Can someone give me an estimate of what a set of 85 lg4 heads that had been pocket ported and portmatched to the intake with the exhaust polished would flow aproximately. I just want this information so that i can put it into desktop dyno. I know that they are sucky heads to start out with, but it is what I have for now, and I know someone who will port them for free.

Thanks

Ben

 

Sorry I don't have numbers, I wish I did though. As far as the heads sucking, at least there not the swirl heads the LO3s have. I've heard these heads respond well to porting. Hell, the L69 cars and the 85'-86' TPI cars all used the same heads, so they can't be all bad. I'm gonna try to find a centerbolt set to swap into my 91' RS.

 

There isn't any real way to give you a specific number that the heads will flow. Everyone that ports heads ports them in a different way so the flow values will be different from head to head and from port to port.

 

use the pocket ported wedge head setting on desktop dyno.

 

According to F'Bird-88, the stock LG4 head's intake port is 167cc from the factory, not the 155cc GM says. He did this by physically cc-ing the passage. Thus it is actually really close to a Vortec L31's 170cc intake port.

Gasket matching, a little hogging out and bowl blending should take it out to around 180cc. That should allow enough flow for around 400hp on a good smallblock

 

Are you serious? The intake flow is nearly the same as the WP 305 Torquers! I am getting these heads for my LO3 for sure! Is that the older style LG4 with perimeter bolt valvecover or the centerbolt heads from an '87? My car had centerbolt heads but my new intake is the old style, so I'll probably get the older heads so I don't have to mod my intake.

 

Yep, but you must remember the S/R's have more meat so they can be hogged out further than the GM stockers, also other important advantages. Heres the good casting number for 58cc cast heads (14022801)
If you looking to do some cheap yet effecient upgrading look for that number, these are side bolt but have the largest runners of the cast 58cc heads.
SSC

 

True, WP heads have more potential, but you pay dearly for it. I don't have $800 lying around, and my 305 isn't wild enough to need a really killer set of heads, so think a set of midly ported LG4s will do just fine. At least they'll be way better than my stock swirl heads. SSC, the heads you mentioned, what years were they availible, could I find them other cars besides F-bods? Side bolts aren't a big deal to me, saves me from having to spend money on intake mods, and I doubt these would cause any problems with all my 91' components.

 

The 305 heads I'm going to port are the "601" variety. They have a 58cc combustion chamber.

(The S/R heads have the more advanced kidney-shaped combustion chambers, much like the Vortec's do.)

It is worth about 10 hp more to have the intake valve enlarged from the stock 1.84 inches to 1.94 inches.

The best source for info and materials to port these 305 heads is available at the Standard Abrasives website. They sell a kit that covers everything.

 

Can't tell you what your results were from porting your heads
but stock, they flow around 185cfm@28".
The ones I ported ("416 castings") came out to 225@.450" intake
and 140@.500" ex. I installed 1.94's and 1.60" exhausts
I did quite an extensive port and polish job, removing about 10cc's of metal out of each port. I also filled in the exhaust heat riser passages with molten alumium (old cast piston) to improve
the ports. The void in the roof near the rocker stud (intake port)
accounts for the extra port volume in these heads. So don't compare them to other 170cc heads. You can fill in that void with epoxy and gain some volosity.
You should be able to have your heads flow tested for about $60.
I'll be doing another set soon and will post those results.
I'm looking to improve the exhaust port this time to around 160.
In desk top dyno, the pocket ported head choice would over
model my heads. They fall somewhere in between stock and pocket ported in this program. Hope this helps...

 

I understand the pocket ported but is the wedge the style of head to choose for this.

Thanks

Ben

 

Yes....

 

The 14022801's are found on early 80's trucks including blazers. They will work fine on your 91 as long as you elongate the intake manifold bolts above 5&6 and of course swap valve covers.
SSC

 

I can only judge the relative merits of the 416 LG4 heads and WP S/R 305 by visual comparison and the way the car runs with the WP's. I did the SA job on the WP's, but didn't have them flow tested.

The port shape is much better, the chamber shape is completely different (although the same volume), the WP's cleaned up much easier (I did one cylinder's worth on a 416 for practice), and the car runs fantastic (no dyno #'s or ET's yet).

The WP's flow 198 @ .400", 213 @ .500 unported. Porting can reasonably be assumed to add 10%.

