question about 86 LB9 heasds and the LO5
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Joined: Mar 2001
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From: Dixon, IL
Car: RS
Engine: 305
Transmission: 4L60
Axle/Gears: 3.42
question about 86 LB9 heasds and the LO5
I'm rebuilding the LO5 for my 84, and need to find a set of heads, so far I haven't found any good 1.94s, but I figured the LB9 heads would work for now
The LO5 motor is a flat tappet motor, I already have the cam and intake (non center bolt) I've read you have to change somethings on the heads to get them to work? is this true? even on a flat tappet engine?
Vic
The LO5 motor is a flat tappet motor, I already have the cam and intake (non center bolt) I've read you have to change somethings on the heads to get them to work? is this true? even on a flat tappet engine?
Vic
Supreme Member
Joined: Jan 2001
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From: Surrey, BC
What do you mean by changin things?
They will bolt right on, the only problem I can think of is the 58cc chambers will yield a higher compression ratio on a 350. Make sure your springs match the cam.
They will bolt right on, the only problem I can think of is the 58cc chambers will yield a higher compression ratio on a 350. Make sure your springs match the cam.
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
You can improve the heads, but you don't have to do anything to make them work.
Improvements would be 1.94" intake valves (requires machine shop work), valve springs as previously mentioned, and screw-in or pinned rocker studs. Some basic porting, especially bowl area work, would substantially improve them. A full porting job following Standard Abrasives Do-It-Yourself Guidelines would be the cat's meow.
If you're worried about high compression, you can unshroud the valves a little while doing the porting and increase chamber volume a little. Most likely, though, the LO5 has dished pistons, so the smaller chambers would actually be beneficial.
BTW, those heads have the slotted pushrod holes, so you don't want to use self-aligning rockers (which I believe an LO5 would have). And, if going from roller lifters to flat-tappet, you'll need different pushrods.
Improvements would be 1.94" intake valves (requires machine shop work), valve springs as previously mentioned, and screw-in or pinned rocker studs. Some basic porting, especially bowl area work, would substantially improve them. A full porting job following Standard Abrasives Do-It-Yourself Guidelines would be the cat's meow.
If you're worried about high compression, you can unshroud the valves a little while doing the porting and increase chamber volume a little. Most likely, though, the LO5 has dished pistons, so the smaller chambers would actually be beneficial.
BTW, those heads have the slotted pushrod holes, so you don't want to use self-aligning rockers (which I believe an LO5 would have). And, if going from roller lifters to flat-tappet, you'll need different pushrods.
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
I'm afraid I wasn't fully with it in my last reply.
LB9's came in different styles through the years. Which castings are these heads?
Pushrod requirement will be dictated by the type of lifters. If flat tappet, you need the earlier longer length.
The way the rockers are guided is dictated by the type of pushrod holes. If earlier style with slotted, you need non-self-aligning rockers. If later with larger rounded holes, then self-aligning. You can drill out the slotted type to use self-aligning rockers. Perhaps that's what whoever was telling you about drilling meant.
They had some wierd mixes out there in the early LB9 days, so you need to know what you've got.
LB9's came in different styles through the years. Which castings are these heads?
Pushrod requirement will be dictated by the type of lifters. If flat tappet, you need the earlier longer length.
The way the rockers are guided is dictated by the type of pushrod holes. If earlier style with slotted, you need non-self-aligning rockers. If later with larger rounded holes, then self-aligning. You can drill out the slotted type to use self-aligning rockers. Perhaps that's what whoever was telling you about drilling meant.
They had some wierd mixes out there in the early LB9 days, so you need to know what you've got.
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