350 Heads vers.305 Heads ZZ4 vers. L98
07-03-2003, 11:33 PM
#1
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Location: Dover A.F.B. Delaware
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350 Heads vers.305 Heads ZZ4 vers. L98
What's the diff??? I ask because I have a 305 Z28 auto....I need a either a rebuild 
(tired of 305)
Or I found rebuilt L98 with heads (No intake, oil pan or other things I don't need) And a ZZ4 short block for about the same price.
Now what I was thinking was if 350 heads are better then 305 heads I was going too go L98....But if 305 heads are just as good as L98 heads or if they can be made better then L98 heads with a little work (I know they can be made better with a lot of work, but I can't see putting a bunch of money into 305 heads) Like I could do myself then I'd rather spend my money on a ZZ4 shortblock and port my heads and intake (and hopefully have enough $$ left over to by some runners)
(tired of 305)Or I found rebuilt L98 with heads (No intake, oil pan or other things I don't need) And a ZZ4 short block for about the same price.
Now what I was thinking was if 350 heads are better then 305 heads I was going too go L98....But if 305 heads are just as good as L98 heads or if they can be made better then L98 heads with a little work (I know they can be made better with a lot of work, but I can't see putting a bunch of money into 305 heads) Like I could do myself then I'd rather spend my money on a ZZ4 shortblock and port my heads and intake (and hopefully have enough $$ left over to by some runners)
07-05-2003, 12:00 PM
#3
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Originally posted by Shaun 90 Iroc
I would opt for the 350 short block. L98 heads.. if no money for better. 350 has some much potential for less money than 305. Or you can do what i did.. buy some Vortec Heads and the SDPC TPI vortec base and the ZZ4 cam =)
I would opt for the 350 short block. L98 heads.. if no money for better. 350 has some much potential for less money than 305. Or you can do what i did.. buy some Vortec Heads and the SDPC TPI vortec base and the ZZ4 cam =)
07-05-2003, 12:36 PM
#5
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Sorry.. well yea.. i would just buy the zz-4 shortblock, i wouldn't use the 305 heads.. Thats just me though.. i always try and get it done fresh and right the first time. You want to leave it with tons of potential.. because if you spend the money maxing out 305 heads with a rebuilt 350.. you are limiting the potential of the engine. In order to increase power from there.. you are looking to eventually get new heads anyway.
07-05-2003, 12:51 PM
#6
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No reason to apologize.....Ok but here's the problem SEVERE BUDGET....I mean from what I've heard you can make 305 heads flow better than Vortech heads....If I can get them to flow that good cheap I can put my money else where (N2O???) What do you guys think a ZZ4 short block with a P/P Intake, SLP runners, Ported plenum, P/P 91 TPI 305 heads, and a 150 shot would run if I could hook it up??
On the other hand a L98 with stock heads and valves, P/P intake, SLP runners, a ported plenum, with a 150 shot.
The ZZ4 has a forged crank (good for later), Stronger rods, and it's new not rebuilt
On the other hand a L98 with stock heads and valves, P/P intake, SLP runners, a ported plenum, with a 150 shot.
The ZZ4 has a forged crank (good for later), Stronger rods, and it's new not rebuilt
07-05-2003, 10:14 PM
#8
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Location: Calgary, Alberta, Republic of Western Canada
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Originally posted by Slow91z
No reason to apologize.....Ok but here's the problem SEVERE BUDGET....I mean from what I've heard you can make 305 heads flow better than Vortech heads....If I can get them to flow that good cheap I can put my money else where (N2O???) What do you guys think a ZZ4 short block with a P/P Intake, SLP runners, Ported plenum, P/P 91 TPI 305 heads, and a 150 shot would run if I could hook it up??
On the other hand a L98 with stock heads and valves, P/P intake, SLP runners, a ported plenum, with a 150 shot.
The ZZ4 has a forged crank (good for later), Stronger rods, and it's new not rebuilt
No reason to apologize.....Ok but here's the problem SEVERE BUDGET....I mean from what I've heard you can make 305 heads flow better than Vortech heads....If I can get them to flow that good cheap I can put my money else where (N2O???) What do you guys think a ZZ4 short block with a P/P Intake, SLP runners, Ported plenum, P/P 91 TPI 305 heads, and a 150 shot would run if I could hook it up??
On the other hand a L98 with stock heads and valves, P/P intake, SLP runners, a ported plenum, with a 150 shot.
The ZZ4 has a forged crank (good for later), Stronger rods, and it's new not rebuilt
If you can't find L98 heads for $50 or so then FORGET about them. You don't need them!
Go to your local wrecker and get a set of 305 castings that end with either 081 or 416. (If the ZZ4 you get has an intake you will need to check what bolt angles it is using--pre-1987 will dictate the 416s, while 1987 and later will want 081s.) Then have them ground for 1.94" intakes and port and polish them according to the instructions linked at the end of my sig. You will be amazed at how much faster you will be!
Lots of us over on www.thirdgen.org are now running these heads. Total cost is about $400 US COMPLETE! And no one is complaining about them
07-06-2003, 01:27 PM
#11
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ALUMINUM L-98 heads are the same thing as ZZ4 heads. 58cc combustion chambers, 1.94/1.50 valves. They use ONLY the earlier style 86-down intake bolt pattern (even when used on L98 Coverttes 87-up) .
CAST IRON L-98 heads are the variety used on F-body L-98 350 motors and have 64cc chambers and 1.94/1.50 valves. They have ONLY the later 87-up bolt pattern.