You can pick up the S/R 305's from Competition Products for about $600 unassembled (which is the way you want them if you're going to port them). After you figure in the machine work on factory heads to open up the intake to 1.94", machine for screw-in studs, and the very likely guides they're going to need, plus the standard valve job, you're looking at close to that amount.

Doesn't answer the original question, but if you're going to spend some money, makes more sense to put it where it will do the most good.

 

For a centerbolt valve cover motor, look for "081" or "083"
heads. They're not too bad a casting and should port up
just as good as the old 601's and 416's. All of these heads need extensive porting, a little pocket port ain' gon'a cut it. the 305
heads should be upgraded with 1.94 intake valves.

 

I don't have the cash to add bigger valves right now, but I assume even with the smaller valves these heads will be an improvement over what I have now.

 

Which casting number would the heads off of an 85 lg4 be. I also dont have the money for the larger valves right now, but have them off and my cousin is porting and gasket matching the intake and exhaust ports along with the intake manifold. I was there while he did the first one, but he hasnt done the second. He removed a lot of material. He removed the material and conoured the shape so it would flow better. I can feel the difference where there used to be a lip it is smothe. Would these be good enough for a 350 except for the intake valve size is smaller. I hope so because that is what they are going on because it was either those or a set of heads from 73 with like 1.72 intakes and 1.4 or 5 exhaust and 76 cc combustion chambers that I have laying around and I know that I would prefer these. I have already talked to people about that though. When I have tested it on desktop dyno it only shows about a 10 hp increase when going to 1.94s, but the one thing that I see is that it would also continue my peak power a bit higher. Any other opinions on how this will do are appreciated.

 

To model stock 305 heads in Desktop Dyno you would pick
"low performance stock ports and valves", with the appropriate valve size. If you just pocket port them, it will not even equal
a "wedge stock ports and valves".

Don't expect to get a head even equal to a 350 head unless
you install the larger valves. You can find good used ones.

"Wedge stock ports and valves" would refer to a decent stock
60's camel back head like 462's with 1.94x150's
or a wp305 torquer out of the box.

 

I tried it with low performance pocket ported stock valves, and wedge pocked ported stock valves and it doesnt change.

 

Those two choices have the same "flow coefficient"
The program is not perfect.

Both those choices will over "model" even a professionally
ported 305 head.

 

So what should I choose to be more realistic. Is there a way to do so. I am choosing them with the 1.84 valves so I dont see how it would be too far off. I understand that obviosly something is off if the two setups which are different are the same in the program but I dont think that I should choose a non ported stock low performance head when we have gasket matched the intake and exhaust runners ( think that is the right term, the part between the valves and the manifolds) and also pocket ported them.

Thanks

Ben

 

Think what ever ya want. But if ya lie to the program,
it will lie right back to ya.

Personally I'd turn the Desk top Dyno off and go work on the
heads... squirt a garden hose in the port and watch where the
water flow is concentrated. ( along the common wall and roof)
and work on those areas.

 

Ben, I havent used DTD in a while well since my sharware version crapped out, so I forgot all of the options. You should be able to lie a bit on there to come up with some close numbers. Try this, select a perforamnce head with the estimated flow numbers of the 305 heads before porting, then to get an estimate select domed pistons that will put you in the same compression range as the stock pistons and the 305 heads. Shoot for somthing that will give you around a 10:1.

Lets see Im getting confused (its late) select a standard bore 350 with a dome +10cc with a 68cc head by my tired reasoning that will gibe you the effect of 58cc heads or atleast you see what im getting at.
SSC

 

Thats cool. Thanks for your help. It is actually more simple than that because it gives you the option of just selecting the compression ratio. I can give it the compression math and tell it that it is a 58 cc head but I dont know what to put for the Piston Down Bore @ TDC. It is the distance from the deck to the top of the piston. Do you know what that would be on a 350. Also what is the standard head gasket thickness.

Ben

 

It also wants to know what the volume above the piston is because it has valve reliefs.

Thanks Again

Ben

 

Anyone know this?

 

Go to the KB performance piston web site.
there are good piston specs for the different available
factory like replacement Silv-o-lite pistons.
Most factory pistons are either .025" or .045" down the bore.
A common flat top 350 piston would have a 5/6 cc valve relief.
Most factory motors have a .015" steel shim head gasket.
About 3.5 to 5cc's. Felpro composite gaskets are .038 to .041"
thick with a bore size of 4.166. CC's range from 8.8 to 9.1cc's compressed. The factory block deck height is 9.025" but varies a little from block to block.

http://www.kb-silvolite.com