https://www.youtube.com/watch?v=nEKITCpNqsY

What I don't understand he calls this a lump port on all his vids.

MBHD

Yeah, a piloted spot face tool would have been too easy. I guess he's just using what he has available to him. Does it actually show him putting the lumps in the head?

To bad he cut to deep into the head at the rise of the floor That head is now pretty thin in that area. It sure won't take much to over heat it and Have it crack in that spot.

I just do not get this guy. I understand the more power thing but that was a crap load of material he removed. Would all the effort he went through even be beneficial? I thought for a street driven motor you wanted the bosses left in?

Yeah,
I do not know where he gets his info from but wherever he did, he needs to get better informed..

Yes, you would leave the boss in for what he was looking for.
Removing the boss just made him lose port velocity & low RPM power, just what he says he was looking to gain, more power down low.

He does not put in lumps, he says lumps are for high RPM power, that is why he did not want to put them in, he is not racing or want higher RPM power, hence he removed the boss he put 8 videos on YouTube .
I would not recommend to use any advise from the vids, for the most part.

MBHD

Had he started taking form top deeper inside he would have had to remove less material to get a flat spot for the bolt. Using a round allen head bolt would have reduced the size of the flat needed. With the shrinking number of machine shops and the increase in the hourly rate maybe a guy willing to experiment can burn up a few not so rare heads and get a handle some improvements. At least he is working on OUR engines!

Leave the bosses in and concentrate on bigger valves and a good valve job, or add lumps and the valve work. That's what I understand for a street motor. I'm debating which to go with for my street 250 myself. Leaving the bosses in is simpler for my integrated head swap out for non-integrated top end.

[quote=Lifeguard
Leave the bosses in and concentrate on bigger valves and a good valve job, or add lumps and the valve work. That's what I understand for a street motor. I'm debating which to go with for my street 250 myself. Leaving the bosses in is simpler for my integrated head swap out for non-integrated top end. [/quote]

Depends on if you want to make more power or not.
The lumps will make more power & increase intake port velocity more than leaving the boss's in.

The short turn radius is where the lumps really help out & increase port velocity.

If you are looking for a good bump in power & low end torque, install a 1.85" intake & 1.60" exhaust valves & add the lumps.

Adding lumps only makes more power if you install larger valves.

MBHD

He lost a great deal by doing what he did. He also shortened the life of that head. Because if he ever over heats it, It will crack just past his bolt head. He took away Over half of what is there to start with. He is lucky he did not cut right thought the floor doing like that.

Yeah, the 1.85"/1.6" valves was already my plan as Santucci says to do with a street build. But he just recommends a good performance valve job and throat work for the street application. Not recommending the lumps until the street/strip build. But, the lumps should work fine for the street application too, making more off idle torque up through 4500rpm or more.

I don't quite understand that part of Santucci's advice -
To me, you would do everything for "Street" that you would do for "Street/Strip" - EXCEPT things that affect driveability or cost too much.

The lumps don't cost a lot compared to any other mod to the motor, they don't take away low end or mileage (in fact they probably improve both).

Things that affect driveability would be stuff like 4.56 gears, a 302 z28 cam grind, etc, but the lumps don't fall into that category.

I'm planning lumps if/when I ever get back to my engine and its mostly street but I'll pass on the z28 cam and 4.56 gears...

Tom's dyno testing clearly shows that the lumps improved HP and Torque on every combo compared to the same head without the lumps throughout the same RPM range. This is data that didn't exist in writing when Leo's book was written, so he was probably basing his thoughts more on conjecture than proof that was available at the time or just didn't want to give credit to something he couldn't give solid proof to. Sissell and Kirby's data has always shown the lumps to be beneficial in all RPM ranges, and Tom's findings just further shows that to be true.

Santucci even says for the street/strip to add the lumps IF you can afford it. I suppose if you have a machine shop do all the work, then it gets pricey, but the lumps themselves are pretty cheap compared to other L6 mods. It's a bit more work on the heads, but it seems like it is the most bang for your buck to go with bigger valves and lumps.

I do not have the Tlowes dyno results, but wasn't there was a test w/lumps installed & stock size valves & had no gain in power?

MBHD

Yes, I forgot the one exception was the bone stock cam engine with stock size valves. Showing I guess that in a stock cam engine that even having a better flowing head wont make an increase in power.

Tom didn't do anymore tests with the stock size valve heads other than the first baseline pulls and the one small valve lump head on the same engine with no other changes. He was thinking that no one would go to the trouble to do a lump installation and still use the stock size valves, even though with the addition of a bigger cam and other bolt-on's that power gains would be expected, just not as much as with bigger valves installed.

Here is a dyno chart showing lump results

292, lp pistons, offy intake, long tube headers

The lump head is a 292 head with 1.94/ 1.6 valves

Torq is always higher at all RPM's with lumps.

stock cam,stock head is BLUE
stock cam, lump 1.94 head is GREEN
Medium perf cam, no lump is BROWN
Medium perf cam, with lumps ORANGE

Also notice the dip in tq at the beginning of the pulls. The vacuum secondary's were pulling in too fast.

Thanks for that Dyno chart.

Did you test a stock valved head 1.72 in 1.5 ex, stock cam w/lumps installed?
Dyno chart for that combo?

MBHD

I'm guessing going with bigger valves, but keeping the bosses with the stock cam would fall somewhere in between the 1.94/lumps head and the 1.72/bosses stock head?

Hank asks
Did you test a stock valved head 1.72 in 1.5 ex, stock cam w/lumps installed?
Dyno chart for that combo?

I did test that combo on the same engine. Results, same power made with both heads. The valves need to be enlarged to see the gain. I have dyno charts, but not digital.

Thanks.

Did you try that combo but w/a larger camshaft also?

Stock size valves, lumps installed, but w/a larger camshaft.

I see you stated, "The valves need to be enlarged to see the gain"

MBHD

See post #81366 above.

Got it.