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Next: Chrysler's Glory Days
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External
Since: Jan 19, 2005
Posts: 65
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(Msg. 1) Posted: Mon Jun 18, 2007 6:29 pm
Post subject: 67 firebird 421 engine swap question
Archived from groups: alt>autos>pontiac (more info?)
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| I'm working on a 67 Firebird with a 326 and an automatic. The 326 needs a
rebuild but I also have a 421 shortblock I'm considering rebuilding instead.
Will the 326 heads work with the 421, edelbrock performer manifold,
performer cam and carb? I'm mostly concerned with having to big of a
compression ratio. I'm looking for good torque numbers for the street.
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>> Stay informed about: 67 firebird 421 engine swap question |
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External
Since: Sep 09, 2005
Posts: 18
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(Msg. 2) Posted: Tue Jun 19, 2007 6:55 pm
Post subject: Re: 67 firebird 421 engine swap question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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It looks like there are 2 different 326's that year, one with 9.2
compression and the H.O. with 10.5.
As for the 421 they usually had 10.5 to 10.75 compression ratio. (unles
you're lucky enough to have a Super Duty, then you're looking at 12 and 13
to 1 !!)
So...if you've got the regular non H.O. 326 those heads would lower the CR
of the 421 to something streetable on todays pump gas.
Remember that pistons make a difference too. You could have dished pistons
that would lower the CR, or domed that would raise it.
If I were you, I'd drop the heads block and pistons off at a good automotive
machine shop and get them to CC the heads and measure the deck height and
pistons, and give you an actual CR number.
I'd build the 421. There's no replaement for displacement!!
Jay S
"Mark C." wrote in message
> I'm working on a 67 Firebird with a 326 and an automatic. The 326 needs a
> rebuild but I also have a 421 shortblock I'm considering rebuilding
> instead. Will the 326 heads work with the 421, edelbrock performer
> manifold, performer cam and carb? I'm mostly concerned with having to big
> of a compression ratio. I'm looking for good torque numbers for the
> street.
> |
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External
Since: Jan 19, 2005
Posts: 65
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(Msg. 3) Posted: Tue Jun 19, 2007 7:03 pm
Post subject: Re: 67 firebird 421 engine swap question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"Jay S" wrote in message
> It looks like there are 2 different 326's that year, one with 9.2
> compression and the H.O. with 10.5.
> As for the 421 they usually had 10.5 to 10.75 compression ratio. (unles
> you're lucky enough to have a Super Duty, then you're looking at 12 and 13
> to 1 !!)
>
> So...if you've got the regular non H.O. 326 those heads would lower the CR
> of the 421 to something streetable on todays pump gas.
> Remember that pistons make a difference too. You could have dished pistons
> that would lower the CR, or domed that would raise it.
> If I were you, I'd drop the heads block and pistons off at a good
> automotive machine shop and get them to CC the heads and measure the deck
> height and pistons, and give you an actual CR number.
>
> I'd build the 421. There's no replaement for displacement!!
>
> Jay S
>
Thank's for the great info, Jay. The 326 is the 250 HP, engine code X1. Is
that the lower CR head? The 421 is a '64 4 bolt mains version engine code
(T) 35B. There's a T as the first digit but I couldn't find a closer code
than 35B. It may have been rebuilt with low miles before it was stored
outside under a cover so I'm going to have to go through it again. I haven't
had a chance to tear it down yet. It has Flat top pistons with 4 deep valve
reliefs.
Mark
>
> "Mark C." wrote in message
>
>> I'm working on a 67 Firebird with a 326 and an automatic. The 326 needs a
>> rebuild but I also have a 421 shortblock I'm considering rebuilding
>> instead. Will the 326 heads work with the 421, edelbrock performer
>> manifold, performer cam and carb? I'm mostly concerned with having to big
>> of a compression ratio. I'm looking for good torque numbers for the
>> street.
>>
>
> >> Stay informed about: 67 firebird 421 engine swap question |
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External
Since: Sep 01, 2003
Posts: 49
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(Msg. 4) Posted: Tue Jun 19, 2007 11:49 pm
Post subject: Re: 67 firebird 421 engine swap question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"Mark C." wrote:
>
> "Jay S" wrote in message
>
> > It looks like there are 2 different 326's that year, one with 9.2
> > compression and the H.O. with 10.5.
> > As for the 421 they usually had 10.5 to 10.75 compression ratio. (unles
> > you're lucky enough to have a Super Duty, then you're looking at 12 and 13
> > to 1 !!)
> >
> > So...if you've got the regular non H.O. 326 those heads would lower the CR
> > of the 421 to something streetable on todays pump gas.
> > Remember that pistons make a difference too. You could have dished pistons
> > that would lower the CR, or domed that would raise it.
> > If I were you, I'd drop the heads block and pistons off at a good
> > automotive machine shop and get them to CC the heads and measure the deck
> > height and pistons, and give you an actual CR number.
