :lmao: Just kidding, here's his solution:

"Thanks Tony, I actually did check under the valve covers and luckily everything was ok. I forgot to update the thread with the actual cause which was a worn out distributor assembly. The mechanical advance assy wasn't always advancing properly. I replaced everything with a new billet electronic distributor and hi-output coil and now everything is back to normal. Thanks for everyone's input!"