GN1 Heads

[87WE4BOOSTED]

What are the determining factors that need to be taken into consideration when upgrading from the stock heads to Iron GN1’s? Upon removal of the old heads, is there anything I must do to the block before I place the new heads on? Any help would help out a lot. :redface: Thanks.

 

[ttypewhite]

I would consider aluminum heads after the 10.20 mark in the 1/4. Stock heads worked are pretty damn impressive to beat ( best bang for your buck). the aluminum heads are bolt ons just like stock. No special block prep required aside from everything being flat and true. FWIW I ran 10.29 with my irons, swapped them out for GN1 and ran 10.22. Picked up dick really. With your mods in your sig, don't look for instant results, cause they won't be there at your level. Not trying to discourage your choice. But I am speaking from experience.

 

[whitehot1]

You will need the correct head bolts or studs for use with the GN1 heads and also new push rods will be needed,the stock push rods will be to short.

Ps, GN1 heads are aluminum - i've heard people refer to champion ported stock casting 8445 heads as GN1's but they are not.

 

[jpwalt1987]

You may also run into the problem of the pushrods rubbing the cylinder head where they go through on the GN1s. I know of a few people , myself included that had to massage the hole for the pushrod. Nothing major until you break into a waterjacket or intake port. I would stick with the ported irons. best bang for the buck. And they are less likely to crack. JW

 

[KevinB]

I'm not sure, but I think the ported Champion irons are ported to match to a Felpro 1200 intake gasket. To get the most out of them, I would recommend a ported intake that has also been ported to fit a 1200 intake gasket.

 

[turbofabricator]

The GN1's are port matched to the stock GM intake gasket. (NOT the 1200 Fel-Pro's)

The GN1 heads are also prone to cracking. I've seen many of them crack. (actaully "most" of them, though the later versions claim to have the cracking issues fixed.) I feel that ported iron heads are the way to go if you are planning on never exceeding 10.00 in the 1/4. Champion does a nice job on the stock iron heads, as do MANY other porting guys. (I don't know any women head porters, for the Buick V6, but my wife has ground on them in the past.) (actually women DO make for good head porters, but just don't ask them if they do "head jobs"! )
Well ported 8445 stock heads will get you deep in the tens, and have gone well into the nines at over 138. The weight loss of the aluminum heads is worth while, but probably only on your back, when installing/removing. As stated above which I agree with, completely, the GN1 heads do work well, but if you have a good set of ported irons, you won't gain a significant amount of power. The complete package needs to be evaluated to see where you need to make changes, if any.
The above is: "Just My Opinion."

 

[87WE4BOOSTED]

The GN1's are port matched to the stock GM intake gasket. (NOT the 1200 Fel-Pro's)

The GN1 heads are also prone to cracking. I've seen many of them crack. (actaully "most" of them, though the later versions claim to have the cracking issues fixed.) I feel that ported iron heads are the way to go if you are planning on never exceeding 10.00 in the 1/4. Champion does a nice job on the stock iron heads, as do MANY other porting guys. (I don't know any women head porters, for the Buick V6, but my wife has ground on them in the past.) (actually women DO make for good head porters, but just don't ask them if they do "head jobs"! )
Well ported 8445 stock heads will get you deep in the tens, and have gone well into the nines at over 138. The weight loss of the aluminum heads is worth while, but probably only on your back, when installing/removing. As stated above which I agree with, completely, the GN1 heads do work well, but if you have a good set of ported irons, you won't gain a significant amount of power. The complete package needs to be evaluated to see where you need to make changes, if any.
The above is: "Just My Opinion."

Thanks guys for the feed back,

I think I will run with a set of Champion Irons. These make sense for my application. I really don’t think I want to get that deep in the 10’s. I do want to break them but don’t want to go past the mark of needing a roll cage etc.

So if I go with the Champion Iron’s, I won’t run in to the problems that I would have run into if I were using GN 1’s? “The GN1 heads are also prone to cracking. ““You will need the correct head bolts or studs for use with the GN1 heads and also new push rods will be needed, the stock push rods will be to short.” I’m trying to get the most BANG for my BUCK without the HASSEL mentioned above.

 

[turbofabricator]

Ported irons are a simple bolt-on. Push-rod length will still need to be verified, as they should even on a stock rebuild. (most engines -Buick V6's- I have built have push rods about .030", or so, too long from the factory.) I would suggest a hydraulic roller cam and roller rockers to get everything right. Have the intake ported to match at the same time, too. Standard ARP bolts are all you need to bolt them on. Even the GN1's have a simple ARP bolt kit available from Champion, too.
By changing anything with your combination, it will effect intake manifold match-up, and push rod length. Head milling, head gasket change (thickness) block milling, valve highth, different casting, factory machining variances, rocker arm variance/brand, ect. all have an effect on how things bolt-up. Just check everything CAREFULLY when building an engine. Not rocket science, just precision. It all adds up to power.