Inliners International Forums General Discussion Hi Performance Lump Porting!

Hi, I know this subject has been beaten to death, but are there any huge benefits justifying the expense of lump ports on a street driven motor? It's a 67 292 w/ '63 6 throw crank, 30 over LPG pistons, 1.84 intake valves, Clifford intake, long tube headers, Crane's hottest grind for this motor(don't remember specs right now), and either a 500 cfm Demon or Edelbrock. Leo's book doesn't really expand on this very much. It's going into a 64 GMC with a 700 R4 and 3.73 gears. Any pearls of wisdom?

The lumps greatly complement an engine such as yours that has bigger valves and a bigger than stock camshaft. If your head still has the bolt bosses in it, then most definately going from that to a lump port will be a huge benefit.

Even for just the street?

Just going from a head that still has the bolt bosses, to installing lumps, even with the same size valves is a pretty big gain in HP and torque. And its not that expensive to do.

Yes, the sum of all the head improvements add up to a much improved torq curve. Don't get stuck on hp with the 292.

The valves will improve flow as will the lumps and your combo will make you smile.

I also suggest 1.60 exhaust valves and to port the head.

Like to know the specs for that cam.
Tom

Advertised duration is 272 intake at .004 lift, exhaust is 284, intake duration 216 at .050, exh. duration is 228 at the same. PN is Crane H-272-2. Apparently, it's meant for the 194-250 family, but still has a fuel pump lobe. Springs have been shimmed, etc. to compensate for the cam. I've got a fair bit into this already, and I have no idea what to do as far as porting. Do I really need to go to a 1.60 exhaust valve?

Sorry, PN is 204541. I gave the grind number.

If your satisfied with what you have now, then no. It's just that more gain can be had for little extra effort or money. If you are planning to tear back into the engine, then this might be something to consider.

Vanherk1, I asked myself the same question of justifying the expense of the lump port, bigger valve head on my 250 build. I read up all that I could, mostly in the old threads on this website and the Stoveblot website. I contacted Tom Lowe, via e-mail, called Tom Langdon (he actually answered the phone and gave me advice for 15 minutes - cool) and then decided to do it.

The difference on my 250 between the stock head (that had a 3 angle valve job performed) and the lump port, larger valve head was NITE and DAY. It went well beyond 'waking up the motor'. Keep in mind that I did a complete rebuild with cam, headers, intake, block decking, ignition and carburation and originally installed the stock head. Then I installed the lump port head, so my comparison was with only the head change. And it was fun too (this is actually my 16 year old son's truck and we've been working on it for 13 months!); I couldn't be happier with the results.

The expense was $100 for the lumps, $110 for the valves (Ferrea valves recommended by T Lowe), $140 for machine shop and $45 for gaskets. I installed the lumps myself.
So when you ask can you justify the expense of it, if you have already spent the money for the cam, headers, intake and carb, then I think $400 is peanuts to complete the job.

Bear in mind that T Lowe, CNC Dude and many others that post on this website have forgotten more about inlines than I will EVER know. And after I got the timing issues worked out on mine, thanks to T Lowe and others, my 250 runs better than I would have ever expected and I have to say my results speak for themselves.

Good luck.

Thanks, all 3 of you. I think I've got the answers that I need. The only difference here is that I've got no real baseline performance measurement, as the truck currently has a beat 350, and the only sixes I've driven were stock integral or slanted. Jim-did you use 1.94 and 1.60 valves? I have Pontiac 1.84 valves and stock 1.50 valves. The only major bummer is that I've already had hardened exhaust seats put inan had most of the prep work for the head already done.. A lot of guys talk about the exhaust side being less important, but is that just in terms of port/runner flow? I guess the exh. valve would be equally important in that equation, though. Thoughts?

I'm using 1.84 int and 1.6 exh. My complete build is decribed in a thread in the engine section that was started last month.

Regarding your head that you've already done some work to, I would recommend getting another head. That's what I did. It cost me $15 from the local junkyard. Then I would keep your current head as a spare or , not so much recommended except to save a few $,strip it to use the intakes on the new head, but that's just me. I kinda like knowing that I have another head that is complete and ready to be bolted on that is in good working order. I always try to have a few spare parts, i.e. carb, distributor, etc, just in case

Your cam has a lot of lift (over .500 if I looked it up right), are you using the stock valve springs?

