how many exhaust man. bolts?

[useRc10]

I'm looking at a crate 350 for my '85 Blazer to replace the 305...Looking at the ones they have at Autozone, they all say 7 bolts hold the exhaust manifold to the heads but i can only count 6 on my truck...am i just missing one or will I have to get new manifolds?

also, does anyone know about these engines they have:
Recon-I part # 708510
and
Proformance - part #s 3350-1 and 2350-1

these prices are better than anything else i've found but i want to make sure they are good and find some hp/torque specs first

Thanks -Nick

[Destructo]

nope, theres six... two on either side of cylinders 1 and 7 and two on the outside of 3 and 5. so there six, same for the other side.

[useRc10]

thats what i thought but the paper says 7...i dont know...i think i'm going up there in teh morning again and see if i can find some specs anyway so i'llfind out

Thanks

[MylilBowTie]

Some heads have 7 bolts, I dont recall the reasons for the extra bolt. Im thinking 305 exhaust manifolds and smog stuff but I dunno.

[CT-Truckster]

some manifols use the 7th bolt hole instead of the sixth at the back of the head I think. There will two bolt holes say behind #8 exhaust. I think only one or the other hole is used. it is there just in case you need it and you shouldn't have have any problems with your mainfolds bolting up. I think only some stock manifolds may use this 7th hole, I have never seen a set a set of headers that use the seventh bolt hole.

[useRc10]

so you're saying i'll be ok buying on ethat says 7 when i only have 6?

[mckpaul]

Just rebuilt my 84 305. The heads have 7 bolt holes for the exhaust manifold. The extra hole is either in the very front in front of the #1 cylinder exhaust port or in the very back behind the #8 cylinder exhaust port (depending on which side of the motor you put the head on) The exhaust gaskets that came with the Felpro kit are three piece gaskets for each side. The middle one is for two exhaust ports with one bolt hole on each end, the other two are for one exhaust port, but one is longer and cut for two bolt holes on one side of the exhaust port hole.

For my application, the driver side manifold didn't use the very front (7th bolt hole) on the head, so the manifold ends just after the 6th hole, and the gasket extends on out around that 7th hole, not used. Guess I could have trimmed the gasket, probably still could with a razor knife if the AC mounting brackets weren't in the way. On the passenger side, however, for some reason the manifold is made a little longer in the back and bolts up using the 7th bolt hole on the head. There are still just six total holding the manifold on, and that #8 exhaust port has one bolt on each side, but it doesn't use that 6th hole, just covers it and uses hole #5 and hole #7, and the gasket is completely covered by the manifold, unlike the driver side where the unused part sticks out.

I'd say what they are saying is the heads on the crate motor have 7 holes for mounting exhaust manifolds so they will accept what ever manifold you have, but you'll only use 6 of the 7 holes.

[useRc10]

great...thanks for the help...-Nick

[Destructo]

Originally Posted by CT-Truckster

some manifols use the 7th bolt hole instead of the sixth at the back of the head I think. There will two bolt holes say behind #8 exhaust. I think only one or the other hole is used. it is there just in case you need it and you shouldn't have have any problems with your mainfolds bolting up. I think only some stock manifolds may use this 7th hole, I have never seen a set a set of headers that use the seventh bolt hole.

Actually now that you mention it, on my 83 305 GMC truck I had I had to use a different hole in the head when I installed headers, but there was still only 6 bolts just there was an extra hole behind #8.

[piecesparts]

Man you had better hold out for the six bolt heads,, you wouldn't want to have an extra hole hanging around without something in it. It would look like a FORD then. Get the motor and bolt your stuff to it, enjoy the work and the results, have a nice day.

[ChevyTech]

Beginning in 1975, some cylinder heads had a extra exhaust manifold mounting hole. The extra hole was required due to a change in passenger side castiron exhaust manifolds to fit some vehicles.

If have noticed, some Camaros use the extra hole.

[useRc10]

thanks...i'm going with a crate largely because its my daily driver...and i dont have a lot of time or mechanical knowledge to build my own