I know it's probably a stupid question, but I'm just curious to know if the LO5 heads could be made to flow decent with some serious porting. I know they're fairly restrictive in stock trim and that I'd probably lose a good bit of low end torque and fuel economy by messing with them, but they're what I've got, and I'd like to see if I could work them over to support 300+ hp. Anybody ever tried this with any success?
Thanks,
Tony

 

i dont recall a LO5 head...so im gonna assume your talking about LO3 swirlport heads...well yea your right...they are junk..porting will get you some more flow, but theyll still suck..
there decent for low end, but the port design really hinders any performance above idle lol

i have a set of LB9 castings..these are the better 305 head..

i have no use for these so if u want them pm me..i have a few other things that would wake 'er up a little

 

Don't waste your time. It will cost you more in electricity and grinding points than a set of halfway decent castings will cost.

 

Close. The LO5 is the TBI 350 used in 87+ trucks and Blazers.
210 hp. 300 tq. I think the heads are swirl port along the same lines as the LO3 ones.
Tony

 

The thing is that the LO5 heads are small chamber (I believe). There seems to be a shortage of small chamber heads around here. I'm trying to build this engine as cheap as possible so If I have to do a good bit of grinding, that's no problem. I get the bits from work for free, and electricity isn't that expensive. I just wonder if it can be done, and if anybody has tried it with success.
Thanks,
Tony

 

f-crazy, how much you want for those LB9 heads?









edited for spelling

 

jason..you have a pm!

 

Out of curiosity, what engine do you have in your car?

 

Anything can be done, given unlimited time and resources. You only have to decide how much labor investment is worth the price of a respectable set of castings.

I've ported mid-'70s smogger heads to 184cc intake runners with 1.94/1.50 valves. They should flow as well as factory 180cc castings, if not better due to teh short side radius and valve bolw treatments.

The question is, "How much is your time worth?"

 

Well, right now about $24.50/hr. but when this job is over, not very much. It'll either be that or sit in front of the computer all day.
Tony

 

To make respectable flows on any "swirlie" heads, the first thing to do is the valve bowl work. If the castings will allow the removal of the swirl "hump" you may have a chance at making some decent flows. If not, you'll find out as soon as you cut out (or possibly, through) the valve bowls and will limit your losses to the time spent. I've cut out the swirl "humps" and found that they are simply extra cast iron on top of the mold, and the mold isn't necessarily contoured to match the "hump" on the cooling jacket side of the valve bowls.

The next thing you'll need to do is examine the castings to determine how much you can safely raise the port runner roof. If you can cut/machine/grind the runner height to at least 90% of the port height all the way through, you'll have a chance at decent flows. Try to maintain a minimum casting wall thickness of 0.150" anywhere in the runners, and at least 0.200" over the deck. You can often look through the cooling passages to determine if the mold core shift is moderate or severe. Severely shifted casting mold cores may make the castings already too thin to safely remove any more material.

I've cut out the bowls without breaking through the castings to clean up the swirl "humps":

 

The answer to your question is yes and I gained 40 HP to the rear wheels. So it is not a complete waste of time.

 

Would it be wise or even necessary to try to reshape the combustion chamber? It seems like the protrusion could stand to disappear, or at least be ground back a little to gain some flow from the intake valve.
Thanks for the help!
Tony

 

Out of curiosity, what did it do for torque?
Thanks,
Tony

 

Also, while I'm thinking about it, I had the idea of running a much higher lift cam and or 1.6 rockers to help offset the effect of the smaller valves. Am I thinking along the right lines?
Thanks,
Tony

 

Well, I got into them tonight. Vader you were right. The swirl hump comes off with no problem. I'm curious now about blending the runners into the bowls. The intake runners seem to neck way down at the transition into the bowls and I'm wondering if I should try it enlarge this, or just clean things up a bit and call it good.
Any thoughts?
Thanks,
Tony

 

Tony,

Take a close look through the coolant openings and try to determine how Much material you have to work with. If I understand your description, the bowl area is significantly larger than the runners, correct? The valve bowls are usually larger out of necessity, since the flow has to diverge at that point and flow to all open areas of the valve as equally as possible. You'll want a fairly deep and straight bowl to be able to hold a volume of air behind the valve. As long as the intake runner doesn't get smaller as it approaches the valve bowl, you should have no restriction problems. If the runner does "funnel" into the valve bowl excessively, you may want to open it as best you can and smooth the transition to the valve bowl. There is a little taper toward the valve in almost all factory castings.

While you're in the bowl area,you can trim the excess casting around the valve guide boss to limit the volume it occupies - there is a lot of unnecessary metal around the stems, and that area can be a good indication of core shift. If the valve is drilled way off-center from the cast guide boss, you can bet the lower mold cores were shifted in that direction. You'll also want to smooth the hump of material at the valve edge (short side radius) so that air doesn't have to reverse its course to flow around the near side of the valve.



Remember that there are cooling passages in there, so you have to limit the amount of material removal. I don't know what the factory design limits actually are, but it seems that most casting walls are at least 0.200" thick on heads with limited core shift. The deck surfaces always seem to be a little thicker, but if the mold cores were skewed when cast, you could have less to work with.

 

Actually, what you mentioned further down was it. The port actually necks or funnels down right as it comes into the bowl. If I had to hazard a guess, I'd say the engineers designed it that way to increase velocity as the charge entered the bowl to increase the "swirl" effect. The engine these are going on is never going to see anything much above 5000 rpm so I don't know If I'll see much of an advantage by enlarging this. I've got enough time in these now that I don't want to wreck the castings.
I'll probably just radius the edges where the runners meet the bowls. I've also cleaned the short side radius up pretty well too.
Now I just need to figure out what to do with the bowl itself. It's kind of got a "spiral staircase" deal going on with what's left over after removal of the swirl hump. Hopefully there's not a water jacket that extends into it. I'll work that and clean up the valve guide bosses like you suggested and probably call it good.
Thanks!
Tony

 

LO5 was also used in the Cop Car Caprices.