No, I've got aftermarket ons-duals with an inner/outer setup.

Has anyone ever thought up a more descriptive name than "lump" for that particular piece of material? I'd insert a smiley face here if I knew how.

Sissell originally coined the term "lump" when he developed that technology, I guess no one ever has thought of calling it anything different.

I'm sure someone could come up with something more specific or definitive, but "lump" is what it's always been called, and another term will reduce the efficiency of all future searches.

In the November - December Chevrolet 292 dyno testing, the dyno runs with a stock engine showed basically no significant difference in horsepower with just the intake lump port installed. However, larger intake valves and cams will probably alter the impact of the intake lump ports.

File #1: Stock Head, Stock Cam, 390 Holley, Offy Intake, 34 timing
File #10: Lump Head, Stock Cam, 390 Holley, Offy Intake, 34 timing


Dyno Run..2500....3000....3500....4000....4500.....RPM
File #1:....142.5....162.....181.....186.5...179....Horsepower
File #10:...142......164.....181.5...185.5...175....Horsepower

What does the chart say about the torque?

MBHD

Horsepower = (Torque x RPM)/5252

For the same RPM, the relative torque readings are going to be proportional. The actual dyno torque readings for the two runs were within 3 ft.lbs. at the same RPM, up to and including 4000 RPM. Both engines were in the upper 290's ft.lbs. at 2500 RPM, and 205 to 210 ft. lbs at 4500 RPM.

Most well tuned normally aspirated 2 valve per cylinder engines are going to develop a torque in ft.lbs. close to 1.0 to 1.15 times their cubic inch displacement. The horsepower output is going to vary more for similar displacement engines, as developing the same torque at a higher RPM creates proportionally more horsepower. For a given engine, torque and horsepower are always equal at 5252 RPM.

So, did the lump port head produce more torque or did the values switch between the two @ different RPMs?


MBHD

The dyno run with the greater torque value swapped back and forth with different RPM's.

As Winter says, the torque is proportional to the horsepower. If my Excel is correct, the 292 engine with the stock head produced a max torque about 1 ft-lbf greater than did the engine with the lump ports. The peak torque was about 1.03 times the displacement in cubic inches, reasonable for a nearly stock, unsupercharged engine on gasoline.

Dyno Run.... 2500.... 3000.... 3500.... 4000.... 4500.... .RPM
File #1:...... 299.4... 283.6.. 271.6.... 244.9... 208.9.. Torque, ft-lbf
File #10:.... 298.3.... 287.1.. 272.4.... 243.6... 204.2.. Torque, ft-lbf

Winter, Hoyt and hank,
The tests being dicussed here were done with 2 stock heads. Both had 1.72/1.5 valves. The only difference being one head had lumps installed. Tried to find out if lumps alone will improve performance. Found out they do not. They must be used in conjunction with larger valves and porting. Tom

Tom and Hoyt,
Thanks for the confirmation.


Tom,
I'm aware of your upcoming numerous planned dyno runs for Chevrolet 250. Here's another for thought:

Substantiate when the intake port lumps become effective, RPM band/camshaft/valve size wise. Confirm if intake lump are worthwhile for lower rpm power band engines, say 4000 RPM and under.

Three different runs with an engine using one your mid RPM cams such as Cams 1,3, or 5:
Run 1) With 1.94" / 1.6" valves
Run 2) With 1.94" / 1.6" valves and intake port posts removed
Run 3) With 1.94" / 1.6" valves and intake lumps installed

Testing lower and higher RPM cams would be informative, but that's a lot of additional work.
I know that giving recommendations is easy when you don't have to do the work.

Lump ports do make a big difference when used with 1,94 valves and unshrouding. My head was already ported, with bosses removed, and the diference, was still noticeable with lumps.

Super6,

Were the lumps installed:
1) alone as the final measure or
2) along with the 1.94" valves and unshrouding the valves.

Super6,
Another question, what are your cam specs?


Winter,
Pertaining to your prior question to me.
On the 292 tests, your test 2 and 3 were performed. Test one would require yet another head. The difference between lump and no lump was about 15hp.

