mismatched heads to vortec

[MF Doom]

well i have mismatched heads on my 350 the drivers side are 882 and the passengers are pretty horrible can't remember the casting numbers but they are the worst of the worst from what i read. I see vortec heads are pretty cheap on craigslist. Would it be worth it to swap them over? It's a daily driver the bottom end is great but it falls on its face on the top end, it takes forever overtake someone. Is it going to be worth all the work?

[Captainfab]

That depends on the condition of the shortblock. You do realize that you would have to purchase a different intake manifold for the Vortec heads correct? If you do go this route, be sure you get actual Vortec heads and not just a set of crappy TBI swirlport heads.

[MF Doom]

Originally Posted by Captainfab

That depends on the condition of the shortblock. You do realize that you would have to purchase a different intake manifold for the Vortec heads correct? If you do go this route, be sure you get actual Vortec heads and not just a set of crappy TBI swirlport heads.

well everything looks good except on the crappy head one of skirts on the springs snapped and the fuel pump lobe is worn out or the pushrod but yes i do know i have to get a new intake. The # to look for are 062 and 906. I'm just wondering if it'll be worth it. I've read that vortec heads can give you much better top end

[Marshy]

Originally Posted by MF Doom

well everything looks good except on the crappy head one of skirts on the springs snapped and the fuel pump lobe is worn out or the pushrod but yes i do know i have to get a new intake. The # to look for are 062 and 906. I'm just wondering if it'll be worth it. I've read that vortec heads can give you much better top end

They are the best flowing OEM head. The part where they really shine is better flow at low lift conditions.

You need to consider what will happen to your compression. The 882 heads are 76cc chambers and the Vortec heads are 64cc's.

Since you mentioned something about the fuel pump lobe being worn, what condition is your cam in? Maybe its time for a new cam or maybe a full rebuild?

[MF Doom]

Originally Posted by Marshy

They are the best flowing OEM head. The part where they really shine is better flow at low lift conditions.

You need to consider what will happen to your compression. The 882 heads are 76cc chambers and the Vortec heads are 64cc's.

Since you mentioned something about the fuel pump lobe being worn, what condition is your cam in? Maybe its time for a new cam or maybe a full rebuild?

Just read up on that. If i have flat top pistons the comp will be too high im assuming. Guess i need to buy one of those cheap scopes and look. How would i go about checking the condition of the cam without pulling it? It runs pretty good now that i rebuilt the carb since it was waaay over jetted. The truck is a daily driver

[Marshy]

Uh, you will have to pull the heads and measure the deck clearance to determine what compression you have. You'll also need to know if the piston is dished or has any reliefs and how large just to begin to estimate the compression ratio. Pulling the heads is the right way to figure all of that out.

To check the cam you could but a cheap mag based dial indicator at harbor freight and check each rocker arm for lift. Someone else might have a better way but I'd be concerned for the health of the engine if you really did have a fuel pump lobe going out. Any idea what cam is in it now? You'd want to know what the lift and duration is to make sure your not going to bind the springs in the vortec head or have pre-ignition with a really high dynamic comp.

[webfoot]

I wouldn't worry too much about running 64 cc heads on a 350, realizing of course, that the heads probably came off of a 350 to start with. But, if you have a wimpy stock-ish cam, it could use upgrading to take advantage of the much better flowing heads. With the intake off already it isn't a horrible amount of additional surgery required.

[StarDust]

Originally Posted by webfoot

I wouldn't worry too much about running 64 cc heads on a 350, realizing of course, that the heads probably came off of a 350 to start with. But, if you have a wimpy stock-ish cam, it could use upgrading to take advantage of the much better flowing heads. With the intake off already it isn't a horrible amount of additional surgery required.

Cam is bone stock i think since i get smoked by v6 OBSs and nbbs lol now I'm not sure if its because c10s are heavy as hell or the 350 is on its way out lol should I just find a matching 882 head? Or is there no benefit .
Edit:this is mf doom wrong account lmao

[Marshy]

I'm confused why you have two accounts....

Anyways, 12cc decrease in combustion chamber is nothing to wink at. I changed my head gasket and reduced my cc by 5cc's and gained around half a point in compression. It should be considered. Of course if your carb and ignition needs tuning then all this talk is for nothing. I'm sure there are plenty of people that have good running 882 heads that could flog a poorly tuned carbed vortec motor.

[storm9c1]

Vortec heads will cause unmanageable compression with the wrong pistons. Yes they come from 350s, but they could push upwards of 9 to 10:1 compression which is OK on fuel injected vehicles with knock sensors and a computer to control timing. I also can't remember if stock Vortec engines used dished pistons or not, I'm pretty sure they did.

Running 10:1 or more compression on a carb engine is nothing to shake a stick at, especially if you want to run 87 gas. It will be a challenge.

