L35's or LB4's

gstacky

gstacky

Member
I know there has been lots of information on the 2 heads on here, but I have never actually seen the answer I am looking for, so here goes:

I am planning on running a stock 4.3, with stock everything including chip. When I get this engine ready to install, is it worth upgrading to the L35 heads? I have both at my disposal, and don't plan on doing anything extreme, and have no clue how to tune, so I want to know can I run L35's on a stock chip with out any issues, or will it help in any way? Or should I just check out the stock heads and use them?
 
blacktyaffair

blacktyaffair

Donating Member
Re: L35's or LB4's

I would run the L35's. I believe you can use them with a stock chip and injectors with no ill effects. Once you are ready for a bit more out of the engine get a tune to compliment the heads and whatever injectors you decide to run. HTH
 
johnboy89

johnboy89

Member
Re: L35's or LB4's

I went the route that you plan on going except went with the L35's and found that my injectors were close to maxing out!!!! Also was chasing a knock issue that I thought was related to the lean condition, but now not sure that it was????

Just remember that you are putting more air into the engine without the engine compensating for it!!!!!
 
Icarus-54

Icarus-54

Donating Old Member
Re: L35's or LB4's

Even up the throats in the intake ports,grind the ramp back about 1/4' and put in decent valves and your stock heads (L-B4's) will work just peachy on a stock motor.
 
midnightbluS10

midnightbluS10

Banned
Re: L35's or LB4's

johnboy89 said:
Just remember that you are putting more air into the engine without the engine compensating for it!!!!!
Click to expand...


Explain please.

He's not upgrading turbos. The stock heads aren't that big of a restriction, either. It's not like they're keeping the stock turbo from flowing its maximum, or at least I don't think so. Larger ports in the L35's? Bigger valves? Same cam? Same stock turbo? Then I don't see where "more air" is coming from.
 
dgoodhue

dgoodhue

BuSTeD 4.3
Re: L35's or LB4's

The engine fueling is controlled by air pressure (map) if you changed the head flow to increase, the ECM will not know the difference. The stock motor at 10 psi will have less air in the cylinder than a l35 head at 10 psi but it will be fueled the same.
 
wildphil

wildphil

I Love My Ty's
Re: L35's or LB4's

I think you would be better off running the lb4 heads. Since you plan on keeping everything else stock including the chip. The stock chip is tuned for the airflow of the lb4 heads not the L35's.
 
Ty92Resto

Ty92Resto

Member
Re: L35's or LB4's

:popcorn:

Going to have the engine rebuilt with nothing but a .30 bore (if needed) and was going to port the heads/intake. I don't mind digging into the tuning threads but just don't want to do something stupid upfront.
 
M

MoJo

New member
Re: L35's or LB4's

gstacky said:
I know there has been lots of information on the 2 heads on here, but I have never actually seen the answer I am looking for, so here goes:

I am planning on running a stock 4.3, with stock everything including chip. When I get this engine ready to install, is it worth upgrading to the L35 heads? I have both at my disposal, and don't plan on doing anything extreme, and have no clue how to tune, so I want to know can I run L35's on a stock chip with out any issues, or will it help in any way? Or should I just check out the stock heads and use them?
Click to expand...

You must replace the stock rocker studs on the L35 heads with ARP 100-7201 in order to convert to fully adjustable lifter pre-load. The OEM or a aftermarket stock replacement camshaft in the LB4 engine has different intake and exhaust cam lobe base circle diameters and the net-lash, non-adjustable rocker studs on the L35 heads cannot correctly set the pre-load at 20 lb. torque. Your pushrod length should be checked but with adjustable lifter pre-load setting, your stock length pushrods may be within limits.That is because the adjustable pre-load setting can vary up to .040" and compensate for incorrect pushrod length.

The L35 lifters (GM-5234670) have .230" travel with .117" pre-load and lock at 20 lb. torque. The LB4 lifters (GM-5234890) have .120" travel with .060" pre-load (or 1-1/2 turn) and use lock nuts.