> >
> > I'd build the 421. There's no replaement for displacement!!
> >
> > Jay S
> >
>
> Thank's for the great info, Jay. The 326 is the 250 HP, engine code X1. Is
> that the lower CR head? The 421 is a '64 4 bolt mains version engine code
> (T) 35B. There's a T as the first digit but I couldn't find a closer code
> than 35B. It may have been rebuilt with low miles before it was stored
> outside under a cover so I'm going to have to go through it again. I haven't
> had a chance to tear it down yet. It has Flat top pistons with 4 deep valve
> reliefs.
>
> Mark
>
> >
> > "Mark C." wrote in message
> >
> >> I'm working on a 67 Firebird with a 326 and an automatic. The 326 needs a
> >> rebuild but I also have a 421 shortblock I'm considering rebuilding
> >> instead. Will the 326 heads work with the 421, edelbrock performer
> >> manifold, performer cam and carb? I'm mostly concerned with having to big
> >> of a compression ratio. I'm looking for good torque numbers for the
> >> street.
> >>
Without knowing the cc's in the 326 heads combustion chamber there is no
way to know what the CR will be. It is possible those 9.5 heads will
increase the CR on the 421.
Stan >> Stay informed about: 67 firebird 421 engine swap question |
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External
Since: Sep 09, 2005
Posts: 18
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(Msg. 5) Posted: Wed Jun 20, 2007 4:33 am
Post subject: Re: 67 firebird 421 engine swap question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"Mark C." wrote in message
>>
>
> Thank's for the great info, Jay. The 326 is the 250 HP, engine code X1. Is
> that the lower CR head? The 421 is a '64 4 bolt mains version engine code
> (T) 35B. There's a T as the first digit but I couldn't find a closer code
> than 35B. It may have been rebuilt with low miles before it was stored
> outside under a cover so I'm going to have to go through it again. I
> haven't had a chance to tear it down yet. It has Flat top pistons with 4
> deep valve reliefs.
>
> Mark
>
>
>
The XI code 326 is one of the engines with 9.2 CR. The head code should be
140.
Check out this site for tons of info on codes:
http://www.pontiacpower.org/
Jay S >> Stay informed about: 67 firebird 421 engine swap question |
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External
Since: Jan 19, 2005
Posts: 65
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(Msg. 6) Posted: Wed Jun 20, 2007 6:33 pm
Post subject: Re: 67 firebird 421 engine swap question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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According to the chart the 421 will have 11.65 cr with the 326 heads. A bit
high for the street, I'd say.
Mark
"Jay S" wrote in message
>
> "Mark C." wrote in message
>
>
>>>
>>
>> Thank's for the great info, Jay. The 326 is the 250 HP, engine code X1.
>> Is that the lower CR head? The 421 is a '64 4 bolt mains version engine
>> code (T) 35B. There's a T as the first digit but I couldn't find a closer
>> code than 35B. It may have been rebuilt with low miles before it was
>> stored outside under a cover so I'm going to have to go through it again.
>> I haven't had a chance to tear it down yet. It has Flat top pistons with
>> 4 deep valve reliefs.
>>
>> Mark
>>
>>
>>
>
> The XI code 326 is one of the engines with 9.2 CR. The head code should be
> 140.
> Check out this site for tons of info on codes:
>
> http://www.pontiacpower.org/
>
> Jay S
>
> >> Stay informed about: 67 firebird 421 engine swap question |
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External
Since: Sep 09, 2005
Posts: 18
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(Msg. 7) Posted: Wed Jun 20, 2007 11:55 pm
Post subject: Re: 67 firebird 421 engine swap question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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"Mark C." wrote in message
> According to the chart the 421 will have 11.65 cr with the 326 heads. A
> bit high for the street, I'd say.
>
> Mark
>
Yup...that's too high alright!
That's too bad.
Maybe you should think about keeping an eye out for a set of heads that will
work with the 421 and keep the 326 complete incase you want to return the
car to original.
Ebay might work if you can find something local so you don't get killed on
shipping.
Jay S >> Stay informed about: 67 firebird 421 engine swap question |
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External
Since: Jan 19, 2005
Posts: 65
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(Msg. 8) Posted: Sat Jun 23, 2007 12:53 pm
Post subject: Re: 67 firebird 421 engine swap question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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There's a 78 pontiac in the local pick a part. I'll see if I can use the
open chamber heads from that.
"Jay S" wrote in message
>
> "Mark C." wrote in message
>
>> According to the chart the 421 will have 11.65 cr with the 326 heads. A
>> bit high for the street, I'd say.
>>
>> Mark
>>
> Yup...that's too high alright!
> That's too bad.
> Maybe you should think about keeping an eye out for a set of heads that
> will work with the 421 and keep the 326 complete incase you want to return
> the car to original.
> Ebay might work if you can find something local so you don't get killed on
> shipping.
>
> Jay S
> >> Stay informed about: 67 firebird 421 engine swap question |
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