Every thing I have searched for on this topic seems to pertain to the tpi. What I've come to believe about these heads are as follows: (1) They must be cast#113 '87-'91...(2) current egr will be inoperable....(3) must change to centerbolt valve covers ....(4) will have to drill and tap for accessory holes....( 5) have larger intake valves,but flow better on the exhaust side than a non vette head...Can anyone add to this?.... Is anyone using them on a lg4 '86 and previous years?.....Thanks

 

i don't think you'll need to tap acessory bolt holes. not sure why they'd flow more than heads offf a camaro, don't see why the egr wouldn't work, it's bolted to the intake. you would need center bolt valve covers or and adapter to use perimter bolt valve covers. then again you've looked in to it i haven't so i may be wrong, for the first time. sorry i couldn't be more definate.

 

Theres no heat riser, thats why the EGR wont work. You can stick it on there, but it wont do nothin.

I dont think you'll have to tap any holes if its a v-belt setup. I know with the serpentine setup there is a hole missing in the passenger side head that I had to drill+tap, but I'm pretty sure v-belt setups do not use that hole. IIRC its the upper hole in the front face of the head towards the exhaust side of the head.

 

Right, no exhaust crossover passage, so the EGR won't work.

Intake valve is the same size as most other 350 heads, 1.94". Don't know about the exhaust flow, factory heads have so much variation it's hard to make generalizations like that, but aluminum is much easier to cast precisely than iron, so it's very possible.

you only have to change to centerbolt valve covers if you don't already have them. It would be fair however to say that they take centerbolt valve covers, like the later iron L98 heads do.

What is it you're really asking? Are you wanting to know what you'd have to do to put them on some particular engine? If so, what engine?

 

I guess I'm really wanting to know if the CCQ-jet and my factory 4bbl aluminum intake will keep up with this set up. My lg4 305 is such a low mileage one that I decided to build on top of that instead of finding a 350 block. I'm in the process of selecting my headers and heads right now. The cam I've purchased is a wolverine blue racer .447/.443 280 dur. I'd like to keep my rochester carb and aluminum intake and still allow the computer to be funtional. I thought if I could find some of these heads at a good price I'd gain a few advantages on the cheap, but so far it seems that they are not easy to find for sale. Thanks for the replys

 

They'd probably be OK for that, but not much of an improvement. In bang for the buck terms, they're not much help in your situation; just port your 416 castings instead.

That cam is a dog, I'd take it back and get something better if I was you. Get a Comp XE256 instead. Take a look at the advertised duration, then compare it to decent cams from Comp, Lunati, Crane, etc. ... a cam with 280 degrees of seat duration should have a .050" duration of around 230 degrees and around .480-.485" of lift; if it doesn't, then all you're getting is a real lopey idle, with none of the benefits like improved upper-RPM performance, and all of the disadvantages like no low end and bad gas mileage and all the other "too much cam" problems. Basically, a monkey-spank cam, not a go-faster one.

 

Actually, this is the cam that Crane recommended for the 305 lg4. Just to be sure I double checked the #'s. It states a .295 cam lift (I & E) , A .443 valve lift (I & E)... 214 @.050 dur. ....280 advert dur. The factors they considered were my gearing (3.42) and plans for headers . Gotta be a big improvement over the lg4 cam I figure

 

For street use, you want a cam that puts the motor's max power band in a range you can use, let's say 1500-5000 RPM in this case. You want as little duration beyond that, that is, you want the cam "cracking" the valves open as little as possible as it opens them, and leaving them "hanging" just barely cracked before it lets them close. That means you want the "advertised" and the .050" duration as close to the same as possible, within the limits of starting and stopping the valve motion without bouncing. And, you want as much lift as possible, within various other limits.

OK... you have a cam with 280 degrees of "advertised" duration. That means the valves are off the seat for 280 out of 720 degrees of crank rotation in one complete cycle. Out of those 280 degrees, 214 of them (the .050" duration) produce meaningful flow. During the other 66 degrees, the valve is not closed, but it's less than .050" open. It's open just a crack, just enough to "leak". It's that "leak", especially at the intake valve opening point, that kills idle and low-end torque.

Now look at the XE256. It has 212 degrees of .050" duration, essentially the same as the one you have; .447" of intake, and .454" of exhaust lift, again comparable to the other; but look at the "advertised" duration. 280 vs. 256 degrees. That means that the one you have is "leaking" compression for 24 more degrees out of the cycle than the XE256, without giving you anything in return! That's why it's a terrible cam: it will not give you one iota more performance than the 256, but you'll be paying the penalties of 280 degrees of rough idle that your carb can't cope with, and the bad gas mileage that goes with poor low-end performance, and the lack of low-end torque too. If you had a cam that had 280 degrees of seat duration, and the now normal 230 degrees of .050" duration that 280 cams have, at least you'd be getting some top end RPM potential out of the deal; but you're not. It's a pitiful cam, good only for that "king of the drive-in" lopey sound along with all of the bad things that go with it, but no performance payoff.

Get rid of it, get the XE256, it will actually work. Anybody that recommends a cam with 280 degrees of seat duration for a stock LG4 has no business recommending cams.

 

Very well written post, RB. That post could actually go in the "Tech articles" section and would benefit many readers, IMO. Thanks for well written, easy to read and nderstand, accurate post.

 

Yes, I agee also, very well said, but when I ordered the cam I made it known that it would not be for a stock rebuilt motor. I told them other things besides the headers and gears- - not sure though? so...what does it take to make use of a cam like this....I'm sure $$$ is part of it It's a" pitiful cam" or pitiful for an lg4? You tell me!

 

And another thing, the packaging states that it's "a cam with good idle for street use in the 1500 - 4500 range". Just thought I'd add that info....

 

Back to the heads: The aluminum L98 heads have 58cc chambers to produce the same power as 64cc L98 cast iron heads on a 350. Just putting them on a 305 will produce the same static compression that it originally had, but due to the heat loss through the aluminum will actually produce less power than all-other-things-being-equal cast iron heads. For use on a 305, they should be shaved to about 52-54cc.

Also, those heads don't have exhaust cross-over passages, so the LG4 EGR won't work without some type of modification. May not be an issue, but may cause pinging at part throttle.

Bang-for-bucks wise, port the stock heads. Putting in 1.94 intake valves and screw-in rocker studs also advised (new valve springs, too, of course).

 

Can't find the l98 aluminums for less than $600 anyways ... s/r torquers are looking better all the time.....Found some 86 l98 cast iron vette heads for $150....Would it cost more to machine those than S/r's......

 

L98 cast iron vette heads would be totally useless for what youre doing. They have 76cc chambers or something silly like that.

The L98 aluminum heads are great if you pick them up cheap and can work on them yourself. Otherwise, it gets expensive real fast.