ddahlgren

Other than changing springs does it all fit together? Thinking 1.6 intake rockers as well. Other than that valve seats on L98 alloy heads do they support larger than stock valves or is stock the max size.

WW7

From what I've read on here from guys that know , it's better to buy aftermarket heads then to have stock heads reworked...You don't get as much for your money reworking stock heads..There are some fairly inexpensive heads on the market now that do the job better....WW

ghoastrider1

stock heads suck. Even vortec heads flow much better. Valve springs can be changed to "Beehive" springs for better lif/valve seal clearance.

89onlyZ51

('88-up 113) L98 and zz4 heads are the same thing except for the springs/locks/retainers. zz4 heads are good to .525 lift, so with appropriate springs, no problems there, even with 1.6's on the intakes. The stock seats can accommodate 2.00 and 1.56 valves, which will give a boost in flow for little $$$ - nothing close to a good aftermarket head, though. You pay your money and take your choice.

ddahlgren

I have the cam already a gift from a friend who wanted more cam for their ZZ4 engine in a Camaro. All I am looking for is 300 to 325 hp and maybe 375 ft lbs. Basically what a 1960's corvette had with a SBC. Yes the tuned port is leaving as is the ABS and everything smog related as in 4 months no more smog check required and not concerned with resale value as it is a driver and not a show car. For right now not settled on what intake and all options wide open right to the point of a carb heck maybe 2 LOL.

cardo0

Well with stock heads u know they will fit w/o any unforeseen issues like exh port location and exh manifolds or intake runner mismatch to intake manifold. And yes u can fit in larger vlvs into the L98 heads - 2.00"/1.55". They are just not thick castings and dont support high power - over 500hp im told. Several shops specialize in the L98 heads (as LT1 equipment too) like TPIS has a "value" ported L98 w/larger vlvs that would beat aftermarket prices. Also Golen engines rebuilds them (or maybe sells ported new L98 heads). The L98 flows pretty good on the exh as is but the intake port is nothing to brag about and is what needs the work. Lingenfelter used to sell an ported L98 head also but i havent seen them on their w/s lately and maybe discontinued.
Yea once u install larger vlvs and better springs your over half way to an aftermarket head like Edelbrock (which has some low prices with high quality) and Trick Flows that are bolt on and go fast.

As usual with the sbc the biggest problem with parts is there are so many choices it makes your head ache.
As others imply your not going to make huge power with the L98 head (and remain reliable) or save huge dollars over aftermarket heads. But they can/will get the job done. IMHO there is no way around some intake port work unless u want to live with mediocre flow and power.

Good luck.

ddahlgren

I am not planning on turning past 5500 to 5800 rpm max. I want 325 to 350 hp and maybe 375 ft. lbs. I don't think I am shooting for the moon here. The ZZ4 cam I have been told is not very aggressive as I do not want to a million upgrades like gears converter and all that jazz either it would be nice if just had a little more go and did not run out of breath at 4200 rpm. Sort of starts to get going then gives up. I equally have no interest in headers either. I am more than likely to just put on a 600 cfm carb and a stand alone HEI than get into chip burning as well. I know I am probably reducing the value of the car but compared to what is my thought. It is not a collector or show quality car it is a driver that is less than perfect but cleans up well.

cardo0

I found this in an older Chev Perf Parts listing and u may like to read it dd:

Special Note For ZZ4 Owners: This kit (LT4 Hot Cam kit) is worth 40HP more when installed in a ZZ4 which will boost the horsepower from 355 to 395, but the ZZ4 comes with the most of the LT4 HOT Cam Kit components already installed. The camshaft and lifters are all that are needed to complete the LT4 Hot Cam conversion on the ZZ4. The ZZ3 and prior versions of the ZZ4 will require the complete kit for the upgrade.
FYI i think they meant vlv springs instead of lifters because the ZZ4 already has roller lifters.

Well i will try and save u some money and suggest u stay with 1.5 ratio rocker arms as flow increases stop above 0.500" lift on the L98 head and i would run the Hot Cam at its 0.492" lift w/1.5 rockers. But thats my opinion so take it or leave it.

Next, simple pocket porting improves flow on these heads and many times u can find pocket porting for less than $200. Yea pocket porting with larger vlvs should be the value upgrades if u cant afford full porting. But im learning not all pocketing porting is the same so shop around if your interested. But most any cyl head shop should be able to upgrade to larger vlvs (2.00"/1.56" w/o larger inserts) for u. So im reading u get 40hp more w/o larger vlvs and larger vlvs are only going to make more.

I kinda like using OEM chevy parts as they are very cheap to find and use with plenty of info available with them. I know the Hot Cam is only $225 itself and the whole kit is under $600 from Jeg's. Hey thats chevy reputation right there - performance and economy. Yea if your content with 350hp u should get there with cam and vlv springs alone. Myself i would upgrade the vlv springs while u have the chance - dont trust the stock springs after how many years?

Good luck.

ddahlgren

I have ported these heads in the past as well as Brodex Brownfield and the GM Bow tie iron ones as well for then Winston cup teams and Nascar modifieds. I did design work for GM on heads The aluminum bowtie heads are mine and many of the features carried over to the Pontiac Winston cup head and the 18 degree chevy. The raised port Brodex *10 is based is based on a very modified -8 I did and sent it to them to cast to avoid all the welding. Managed Winston cup engine shops Winston cup engine shops and the production of the Callaway twin turbo engines. I kind of know my way around a race engine just ages since looked at an L98 head or know it's long term service issues. I have not looked at an L98 alloy head for over 25 years LOL.

cardo0

With that resume' dd u should be the one answering questions here. And ive had the idea of using 18 degree heads on a street car for a long time - something to annoy the LS folks with. Chevy is the only mfr of 18* heads with small enough runners for this but thats because they are "unported" castings - all the other mfr 18* heads have huge port volumes. But porting a set of 18* heads just for street/strip use aint gonna be cheap so it remains a cool idea for me.

