Will Vortec heads from a 350 fit a 305 without mods? I have heard two different things.

 

They definitely fit, if you mean, bolt up. But you will lose quite a bit of compression because the 350 Vortec heads are 64cc chambers, so you'd probably drop to around 8.5:1 (just a guess). Might be able to gain a little back with a .015 shim head gasket. The best option would just be to mill the heads down a little until you're close to the stock size 58cc chambers. It's a fairly common mod though, especially if you can pick them up for a good price.

Just remember, you need a Vortec specific intake manifold too.

 

I've been running the Vortec's on my stock bottom end since December '01. Bolted them on stock with a spring upgrade and clearance for 1.6 rockers in the pushrod slots. LT4 cam, Edelbrock RPM Intake, Edelbrock headers.

This pic was in Feb '02 I think

 

Couldn't you change pistons to some domed ones to keep the compression up? That would be expensive, though.

Did you mill the heads to keep the compression?

 

Yes you could install higher comp pistons but I would not spend that on the 305. I would build up a larger bore engine.

The compression issue is overstressed in the case of modding a stock block 305. Yes try to get the ratio that you want if are building an entire engine. ie: a 350

No milling.......runs on reg unleaded with a very modified timing table it runs great, pulls great, and has little knock.

Thanks to BronYrAur and Dewey both for help with the timing.

 

Glad you got it running nicely.

Ever get track times from her?

 

I'll probably cheap out and get some aluminum L98s. Same combustion chamber, they flow pretty well and I don't think I will need another intake. I'll probably port them and then save for a LS-something.

 

Alum L98s use the old style SBC intake manifolds up to 1987. Nifty anyway because then you can get a non egr intake manifold for a 4 barrel carb and get a TBI adapter. They also have centerbolt vavle covers making it a pretty unique head using pre 87 intake with 87+ centerbolts.

Just for general information the Alum. Vette L98s heads are also the heads that come on the infamous ZZ4 crate engine.

 

Nope............been wanting to but since it's still my only daily driver and not wanting the wife to have tote me around I've put it off untill spring and I get a fresh clutch and a posi unit in it and my truck back on the road.

But.......I've got to say that it has the best drivibility since the mod's in '01'. Cold weather driving and even the idle has improved with time and TunerproRT and some guidance in the right direction. Without the help around here it would not have happened!

 

I knew those were the ZZ4 heads. I have a friend that told me that one. Will they bolt to a 91 TBI intake though? If they will, I will seriously look into some.

 

Is your friends name camaro rs ls7?

I was wrong earlier you will ne the pre 86 intake manifold but people have made the 87+ fit them. Have to search for that one couldn't tell you how.

 

Hey DM glad to hear you got it running better, I almost have mine back on the road after pullin the heads and putting the screw-ins in. Make sure you post your results after you do the tuning in the spring. Good luck man

91_5.7, the 91 TBI intake won't just bolt up to the ZZ4 heads, you'd have to elongate the center 2 bolt holes on each side of the intake, because the angle is different.

 

Thanks and glad to hear that you've about got yours repaired.

What studs did you end up using on your heads?

DM

 

I just had the machinist put in the ones he had at the shop. They're 7/16" screw ins with the top half still being 3/8" studs, I didn't want to go replacing rockers and everything. Hopefully this car will stay running good now and stop breaking things ha.

 

I have debated getting some vortecs too. I have also heard you need to modify the egr plumbing to get it to work properly? Anyone know exactly what to do there?

Are the stock L03 187 Swirl ports 58cc? If so, considering a new thicker gasket with new heads how many cc's should the heads be to get a compression ratio of 9:3 - 9:8 to 1?

 

Yes there 58CC...you wouldneed a thinner gasket to achive that compression.

 

My 305 is 10.3:1. 081 TPI heads that have been milled down and cc at 55cc, .020" nominal 305 shim head gasket, flattop pistons with 6cc of valve reliefs, decked block to .020" deck height. The block is also .040" over.

I am not sure how GM built the L03. The older LE9 and L69 were built with the same compression ratio but got there in different ways. The L69 had 58 cc chambers and a flattop piston. The LE9 had a dished piston with 52 cc chambers. Both were 9.5:1 advertised. The LG4 used a dished piston with a 58 cc chamber and was 8.6:1.

Should be fairly easy to keep 9.3-10:1 on your L03. Keep in mind the deck surface on the 350 vortec heads is not the thickest. Your best bet is to run the thinnest shim style gasket you can find, mill the heads what you can, and just run with it.

 

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I'm sorry but I don't remember but what vehicle is this in?

And is this the refered to "roller cammed 305" in another thread?

DM

 

The engine is in a 1983 G20 van with a 2,800 stalled 700r4 and 3.73 gears. It has heavily ported 081s on it along with L69 style flattop replacement pistons.

Very well could be!

Do you call this a "roller cammed 305"?

http://www.cranecams.com/?show=brows...tType=camshaft

I wish this particular engine had Ported Vortecs on it. With a 2" bore marine intake and my current 454 TBI. Maybe 300+ RWHP through cast iron exhaust manifolds and the stock Air Cleaner.

 

Yep.......that's a nice cam