69Rat

Anyone have an idea on how to reduce the compression ratio on a 454 BBC. Mine is an LS5, and is about 10.25:1 ratio. I have to detune the crap out of it to keep it from pinging. Any idea on a way to reduce the ratio without plugging new pistons?

:confused:

Fevre

Bigger cam to bleed of comp (narrow lobe seperation), thicker head gasket, larger comb chamber heads, higher ratio rockers

Bigger cam would be the funnest. :)


[Modified by Fevre, 11:04 AM 7/18/2003]

Stingray Mark

:D If you really want to de-tune it you can start by putting a honda sticker on it and a wing :lolg:

Fevre

Hold on! Thought that just made it faster. :confused:

69Rat

:lol:

Funny..... I was looking for more like adding bigger chambered heads... anyone using the Performer RPM heads on a 454? If I have to pull the pistons.. I'll go all our and make it a 500+ motor. :reddevil

Matt Gruber

there is a chance it could be re-tuned.
post the advance curve
and the exact problem(like pings light throttle at 2000, pings medium throttle 2300, pings above 4000 WOT)etc

Corey_68

What is your timing set at? 10:25:1 isn't THAT bad w/ iron heads, not enough to see any major ping. I would look there before I do anything else. :cheers:

1979toy

Retarding the cam 4 degrees will lower your effective compression ratio. I do however agree with others that this should not be too much compression.

68shark

Agree with Corey 68 and others....10.25 is not high enough to have this problem. Check timing, maybe carbon build up also? Dual pattern cam will bleed off cylinder pressures at low rpm, but of course this isn't exactly a simple fix. I'm not experienced with BB engines, but if a SB, would suggest keep initial timing below 10BTDC and see how that works. I presume you are running 93 or better octane? If not, try Sunoco 94 and see what happens.

69Rat

If I run octane boost, or race gas it runs fine. It only pings (slightly) under full throttle runs...usually over 4000 rpm. I have a wierd heat issue as well. It has a 180deg stat, but still runs 195-200 all the time. Any ideas? I just bought it from my brother, and I'm in the works to do ALOT of changes in and out.

I love the forum! Thanks! :thumbs:

Matt Gruber

Assuming everything else is working right:
The dist. advance weights have a stop pin with a bushing. the bushing needs to be replaced so that total advance is a few degrees less.
Others will chime in i'm sure. :cheers:

68shark

195/200 is not overheating by any stretch, but seeing your car is pinging (without really high compression), I'd check the temp with a infrared gun to make sure. If engine running hot that can tend to induce pinging. This is basic stuff: 1. keep engine at proper operating temperature
2. timing set properly (including right vacuum advance...see SWCDuke posts in C1/2 section).
3. mixture not too lean (running lean increases heat)
4. no carbon buildup
5. use right grade of gas, suggest 93 octane.

Nail these and it shouldn't ping.

Lasse

Do you know the cam numbers?

It's better and easier to change the cam or heads instead of pistons, but check for carbon buildups and the total timing first (34-38 degree without vacuum advance @ ~3000 rpm)

I've heard that you can wash the carbon away by pour some water in the carb while the engine runs about 2'-3' rpms. True or not?!


[Modified by Lasse, 11:32 PM 7/18/2003]

Scooter70

A friend of mine just told me this one the other day. Once I get my top end back together, I'm going to do it. He says to make sure you don't do too much too fast or you'll mess it up for sure. The idea is that the water turns to steam inside the motor and the steam cleans the carbon deposits off.


[Modified by Scooter70, 11:22 PM 7/18/2003]