If you do not install the ARP 100-7201 (3/8"-24 x M10-1.50 base) rocker studs in order to convert to fully adjustable lifter pre-load, your engine will have an annoying lifter knock and will get progressively worse. If you find that the ARP 100-7201 studs are too short, you must drill out the 10mm stud hole threads, re-tap them and install 7/16" TimeSerts (Big Sert) for ARP 134-7101 rocker studs. Those rocker studs have .220" longer adjustment threads. That is what I had to do when I installed 1993 L35 ( cast #14099064 ) heads on my 1991 LB4 engine. .I first tried the ARP 100-7201 studs, with two 1/8" thick washers under the jam nuts. I decided to remove the heads and take them back to the machinist so he could drill out the 10mm threads, retap the stud holes and install 7/16" TimeSerts for ARP 134-7101 studs.

My LB4 engine has Comp Cams full roller rockers, Comp Cams 09-412-8 camshaft and Comp Cams 875 reduced travel lifters. With a stock camshaft and lifters, you may be able to use ARP 101-7201 rocker studs. . It would be a good idea to have the stud holes drilled and tapped for 7/16" TimeSerts (Big Serts) and install ARP 134-7101 studs before you install the heads so you will not have to remove them if the ARP 100-7201 studs are too short. . .
 
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johnboy89

johnboy89

Member
Re: L35's or LB4's

When I installed mine I did none of this, I installed the heads torqued them to 20 ft/lbs and that was it. Everything I read before installing the heads was that they were bolt-ons??? I'm curious if anybody has had this annoying lifter knock you describe after instaling them?



n
MoJo said:
You must replace the stock rocker studs on the L35 heads with ARP 100-7201 in order to convert to fully adjustable lifter pre-load. The OEM or a aftermarket stock replacement camshaft in the LB4 engine has different intake and exhaust cam lobe base circle diameters and the net-lash, non-adjustable rocker studs on the L35 heads cannot correctly set the pre-load at 20 lb. torque. Your pushrod length should be checked but with adjustable lifter pre-load setting, your stock length pushrods may be within limits.That is because the adjustable pre-load setting can vary up to .040" and compensate for incorrect pushrod length.

The L35 lifters (GM-5234670) have .230" travel with .117" pre-load and lock at 20 lb. torque. The LB4 lifters (GM-5234890) have .120" travel with .060" pre-load (or 1-1/2 turn) and use lock nuts.

If you do not install the ARP 100-7201 (3/8"-24 x M10-1.50 base) rocker studs in order to convert to fully adjustable lifter pre-load, your engine will have an annoying lifter knock and will get progressively worse. If you find that the ARP 100-7201 studs are too short, you must drill out the 10mm stud hole threads, re-tap them and install 7/16" TimeSerts (Big Sert) for ARP 134-7101 rocker studs. Those rocker studs have .220" longer adjustment threads. That is what I had to do when I installed 1993 L35 ( cast #14099064 ) heads on my 1991 LB4 engine. .I first tried the ARP 100-7201 studs, with two 1/8" thick washers under the jam nuts. I decided to remove the heads and take them back to the machinist so he could drill out the 10mm threads, retap the stud holes and install 7/16" TimeSerts for ARP 134-7101 studs.

My LB4 engine has Comp Cams full roller rockers, Comp Cams 09-412-8 camshaft and Comp Cams 875 reduced travel lifters. With a stock camshaft and lifters, you may be able to use ARP 101-7201 rocker studs. . It would be a good idea to have the stud holes drilled and tapped for 7/16" TimeSerts (Big Serts) and install ARP 134-7101 studs before you install the heads so you will not have to remove them if the ARP 100-7201 studs are too short. . .
Click to expand...
 
M

MoJo

New member
Re: L35's or LB4's

I am referring to installing L35 heads on a 1986 - 1991 LB4 and 1991 ZR9 Syclone engine.

Did you have 1986-1991 LB4 cam and lifters in your 1992 GMC Z79 Typhoon when you installed the L35 heads? All 1992 - up camshafts have symmetrical cam lobe base circle diameters and lifters that have .117" pre-load. The 1992 - 1995 L35 and Z79 engines that have stock cams and stock lifters will work with L35 heads with no changes..
 
johnboy89

johnboy89

Member
Re: L35's or LB4's

MoJo said:
I am referring to installing L35 heads on a 1986 - 1991 LB4 and 1991 ZR9 Syclone engine.

