Post by Rinconrolla on Mar 14, 2011 13:56:35 GMT -5
Enlarging the capacity of an engine has been around as long as engines have, and that exact process for the 4AGE is not a new formula.
Way back in the late 1980Œs HKS introduced the 5A-GE kit. This kit comprised of a stroker crank and rods, that fitted the standard 4A-G block. The one of biggest problems with the 5AG kit is balance, balance, balance. Your obviously going to want to rev your engine to infinity and beyond, and the crank will need balance. The second part if the problem is block. The block journals need grinding out to accept the larger crank, and crank bearings. This in itself is not a big problem, but again make sure your engine builder is aware that the crank is bigger and work that needs to be done.
Again we turn to the 7A-FE.
Using a 7A-FE block again to make a big cube high revving engine is not a cheap or simple option. first up a custom set of pistons may be needed, companies such as Wiseco and Mahle can make custom pistons for you, but will not be cheap. The second part is a set of forged conrods, in place of the spindly, tooth pick 7A-FE rods. recently there has been a lot of need for forged 7A-FE rods for high comp and turbo motors and a few are now starting to provide them for the discerning buyer, although there still isnt a huge market for them.
The 7A-FE block is quite strong, but because its a grandma-spec engine the water galleries and oil galleries only the bare minimum of what is needed. This is again where your engine builder will need to be on the ball as the both the water and oil galleries will need to be opened up to allow greater flow.
Once the 7A-FE block has been assembled with the high comp pistons and forged rods, your head will need to go on. This can also be problematic as the 7A-GE now becomes an interference engine! Timing will need to be spot on to avoid bent valves and damage to the head.
The 7A-GE can also be bored out using an 83mm piston. The standard 7A-FE capacity is 1789cc, but using the 83mm pistons increases it to 1880cc or 1.9ltrs. Mark Yager (of Yager Performance) has been making these for a number of years for clubmans and will fit what ever head you want.
There are a lot of inherent problems in doing the 7AG conversion, but the benefits FAR out weigh the negatives. If Chris OfShannessey can come outright 2nd for the year in IPRA then it cant be a bad thing!
RS YASU also make a wicked big cube 4.5AG. Using the 83mm piston (usually a CA18 or Mazda BP1800 piston) the block is bored to accept the larger piston and given a higher comp as well (around 11.5:1). This can really only be done with the 16v engine, due to most 83mm pistons being for 16v engines. If you were going to do this with a 20v engine custom pistons would need to be used to allow for the extra valve cut.
The difference with the 5A-G kit and RS YASU 4.5AG, is that the 5A-G kit will work with ANY 4A-G with a minimum of fuss compared to the RS YASU 4.5AG which is best used with 16vfs.
Hopefully by now you have an idea of what goes into a good N/A engine and can make a informed decision if N/A is the road you want to take.
Stay tuned again for part three of our AE86 Tuning Guide!
Source of Story www.hachiroku.com.au/blog/?p=1667
Way back in the late 1980Œs HKS introduced the 5A-GE kit. This kit comprised of a stroker crank and rods, that fitted the standard 4A-G block. The one of biggest problems with the 5AG kit is balance, balance, balance. Your obviously going to want to rev your engine to infinity and beyond, and the crank will need balance. The second part if the problem is block. The block journals need grinding out to accept the larger crank, and crank bearings. This in itself is not a big problem, but again make sure your engine builder is aware that the crank is bigger and work that needs to be done.
Again we turn to the 7A-FE.
Using a 7A-FE block again to make a big cube high revving engine is not a cheap or simple option. first up a custom set of pistons may be needed, companies such as Wiseco and Mahle can make custom pistons for you, but will not be cheap. The second part is a set of forged conrods, in place of the spindly, tooth pick 7A-FE rods. recently there has been a lot of need for forged 7A-FE rods for high comp and turbo motors and a few are now starting to provide them for the discerning buyer, although there still isnt a huge market for them.
The 7A-FE block is quite strong, but because its a grandma-spec engine the water galleries and oil galleries only the bare minimum of what is needed. This is again where your engine builder will need to be on the ball as the both the water and oil galleries will need to be opened up to allow greater flow.
Once the 7A-FE block has been assembled with the high comp pistons and forged rods, your head will need to go on. This can also be problematic as the 7A-GE now becomes an interference engine! Timing will need to be spot on to avoid bent valves and damage to the head.
The 7A-GE can also be bored out using an 83mm piston. The standard 7A-FE capacity is 1789cc, but using the 83mm pistons increases it to 1880cc or 1.9ltrs. Mark Yager (of Yager Performance) has been making these for a number of years for clubmans and will fit what ever head you want.
There are a lot of inherent problems in doing the 7AG conversion, but the benefits FAR out weigh the negatives. If Chris OfShannessey can come outright 2nd for the year in IPRA then it cant be a bad thing!
RS YASU also make a wicked big cube 4.5AG. Using the 83mm piston (usually a CA18 or Mazda BP1800 piston) the block is bored to accept the larger piston and given a higher comp as well (around 11.5:1). This can really only be done with the 16v engine, due to most 83mm pistons being for 16v engines. If you were going to do this with a 20v engine custom pistons would need to be used to allow for the extra valve cut.
The difference with the 5A-G kit and RS YASU 4.5AG, is that the 5A-G kit will work with ANY 4A-G with a minimum of fuss compared to the RS YASU 4.5AG which is best used with 16vfs.
Hopefully by now you have an idea of what goes into a good N/A engine and can make a informed decision if N/A is the road you want to take.
Stay tuned again for part three of our AE86 Tuning Guide!
Source of Story www.hachiroku.com.au/blog/?p=1667