How adequate are stock heads?

[Edmond]

I was pondering this question today. How adequate are they? Now much power could the 1.94/1.5 valves be good for? Could they achieve 325 horsepower for the L98?

I was thinking about what to do with my heads later this year. 1.6 roller rockers are definite. What if I rebuilt them to stock spec and ported the opening from the intake manifold?

 

[MoeJr]

If you have the heads ported I would think they would support 400HP.

 

[Edmond]

If you have the heads ported I would think they would support 400HP.

With bigger valves, right?

 

[MoeJr]

No with stock size valves. Going from the 194/150 to 202/160 may net you 5 hp on a 400 hp engine.

 

[Vettefan87]

My brother was telling me about the Lingenfelter book he was reading on small blocks, and said the L98 heads once ported are really good for a street machine.

 

[tnovot]

What if I rebuilt them to stock spec and ported the opening from the intake manifold?

Edmond -
Not sure what you mean by stock spec. As long as you are going to have the heads done (valve guides checked and/or refurbished and the valves ground), get a good 3 angle valve job and at least a stage 1 porting. Having the heads and intake ported to match and blending the flow off the valve seat really helps.

I agree with Moe that 1.94 & 1.5's would be good for street use. Many early H.O. double hump heads were 1.94's and they made good power.
Terry

 

[bossvette]

http://www.amazon.com/exec/obidos/t...f=sr_1_9/102-9960560-1472926?v=glance&s=books

here is a good reference, Ligenfelter used the stock Aluminum heads on most of his builds

 

[SPANISHVETTS]

Boss – that is one of my favorite books. I am glad to see it back in print, there was a time just before JL’s death that it was almost impossible to find. Every one who builds or dreams of building SBC should have a copy or two in easy reach. Here is the copy I gave to my Polish friends at Corvette Club Poland in Warsaw.

Edmond Go with a serious porting job and have the seats 3 angle ground as suggested by tnovot… You will run out of $$$ on the intake long before the stock valves stop passing gas. Back when Thunder had the L98/350 with stock ported heads it dynoed at 289rwhp with the stock TPI(well ported) and exhaust. 289X1.20= 346++ HP at the flywheel.

 

[Edmond]

I had that Lingenfelter book, maybe I should've never gotten rid of it!

 

[Vettefan87]

I had that Lingenfelter book, maybe I should've never gotten rid of it!

Craig has it about read cover to cover in about three days. I am going to have to read it just to understand what he is talking about. One thing he did say is that Torque is what you want for a street machine. He said not to change the runner lengths if you still want to feel the same gobs of torque.

 

[Edmond]

I'm thinking about Arizona Speed and Marine runners with a ported plenum and ported intake.

 

[Vettefan87]

I think he said a superram, and stock runners or larger runners was the ultimate best for torque, I am not sure I will have to start reading.

 

[thirdtimevetteowner]

I have a question about the stock alum. heads. Will the stock springs support 1.6 rockers? Or would they reach coil bind, or not have enough clearance between the coils at max lift? I have searched all over trying to find the specs on them, to no avail. Any help would surely be appreciated. I have a set of Comp Pro Magnums, hardened guide plates, and pushrods, sitting in the boxes waiting, but reluctant to install them for the obvious reason. They were meant for a 350 my son has in his S-10, but I know for SURE his springs won't handle them, so we went with 1.5's on it. Thanks in advance.


Rich

 

[Vettefan87]

I have had 1.6 RR's on my vette for about 2000 miles, and no problems.

 

[SPANISHVETTS]

I have a question about the stock alum. heads. Will the stock springs support 1.6 rockers? Or would they reach coil bind, or not have enough clearance between the coils at max lift? I have searched all over trying to find the specs on them, to no avail. Any help would surely be appreciated. I have a set of Comp Pro Magnums, hardened guide plates, and pushrods, sitting in the boxes waiting, but reluctant to install them for the obvious reason.

You should be ok to 5 grand or so. Are you running auto or manual tranny – I would hate to miss a shift with the 1.6s on stock springs.:ugh

They were meant for a 350 my son has in his S-10, but I know for SURE his springs won't handle them, so we went with 1.5's on it. Thanks in advance.
Rich

We just parted with our SBC powered S-10. (Impossible to register in Spain.) What a stump pulling tire ripping sumB!tc# that was. I loved to slowly add power while a BMW M3 was trying to pass me and then stomp it just when he was wound out and shifting.:W That darn thing would light up the tires at 80 MPH when it down shifted!

 

[vetteboy86]

I would recommend that Ligenfelter book to anyone.

Edmond, the L98 Aluminum heads are one of the better heads out there. It is hard to explain in words, but just get that book back and read. The best thing you can do to help these heads is the bigger valves, three angle valve job, and pocket port them. It is important to know that stock they are 58 cc which is small, and could produce higher compression. Also they have a good EI ratio, which corresponds to the interport realtionship. Exhaust port flow is expressed as a percentage of the intake port flow at a specific valve lift. In other words, you want to get air in, but getting exhaust out is extremely important. You can port them slightly and have a great street head. I wouldn't get rid of them unless you were going to a full race engine. Remember that if bigger was always better everyone would run the 220 cc intake. This is not always the case. The stock head is 163 cc and a mild port job that would enlarge them to 180 cc is ideal for street.

ONce again get the book and read it cover to cover more then once.

 

[thirdtimevetteowner]

Thanks for the info, you guys. It's an automatic Vettefan, so I'll just per it in D, and stomp on the pedal til I see the elapsed time and MPH light up at the far end of the track.

We can hardly wait to fire the S-10. He was wiring up relays and such yesterday, so it's close to being ready to oil up, then "fire in the hole!" One thing for sure, he ain't talking me into a grudge race!! lol We're looking for 11's, if it'll hook at all.

Funny stuff, SPANISHVETTS.

Thanks again. Now all I gotta do is get rid of those pesky oil drippers, but it will be worth it.

 

[Vettefan87]

Thanks for the info, you guys. It's an automatic Vettefan, so I'll just per it in D, and stomp on the pedal til I see the elapsed time and MPH light up at the far end of the track.

Don't do that, manually shift through all the gears... Throw the gear selector down into 1, and shift at about 4700 on the dash, which will ultimately mean about 4900-5000, since our tach's are somewhat slow. It is a blast if you have never done it before, definetly an adrenaline rush.

 

[vetteboy86]

The stock valve springs will probably only support the 1.6 rockers at 5500 RPMs. Or so I have read.

 

[MoeJr]

Will the stock Valve covers clear 1.6 Roller Rockers? Be a cheap mod for my 84.