02sierraz71_5.3

iTrader: (2)

Ive taken .050 off my heads and even though my SCR is around 10.5 (5.3 LM7) and DCR is just over 8 I have problems with KR.

Is it possible that milling too much can effect the general area/shape of the CC as to make it more prone to detonation, I know with increased compression comes chances of detonation but I seem to have more of a problem than others with the same DCR/SCR.

Is it better to use a slimmer gasket and mill less? Quench?

Mods: if this isnt the right spot please move the thread

SStrokerAce

iTrader: (2)

No thats not too much, but you can have issues with lining up the intake to the heads at that much.

Are you sure about all of your specs?

You might have too much quench now if you haven't changed gaskets... also depends on the block material as well.

Bret

02sierraz71_5.3

iTrader: (2)

Its been a couple years since I did all the work but if memory serves me its close enough. The gaskets are stock, .054

Ive never understood the intake not fitting theory on these motors with all the space inbetween the intake and valley plus the angle I cant see .050 being a problem. But I could be wrong. I have sprayed the entire thing down with carb cleaner hoping for a miss and nothing. One other thing is that B1 is always leaner than B2 (still using stock 02's) Ive swapped 02's changed injectors everything I could think of.

SStrokerAce

iTrader: (2)

With the .054 gaskets you definately could have knock issues, I've found that with thick gaskets like that and low 8's DCR. If you switch over to a smaller bore .036" thick gasket then you should get a slight increase in compression AND take most of the knock out of the situation... it's a win, win.

Bret

Sport Side

iTrader: (6)

Bret,

What gaskets are your customers using?

02Sierra,

When are you experiencing KR? I'm using a 214-108LSA/ICL cam, .030'' milled 5.3 heads, .043'' gaskets. I haven't gone WOT yet, but I have up to 5* of KR when I tip in the throttle. Timing is only set to 25*.

02sierraz71_5.3

iTrader: (2)

I get low rpm kr under 2k with the converter locked at highway speeds with only 21-20 degrees of timing Ill get 1-4 when I mash the pedal and at wot as soon as I get over 80 mph it tends to pull around 1-2 degrees the higher the mph the frequency of kr increases.
Sensors have allready been tweaked and I cant hear it.
None of my knock is tip in, you can tune that stuff out. The problem is high load situations.

Tell me more about this. What happens/why?

Moddoo

iTrader: (4)

Hey Guys,

I don't know if this will help, but,

Here is a pic of my timing with my 10:1 SCR 8.4 dcr truck

This table is safe (0 KR) even pulling a trailer, (approx 3000#)

Even lugging up a hill at 1400 in OD locked.

Maybe this will help you get an idea of what to expect with higher compression.

My truck is no baby at low rpm.

Try backing of the timing a bit and see how it feels.

SStrokerAce

iTrader: (2)

I would just have Cometic make me a custom gasket, to the specs I need. Even a 3.910" x .036" would be a pretty much stock item for them.

I'd back the timing off some, like Moddoo has and that should take care of it for you.

The tighter quench and higher compression WORK because the extra fuel that is far away from the plug preignites because it's not forced out of the quench area with that large amount of quench, by tightening it up you cause the mixture to be more turbulent, get pushed out of the far reaches of the chamber and burn better. Smokey Yunick found this out decades ago and it's always worked like a charm.

Bret

02sierraz71_5.3

iTrader: (2)

I didnt know that, good info thanks. My timing table is more conservative than his. At wot Im only running 25-22 degrees of timing depending on the temp and g/cyl. Ive run my best times at 22 because after the 1/8th it tends to pull timing. Going from my stock gasket to something in the .036 range is like milling .07x Im wondering about clearance even though I have a smaller cam 222/222 112/112 .566/.566 xe type lobe.

02sierraz71_5.3

iTrader: (2)

Is pe enrichment rate at max? Id also drop the pe enable rpm to around stall speed.

NassyVette

iTrader: (22)

Sportside...check your PM box, its full.