So now i have to ask u what u think of using cams with more lift than the head can make more flow with? Some say the extra lift gets the vlv open sooner and makes more "flow area". Myself i dont want to use larger 1.6 rockers unless the hp gain is possible as higher ratio rockers add spring stress and sometimes a lot more parts and cost.

ddahlgren

It depends if the flow does not go up any more or if it goes down with more lift. A lot of that has to do with chamber shape and short side radius leading to the seat. I think 18 degree heads can be had for reasonable money and CNC porting has brought the cost down a bunch now. My wrists are shot now and have been for 20 years from the previous 15 with high speed grinders doing heads and manifolds. I did take a look at the GM performance 23 degree head and looks like a very nice piece for a 355 and street use. Even with the experience I do have I am quite willing to listen to others that have more current info than me. A smart engineer spends much more time listening than speaking as well. I have been involved tuning 5 liter SBC with 18 degree heads and they run great! For street use you really want to look at sports car engine setups as they are much more flexible as far as power band goes.

So to answer you original question if the flow goes flat use faster rockers and investigate larger valves especially the intake side as the deltaP is much less. Larger valves weigh more but like adding higher ratio rockers for area under the curve. Good valves weigh very little more. They other thing seldom fully explored is the backside angle on the valves. There is a bunch to be found there. So if the flow stays flat or only drops a CFM or 2 keep adding lift to find where it reverses. If you get to that lift and possible to get there with a good cam you have add rocker ratio rather than cam. Big lift cams add duration for the ramps and that kills midrange torque. A car with no midrange on the street is annoying at best. Good valve springs are readily available and no one I know hot rods and engine with plans on it lasting 50k miles between major service.

As far as ratios go in 1988 I was up to 1.7 on a short track SBC if that tells you how I feel about them. Back then there were none for a SBC so used BBC rockers and moved the studs. Biggest thing with a ratio change is to get the pushrod length or guides and stems will fail quickly.

Cylinder heads are all about hp goals you have in mind with how many inches and how hard you are willing to spin it.

Any other thoughts I might adds feel free to ask.

cardo0

Yes, reliable information is difficult to come by as what may have worked for someone with 355" motor may not work for a 383" or 396" motor let alone the big inch small blocks.

U mention 5ltr sbc and in my previous location of California trying to pass CA smog the smaller stroke small blocks were the only answer using the smog legal small pipe shorty headers and wide LSA cams. The larger displacement sbc would mostly choke on the smog legal parts available. And if u look at the Ferrari s and other hi-po imports thats seems like the direction they went with hi rpm smaller displacement motors. Have relocated to Nevada now so not an issue anymore but it still has me wonder if big inch sbc are any faster assuming they have lower VE as the c.i. increase. What im reading these days says the heads and vlv sizes dont keep up with the c.i. increases and VE goes down. But where is the sweat spot i would like to know - no one is talking this.

Im getting the impression that a street head has more concern for swirl than total flow and added lift can cause a bad tumble on a street combination. High lift and flow that may work well in a full race motor could hurt lower rpm performance. Thats why i consider a heads flow once it flattens out to be counter productive with greater lift. And really u can spend alot more for greater rocker ratios as better springs, studs and rockers may be needed. I think 1.7 rockers can make a tiny cam come alive but could be counter productive to cams already at the heads flow limit.

Well thx for sharing is was helpful to read your experiences here.

Mike 92LX

The amount of crap in this thread amazes me

You can get a stock L98 head to support 300-340HP even with the stock valves na. In long run the aftermarket heads are a better deal but you gain some weight due to the thick deck. You need to decide what intake and rpms you want the car to shift at-in other words do you want to keep TPI or upgrade to a shorter runner intake

I have found the ZZ4 cam to work perfect with 1.5 rockers,long runner tpi intake and stock prom. ZZ4 cam is not the GM hot cam. For some reason every time I changed an L98 with a long runner intake to 1.6 rockers from 1.5 with that cam car gained nothing even retuning it.

Tom400CFI

I'm not sure what '60's SBC made 325 hp (in today's method of ratings). The "Baddest" 60's SBC that I am aware of is the LT-1 and that barely peaked where a stock LT1 peaks...and had way less torque and area under the curve. If you are trying to get "60's small block performance", you're probably already there.

(I'm not saying that you shouldn't want better though) ;-)

ddahlgren

Perhaps the Muncie 4 speed and 3.73 gears made the 60's cars feel sportier than they were to me. Did drive off and on a friends late 60's BBC Corvette with 3 carbs and 4 speed and while handled rough it had loads of straight line zip.

ddahlgren

The car is a porker already and 20 lbs not a deal breaker just don't want to pour money down the rabbit hole for 50 to 60 hp. and 900 for heads sounds pricey and seldom does everything else fit back on. Given an unlimited budget it would be a 396 SBC with a Tremic 5 speed and 3.90 gears but don't have that budget. so 50 or 60 more a welcome thing with porting and a cam change. Everything emissions related can leave as in CT no more inspections needed. If not possible on a modest budget time to move on to a different platform.

cardo0

I read this again. I cant touch this.

Thx again.