307 intake manifold compatibility

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86MCSS86

Not-quite-so-new-guy
Jul 2, 2014
47
3
8
I'm looking to replace the intake on my brothers 88 cutlass supreme classic the reason being is that a bolt for the thermostat housing broke. Machine shop says it would be cheaper to replace it and since local junkyard is having a 1/2 sale maybe he's right. So now are there any I should steer away from are any better than others or do I just get one off any olds 307? Or maybe tips to get bolt out. The bolt sheared off with only about 3/16" on top of the intake.
 

88hurstolds

Royal Smart Person
Jun 24, 2008
1,747
652
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No, any intake will NOT interchange.
You will have port mismatch with the 7A heads and have horrible performance if the engine will even run right given the fact that the intake heads on those roller engines are much smaller due to the need to increase the intake velocity with the swirl port design of the 7A heads.
You need an A5 intake from a 7A headed 307 85-90 VINY or 86-90 VIN9.
Most people are throwing these intakes out because they are useless otherwise, I am sure someone has one on here for free since they are basically scrap aluminum.

If it were me I would just tack weld a nut to the top or grind in a slit to get a screw driver on there and some heat.
Worse case drill and tap out the bolt...
The mechanic sounds like an idiot or a thief if he thinks it's easier to just swap the intake...
New intake, carb and T-stat gaskets, not to mention the amount of labor being charged to spend the time doing this...
 
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86MCSS86

Not-quite-so-new-guy
Jul 2, 2014
47
3
8
Thanks for the suggetions and the information. I will try cutting a slit if that doesnt work I will have to get someone to come to my house to weld a nut on it since I don't have a welder.
 

williamattop

Master Mechanic
Apr 9, 2014
455
53
28
Appleton WI
No, any intake will NOT interchange.
You will have port mismatch with the 7A heads and have horrible performance if the engine will even run right given the fact that the intake heads on those roller engines are much smaller due to the need to increase the intake velocity with the swirl port design of the 7A heads.
You need an A5 intake from a 7A headed 307 85-90 VINY or 86-90 VIN9.

Good catch. I completly forgot to consider this and I am happy somebody clarified before he went out and bought anything.


I may have been in shock still by what he stated the "machine shop" told him to do over a broken bolt. Things like removing a single broken bolt guys do for free around here.
 
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