Also the lumps seemed to take affect from the beginning of the pull with a tq increase. Testing also showed a 1.94 intake valve produced the most tq. Tom

Winter: previous combo: bolt bosses removed , pocket porting and stock 1,72 valves: Dynoed 226 rwhp, shuting early, at 5200 rpm due to fuel pressure problems, now fixed by a brand new Holley Blue pump. Presente combo: same head, with 1,94 intakes 1,50 exhausts custom built lumps and unshrouded to around 1/4 inch clearence to chamber wall. Didn't dynoed yeat, but I think I gained around 10 to 15 hp (seat of the pants). Remember, its a 266 cu.in. engine, (250 bored to 4 inches) a hot street cam, mild compression (9,5:1), headers and a Holley 600 double pumper. Tlowe: the cam is an Isky 525B, .525 lift, 238° @.050 and 109 lobe center. I think the benefits wold be much more noticeable with more compression and webers.

Tom and Super6,
Thanks for the replies.

Wonder what kind of clearance Tlowe has w/his 1.94" valve to chamber wall?

Compression makes a world of difference,(night & day)that's why I recomend & used the small chamber 194 head.

Side drafts are a huge improvement alone, it will net 40-60 HP increase over a stock intake.

Torque will lengthen 1500-1800 RPM
Midrange torque will be significant.

MBHD

Hank, for sure, Webers DCOEs or even IDFs do make a big difference in torque, throttle response and even HP, just because the cylinders doesn't need to pull air from a big plenum, changing direction every time. For cost reasons, I opted for a cast aluminum Folego intake and a Holley 4150 600 cfm. The big cfm, for a street 250 helps a lot at the top end (6.000 rpm). Here in Brazil, the standard equipment for performance 250s is the triple webbers, down or sidedraft, but there are some racers running single for barrels with great success. Lump porting, on the other hand, isnt so popular, Brazilian builders limit the porting to bigger valves, blending and wing shaping the intake boss, basicaly, but this is changing. I believe, Douglas Carbonera was one of the first racers to use lumps in his 11 second street Opala here in Brazil. His engine burns etanol and has 15:1 compression . There is no doubt, that lump porting is the only way to really improve the flow in siamese port head, and reaaly can wake up the mill even on mild aplications, such as mine.

Even if you don't install lumps, removing the intake bolt bosses completely will gain over 30 CFM of airflow. By comparison, knife-edging the boss does very little.

Super6,
Do you have a pic of the Folego intake?

I see guys in Brazil using single 4 barrels,but it seems they are blowing through them w/a turbocharger.

I had told Douglas to try a lump port out & Larry,AKA Twisted6 was nice enough to give him a set.
He ran in the high 11's w/his old engine.

His newer engine blew up, so he did not even make it to a track, only did some dyno time.
Forgot what HP it made,430HP or there abouts?

Boring to 4" is too big in my opinion & that is the problem Douglas is having,bores are too thin.

I think the best intake set-up for an inline isside draft w/ DCOE's,or F.I.
(fuel injection).

But guys that broke all the records in HP & track ET seem to have made custom 2 4 barrel sheet metal intakes,but that would be used for all out racing,probably not too nice for a street car.

I had 3 48 MM DCOE's,too big really for my 254 CI, but it had 12:1 compression (that's 2 full points more compression than the open chamber head)(Probably would have been better w/45's),but the side draft manifold & Webers I had was the best intake & carb combo I ever ran.
I will also say,the chamber wall was not unshrouded too much for the intake as I was trying to get the most compression possible.
Never flow tested the head,it probably flowed worse than the open chamber 1.94" head, but the compression,really bumped up the torque band & torque is what you can really feel.

Literally it was a day & night difference!

If I would have not wasted all my time & $$$ spent on 2 barrel, 4 barrel carbs AFB's,AVS 400-625 CFM,Quadrajets 700- 800 CFM,Rochcehester dual jets small & large,Holley 500 2 barrel 350 2 barrel,Holley 600 Vac sec,600 double pumpers,Thermoquad 850 CFM (just to try it out),& different intakes (Offy, Clifford) & started w/the Webers,well,,,, my Camaro would have been kicken most of those V-8 thingys I raced years ago.

