C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

L98 Mods

Thread Tools
 
Search this Thread
 
Old Jan 12, 2006 | 10:40 AM
  #1  
zapc's Avatar
zapc
Thread Starter
Instructor
15 Year Member
 
Joined: May 2005
Posts: 193
Likes: 8
From: West Islip NY
Default L98 Mods

hey people

been lurking for a year or so, unbelievable bunch of people we got here
supporting our hobby, anyhow I know this has been beat to death, yes I have researched older posts,someone please step up to the plate and give me part#s and all specifics, not just suggestions on my planned upgrades.I also apologize now for the long post

got an 87 vert automatic, only 41,000 miles. It's got bad valve guide seals, what I am looking to accomplish is High 12's low 13's (enough to keep up with stock modern muscle)I can get a set of 113 heads cheap(like $400.00) I figure at least another $500 or $600 to get them lightly ported and a 3 angle valve job. If I went with larger valves I'm sure I'd start to be in the range of aftermarket heads which is out of my $range right now.I probably will not go with headers (want to keep it stock looking) already have cat back flowmasters and plan to lose the precats and go with a high flow catand front y pipe. I want to do a cam,timing chain,roller rockers if necessary. I want an aftermarket lower intake, and runners but will probably stay with a ported upper plenum.Is this a doable situation? I will also do gears and a converter asap.

here are the specific question's

1 what to do to heads( Should I just do up the stock ones) or go for the 113's, and what do I do to them?please be specific

2 What cam,Intake,and runners? please be specific


thanx all

chris
Reply
Old Jan 12, 2006 | 11:59 AM
  #2  
vader86's Avatar
vader86
Team Owner
20 Year Member
Liked
Loved
Community Favorite
 
Joined: Sep 2001
Posts: 62,125
Likes: 1,727
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Default

Read my website for starters, there are pages there that will go into this question.
Reply
Old Jan 12, 2006 | 12:31 PM
  #3  
zapc's Avatar
zapc
Thread Starter
Instructor
15 Year Member
 
Joined: May 2005
Posts: 193
Likes: 8
From: West Islip NY
Default

been to your site before, great job, but again not specific enough as to cam selection and exact head work. I've been down this road of modifying cars so many times with differing results, this time with the enormous amount of knowledge and experience this group has I refuse to waste any money on less than perfect $ for $ results.

thanx

Last edited by zapc; Jan 12, 2006 at 12:33 PM.
Reply
Old Jan 12, 2006 | 02:03 PM
  #4  
Red Tornado's Avatar
Red Tornado
Team Owner
 
Joined: Sep 2002
Posts: 22,209
Likes: 12
From: OBAMA IS HITLER
Default

well you're going to run into a problem right off the bat. for some reason you're saying you want your exhaust to remain in stock form. the L98 stock exhaust is one of the worst and most restrictive setups. to make H/C/I work, you better start with your exhaust and that means nothing less than long tube headers, dumping the precats.
Reply
Old Jan 12, 2006 | 02:23 PM
  #5  
JAKE's Avatar
JAKE
Le Mans Master
10 Year Member
 
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Default

I recommend starting at the bottom and working up Here's why:

Certain parts are easier to exchange than others. If you begin by a change of heads - which in my opinion is really the foundation for all other mods - you can more easily change the camshaft at the same time, since most of the parts will be have to removed anyway.

So why change the heads, calling for removal of lots of parts, then have to remove many of the SAME parts later to change the cam.

So do the cam and heads at the same time.

If you budget can stand it, install a set of full length headers at the same time as the heads/cam change. You've got to pull the exhaust manifolds anyway to get the heads off. For a 350 engine go with 1-5/8" OD headers which work better than the larger 1-3/4" jobs.

The intake setup, since it's on top of the engine, can then be changed sometime down the road without disturbing many of the parts you had to deal with in the head and cam change.

Specifics:

CYLINDER HEADS: I recommend not fooling with the stock heads. Instead I'd go with a set of Edelbrock RPM aluminum heads, part # 60739 - all the specs are on Edelbrock's site. They're under $1,000 fully assembled and ready to bolt on and are readily available.

Check Summit Raciong Equipment or Performance Automotive Warehouse for the best price.

CAMSHAFT: I recommend calling CompCams (toll free) and ordering a custom ground hydraulic roller grind CS 3312/3313HR112 (212/218@ .050) or

If you want a little more top end with a SLIGHT, but hardly noticable loss in low end torque CS 3313/3314HR114 (218/224@ .050)

If you can degree in the cam, order it with ZERO Advance ground in. If you can't, order it with 4 degrees of advance ground in.

