my 88 iroc
Thread Starter
Junior Member
Joined: Jan 2007
Posts: 41
Likes: 0
From: in a small town
Car: 88 iroc
Engine: 305
Transmission: 5 speed
Axle/Gears: dount know
my 88 iroc
i have a 88 iroc 305 multi port 5 speed and need some help. i have a 350 out of a 72 pick up can i just swich out the 305 block for the 350?will every thing bolt up?(heads etc) can i just use the heads that are on the 350 or do i have to use the ones from the 305?plan to stay with the multi port system. do i have to get a new bell houseing?if i can use the 350 heads and block what would the max rpm's i would what to turn my 305 red lines at 5500.
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Welcome aboard thirdgen.org.
There are some issues with an older engine like a '72. The bellhousings are the same, and your accessories will mount up, but that's about where the good news ends.
The crankshaft has a two-piece rear main seal, which means the flywheel mounting is different than your '88. Not a big deal, but it means you need a flywheel for the '82-'85 application 3rd gen V8.
The '72 engines also had the dipstick on the driver's side, and the tube for it goes right where the stock exhaust manifold lives. The easiest solution is to get tubular headers, but if you don't do that, you're going to have to either get a flexible dipstick tube (such as Lokar), or carefully bend the stock tube to fit.
Probably the biggest issue is the heads. First, '72 truck heads are very poor. Second, the intake mount bolt pattern is slightly different, as your '88 base has the center two bolts on each side at 72 degrees instead of 90 degrees like the rest (and all of the '72 bolts). Not a big deal, again, you just need to elongate those holes in the base so the bolts will fit. However, since the heads are poor, anyway, it makes more sense to put your 305 heads on the 350 shortblock for a couple of reasons: 1) so the intake base mounts directly, and 2) better performance results. The truck engine also has dished pistons, most likely, so the smaller chambers of the 305 heads will increase compression to a more reasonable level. If the 350 shortblock needs to be rebuilt, that's a good time to put pistons in that match the 305 heads for really "good" compression.
Overall, the 350 shortblock is a good starting point, but you need to work around those issues, and the 305 heads (since your engine is TPI) are the best ones to use on it.
Redline depends upon the total engine "package". The TPI doesn't make good power above 4800 RPMs without aftermarket modifications such as shorter runners. The cam is a big factor in powerband as well. So, the power redline is about 5000 RPMs, while the mechanical redline is probably in the 5500 range, limited mostly by valve springs.
There are more details about this swap, making the heads better, what cam to use, TPI upgrades, what headers to use, etc. How much information do you want and/or need?
There are some issues with an older engine like a '72. The bellhousings are the same, and your accessories will mount up, but that's about where the good news ends.
The crankshaft has a two-piece rear main seal, which means the flywheel mounting is different than your '88. Not a big deal, but it means you need a flywheel for the '82-'85 application 3rd gen V8.
The '72 engines also had the dipstick on the driver's side, and the tube for it goes right where the stock exhaust manifold lives. The easiest solution is to get tubular headers, but if you don't do that, you're going to have to either get a flexible dipstick tube (such as Lokar), or carefully bend the stock tube to fit.
Probably the biggest issue is the heads. First, '72 truck heads are very poor. Second, the intake mount bolt pattern is slightly different, as your '88 base has the center two bolts on each side at 72 degrees instead of 90 degrees like the rest (and all of the '72 bolts). Not a big deal, again, you just need to elongate those holes in the base so the bolts will fit. However, since the heads are poor, anyway, it makes more sense to put your 305 heads on the 350 shortblock for a couple of reasons: 1) so the intake base mounts directly, and 2) better performance results. The truck engine also has dished pistons, most likely, so the smaller chambers of the 305 heads will increase compression to a more reasonable level. If the 350 shortblock needs to be rebuilt, that's a good time to put pistons in that match the 305 heads for really "good" compression.
Overall, the 350 shortblock is a good starting point, but you need to work around those issues, and the 305 heads (since your engine is TPI) are the best ones to use on it.
Redline depends upon the total engine "package". The TPI doesn't make good power above 4800 RPMs without aftermarket modifications such as shorter runners. The cam is a big factor in powerband as well. So, the power redline is about 5000 RPMs, while the mechanical redline is probably in the 5500 range, limited mostly by valve springs.