305 heads are all cast iron and have combustion chambers around 58cc with valves that are as small as 1.74/1.50 (early heads) and as big as 1.84/1.50 (later heads). They could be had in either the early style 86-down bolt pattern or the later style 87-up bot pattern depending on year and application. If they use centerbolt valve covers then they have the 87-up style intake bolt pattern. They can be modified to take a larger 1.94 intake valve but the ports are still slightly smaller than any 350 head, at least on the intake side, and the valve centerlines are slightly closer together to fit down the bore of the smaller 305 engine (which is wy 1.94/1.50 is about as big as you can go with them).
Out of the box, L-31 Vortec heads will hand any of the above heads their a$$. Vortecs have 64cc chambers, 1.94/1.50 valves and require a Vortec-specific intake to bolt on (totally different bolt patern and intake port shapes than any of the above heads).
CAST IRON L-98 heads are the variety used on F-body L-98 350 motors and have 64cc chambers and 1.94/1.50 valves. They have ONLY the later 87-up bolt pattern.
305 heads are all cast iron and have combustion chambers around 58cc with valves that are as small as 1.74/1.50 (early heads) and as big as 1.84/1.50 (later heads). They could be had in either the early style 86-down bolt pattern or the later style 87-up bot pattern depending on year and application. If they use centerbolt valve covers then they have the 87-up style intake bolt pattern. They can be modified to take a larger 1.94 intake valve but the ports are still slightly smaller than any 350 head, at least on the intake side, and the valve centerlines are slightly closer together to fit down the bore of the smaller 305 engine (which is wy 1.94/1.50 is about as big as you can go with them).
Out of the box, L-31 Vortec heads will hand any of the above heads their a$$. Vortecs have 64cc chambers, 1.94/1.50 valves and require a Vortec-specific intake to bolt on (totally different bolt patern and intake port shapes than any of the above heads).
07-06-2003, 02:56 PM
#12
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Ok so I have 91 305 heads....If I put 1.94 valves in and P/P them how good would they run compaired to say Stock Vortech's??
And should I do some bowl work to drop the compression....58cc's would be like what 11/1 or something??
And should I do some bowl work to drop the compression....58cc's would be like what 11/1 or something??
07-06-2003, 06:52 PM
#13
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Bowl work does nothing for compression ratio. It just increases flow. Compression ratio is dictated by combustion chamber size and piston top design.
From what I've read in CC, HR, PHR, & CHP stock vortec heads will outflow, ported double hump heads, or even bowtie heads. You should be able to pick up some vortecs for about half of what the L98 heads run. Unless you do your own port work, you'll pay almost if not more than that trying to get your 305 or L98 aluminum heads to flow even close to the votecs. Don't look just at flow numbers either, velocity plays a major role in head design and that is also where the vortecs do very well. There is a place that does redo the vortec heads to run with non-vortec intakes.
Something else to consider. Aluminum heads can run smaller chamber volumes with lower octane fuel than cast iron heads. You may get by with running 11:1 compression w/ aluminum heads on 93 octane pump gas, but I seriously doubt you'll run 93 octane w/those 305 heads @ 11:1 and not detonate. I ran 64CC iron heads w/ flat tops and had to run 92 or 93 octane or have a pinging engine. If you have the cash to run fuel above 92 octane then you have the cash to buy some decent aftermarket 350 heads. I understand being on a budget, but with heads you tend to get what you pay for. This is not the area to get cheap in. You'd be better off running stock heads while waiting and saving your $ to buy something decent.
From what I've read in CC, HR, PHR, & CHP stock vortec heads will outflow, ported double hump heads, or even bowtie heads. You should be able to pick up some vortecs for about half of what the L98 heads run. Unless you do your own port work, you'll pay almost if not more than that trying to get your 305 or L98 aluminum heads to flow even close to the votecs. Don't look just at flow numbers either, velocity plays a major role in head design and that is also where the vortecs do very well. There is a place that does redo the vortec heads to run with non-vortec intakes.
Something else to consider. Aluminum heads can run smaller chamber volumes with lower octane fuel than cast iron heads. You may get by with running 11:1 compression w/ aluminum heads on 93 octane pump gas, but I seriously doubt you'll run 93 octane w/those 305 heads @ 11:1 and not detonate. I ran 64CC iron heads w/ flat tops and had to run 92 or 93 octane or have a pinging engine. If you have the cash to run fuel above 92 octane then you have the cash to buy some decent aftermarket 350 heads. I understand being on a budget, but with heads you tend to get what you pay for. This is not the area to get cheap in. You'd be better off running stock heads while waiting and saving your $ to buy something decent.
07-06-2003, 07:49 PM
#14
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Location: Calgary, Alberta, Republic of Western Canada
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Originally posted by Slow91z
Ok so I have 91 305 heads....If I put 1.94 valves in and P/P them how good would they run compaired to say Stock Vortech's??
And should I do some bowl work to drop the compression....58cc's would be like what 11/1 or something??
Ok so I have 91 305 heads....If I put 1.94 valves in and P/P them how good would they run compaired to say Stock Vortech's??
And should I do some bowl work to drop the compression....58cc's would be like what 11/1 or something??
That tell you something? And what do you want for $400?
Yes, do bowl work. But it is on the wrong side of the valve to effect compression.
58 cc chambers seldom send you over 10:1 but check all your numbers to be sure. Personally, I prefer less than 9.5:1 so I can run 87 octane.
Last edited by Sitting Bull; 07-06-2003 at 07:51 PM.
07-07-2003, 12:16 AM
#15
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Location: Calgary, Alberta, Republic of Western Canada
Posts: 550
Originally posted by Zepher
You have one long sig.
Some people like 305 heads for the smaller chambers to increase compression ratio.
Are the Vette L98 and ZZ4 heads pretty much the same?
You have one long sig.
Some people like 305 heads for the smaller chambers to increase compression ratio.
Are the Vette L98 and ZZ4 heads pretty much the same?
You ready to start handing down your used speed parts to your poor cousin north of the border???
Just kidding ...