If your existing roller lifters are in good shape, reuse them. The heads I recommended will have the valve springs required for the cam if you specify them when you order. They come at NO extra charge. Just tell Summit or PAW, etc., the cam you're running. They'll send you the heads with the correct valve springs.

Contact Alvin at Chips@PCMFORLESS.COM and have him re-burn your PROM to accomodate the mods. Get the parts first so he can program the PROM specifically for them.

Get a copy of TPIS Insider Hints book which details other mods you can make yourself to improve airflow. It's available for online ordering at their site.

Hope this helps.

Jake
Reply
Old Jan 12, 2006 | 03:38 PM
  #6  
zapc's Avatar
zapc
Thread Starter
Instructor
15 Year Member
 
Joined: May 2005
Posts: 193
Likes: 8
From: West Islip NY
Default

thanks jake

my intentions were to do heads,cam and intake at the same time,
I was hoping to get away without going to long tube headers, just with cat back, new high flow cat & no precats but if I have to use headers I will. also if I have to go the superam route I will, but was hoping to keep the stock upper plenum just ported,someones intake and runners,
(not sure which ones are best yet) from most of the reading I have been doing most people seem to recommend the zz9 cam and afs heads,
obviously youve had luck with your recomendations?
Reply
Old Jan 12, 2006 | 05:04 PM
  #7  
rlane5's Avatar
rlane5
Pro
20 Year Member
 
Joined: May 2002
Posts: 635
Likes: 6
From: New Jersey
Default

Zapc,
Jake gave you some good advice, I would buy a set of aftermarket heads for the simple reason, after you pay $400 for 113 heads and have them redone you're going to spend at least $1000 and they may not flow as good as an aftermarket head. Dart, AFR, edelbrock and every else make a good head for a reasonable price ($1000 and up range). I have a set of Dart 180 Iron Eagles that I brought bare from summit and had a local head guy do them for me. He said it would be better for me to go and buy a new set of head and let him assemble and clean them up (mild porting) and I would come out cheaper than doing a set of old stock heads and have them ported to flow the same of air. (CFM) My original goal was mid 12s in a S15 truck, It would run that in the heat easy. The bottom line is heads and a good cam.(I like the GM HOT CAM) an engine is a pump the more air and fuel atomized and burned the more power it will make
Reply
Old Jan 12, 2006 | 05:14 PM
  #8  
vader86's Avatar
vader86
Team Owner
20 Year Member
Liked
Loved
Community Favorite
 
Joined: Sep 2001
Posts: 62,125
Likes: 1,727
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Default

If you want to go with 113s, I would be sure to get a recommended spring for the cam you pick, 10* locks, titanium retainers, 3-angle job, some of that will depend on who you get to do the actual work because they may call it "stage 1 or stage 2" porting. I know a head range recommendation is on there, I just dont list specific part numbers.

Camshaft selection requires a set goal, which is why I havent put much about that on my website yet. There are so many directions you can go. I believe this should be on there, but if youre going this stock-looking route, I would be down to the Accel 211 or TPiS ZZ9, or perhaps something slightly larger than either of these offered by CompCams or whomever.

There should also be flow numbers there that will allow some comparison between the intake bases, but from a quality standpoint on any intake parts you need to look more to TPiS or Edelbrock over Accel. Superram is another monster in itself, but aside from quality problems that may creep in, I see no reason not to use it on most L98s.
Reply
Corvette Stories

The Best of Corvette for Corvette Enthusiasts

story-0

150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

 Joe Kucinski
story-1

8 Coolest Corvette Pace Cars (and Replicas) of All Time

 Verdad Gallardo
story-2

Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)

 Joe Kucinski
story-3

Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!

 Verdad Gallardo
story-4

Top 10 Corvettes Coming to Mecum Indy 2026!

 Brett Foote
story-5

Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!

 Michael S. Palmer
story-6

10 Revolutionary 'Corvette Firsts' Most People Don't Know

 Joe Kucinski
story-7

5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2

 Michael S. Palmer
story-8

2027 Corvette vs The World: Every C8 vs Its Closest Competitor

 Joe Kucinski
story-9

10 Most Common Corvette Problems of the Last 20 Years!

 Joe Kucinski
Old Jan 12, 2006 | 05:16 PM
  #9  
JAKE's Avatar
JAKE
Le Mans Master
10 Year Member
 
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Default

Originally Posted by zapc
thanks jake

my intentions were to do heads,cam and intake at the same time,
I was hoping to get away without going to long tube headers, just with cat back, new high flow cat & no precats but if I have to use headers I will. also if I have to go the superam route I will, but was hoping to keep the stock upper plenum just ported,someones intake and runners,
(not sure which ones are best yet) from most of the reading I have been doing most people seem to recommend the zz9 cam and afs heads,
obviously youve had luck with your recomendations?
The ZZ9 gets nice reviews from guys who run them. In fact I had one in my engine when it was a 355. I didn't recommend it because it's so pricey and suspect quality control.