There are more details about this swap, making the heads better, what cam to use, TPI upgrades, what headers to use, etc. How much information do you want and/or need?
Thread Starter
Junior Member
Joined: Jan 2007
Posts: 41
Likes: 0
From: in a small town
Car: 88 iroc
Engine: 305
Transmission: 5 speed
Axle/Gears: dount know
Welcome aboard thirdgen.org.
There are some issues with an older engine like a '72. The bellhousings are the same, and your accessories will mount up, but that's about where the good news ends.
The crankshaft has a two-piece rear main seal, which means the flywheel mounting is different than your '88. Not a big deal, but it means you need a flywheel for the '82-'85 application 3rd gen V8.
The '72 engines also had the dipstick on the driver's side, and the tube for it goes right where the stock exhaust manifold lives. The easiest solution is to get tubular headers, but if you don't do that, you're going to have to either get a flexible dipstick tube (such as Lokar), or carefully bend the stock tube to fit.
Probably the biggest issue is the heads. First, '72 truck heads are very poor. Second, the intake mount bolt pattern is slightly different, as your '88 base has the center two bolts on each side at 72 degrees instead of 90 degrees like the rest (and all of the '72 bolts). Not a big deal, again, you just need to elongate those holes in the base so the bolts will fit. However, since the heads are poor, anyway, it makes more sense to put your 305 heads on the 350 shortblock for a couple of reasons: 1) so the intake base mounts directly, and 2) better performance results. The truck engine also has dished pistons, most likely, so the smaller chambers of the 305 heads will increase compression to a more reasonable level. If the 350 shortblock needs to be rebuilt, that's a good time to put pistons in that match the 305 heads for really "good" compression.
Overall, the 350 shortblock is a good starting point, but you need to work around those issues, and the 305 heads (since your engine is TPI) are the best ones to use on it.
Redline depends upon the total engine "package". The TPI doesn't make good power above 4800 RPMs without aftermarket modifications such as shorter runners. The cam is a big factor in powerband as well. So, the power redline is about 5000 RPMs, while the mechanical redline is probably in the 5500 range, limited mostly by valve springs.
There are more details about this swap, making the heads better, what cam to use, TPI upgrades, what headers to use, etc. How much information do you want and/or need?
There are some issues with an older engine like a '72. The bellhousings are the same, and your accessories will mount up, but that's about where the good news ends.
The crankshaft has a two-piece rear main seal, which means the flywheel mounting is different than your '88. Not a big deal, but it means you need a flywheel for the '82-'85 application 3rd gen V8.
The '72 engines also had the dipstick on the driver's side, and the tube for it goes right where the stock exhaust manifold lives. The easiest solution is to get tubular headers, but if you don't do that, you're going to have to either get a flexible dipstick tube (such as Lokar), or carefully bend the stock tube to fit.
Probably the biggest issue is the heads. First, '72 truck heads are very poor. Second, the intake mount bolt pattern is slightly different, as your '88 base has the center two bolts on each side at 72 degrees instead of 90 degrees like the rest (and all of the '72 bolts). Not a big deal, again, you just need to elongate those holes in the base so the bolts will fit. However, since the heads are poor, anyway, it makes more sense to put your 305 heads on the 350 shortblock for a couple of reasons: 1) so the intake base mounts directly, and 2) better performance results. The truck engine also has dished pistons, most likely, so the smaller chambers of the 305 heads will increase compression to a more reasonable level. If the 350 shortblock needs to be rebuilt, that's a good time to put pistons in that match the 305 heads for really "good" compression.
Overall, the 350 shortblock is a good starting point, but you need to work around those issues, and the 305 heads (since your engine is TPI) are the best ones to use on it.
Redline depends upon the total engine "package". The TPI doesn't make good power above 4800 RPMs without aftermarket modifications such as shorter runners. The cam is a big factor in powerband as well. So, the power redline is about 5000 RPMs, while the mechanical redline is probably in the 5500 range, limited mostly by valve springs.
There are more details about this swap, making the heads better, what cam to use, TPI upgrades, what headers to use, etc. How much information do you want and/or need?
Thread
Thread Starter
Forum
Replies
Last Post
mustangman65_79
Body
3
Aug 11, 2015 03:17 PM
