7 AGE build advise

[ktm]

Looking to get some input on a 7AGE build. This motor will go in an off road car looking to get as much torque as I can,with at least 170 HP. I would like to be able to run the engine on pump gas.I will be using a 16v small port head , an Electromotive ignition and a single down draft webber. I'm currently running a stock 4 age with the webber and Electromotive ignition.

[oldeskewltoy]

Looking to get some input on a 7AGE build. This motor will go in an off road car looking to get as much torque as I can,with at least 170 HP. I would like to be able to run the engine on pump gas.I will be using a 16v small port head , an Electromotive ignition and a single down draft webber. I'm currently running a stock 4 age with the webber and Electromotive ignition.

There are 2 KEYS to a proper 7AG build:

1) the 4AG timing belt drive sprocket doesn't correctly line up to the timing marks. You can either purchase a properly re-spline sprocket, or use a piston stop to determine TDC - this last bit you should do either way, especially when it comes to cam timing.
2) Either use a custom made piston, OR if you use a 4AG piston, make sure you have the blocks surface machined so the piston provides the proper gap between piston and head - aka "squish". This gap (7AG) should be no less than .034", and no more than .047"

4AG these clearances are a few ten thousandths tighter, but since the 7A rods are longer I'm accounting for a tiny bit more rod stretch.


Bearings clearances: Mains set in the middle of the FSM specification, rods set a tiny bit loose of the middle specs.

The rest is up for discussion...

My opinion for 170hp with maximum low end power(torque)... Pair of exhaust Cat Cams 7105136, properly ported O/S valve head, 11 to 1 comp ratio


edit - what size/type of Weber??

[sirdeuce]

Lots of info here, lots of posts. Read up, and take your time. As for the cam timing issue, I believe Yoshi offers a cam sprocket the has been machined with the proper timing for the 7AGE.

[ktm]

44 Webber Its a bit to big for the stock engine, this is the way it came when I bought it.

[yoshimitsuspeed]

By torque you mean low end power. A more accurate way to say it is you want 170 with the broadest power curve possible.
Torque is meaningless until you add RPM and then you can quantify the rate at which it can do work. IE power.

Are you looking for 170 wheel or 170 crank?
Honestly I would shoot for 170 wheel. This should be no problem and still give you a nice broad power curve.
I am getting a few of my own cams made. One is a 265 by 8.7 lift that I am bringing out to compete with the Poncams. This would be a pretty good choice IMO.

For the bottom end I would just ditch the stock 7A rods. I have a rod that is designed to work with 4AGE pistons with full floating wrist pin and the proper length to put the piston flush with the deck as the 4AGE is.
My broached timing gear will compensate for the timing change of the higher block. Like OST said it's always a good idea to check it though.
http://matrixgarage.com/store/7a-ge-engine-components

I would really suggest EFI though. You say it's an offroad car. EFI is better in general but on an offroad vehicle in this day and age I would consider it to be the only option. EFI will adapt to altitude and weather changes better, it doesn't care about vibration or angle, once the tune is dialed in it doesn't need tweaking or tuning unless you make changes.

[ktm]

You described exactly what I'm looking for with the power. I will be in touch when I get ready for parts. Thanks

[sirdeuce]

44? IDF or IDA? I know the single IDA on the VW boxer was a little better across the curve than the IDA. The IDA was a bit peaky. But your goal of 170, I'm guessing crank, HP is doable with a single. If you want anything more I'd say duals are the way to go, or go back to the EFI.

[oldeskewltoy]

Which head are you planning on using??

[speedmaster]

i blew up my 7a 20v last week at 190hp 180nm on the wheel. the gasket was too thin and the valves hitting the piston. was using miata pistons. gonna go at it again with thicker gasket and see if i can get anything over 200hp.

[oldeskewltoy]

i blew up my 7a 20v last week at 190hp 180nm on the wheel. the gasket was too thin and the valves hitting the piston. was using miata pistons. gonna go at it again with thicker gasket and see if i can get anything over 200hp.

**IF** the piston wasn't hitting the head...... Better to add flycuts to your pistons to clear the valves... try to keep the gasket tight

[speedmaster]

i blew up my 7a 20v last week at 190hp 180nm on the wheel. the gasket was too thin and the valves hitting the piston. was using miata pistons. gonna go at it again with thicker gasket and see if i can get anything over 200hp.

**IF** the piston wasn't hitting the head...... Better to add flycuts to your pistons to clear the valves... try to keep the gasket tight

piston had valves pocket done . just that the gasket used was 0.3mm thick only. compression test at 300psi. new setup now is to keep the compression at 240-250psi with 0.8mm gasket

[yoshimitsuspeed]

This is exactly why I can't understand people wasting their time with pistons made for another motor.
Suck it up and buy proper pistons. It will pay in the long run.
HG thickness is really not important. What is important is squish gap. What is your deck clearance with those pistons?
It would be an almost impossible waste of time and energy to CMM those pistons to a point of knowing they would work as well as a piston designed for the 4AGE.
By going with a thicker headgasket you might find the motor more likely to detonate and you will likely not be able to make as much power before it does.

[oldeskewltoy]

This is exactly why I can't understand people wasting their time with pistons made for another motor.
Suck it up and buy proper pistons. It will pay in the long run.

nice to hear this change of opinion.... in the past you and I have heatedly discussed this... THE proper piston for the application is the best solution...

"THE proper piston" = means the best piston for each engine is the piston designed for said engine....

[yoshimitsuspeed]

This is exactly why I can't understand people wasting their time with pistons made for another motor.
Suck it up and buy proper pistons. It will pay in the long run.

nice to hear this change of opinion.... in the past you and I have heatedly discussed this... THE proper piston for the application is the best solution...

"THE proper piston" = means the best piston for each engine is the piston designed for said engine....

I just meant a piston designed for the motor and the application. I still don't think it's worth it to run custom pistons on a build with less than 304 cams. Even then a few different basic designs would cover the vast majority of bigger builds. The exceptions I could see is if you were to shave the head so much a shelf piston would hit it or if you CNC machined your combustion chambers. Then you could run a piston with crazy tight dome tolerances.
I have never talked to anyone so obsessed with needing custom pistons for custom builds. Toda, Hasselgren, TED etc all have shelf pistons that they run in various builds. Not all but many.

With that said there is a big difference between not running a custom piston for that extra 1% vs running a piston that wasn't even designed for the motor that could have different compression height, valve spacing, valve centerline, pentroof angle and centerline or maybe not even designed for a pentroof chamber etc.
There is a time and a place for custom pistons. On sub $10k builds it's rarely necessary, practical or worth it.

[ktm]

Which head are you planning on using??

I will be using a small port head

[oldeskewltoy]

Which head are you planning on using??

I will be using a small port head

What manifold, with which Weber?

[ktm]

Fat performance makes the intake manifold the carb I have is a 44 webber IDF

[speedmaster]

or my custom made adapter