Also, I had mine checked on a computerized cam checker at Dennis Wells' Racing and the specs were way off from what the advertised specs are. I suspect it's a quality control issue.

Also, I've read in one of the mags that it gives best performance when installed 1.5 degree retarded.

I didn't recommend Air Flow Research heads (if those are the ones you are referring to) for two reasons:

1. There have been some serious quality control complaints on their heads on not only this Forum, but on ThirdGen. Org too, just to name the two I know of. There have been many posts on that quality control issue and even AFR has posted trying to comfort/justify/explain/placate (choose which word you like best) the complainants. I'm not sure those posts are still available for review, but the back and forth went on for quite a while.

Some guys posted true "horror" stories and even posted photos of their heads with hundreds of tiny holes in the castings. Others complained of excessive valve to guide clearance, etc., etc.

Still others posted they had no problem at all.

So my conclusioin is you'd be taking pot luck. I just have no confidence in their product in spite of their outstanding flow numbers.

2. Availability absolutely sucks. Last time I saw a post on this, guys were waiting for months to get a set.

Even though Edelbrock heads don't flow as well as AFRs, their quality control has the highest rating in the industry. They have a something (forgot the name) 9000 rating, which is a good as it gets.

Now, I want you guys to pay attention here: I DO NOT want to get into another back and forth on this issue. Poster asked for my specific recommendations and I gave them and, now, even the reasons.

These are my views and I'm entitled to 'em so, please, leave me be.

Jake
Reply
Old Jan 12, 2006 | 05:20 PM
  #10  
Nathan Plemons's Avatar
Nathan Plemons
Race Director
15 Year Member
 
Joined: May 2001
Posts: 14,165
Likes: 9
Default

Originally Posted by JAKE
For a 350 engine go with 1-5/8" OD headers which work better than the larger 1-3/4" jobs.
Not intending to turn this into ANOTHER header war, but you might want to qualify this with some RPM information. If you're intending to remain in the basically stock RPM range (which he would likely be doing if he retains the stock intake) then I would very much agree that 1 5/8" headers are likely your best bet. If you intend to raise the redline of the motor significantly then there could be a point where 1 3/4" headers begin to show a better gain.

People will immediately argue that 1 5/8" headers will give you more low end torque, thus I will clarify what I mean in saying that although 1 5/8" headers may give you more low end torque it is possible that 1 3/4" headers will provide a horsepower gain in the upper RPM range that outweighs the "loss" that they have over the 1 5/8" in the lower range.

The short answer is that 1 5/8" is not ALWAYS better nor are they ALWAYS worse, it depends on a per application basis.


Regardless of whether you believe in 1 5/8" or 1 3/4" headers, doing an intake, cam, and heads WITHOUT doing headers is like pizzing in the wind.

Last edited by Nathan Plemons; Jan 12, 2006 at 05:23 PM.
Reply
Old Jan 12, 2006 | 06:25 PM
  #11  
CorvAdel's Avatar
CorvAdel
Racer
15 Year Member
 
Joined: Nov 2004
Posts: 445
Likes: 0
Default

I recently did what you said you were thinking of doing, with NOT going for headers. I did not use headers as I needed to use original ex. manifolds. These were cleaned up at the welds and slightly en-largened. I also did not have unlimited bux so had to be selective. Mine is an 87 engine, with mildly ported stock heads..flow 215 in. and 175 ex. at 550. Match ported stock base, runners, plenum and 52tb, 89 injectors, stock valves, zero deck, balanced crank, 30 over stock pistons, h. balancer etc., 2000 tc, B & M hard-shift kit, 21/2" split ehx. with no cats, and balance-joined about 1/2way along the length, 2 resonators and 2 hi-flow mufflers. 3.07 rear, and living in Australia I had to get a mail chip-tune, which apart from a small "burst" ping, performs well. I have not had it dyno-ed yet, but can say that it has plenty of torque, is very responsive and much quicker than stock.. Having done the above I can now see why people go for different runners. My engine pulls quite hard but tapers off after 5000rpm. It will rev to just over 6 but doesn't seem to pull significantly over 5. I get the feeling that a better intake, tubes and plenum would cure this...and the addition of headers wouldn't hurt.
Hope this has been of some help...I know how unnerving it is to make decisions about perf. mod's....esp. camshaft. This was, in my mind, the most important decision. After much research I took the advice of the chip-tuner who, after I told him I needed low-to mid-range torque(not top-end HP), suggested an LPE211. I went with it and am very happy about its performance. Is a ZZ9, CC, Crane grind any better? I am not the expert and can't answer this, but can say my PLE does what I want it to do. Good luck with your decision-making and choices...
Reply
Old Jan 12, 2006 | 07:03 PM
  #12  
86VX1's Avatar
86VX1
Drifting
15 Year Member
 
