What's the difference between post/pre '87 heads
Thread Starter
Melting Slicks
Joined: Feb 2002
Posts: 2,699
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From: The Black Hole LA
What's the difference between post/pre '87 heads
Looking at a set of aftermarket heads, but they are according to the part # pre '87 heads. Whats the difference and will it matter that much?
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
In mid 86, GM switched to aluminum heads on the Vette. Prior to that, they had iron heads, had press-in rocker studs, slots in the heads instead of guide plates, straight spark plugs (vs angle plugs), etc.
The combustion chamber volume may have been different too. I'm not sure if the very first aluminum heads took center bolt valve covers or, like all the earlier SB heads, perimeter cover bolts.
What are the specific heads you're considering? Maybe from that I'll know more.
Jake
The combustion chamber volume may have been different too. I'm not sure if the very first aluminum heads took center bolt valve covers or, like all the earlier SB heads, perimeter cover bolts.
What are the specific heads you're considering? Maybe from that I'll know more.
Jake
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
I have the same heads.The only differences are the rocker cover monting bolt positions.
If you check their site
TFS- 30400001 is the same spec as TFS- 30400005
except the 005 is listed for 87 and later
ifferent rocker covers.
I bought the cheaper ( more common ) ones and invested in a new set of covers.
If you check their site
TFS- 30400001 is the same spec as TFS- 30400005
except the 005 is listed for 87 and later
ifferent rocker covers.I bought the cheaper ( more common ) ones and invested in a new set of covers.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Originally Posted by hz900
Trick flow TFS- 30400001. I've got a 90 model.
I just ran across these today but I've got limited time to decide.
Otherwise I'll be buying dart pro 1's
I just ran across these today but I've got limited time to decide.
Otherwise I'll be buying dart pro 1's
Is your engine reverse cooling?
Jake
Racer
Joined: Aug 2002
Posts: 386
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From: Lancaster Lancashire
Originally Posted by hz900
Looking at a set of aftermarket heads, but they are according to the part # pre '87 heads. Whats the difference and will it matter that much?
If you have a 'stock' manifold, you will need pre 87 heads unless you elongate the centre holes on your intake manifold and either spot face it or use tapered washers under the bolts. You will still have the issue of the valve covers though.
I think they may well be perimeter bolt fittings.
However, it maybe worth checking with the vender as many after market heads now are drilled for both types of valve cover. They might just mean the intake bolts are pre 87. I think any will fit, you just might have to change things such as valve covers etc. ..Anyone else ??
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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In 86 when they switched heads, they went to center-bolt covers, so I'm not exactly sure what they mean by pre-87.
I guess they mean its meant for perimeter-bolt covers, thats the only change to the heads that might matter.
Usually they are drilled for both types.
I guess they mean its meant for perimeter-bolt covers, thats the only change to the heads that might matter.
Usually they are drilled for both types.
