How to check if I have a 1g head.

[Jordanbutter]

A friend of mine that is a mechanic was looking at my car the other day and after looking at the head he said it looked like a salvage or at least replaced head. Now my first response is pure joy thinking it might be a 1g head. I bought the car used and there is no record of a head swap. How can I know if its a 1g or 2g head and is there anyway to tell for sure if it is salvage?

 

[Dream On]

Look at the intake ports. The ports on a 1g are huge compared to a 2g head.
http://www.roadraceengineering.com/eclipsetech/headswap/1g2gheadswapintakemanifoldlg.jpg
here's a pic of intake manifolds since I couldn't fine a pic of the head ports, but the difference is like that.

If it's a 1g 6 bolt head, check the studs for the exhaust manifold. The outermost ones will be the same size as the rest. If they're larger, it's off a 7 bolt, but it could still be from a 1g 7 bolt. You could also check the size of the holes for the head bolts. 1g's are a certain size, and the 2g's are different.

 

[Black Venom]

"If it's a 1g 6 bolt head, check the studs for the exhaust manifold. The outermost ones will be the same size as the rest. If they're larger, it's off a 7 bolt"

I wouldn't go by that, my outer most exhaust studs are larger on my 6 bolt. My friends 6 bolt is the same way and yes they are 6 bolt heads.

 

[Jordanbutter]

Well I'm pretty sure its not a 1G intake manifold cause it doesn't have the ECI MULTI on it. But could you have a 1g head and a 2g intake mani?

 

[95blackGsTurbo]

1g head will have the cam sensor on the driver side. Unless if was off of a 93 or 94 in which case you would look at the head bolts.

 

[Dream On]

"If it's a 1g 6 bolt head, check the studs for the exhaust manifold. The outermost ones will be the same size as the rest. If they're larger, it's off a 7 bolt"

I wouldn't go by that, my outer most exhaust studs are larger on my 6 bolt. My friends 6 bolt is the same way and yes they are 6 bolt heads.

Well it probably didn't come that way from the factory. You probably just have a 1g 7 bolt head.

 

[nightspeed87]

1g head will have the cam sensor on the driver side. Unless if was off of a 93 or 94 in which case you would look at the head bolts.

Ive never seen a cam angle sensor on the driver side of the head before on any 4g63, that is were the timing belt and cam gears go, and I have a 93 7 bolt head in my garage and a 6bolt engine (including head) on my car...
The only way he can really tell if its 1g or 2g is by looking at the manifold ports,
looking at the entire intake manifold itself and I believe the throttle body is larger on the 1g, and by checking the stud sizes.. I believe the 6bolt used 12mm head studs and the 7 used 11... ( If it doesnt have a 1g manifold ( which is clearly different than the 2g) then its probably a 2g head because there is no reason why any 1gers would use the smaller 2g manifold... Thered be no point... Sorry to say You most likely got a used 2g head. But just port that sucker out and youll be ok.. )

 

[Talesin]

The only way to tell at-a-glance is the intake ports or possibly the little blowby mechanism (I assume that's what it is) on the passenger-side (I can only speak for the '90 head, which is 'humped up' and gold in color, as opposed to the 1Gb head which is flat and has passages 'knotted' through it).
2G intake ports are roughly an inch tall, 1G ports are roughly two inches tall, stock. If anything's been ported, all bets are off.

The more important bit is to look at the intake ports and the ends of the intake manifold runners. If they're size-matched, it'll get air into the cylinders MUCH more effectively than mixing a 1G head with a 2G manny or vice-versa, due to the increased turbulence in the air path.

As for the larger outside exhaust manifold studs... it's common practice to remove the outermost studs and re-drill/tap for the beefier ones.

Cam angle sensor, from what I've seen, is pretty much movable as needed. The 95-96 had the CAS just behind the intake cam gear, but the 90-94 and 97-99 both have it on the passenger end, albeit with the 97-99 using a funky non-adjustable sensor.

Head stud size is true, but that'll just tell you if it's a six bolt or a seven bolt head. Plus, the seven bolt head can have the headstud passages bored out to allow fitment onto a six-bolt block.

 

[Black Venom]

"Well it probably didn't come that way from the factory. You probably just have a 1g 7 bolt head."

In caps it doesn't show there are different sizes of studs to differentiate the 1g and 2g heads from. It shows there are 8's and two 10's for both cylinder heads. Then to make sure my date stamping worked, I checked on the head bolts for 1g's and 2g's. There was a small bolt for 2g's and the same one listed for later 1g's, then a larger one for earlier 1g's. However I did only research under the d27a and d33a chasis codes.
If you know of another way to tell what each came with from factory please let us know.
BTW I know it's a 6 bolt head,slightly ported.

 

[dave99gst]

97-99 head has CAS in same position as 1g CAS