Joined: Oct 2005
Posts: 1,259
Likes: 0
From: bakersfield cali
Default

i agree with jake, i don't know about the quality control issue but definitely the heads are the center piece of a performance build

Last edited by 86VX1; Jan 12, 2006 at 07:05 PM.
Reply
Old Jan 12, 2006 | 07:44 PM
  #13  
88BlackZ-51's Avatar
88BlackZ-51
Race Director
Photogenic
Photoriffic
Liked
 
Joined: May 2003
Posts: 10,749
Likes: 41
Default

Originally Posted by Hot Rod 90
well you're going to run into a problem right off the bat. for some reason you're saying you want your exhaust to remain in stock form. the L98 stock exhaust is one of the worst and most restrictive setups. to make H/C/I work, you better start with your exhaust and that means nothing less than long tube headers, dumping the precats.


i agree, i gained around 30hp/30 tq.
Reply
Old Jan 12, 2006 | 10:03 PM
  #14  
zapc's Avatar
zapc
Thread Starter
Instructor
15 Year Member
 
Joined: May 2005
Posts: 193
Likes: 8
From: West Islip NY
Default

thanx
people

did not want to start the usual bickering, was hoping several of you would chime in to the specifics you were running and how happy you were with the results, and what not to do,

unless someone else has any suggestions it seems I will follow jakes advice, have always been an edelbrock fan,was hopin more of you were going to tell me to stick with the ported 113's. I have heard about the problems with the air flow research heads. keep in mind people that I'm not looking to build a racecar (yet anyway Ha Ha)just keep up with modern muscle. with the edelbrock heads and the comp cam is it necessary to do the chip right away? I hear that mass air is more agreeable to a cam change, or is it the heads that will get me
Reply
Old Jan 12, 2006 | 11:23 PM
  #15  
mike43725's Avatar
mike43725
Advanced
 
Joined: Feb 2005
Posts: 77
Likes: 1
From: zanesville ohio
Default

i agree that heads are the foundation of anything and a good cam. as far as what heads to get if were going to go aftermarket i would probaly go with dart heads, but i have the cast iron factory heads on my 85 that are ported, milled, three angle valve job and 2.02 valve the work great. i also reccomend the comp cam part # 12-402-4 212 int 218 ex. it works great and has that muscle car idle. make sure to port match your intake, and this really important CUSTOM BURNED CHIP. as far as exhaust i would go with true duals and good mufflers, headers are a personal preference in my opinion.
Reply
Old Jan 13, 2006 | 12:03 AM
  #16  
sami85L98's Avatar
sami85L98
Le Mans Master
 
Joined: Apr 2005
Posts: 8,077
Likes: 4
From: Scarborough ONTARIO
Default

Read Vader86 website, its just plain awesome read it first than have questions ? post a thread here. Period.

Vader86: I just installed SR and i printed ur installation instructions along with SR pictures thanks a lot for that help, it sure helped me. Kool website and many thanks for sharing.
Reply
Old Jan 13, 2006 | 12:36 AM
  #17  
cv67's Avatar
cv67
Team Owner
15 Year Member
 
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
Default

The 195 size of the heads will work well if you opt for the Super Ram intake. I dont feel the TPI setup could ever flow enough air to keep up with a head that size. JMO though.
Should you go with a ported/aftermarket TPI setup, I'd stick with a cyl. head no bigger than 180'ish. AFR, Dart, etc make some great product, spend your money on the heads if anything. Dont let the small runner size fool you, they will still outflow any TPI "long tube runner" type setup and make gobs of torque for the street.
Reply

Get notified of new replies

To L98 Mods

Old Jan 13, 2006 | 08:59 PM
  #18  
gear-head2's Avatar
gear-head2
Instructor
20 Year Member
Conversation Starter
All Eyes On Me
 
Joined: Apr 2004
Posts: 166
Likes: 4
From: Moneta, VA
Default

I was all set to buy the Eldenbrock heads until I found the 180 cc Pro-1 Dart heads. Definitely worth a second look.

