Some new info on swirl ports, not my project, but still cool if you ask me.

Groovy Heads Project

I can't help but think of what it would have done with PE air/fuel ratios in the high 12s instead of mid 11s! 180+ RWHP would definately be possible, IMO!

 

I agree on the air:fuel ratio. All his runs were too rich.

His engine power is low as well (145 rwhp before mods). Compare this to a very-well-running low-mileage stock Caprice 9C1 LO5 dynoed 168-170 rwhp, consistent with an approx 17% drivetrain loss from a 205 fwhp engine (owner is a member of the Toronto-area Impala SS owners group).

So his engine must be tired in some way because he's missing approx 25 rwhp even before the mods to the head. OTOH he did perform a before/after test, where the before condition was 160+ kmiles on a stock engine, and the after test was post head cleanup and mods. So the test is meaningfull.

Too bad he didn't do a little porting on the heads. And he hasn't (yet) posted on what his new fuel economy is.

 

Without a doubt it is probably the cam lobes going or worn down. I would be willing to bet that a cam swap would bring the power back, something along the lines of a Summit K1102, Melling MTC-1, Federal Mogul CS1014R, etc.

 

Forgive me, but why did he make that cut across the combustion chamber?

 

Read these threads:

what do you guys think of this? :: Speed Talk - Auto Racing Forum

what do you guys think of this? Part II :: Speed Talk - Auto Racing Forum

Analyze burn pattern :: Speed Talk - Auto Racing Forum

Larry's Soft Head :: Speed Talk - Auto Racing Forum

 

My biggest question is. Whad does a dyno look like, for the stock heads, with just the compression bump. And, what does the dyno look like, with stock compression, and the grooves cut.

I wonder how much of that gain was just having a clean chamber, and a full point of extra compression.

 

Stock (theoretical) CR is 9.0:1 on the trucks (dished pistons; cars have 9.3:1 without dished) and it looks like he gained approx 1 point in CR based on the reduction in chamber volume. If you accept 2% gain for a 1 point increase in CR (see J.B. Heywood, p. 182 Figure 5-9 for example), then the hp gain from the compression change would be approx +3 hp on a 145 hrwp pre-mod value.

hp gain from compression increase (via faster full burn) works better in going from 7.0 to 8.0, than it does from 9.0 to 10.0.... so the gain is a progressively smaller change for each point in CR. So IMO the +21 hp chnage is more from a faster and/or more complete burn, than it is from the CR. increase

It would also be useful if he had reduced the ignition advance --- he might actually have too much if he's using the stock ECM tables. IOW there might be more power available had he backed off the timing slightly... if the faster/complete burn is really occurring.

 

Interesting.

What about the multi angle (3?) valve job and the refaced valves? Did this improve low lift flow and cylinder seal? How much did that contribute to the power increase?

 

Holy cow...

People are talking about me... I figured I best sign up and defend myself!

Thanks for the comments on my web page and project.

1. My power numbers are a bit low because I forgot to lock the torque converter up when I did my initial run. I forgot that in a '95 4L60E there are 2 solenoids for lockup, not just one, so all the power runs I did was in 3rd w/out lockup. I thought of this as I was driving in to do the 2nd power run. For comparison, I did do one of the second runs with it fully locked up and peaked out at about 170 hp.

2. Other than the head mods, that is a fully stock 350 w/ 165k miles on it. I imagine there is a bit of wear on the rings, however it doesnt smoke or burn any noticible amounts of oil. Also remember this is a 4x4 so I have trans losses and a tcase loss. Might be why the rwh seems a bit low. Also the old valves were piled with crud on the top side, it looked like a goose pooped on each one, so someone must have run around w/bad plugs and wires for a while at one time, so I can't see them flowing very well at all like that!

3. As far as I know the stock comp ratio should be 9:1. I measured the old head gaskets and they were 0.030" instead of 0.040" so I'm only guessing it was 9:1. The modified heads were decked 0.060 and I used a 0.015 head gasket. I estimate my new comp ratio to be about 10.2:1, about as far as I can go w/out changing pistons.

4. I do agree with you on the AF ratio... that thing is pig rich in open loop. The graph there is the wideband after the cat as well (although thats a cat with 165k on it, so probably not working as optimum anymore). In closed loop on the highway the old heads had very little fuel trim adjustments, both long and short term stayed right at 125, with the new heads, the short term sits around 130, long term around 110. So I assume (and someone feel free to correct me) that my throttle enricment seems a bit lean, but the overall AF is now a bit too rich as its leaning back on the long term.

5. I have done some timing adjustments since, as Ihad just a very slight amount of knock between 1000 and 1800 rpm under light load. I retareded it about 3.5 degrees and its for the most part gone away and I seem to have a much improved torque-iness from 1500 to 2300 rpm. Has some real nice pull it never had before. It would be interesting to do another dyno run and see what its doing now.

6. One of the thing this is supposed to do is help milage and reduce knock. I'm running the engine on 87 octane just fine even with 10.2:1. Like I said there was just a small hint of knock, but a few degrees retarding the timing cured it. My milage has gone up maybe 1 mpg, but that I am still working on. Many who've tried this said EGT went down significantly, so I am awaiting an EGT and a wideband o2 controller to put in there. What I am planning is to use the wideband and set up the controller to output a narrow band o2 signal at leaner and leaner mixtures and keep an eye on my EGT. Basically try and lean it out till I see normal EGT temps and see how it runs power and performance wise.

Now a question for you guys... What would be a normal EGT temp for a standard 350?

Feel free to comment!
Thanks guys!

Garrett

 

One 1993 Caprice 9C1 (with copcar LO5, 205 fwhp) that I know of measured 170 rwhp in bone stock condition, but the converter is not supposed to be locked (by the factory) during WOT. Your test showed 170 rwhp (locked) vs 165 rwhp (unlocked, 2nd test) so the converter is eating roughly 5 rwhp from slip.

And thanks for the reminder on why the stock rwhp was low --- I've seen carbon accumulation (fused oil + EGR residue) on SP head engines, located on the backside of the intake valve(s) that obstructed most of the port, and the crud in the ports, chambers and ring wear all certainly could be reasons why the unmodified dyno values were low.

But that also means that some of your observed power gain was from cleaning up the chambers/valves/ports from crud. So it's harder to separate the torque & power gain due to the slot-modification vs gains from head cleanup.

FWIW the L99/LT1/L31 iron head engines run 10.0:1 CR and can run on 87 octane; these have less swirl but more squish than the swirl port heads, and AFAIK they run something like a max of 32 deg advance at WOT. So in your case, 10.2:1 with (probably) higher swirl and 87 octane should be fine.... you just have to make sure you don't have too much advance.

I don't know what the EGT is for a typical LT1/L31 engine for comparison. You'll probably have to dig into the web for that, as few people measure EGT.

 

I was waiting to see comments about the dremel grooves cut into the intake port. I have an open mind on all this, but it seems that creating turbulence there would impede the flow and reduce the power output. I understand this was done to improve fuel atomization. Without a stand alone test of this modification is it fair to speculate that the engine would have done better on the dyno without it?
Also, to reduce detonation I've been advised to remove sharp edges in the combustion chambers. I'm no expert (not even close) but I would have slightly radiused everything. Would that have helped?

 

Hi,

I did make sure to knock all the sharp edges off the combustion chamber. If you look through my pics, they are a progression of the intial groove cuts, the decking, and the finished product. The three most bottom pics are the final ones, you can see I even took a file and went around the outside of the combustion chamber to make sure there wasnt a sharp edge from the decking. Its hard to take pictures that show all of that.

Garrett