Getting the most out of your 7A-GE hybrid build

A 7AGE is a hybrid motor that uses a 7AFE block, crank and sometimes other bottom end components and a 4AGE head and other components to make a 1.8 liter stroker motor.

You can do this with any 4AGE head including largeport, smallport, silvertop or blacktop.

There is not a lot of difference between a good 4AGE build and a good 7AGE build but here we will discuss those differences as well as how to pick the right combination of parts to get the most out of your build.

One of the biggest issues to address is the cam timing. The 7A block has a 14.5mm taller deck height. This requires a longer timing belt but it also changes the cam timing. There are a few ways to address this but the simplest way to get back to stock is with a timing belt crank gear that  has been broached to fix the timing.

We offer an OEM crank gear that we rebroach to perfectly account for the change in timing.

Next you need a timing belt. This can get confusing since there are so many head and tensioner combinations.
I don't currently have a belt available for the Blacktop tensioner. Most people switch to the 16 valve oil pump and tensioner. With these two components the silvertop and blacktop can both use the stock 16 valve timing belt. This is because the 20v cams are much closer together and require a shorter belt than the 16v.

This is great because there are many high performance belts for the 4AGE. Such as Toda, Tomei,  Gates Racing  and others.

With the 20v head and the 16v belt you will also need this tensioner.

The 16 valve motors require a longer belt. This 117 tooth belt is the most common solution.
The downside is that this belt requires you to run the 7AFE oil pump and tensioner. The 4AGE pump and tensioner does not allow enough throw to tighten the belt.  The 7A pump positions the tensioner a little bit differently allowing you to tension the longer belt.
Unfortunately the 7AFE pump is smaller and does not pump as much oil. This should be a non issue for a mild build, or daily driver type build.

If you are going for a performance build the latest revision high volume 4AGE oil pump will be a much better choice. To run that you need this belt.

The last big difference you will encounter is the rods and pistons. You will not want to use the 7A pistons because they are not designed around the head.  You can use 4AGE main bearings however the rod bearings are a different size so you will need to use 7AFE rod bearings. There are a couple other notable differences. The 7A rods and pistons are press fit pins instead of floating wrist pins like the 4AGE. If you decide to use the stock rods with 4AGE pistons you will need to get the rods modified for floating wrist pins. The 7A rods also put the pistons about .6mm below deck. You will need to compensate for this with the headgasket or by shaving the deck.
The much easier solution to this problem is our 7AGE rod. It has been made specifically for this conversion and solves all the above problems. The small end is designed for 20mm 4AGE pistons and floating wrist pins. It is also .6mm longer to put the piston flush with the deck. These rods are also much stronger and should be able to take anything you can throw at them.

One other thing to remember is that the added stroke of the 7A will change the compression ratio of a given piston. Going from 77mm stroke to 85.5mm stroke makes a significant difference on the compression ratio so when you are doing calculations don't forget to factor this in.
I will do one calculation as an example of the effect of this. NA largeport pistons are 9.3:1. In a 7A with the same deck height the same pistons with a largeport head would have 10.1:1 compression.


Then there is engine management. Of course aftermarket engine management will be the best option however it is possible to get the stock 4AGE ECU to run a 7AGE about as well as it ran the 4AGE with some monitoring and and tweaking. This is something that needs to be addressed more on a case by case bassis.

These are the big key points. I will continue to add to this as I have time.
Other than that the parts and theory will be much the same as a proper 4AGE build. Most people underestimate the importance of pairing the right parts to get the right results.
Many people have made guides to help people make x power with x mods. I dissagree with most of these build paths but I do not have one of my own because the way to get the most out of a build is to address it individually and tailor a parts list and build plan specifically for the application. The further you push things the more true this will become.

We are happy to give our input on parts selection and build strategy. Feel free to contact us if you have any questions on your build.


For information on calculating compression, squish and other important related details read this page.

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