The Stovebolt Site Forums The Shop Area Engine Shop 250 Chevy Intake port mod

One of the Inliner racers at the Redding "Inliner and /6 rumble" showed me a port trick on the 250 Head to increase flow in the intake port.
The head bolts drop through the casting right in the middle of the intake ports.

He "cuts" the cast iron "Tube" out of the port, then uses a shorter head bolt in the bottom of the port. Some people tap the hole that the bolt originally was mounted through on top and plug it. His method is to use a Freeze plug to seal the upper bolt hole.

Anybody done this mod?

CJ

I,ve heard about it for many years. The guys that race the 292,s do it to there heads.

i reciently purchased leo santucci's chevy inline six power manual. very very good information on this topic. i had a hard time finding the book though. if you would like any more information on this you can send me a pm or email and i will pass on what i can.
~dave

PM Sent!

Hopefully the increased port volume won't send my poor old pickup over the edge.

CJ

i just stopped short of doing that on my last rebuild. i kind of toyed with the idea. i just settled for a comp 3 angle valve job. i want to try milling it out myself on the next one i do. i don't know, that would be a lot of work for my mill. does he just do the three bosses in the intake ports? i for one would feel better about the tapped plugs than freeze plugs. i think you would have to do a lot of other work as well like higher lift cam, bump up compression, plan out induction to get a real improvement with boss removal. was he installing bolt in lump ports as well. a guy from inliners international sells them on ebay. i want to try his on my next rebuild. that would def be way to go if removing the bosses. well good luck and let me know how it works. hr

Does anyone market a roller cam for the 230/250/292 engine? I've got a few ideas about hotrodding one for a round track dirt racing class I'm interested in. Basically, the sixes can run a bunch of modifications they won't let the V-8 guys get away with, such as roller cams, multiple carbs, etc.
Jerry

Jerry, I think there are a lot cam choices for the six, you just have to dig a little bit to find them.

As far as the LUMP ports, they do work, its been proven, but its not as easy as just bolting them in. There is a lot of shaping to do in the port and around the valve face. My dad has a Superflow bench used to check air flow on heads. We did some work on one of my 250 heads using clay. We found a small lump at the front of the port going around the head bolt boss helped a bunch on low lift flow. Even up to .500" lift the flow was better then stock. I don't have the numbers but it was quite a bit better. We added the bigger exhaust valves (1.6") I think, and ported them as well. You can really get some flow from the exhaust, they are real close to the SBC in design. After I changed the clay to epoxy, we installed it and drove for a year with a slight miss. From What we could find, the exhaust was out flowing the intake and causing a lean condition at high rpm and heavy load. No matter what I tried, I could not cure it. I reinstalled the stock head with no other change, and the problem went away.

All this tells me there is a bunch of stuff in the flow area that I don't understand. I think the real racers raise the roof of the port and add the lumps to get the short side curve up to a better angle. If you look at a stock head the floor is lower then the valve face and the air has to dip down and back up to exit in to the chamber. By rasing everything, you can eliminate the dip. Also, the removing of the bolt hole boss doesn't add much flow, it just helps in directing the air in and around the port chamber.

Read up before cutting, you might save your self so time. Check the Inliners site if you don't. they do some pretty cool stuff.

Joe

VERY cool info joe!! i bet we all wish we had a way to check flow. i wonder what would have happened if you had just added the intake lump. on mine i added oversized valves and really just pollished and smoothed all the ports. i would love to know exactly what to do before i start cutting, i don't need to reinvent the wheel. did you see that sissell head that was listed on ebay prob a year or so ago. it was cracked but it would have been so cool to look at for a novice like myself. i still want to try the bolt in lumps sold by "mr hot rod 6" at some point. but i'm no racer so it's all just for fun. hr

"mr.hotrod6" sells these heads and other speed
parts for the 194 to 292 series inlines on ebay as does Larry Griffin over on inliners from his shop in FLA. None of these heads are
inexpensive.Lots of
machining involved, but worth it I'm told.

From all that I have read, a good clean up of the ports and bigger valves is all thats needed for a general street driven hotrod. The real modified heads are for true high rpm race engines. The ones that really run good are screamers, 7000 + rpm! They need to do that to get the HP numbers.
If you want quick easy HP, through a turbo on it, then the head ports don't really matter. A turbo will force the air though any crappy port out there...... Joe

DrewP, That's Larry Page aka Twisted6 on Inliners. He has a web site;

http://www.t6racing.org/id4.html

There is quite a bit of information on his web site about modifying heads, besides the parts he has for sale. Anybody that's considering modifying a 194 to 292 head, I would recommend visiting his web site.

I can only wish I knew as much as he does.

Larry

[QUOTE]Originally posted by LGriffin:
[QB] DrewP, That's Larry Page aka Twisted6 on Inliners. He has a web site;

http://www.t6racing.org/id4.html
HaHa. Sorry about that. too many web sites floating in my pea brain.

Wow!

Well, from what I'm seeing, this mod is not going to be a good choice for my street rig. I think I'll leave the 7000 RPM blasts for the drag racers.

Twisted6's mod looks like a great setup for the strip!

CJ

there were pictures of those new style valve covers on the inliners site a while back, too cool. i like the agjustable cam gears and two peice timing cover i have seen over on ebay too. i guess a lump port 7000 rpm engine might have a more suitable place than in a early 60's chevy truck but i still plan on it some day. good topic, blue c10. hr