Vortec heads are a great upgrade, but you must figure out what pistons you have and what your CR will be. To do it right, you should also calculate dynamic CR with the cam setup as well.

[Marshy]

Originally Posted by storm9c1

Vortec heads will cause unmanageable compression with the wrong pistons. Yes they come from 350s, but they could push upwards of 9 to 10:1 compression which is OK on fuel injected vehicles with knock sensors and a computer to control timing. I also can't remember if stock Vortec engines used dished pistons or not, I'm pretty sure they did.

Running 10:1 or more compression on a carb engine is nothing to shake a stick at, especially if you want to run 87 gas. It will be a challenge.

Vortec heads are a great upgrade, but you must figure out what pistons you have and what your CR will be. To do it right, you should also calculate dynamic CR with the cam setup as well.

Yup, that was what I was getting at. Well put. And yes, the Vortec 5.7L did use dished pistons but had a healthy quench band. Nothing quite as big as the old ask tray type pistons of yesterday.

[webfoot]

Even flat top pistons commonly have 4 cc worth of valve reliefs "dish" in the top.

You 2 make it sound like anyone who is going to run 64cc heads on a 350 is going to blow their motor up. Not true. it is a very common swap. But, like I said it doesn't make much sense to swap out to the vortec heads if you are going to leave that stock cam in it. If he pulls the heads off and there are some domed slugs in there, then of course no.

I've built and run a 383 with 64cc heads and flat top pistons (carb & HEI) that does not detonate. It used premium fuel but I'd rather run non-ethanol premium in all of my old rides anyway. Its still pump gas. This is on a car that was and still is flogged on an 1/8 mile track, shifted at 6200 RPM using the "wimpy" 400 rods, every weekend for the past 2 summers..

When you buy aftermarket heads, you typically have 2 choices, 72 cc or 64 cc, and thats not because they want you to blow your motor up, or drive around for thousands of trouble free miles.

[storm9c1]

I never implied it would "blow up." I said it could be a challenge if compression (both dynamic and static) aren't considered. That is a fact when changing heads. And I have seen guys get burned by this (using flat tops with Vortec heads and the wrong cam combo), myself included. They had to run a terrible timing curve just to keep it from pinging at mid-RPM. This is on the road, climbing hills, pulling loads etc. (ie: like a truck does). Not at the track with quick 1/8 mile WOT runs. Two totally different use cases that are tuned differently.

Just trying to set expectations here. All I am trying to convey is to think it through and do some due diligence before slapping smaller cc heads on something.

We should also ask what the OP wants to do with the vehicle. And if running 92 octane forever is OK or not. etc etc. Just trying to get people thinking, that's all. I like Vortec heads and wouldn't build a basic SBC without them. But I'd also carefully choose pistons and cam.

[Marshy]

Originally Posted by webfoot

Even flat top pistons commonly have 4 cc worth of valve reliefs "dish" in the top.

You 2 make it sound like anyone who is going to run 64cc heads on a 350 is going to blow their motor up. Not true. it is a very common swap. But, like I said it doesn't make much sense to swap out to the vortec heads if you are going to leave that stock cam in it. If he pulls the heads off and there are some domed slugs in there, then of course no.

I've built and run a 383 with 64cc heads and flat top pistons (carb & HEI) that does not detonate. It used premium fuel but I'd rather run non-ethanol premium in all of my old rides anyway. Its still pump gas. This is on a car that was and still is flogged on an 1/8 mile track, shifted at 6200 RPM using the "wimpy" 400 rods, every weekend for the past 2 summers..

When you buy aftermarket heads, you typically have 2 choices, 72 cc or 64 cc, and thats not because they want you to blow your motor up, or drive around for thousands of trouble free miles.

You're imagination is running wild man, no one said it would blow up. Only thing I said was that the increase in compression should be considered and rightfully so. The OP doesn't seems to know if he has dished or flat top pistons so it stands to reason that he's unsure what his compression is let alone his quench or deck clearance. Which is all fine but bolting on 8cc's smaller heads isn't a good idea IMO without validating some other parameters of his motor. Maybe the OP doesn't want an engine that uses 94 octane. If the OP doesn't care then by all means, just slap them on and pump some 94 octane in it and hope for the best. Or take the route a typical engine builder would do and understand the specs of the engine and what the change would have on it.


OP, here's an example with a whole bunch of assumptions to make my point...

Specs: a 350 bored 0.030" over, standard stroke and rods, flat top pistons with -4cc of relief, 0.020 deck clearance, and a 4.100 diameter head gasket with a crush thickness of 0.026", using 72cc heads, compression = 9.6:1

Change to 64cc chamber heads and the compression = 10.5:1

With a stock'ish size cam that would be too much compression to regular fuel. I'd have to make some more assumptions about cam profile to determine the dynamic compression but it would likely result in you needing a high grade pump fuel (or possibly higher like 100 octane).