85 C4.

I think I cracked a head today, or blew a gasket.. Car was idling, and threw a CT sensor code, and the fan didn't start. Aux fan switch is apparently defective (*facepalm*) and now it blows its coolant out the rad cap like a small geyser.

Question: If I have to take it apart, I want to make it better..

The engine is new. I dunno what they've done to it. I don't know what is in there, but I was wondering about the vortec truck heads.

What does it take to add them to my engine?

Differences in push rods? Exhaust ports shape/compatibility with current exh manifold? Rockers?

I know the valve covers are different, and the intake angle is different (So, I'll need an aftermarket TPI base to match)

Is there anything else I should know about this? Particular year heads to look for? (I may already have a set of 97 heads, actually)

Any help is appreciated.

 

Any change in the heads or cam will require a tune.... and the 85 ECM is a PITA to tune. I have one. You'd probably be better off retaining the stock heads if you aren't going to go all out with it. Just my opinion.

 

I was going to dump it eventually anyway.. I already have an 89 165 computer and electronics in a box at the shop for it.

 

It looks like the combustion chambers are smaller.. Creating problems only new pistons can solve.

The base is a custom aftermarket piece, of course. About 4 - 5 hundred.

This is more complicated than it looked at first.

 

A tune is not "required" w/new heads, especially mild ones like vortec when you're keeping the same cam, intake, etc. A tune may be desirable....or ideal, but it is not required and to say that is misleading.

The stumbling block w/Vortec heads is really in one place; the flange between the lower intake manifold and the head. The bolt pattern is different and the ports are raised in the vortec head, so getting an intake gasket to fit/match/seal is challenging.

It's doable; a couple friends and I put Vortec heads on an '84 CFI. We drilled/tapped new intake bolt holes in the head, then made plugs for the old bolt holes out of cut-off bolts. It worked out great for us. IT's doable, but does require some fiddling to make it fit/work and port matching would help too. I don't believe there is a significant difference in combustion chamber volume. We had no issues w/compression or detonation after the swap.

To address your questions specifically:
Differences in push rods? No

Exhaust ports shape/compatibility with current exh manifold? Exhaust port mismatch will be no worse than it is w'your stock heads and too-small stock exhaust manifolds already are mismatched.

Rockers? Vortec heads use self aligning rockers, your car dose not. You car has guides for the pushrods cast/machined into the heads. THe rockers are physically interchangable, but you would want to use the stock vortec, or any "self aligning" SBC rocker w/the Vortec heads.

I know the valve covers are different, and the intake angle is different (So, I'll need an aftermarket TPI base to match). No. The "intake angle" is not different and you don't NEED a new base. As outlined above, a new base would be easiest to bolt on and "ideal" but it is not...."required". Valve covers you can use any "Vortec" valve covers (which will all be stamped steel) OR any later C4 "Corvette" valve covers that have center bolts. Including LT1.

 

Any advice RE:

1) 85 power accessory mounting on Vortec heads?

2) Using thicker than stock head gaskets?

 

No. I don't see your problem w/accessories.

As I said above, we did it on an '84, which has accessories that bolt on in the same place as an '85. There was no issue with mounting of the accessories.

Compression will be about 10:1 w/ the 64cc chamber and flat pistons. You can use thicker head gaskets but that will reduce the efficiency of the Vortec combustion chamber.

 

TY Tom!

 

vortec heads..I have gone thru the process. the rockers MUST be self aligning..my first set I simply removed from a late 90s pick up with a vortec engine. cheap. I have since bought a set of 1/6 roller rockers that are self aligining.. Scorpen is the brand. No need for guide plates and is recommended not to use them. Push rods are the same as regular. Vortec manifold has only 8 bolts to the vortec head, regular manifold(and head) is 12. Any centerbolt valve cover will fit tho with roller rockers you may have to clearance drippers. Spark plugs are angled, L-98 are straight.--- may cause difficulties for tune up. 062 is the votec head you want, there are a couple of different ones. Vortecs are iron, not aluminum.Eldebrock supplied gaskets with my manifold and also when I bougth the runners so cant advise on those. prices..Indiana craig list has a machine shop that sells them for 350 bucks a pair. That's where I bought mine cause its local.You should be able to find them around the same price. Mine were fresh machined. Eldebrock manifold cost me just under 500 bucks new from Summit..same for runners. I am a over the road driver so I picked them up at Summit in Ackron, Ohio, saved on shipping. I have a set of Headman headers that really have close issues with one of the spark plugs..at tune up time, I have to use an open ended wrench to remove the plug(one plug)..no room for a socket.I haven't found out yet if they make special headers for that swap for our vette..mine is an 86. With the expense of the manifold and big runners ( you can use you old stock runners if you chose) one gets in the price range of eldebrock heads or close to AFRs, which fit your manifold/engine. good luck. take pics. Oh, all extras fit,,alt, air cond., ect.

good info site for vortec head

http://www.superchevy.com/how-to/97458/

 

Good article.. Thanks!

 

an issue to consider, is maintaining EGR, a consideration and do the Vortex heads have an exhaust heat riser?

 

No heat riser.. Yes to EGR.

 

I did some research for aftermarket heads; the car in question required EGR so the heads had to have a heat riser; boy does that limit selection, but they are out there.

Easiest way, just go to Summit's website and see / compare whats available.

Vortec heads are cheap, but besides the lack of EGR compatability, they have several shortcomings that (more pricey) aftermarket heads already address; amongst those, small vavles, a weak spring package, and tolerate only cams with minimal lift...forget about using 1.6 rockers if that was part of your plan.

Of course all these issues can be addressed and overcome, but by then the costs have mounted and those vortec heads may not seem the bargain they once were. Oh, add in a vortec dedicated manifold too.

 

Are you sure about that? I think they use a tube from the exhaust. I know both the SD and the Edelbrock Vortec manifolds have an EGR provision?

I'm happy with the valves. I want a peppy street car with a power band that reflects that. I have no interest in staying spun up so tight it's not fun to drive in traffic. The rocker issue and springs are addressed fairly easily. I have a good machine shop and there's even tools to do it at home. Just not a concern, imo.

Related:

http://www.superchevy.com/how-to/97458/


Yeah.. But if they're not cracked (Barely even looked at them, actually) they're just sitting in the back of my shop for free. That really helps out on the cost.

Yeah, that's an issue. I see workarounds here, but if I do it I'll just buy the dedicated part. SD or the Edelbrock 3817. 400 to 500 new.

 

funny, I have 1/6 roller rockers on my vortecs. EGR IS a pipe from the exhaust. Its not about valve size, but flow velocity. Vortec velocity is 25% more than Sportsman2 heads at 0.500 inch lift. 1.94 intake and 1.50 exhaust. I have beehive springs on my heads ,giving me up to 480 of cam lift, which, by the way, I don't have cause its a street engine WITH manners. Yep, the intake is pricey but there are used ones out there for sale.With the money I have invested in my Vortec set up, I could have bougth a set of aftermarket aluminum heads but that's it.Would still have to buy a better intake,ect. Vortec heads strong point is the torque down low..lots of tourque down low. Tourque wins drag races if all else is the same