Hi, I have a '91 Z28 that has a 305 TPI engine in it. I'm currently in the process of replacing the stock intake with a Weiland 7540 Stealth RAM... and now that I've gotten down to the heads, I am considering replacing the heads with aftermarket heads while I'm at it. The heads have a lot of carbon build up and I know for sure the valve stem seals are leaking in one or more cylinders. But the engine is 30 years old with 150k miles on it! Can anyone give me a suggestion for aftermarket heads?

This car is a street car that I like to drive around town on weekends, so I'm not looking for anything nuts. Just something new with maybe a small amount of performance gain. It looks like there are a ton of options to consider so I'm like a deer in headlights when it comes to picking out a decent set of heads.

Thanks in advance!
Jeff

 

they don't make a lot of performance heads for the 305 which I always thought was stupid considering how many were put into cars. when I was searching the heads that kept coming to the top of the heap were the trickflow 23 heads. they have good reviews and are made to add performance to a 305. you can actually bump your compression a tad.

 

You could see if you can find a set of 305 Vortec heads (059 casting, I think). It would provide a decent bump for you. The downside is that you'd have to switch to a Vortec bolt pattern intake which doesn't make a lot of sense if you already bought a new intake.

As far as aftermarket heads go... I guess I really can't recommend going that route. Most of the 305 heads I'm familiar with are marketed towards circle track racers that have to meet certain rules. You could potentially put larger heads on, but I don't think you'd be happy with that, either. 601 and 416 heads came in the l69 engines and aren't too bad with some porting. There's several threads on them around here somewhere.

If you're going to purchase aftermarket heads, you may wish to just see if you can find a relatively cheap 350 short block to purchase and install them on. Maybe throw a cam in while you're at it. You'll get a lot more for your money that way. Depending on your location, you might even be able to just get an entire L31 Vortec from the junk yard for $300-ish. Check bearings, install your go-fast parts, and have a heck of a lot of fun.

 

The heads he has now are basically 416es with a center bolt pattern. The Trick Flow 23 degree heads mentioned look really good and they're not that costly. If I were on a budget I'd try to find someone that could port the irons out and replace the seals if the guides aren't shot. Conversion to positive seals would be nice and if you get the small ones you could bump up your cam some.

Also, to be sure you're aware you'll need ECU recalibrations for this stuff. Maybe larger injectors something like some 24-28lb/hr. Should run pretty well when done.

 

I like the "Engine Quest" Brand iron heads. They have Vortec style combustion chambers and a thicker deck surface, according to the manufacturer. I have not them.

https://enginequest.com/enginequest/...chevrolet-350/

Popular Hotrodding used them in their "Sledge Hammer $3500 447 HP build.

https://www.hotrod.com/articles/0611...c-small-block/

Another link(I have not read this one yet)
https://www.hotrod.com/articles/0710...-engine-build/

 

The Engine Quest heads in that article are the same as the Pro Topline 906\350C heads I run. Engine Quest purchased them when Pro Topline went under. They're basically just reproduction Vortec heads with some mild improvements. Thicker decks, better casting, screw in studs, etc. Stock they have 64cc combustion chambers which will drop compression on the 305.

They also make 305 heads that, again, are basically reproduction 305 Vortec heads. They might make them in the old style bolt pattern, though, instead of Vortec only. But if you're set on going aftermarket heads, just go for some decent aluminum heads right out of the gate.

 

The Engine Quest(EQ) head used in the "Sledgehammer " engine build had the bolt pattern that allowed our TPI manifolds and rocker covers to bolt on. "Jorlain" I am considering EQ heads if I build a TPI L98 to replace my LB9 TPI 305 AT, in my '89 IROC Vert. What can you tell me about your EQ experience? PM if you prefer. Mike

 

Read this post to see what Ja85Z28 did to his L69 305: https://www.thirdgen.org/forums/tech...-aerohead.html

 

Thanks for the tips everyone! I guess, now I'm leaning more towards taking the existing heads off and taking them to a machine shop to be cleaned/rebuilt. My thought it to just do the minimal to rebuild the 305 since it's so old and save the money for a future 350 engine swap. Now, if I took them to a machine shop, is there anything special I should think about besides cleanup? I.e. is it worth porting or no? And is it fair to assume that changing valves/rocker arms isn't really going to do much from a performance perspective?

Thanks,
Jeff

 

Just have them pocket ported.