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Old 01-18-2005, 06:31 PM
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l-98 corvette heads

hi
do l-98 heads flow good after a full port job
and can they feed a 400hp engine with the 1.94/1.5valves


a nother qeustion is how bad are small cracks a round
the head bolt on the under side of the head a guy told me
this was normal for these heads (so i gave him the look ???lol)

thanks martien (holland)

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Old 01-18-2005, 07:35 PM
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Here are the flow numbers for these heads in stock form, from Chevy Hi Performance magazine:

Lift.................Intake.................Exhaus t
0.100.............50.......................49
0.200.............120.....................96
0.300.............160.....................123
0.400.............186.....................140
0.500.............196.....................155
0.600.............199.....................159

These numbers will support about 400 HP on a well built engine, maybe 350 HP on a more mild one.

I did some porting on these heads and got these numbers:

Lift..................Intake...................... ......Exhaust
0.100..............58.0......(+8.0)............... 49.7......(+0.7)
0.200..............122.5....(+2.5)...............1 00.7....(+4.7)
0.300..............178.8....(+18.8).............10 3.9....(-19.1) <-- bad test
0.400..............215.2....(+29.2).............15 7.5....(+17.5)
0.500..............224.1....(+28.1).............16 1.0....(+6.0)
0.600..............230.4....(+31.4).............16 3.5....(+4.5)

These numbers will support about 460 HP on a well built motor and about 400 HP on a more mild one. I was shooting for 500 HP from this port job and I was not satisfied with these numbers so I am currently doing more porting to them. You can look at my work so far in the attached file, to give you an idea of the kind of porting that will get the above gains.


As for the crack around the bolt hole, I would not take a chance with it on a high performance motor, too much stress may cause the crack to gradually spread into a water jacket, causing a leak, or spread into a combustion chamber possibly causing the head to fail. I would get it repaired by a skilled machinist. Usually aluminum heads are much less costly to repair.
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Old 01-18-2005, 07:53 PM
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Re: l-98 corvette heads

Quote:
Originally posted by martien bierlee
hi
do l-98 heads flow good after a full port job
and can they feed a 400hp engine with the 1.94/1.5valves


a nother qeustion is how bad are small cracks a round
the head bolt on the under side of the head a guy told me
this was normal for these heads (so i gave him the look ???lol)

thanks martien (holland)
If there is a small crack starting out of a bolt hole, it's an easy fix. Have your machinist sleeve the hole, if the crack extneds a little further out, you can pin it and you'll have no problems.


Brian
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Old 01-19-2005, 02:23 AM
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thanks guys
were the ported heads out fitted with bigger
valves (the heads look very good) then 1.94/1.5
and how about the self alinging rockers
gen yoe replace them for something els
(roller tips) using hardned guide plates and push rods


thanks again martien
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Old 01-19-2005, 09:46 PM
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Yes they were fitted with larger 2.000 and 1.560 valves, screw in studs, guideplates, and .090 machined from the valve guide bosses. I have 1.6 roller rockers for these heads, the heads needed to have the pushrod holes machined for that as well. If you have the guideplates installed you don't need the self aligning rocker arms. If these are heads you are rebuilding, you might want to have the valve guides checked for wear as well.
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Old 01-21-2005, 03:26 PM
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thans for the good repys
i ve you have to select between
these heads 462 fully ported 1.94/1.5or
the l 98 heads also ported witch will it be


engine 383 chevy 4bolt
edel rpm mnifold
edel 600cfm
headers 2.5 dual syst
cam 230 in 230 ex lift both 0.480
roller tips 1.5
windage tray

martien
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Old 01-22-2005, 12:17 AM
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Personally, I would go with the L98 heads. The power potential of either of these heads depends on how they are ported. while the 462's may flow a little better to begin with, they are iron heads which means they are heavier and will not be able to tolerate high compression as well as aluminum. The L-98 aluminum heads are easier to port, will handle higher compression, and weigh about 50 pounds less. Just be careful running either of these heads on a 383. with the 462 head's 64cc chamber you will be around 11.2:1 compression, and with the L98 head's 58cc chamber you will be over 12:1 if you use flat top pistons and a zero deck. You might be able to use the aluminum heads with this much compression if you use octane boost and premium fuel, but the iron head, even with slightly less compression, would be playing with fire. You could use a dished piston if you need to lower the compression.
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