Did you have 1986-1991 LB4 cam and lifters in your 1992 GMC Z79 Typhoon when you installed the L35 heads? All 1992 - up camshafts have symmetrical cam lobe base circle diameters and lifters that have .117" pre-load. The 1992 - 1995 L35 and Z79 engines that have stock cams and stock lifters will work with L35 heads with no changes..
Click to expand...

I'm not sure I'm reading your post correctly, from a thread last year you mention that you don't need to do anything??

http://www.syty.net/forums/showthread.php?t=86788&highlight=L35

My block came from a Syclone I believe so it should have had a stock LB4 cam??? Did they change the cams on the Typhoons in 92????
 
M

MoJo

New member
Re: L35's or LB4's

1986 - 1991 LB4, ZR9 cam............ GM 10088148 w/o bal.shaft,. unequal cam lobe base circles
1992 - 1993 LB4, Z79 cam.............GM 10144176 w/o bal.shaft, equal cam lobe base circles
1992 - 1994 L35 cam.....................GM 10144047 bal. shaft, equal cam lobe base circles
1995 L35 cam...............................GM 10241693 bal. shaft, equal cam lobe base circles (same as 1992-1994)

My previous discussion was before I tried the ARP 100-7201 rocker studs and determined they will not permit a fully adjustable lifter pre-load . I removed the L35 heads and the ARP 100-7201 studs.and washers took my L35 heads back to my machinist. He drilled out and tapped the stud holes and installed 7/16" TimeSerts (BigSerts) for ARP 134-7101 rocker studs. .

I have a different valve train. My LB4 engine has a Comp Cams camshaft which has 1.190" diameter cam lobe base circles on the intake and exhaust lobes. . The 1987-1991 LB4 Z engines have cam lobe base circles that are 1.380" intake and 1.335" exhaust. ( I suppose that is to compensate for the valve rotators on the exhaust valves) The 1992-1995 L35 W engine has symmetrical cam lobe base circles that are both 1.260" diameter which makes the L35 net-lash lifter pre load setting impractical of not impossible. . The 1992-1995 L35 W engine has lifters that have a .117" pre load.at 20 lb. torque. The LB4 Z lifters have a ,060" pre-load.setting or about one turn. (.060" x 24 threads per inch = 1.44 - .500" for 1.5:1 rocker arms = .94 or about one turn )

I am using Comp Cam 875 "reduced travel lifters" which mean they have a lifter push rod seat that is .060" deeper at 2.600" height at zero pre load. Stock lifter push rod seats are at 2.660" height at zero pre load. . The Comp 875 lifters has a pre-load of only .004" pre-load or 1/8 turn from zero pre load. . The Comp Cams lifters combined with the Comp Cams 1.190" diameter (.070" smaller) cam lobe base circles along with the .056" higher push rod seat than a stock lifter, enables me to use Comp Cams 7940 chromemoly push rods that are 7.200" long and are the same same length as stock push rods. If you use your stock 1987 - 1991 LB4 Z cam and lifters, ARP 135-7101 rocker studs, with the 1992 - 1995 L35 W heads and camshaft, the LB4 Z push rods may be to short by .120" intake and .075" exhaust. That much difference in push rod length is beyond the range of your LB4 Z lifters (GM 5234890) which have adjustment range of .120" . The 1992-1995 L35 W lifters (GM 5234670) have .234" adjustment range and a net lash (non-adjustable) setting of .117" . However, the L35 lifters would have a adjustable pre load range from .077" to .157" with ARP-134-7101 rocker studs.. .
 
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gstacky

gstacky

Member
Re: L35's or LB4's

Good info, thanks guys, I think I'll just stick with the stock heads, fyi the engine I'm using is from a 93 Ty, and I had never heard of the differences in the cams before, useful information.
 
It's just a six

It's just a six

Super Member
Re: L35's or LB4's

Can you just install screw in studs & standard push rods (1986 - 1991 LB4, ZR9 cam.) & adjust them regardless of which cam you are using?
 
dgoodhue

dgoodhue

BuSTeD 4.3
Re: L35's or LB4's

MoJo said:
1986 - 1991 LB4, ZR9 cam............ GM 10088148 w/o bal.shaft,. unequal cam lobe base circles
1992 - 1993 LB4, Z79 cam.............GM 10144176 w/o bal.shaft, equal cam lobe base circles
Click to expand...

Our stock SyTy cam is part number 10214714 which is slight different than the regular LB4 cam.
 
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