If you have interest in flow numbers, check out this comprehensive list of heads, excellent.

http://users.erols.com/srweiss/tablehdc.htm

Reply
Old Jan 13, 2006 | 11:10 PM
  #19  
JAKE's Avatar
JAKE
Le Mans Master
10 Year Member
 
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Default

Originally Posted by gear-head2
I was all set to buy the Eldenbrock heads until I found the 180 cc Pro-1 Dart heads. Definitely worth a second look.

If you have interest in flow numbers, check out this comprehensive list of heads, excellent.

http://users.erols.com/srweiss/tablehdc.htm

Of course, there are a lot of excellent heads available on the market, but don't forget to factor in all the variables when you're comparing heads.

As the site said, you want the best flow WITH THE SMALLEST PORT VOLUME and (which gives you - my words) the HIGHEST VELOCITY. It also said that VELOCITY is just as important as flow, which many to fail to take into account.

Most drool over maximum flow numbers and brag about them like they're money in the bank - more being better - yet the site clearly says to look at port volume and .400 lift flow and, also, to ignore any flow numbers near or above the max amount your valves will lift. It's also a good idea to look at average flow numbers too.

So comparing a 170cc port head with a 180 cc port head is sort of an apples and oranges comparison, albiet a small one, but they are two different animals. A friend of mine was able to get his 15 degree Brodix heads to flow 340 CFM @ .700, but the intake ports had to be opened to 262 CCs to get there. That's almost 100 cc's more than what my intake ports are. Guess what that does to velocity, especially down low.

For a street engine, all you need do is look at the comparison between the BB Chevy rectangular port heads Vs the oval port heads for the same engine. The smaller port heads win out in power production in the RPM range street engines normally see.

I've run both Rectangular and Ovals on the same 468 BB street engine and the difference is enormous. Above 6500 RPM or so the Recs take over, but you must ask yourself, how often is you street engine going to be above 6500. Mine never sees anything approaching that RPM on the way to Albertson's. LOL

So, bottom line: Don't let maximum airflow be the determining factor in your selection of a set of heads. Look at the big picture.

Jake
Reply
Old Jan 15, 2006 | 02:12 PM
  #20  
zapc's Avatar
zapc
Thread Starter
Instructor
15 Year Member
 
Joined: May 2005
Posts: 193
Likes: 8
From: West Islip NY
Default 113 heads

well the new monkey wrench is that I got the 113 heads for $200.00.
could,t pass them up. gonna get them ported and redone. for my plans (remember just looking to keep up with new muscle) do I really need to
go with the larger valves or just go stage 1 porting and gasket match everything.
Reply



All times are GMT -4. The time now is 06:05 AM.

story-0
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

Slideshow: From C1 to C8 we compare every Corvette generation by the numbers.

By Joe Kucinski | 2026-05-12 16:54:12


VIEW MORE
story-1
8 Coolest Corvette Pace Cars (and Replicas) of All Time

Slideshow: Some Corvette pace cars became collectible legends, while others perfectly captured the look and attitude of their era.

By Verdad Gallardo | 2026-05-11 09:50:51


VIEW MORE
story-2
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)

Slideshow: Ranking the top 10 Corvette engines by torque output.

By Joe Kucinski | 2026-05-05 11:58:09


VIEW MORE
story-3
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!

Slideshow: A Corvette pace car nearly matching IndyCar speeds sounds exaggerated, until you look at the numbers.

By Verdad Gallardo | 2026-05-04 20:03:36


VIEW MORE
story-4
Top 10 Corvettes Coming to Mecum Indy 2026!

Among a rather large group of them.

By Brett Foote | 2026-05-04 13:56:44


VIEW MORE
story-5
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!

Slideshow: the top 10 things Corvette owners want in the C9 Corvette

By Michael S. Palmer | 2026-04-30 12:41:15


VIEW MORE
story-6
10 Revolutionary 'Corvette Firsts' Most People Don't Know

Slideshow: 10 Important Corvette 'firsts' that every fan should know.

By Joe Kucinski | 2026-04-29 17:02:16


VIEW MORE
story-7
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2

Slideshow: Should you buy a 2020-2026 Corvette or wait for 2027?

By Michael S. Palmer | 2026-04-22 10:08:58


VIEW MORE
story-8
2027 Corvette vs The World: Every C8 vs Its Closest Competitor

Slideshow: 2027 Corvette lineup vs the world.

By Joe Kucinski | 2026-04-24 16:12:42


VIEW MORE
story-9
10 Most Common Corvette Problems of the Last 20 Years!

Slideshow: 10 major Corvette problems from the last 20 years.

By Joe Kucinski | 2026-04-14 16:37:05


VIEW MORE