Best 1/4 mile time w/a Clifford & 500 AFB carb was a 14.3 @ about 3400 ft altitude track, corected to 13.8.
That was a big chamber head 10.0:1 compression 1.94" in. 1.60" ex

Same short block,this time w/the small chamber head 12:1 compression Clifford 4 barrel 500cfm AFB 1.9" in ,1.60" ran 13.8- 14.00 uncorrected time, same track. Corrected time of 13.3 -13.5 range.

Not really all that fast, but it was & always has been a street car & still will be a street car,,whenever that will be,,? LOL.

I knew about the lump port back then, but could not afford to send my head to Sissels to braze in the lumps.

So instead of the lump port head, me & my friend made & flow tested an upper lump port that is attached to the upper portion of the port.These were done over 20 years ago.
Here is how it is attached to the upper portion of the port:

Here is the upper lump,it did not turn out so well, but I was in a rush & was shaping a billet piece of aluminum to form to the top of the port,not so easy.
Here is sorta of how it should have looked:



MBHD

The Folego intake, is basically a Clifford copy. I made my own lumps, cast out of aluminum, molded from epoxy, and they are atached from the deck surface, much like Larry's "Twisted 6" and Tlowe's. About some guys using the 4 barrels in blowthru configuration, this is true, but my brother tried this in his 53 belair, powered by a 250, with marginal results. The consistency wasn't good, and the carb didn't like the boost. He was using a Bosch GTI pump, and boost referenced regulator. Now, he switched to a custom made sheetmetal intake, with EFI, controlled by a brazilian Digipulse Full ECU. The setup employs 12 injectors, 6 from a Chevy Omega, and more 6 Ford Racing injectors when the boost comes in . the throttle body is 70 mm, from a mid 90's Alfa Romeo. The exhaust manifold is a SPA cast iron, and the turbo is a MP .70. i think it cranks out about 350-400 HP, and the torque.... it's unbeliveable. You see, here in brazil, we need a good dose of ingenuity and craftsmaship to make hot rodding happen!

Super 6, here too (ingenuity) if you want to do it without going broke.

That does sound like a neat setup, thank you for posting it.

From my point of view here in the US.

It looks like to me there is more aftermarket parts & more support for the Chevy 6's than there (Brazil) are here. Not too sure about Argentina,,but they seem to make aftermarket parts there also for inline Chevy 6's.

Plus,drag racing & just any type of racing & hopping up Chevy 6's in general,seems to be more poular there in Brazil,I could be wrong?

Do you live close to Douglas?

MBHD

Hank, I think your right. Mostly because the popularity for the Chevy 6 here in the US has come and gone as far as the manufacturers are concerned. Sure on here there seems to reflect a large amount of interest in them because its about inlines, but compared to the 30-40+ million other Hot Rod markets in the US parts are availabe for, the 6 cylinder probably equals some decimal of a percentage of 1% of the total performance market. But in South America in general, the Chevy 6 to them, is as the SBC is to us in the US, mainly because its one of the only few engines they have there in those countries to race and hot rod. So its kinda' their Small Block Chevy in a way. Its my understanding that V8 cars have never been available there off the showrooms, so any V8 they want to build up has to be shipped there from a country that has them, like the US.

CNC-Dude, in a certain way our inline sixes are like your small blocks. In the late sixes thru the seventies we had commercialy availabe V-8s, the brazilian Ford Maverick, Galaxie and the Dodge Dart Family. The Ford F-100 and the 67/74 Galaxies, came equiped with the 272/292 Y-Block. later 75/83 versions of Galaxies and F-100 with the 302 windsor family. The Maverick was equiped only with the 302, but some previous versions with a Willys-Overland (a long story) inline 6, and the 2.3 inline four. Mopar equiped their cars and pickups with the 318 LA family v-8s. I believe in Argentina, they did'nt have v-8s, only inline sixes, both from chevrolet and chrysler of the 250 and slant six families, respectively. In argentina they produce excelent parts for the 250/292, from cams to pistons and rods. One of the most proeminent race car/engine bilders of latin america, Oreste Berta built a 12 port head in the 60's and 70's. Berta was also known for his four cam, 32 valve Formula 1 v-8 engine,designed to compete head to head with the Cosworth dfv, but the project dyed in the 70s due to lack of funds. Juan Manuel Fangio, another famed racer from the pampas, used to race a 1940 Coupe "carretera", in the mid 50s that was equiped with a souped up 235 inline 6.