2G 1G 6-Bolt Head on a 2G 7-Bolt Block?

[VT_4G63]

I want to double check that it is OK to mount a 1G 6-Bolt Head on a 2G 7-Bolt block?

I read somewhere once that this was OK because the dowel pins on the block are what align the head, not the head studs. Also the 7-Bolt Head studs are smaller by 1mm in diameter than the 6-Bolt head studs so that doesn’t pose an issue either (I can’t remember the specific sizes of the 2, I think 11mm and 12mm?).

I recently purchased a 1G head in great condition with a lot of upgrades, and the valves are holding perfect vacuum pressure. So I would like to use that on my recently refreshed and upgraded 7-bolt bottom-end that I’m about to drop back into my Spyder.

Please let me know if this is ok to do.

Thank you,
Ron

 

[pauleyman]

Yes it bolts on. Keep in mind you will need a different intake manifold and if I recall not all heads have a provision for a 2g cam sensor so you need to deal with that and a possible cam change too.

 

[VT_4G63]

Yes it bolts on. Keep in mind you will need a different intake manifold and if I recall not all heads have a provision for a 2g cam sensor so you need to deal with that and a possible cam change too.

Ok, thanks for the reply.

I have a 1G intake manifold ready to go that I was going to run if I swapped this head.

As far as the cam sensor goes the 7-bolt originally in the chassis is a 2GA, so I’m dealing with the cam sensor on the cam sprocket to begin with. Was maybe going to run a black top cam angle sensor I have, regardless of the head I go with.

As far as cams, I was going to run the BC 268/272 combo. The 1G head I’m going to swap in has dual valve springs, which is an upgrade, but probably overkill, as well.

 

[jdxnc]

Keep the 2g crank sensor and switch over to a 2GB cam sensor, it's more accurate than the 1g CAS.

 

[Justin DuBois]

Keep the 2g crank sensor and switch over to a 2GB cam sensor, it's more accurate than the 1g CAS.

^^^^^\what he said

 

[biglady112]

Keep the 2g crank sensor and switch over to a 2GB cam sensor, it's more accurate than the 1g CAS.

Name me an instance where a car has performed better or had an engine failure from a less accurate 1G cam angle sensor?

Because in 25 years I have never been able to put a blame on one or seen a difference in how a car acts.

I don’t deny on paper the difference in how they function but, we don’t drive and race on paper.

 

[1990TSIAWDTALON]

Even the Green top CAS's I run, do a fine job and I don't see failures from them (never yet). I've never ran a crank sensor but 6 of one, half a dozen another, they both are doing the same job the way I see it and I agree with @biglady112 .

 

[jdxnc]

Name me an instance where a car has performed better or had an engine failure from a less accurate 1G cam angle sensor?

Because in 25 years I have never been able to put a blame on one or seen a difference in how a car acts.

I don’t deny on paper the difference in how they function but, we don’t drive and race on paper.

For 99.9% of people it will not cause any performance difference or be the direct cause of an engine failure, however, coupled with the 2g ECU without ECMLink, it will often trigger a CEL for a false misfire. Even with ECMLink, if you have misfire detection turned on, it will cause a false misfire and shut down one coil on some cars.

The other main advantage to the 2g setup is no dicking around with a timing light and adjusting the CAS, it's locked at the correct timing. To that I have seen a 1g CAS come loose and swing all the way to the full retard setting, luckily.

Given the opportunity, I'd stick with a 2 piece crank/cam setup every time.

 

[biglady112]

For 99.9% of people it will not cause any performance difference or be the direct cause of an engine failure, however, coupled with the 2g ECU without ECMLink, it will often trigger a CEL for a false misfire. Even with ECMLink, if you have misfire detection turned on, it will cause a false misfire and shut down one coil on some cars.

The other main advantage to the 2g setup is no dicking around with a timing light and adjusting the CAS, it's locked at the correct timing. To that I have seen a 1g CAS come loose and swing all the way to the full retard setting, luckily.

Given the opportunity, I'd stick with a 2 piece crank/cam setup every time.

I can’t deny that I have seen a cam angle sensor come loose. Shit, it happened to us at Bonneville and it fully ADVANCED the cam angle sensor and fire slotted the head at 200mph.

That had nothing to do with the cam angle sensor though. It had to do with the owner moving all four motor mounts to solid mounts (home made, all steel on all steel mounts) and not securing the nuts correctly. The turbo also broke all of its bolts on the pass before, melted his zip tie holding the dipstick down and caused a small engine fire. Needless to say he was kind of always the problem when I came to helping with that car.

But, we still never had a cam angle sensor itself not function. And I have never had one I personally installed and timed ever come loose. Not all mechanics are created equal there.

I won’t touch a 7 bolt or any of its damn sensors. That is another topic and argument however. I do everything I can to make every car fully a 6 bolt setup. At the same time, I don’t own a 4g63 and have not for years and likely never will again. Just merely sharing my experience.