“While I’m this far….?”

M

Montana

Member
I must have said this to myself daily for the past few months & I end up going deeper into my corvette engine. So I need some advice on what I should &/or perhaps not do.

My vette is an 89 w/around 72k miles on her. I finally decided to pull her from close to a decade of hibernation to replace the stock fuel injectors. Then I found the water pump leaking & while I was this far…. I kept going deeper & doing more. Currently I just pulled the balancer off as I get ready for a TPIS Super L98 cam’s arrival. Naturally I keep looking at the heads thinking, “I’d really like to put thinner head gaskets on her & maybe port the original heads some too. Thus I could use some guidance as to how far I keep going or do I stop at the cam replacement? I’d hate to not do something that’s really advisable while I’m this far torn apart. Thanks!
 

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Ill try here to prevent you from making a very common mistake!
do yourself a big favor and if you can possibly afford to, sell or junk the existing OEM cast iron or aluminum heads ,
as they are decades old technology and not nearly up to date , and by todays tech, very restrictive as is the OEM TUNED PORT INTAKE

the stock corvette TPI made 245 hp, you can rather easily (but not dirt cheaply)
make double that with the correct mods yes it can be very satisfying, and rewarding to do your own mods

1989 Corvette Specs – National Corvette Museum

www.corvettemuseum.org www.corvettemuseum.org

spend the time and effort to read through the links and sub links
yeah it will take you a couple days,
but it will save you weeks of wasted effort and lots of wasted cash
step back, make a few notes, ask questions, it will save you a great deal of wasted cash and time,
to have a well made plan, and stick to a proven formula.
think about what you would want to own, the potential cost and your skills,
you could easily have an 11-12 second or faster corvette,
but it won't be dirt cheap or done in a week or two,
and yeah, it can be done in small stages on a reasonable budget while you learn skills

Id certainly strongly consider swapping to a 7 quart baffled oil pan to increase durability
and better cylinder heads, as the combo of better flowing heads and a new cam ,
could easily boost power more than 70hp, add a better intake and exhaust, and you could easily
be looking at more than 130-150 plus hp,increase over stock components,
be aware most changes require other changes to maximize potential results
example
a kick ass cam, might require a 3.73:1 rear gear and a 3200 rpm stall converter to max results

Ideal TPI Build?

Grumpy, I'm interested in your expertise. I roamed around your site some today, so if this has already been discussed please post a link to the discussion. If you were to pick the best heads and cam combo for a SBC with a ported, stock tuned port setup, what would it be? I realize you can get...
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Cheap Good Cylinder Heads

Where do you find good and cheap cylinder heads? A set of these for $280 + valves + springs, reuse old rocker arms = $400 https://www.ebay.com/itm/393005918509 https://www.ebay.com/itm/322892146731 https://garage.grumpysperformance.com/index.php?threads/sellecting-cylinder-heads.796/page-2 Buy...
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can you get there with TPI

Good morning, Grumpy. I have come across your name and posts in various Vette forums when looking for tuned port injection information. Here's my story.....I have a 69 Camaro with a 355 (started as 10.25:1, 300 hp 350 out of '70 Nova. flat top pistons with 4 valve reliefs) 041 pocket ported...
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just how restrictive are the stock TPI engine components?

I get this question frequently so let me point out a few things http://garage.grumpysperformance.com/index.php?threads/relocating-the-mat-manifold-air-temp-sensor.10349/#post-42530...
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factors you need to think about in your engine combo

displacement http://www.archive.org/details/3dAnimat ... InjectedV8 viewtopic.php?f=53&t=204 viewtopic.php?f=53&t=247 viewtopic.php?f=53&t=343 viewtopic.php?f=69&t=5357&p=16030#p16030 viewtopic.php?f=53&t=852 viewtopic.php?f=53&t=141 viewtopic.php?f=53&t=253 viewtopic.php?f=44&t=427...
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C4 Larger Intake Runners L98 TPI

C4 Larger Intake Runners L98 TPI Hi guys, I'm new to the forum have had my 85 Greenwood Corvette for five years and have started to look for more power, was thinking of upgrading the inlet runners in between the intake manifold and the plenumn, i believe there is a larger set available, was...
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tips on building a TPI 383 C4

I got asked if building a 383 rather than just rebuilding the current 350 would kill a corvettes mileage, well having done that several times and having done it with both the earlier carb equipped c3 and later TPI corvettes plus several cross fire and efi custom configurations,I can say that...
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basics of starting a 383 sbc combo planing

I'm needing some help with my 383 stroker of all the block is Bored 30 over the stroker kit is a 3.75 inch stroke with 6-inch rods and -10 CC dish top pistons the heads I went with some edelBrock E210 witch are a 64 CC chamber and a 210 cc intake runner with maximum lift 650. I have 1.5 roller...
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1986 iron head l98 corvette valve spring question

yes, its slowly but surely improving and will be a fun car once its completed, I hope the headers are designed to work and provide adequate clearance for the spark plug angles, you ordered on the heads you've selected. The new heads have the same spark plug angle as factory ones I removed, only...
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sellecting cylinder heads

you might want to watch this, its comparing the vortec SBC heads vs a CNC aluminum 210cc SBC head on a 383 (yes a head that large actually works and has a great deal more low and mid rpm torque that you may have been lead to believe, with 210cc ports and yes there are better heads in the...
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exhaust, thinking of your options

After going back and forth many time I have decided to go with the OEM exhaust manifolds that came on my LS376 /480 crate engine. It's documented in multiple tests/articles that they flow exceptionally well for a mass produced OEM exhaust. Anyway, since I have a new MIG welder, chop saw, and...
garage.grumpysperformance.com
 
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Welcome to the forum Montana !WelcomeToGrumpy's.gif

You have done yourself a favor and stepped back to reconsider your options
and ask some questions, you will be glad you did !
 
Thank you for all the information, I’m sure it will be very helpful. I bought my vette over 20 years ago now & chose it because it had every possible option except the B2K. I was heavily into autocrossing & this was from the factory with all the race ready goodies. As time went on I did a few track days at a local road course but life with young kids took over. One of my original fuel injectors started to fail & thus she was parked. Once I got back to playing with cars I gave my attention to my 37 coupe & started to learn some mechanical skills. Well this past fall as I looked at all my old cars not running & I figured the Corvette would be the easy fix & on the road again. Yeah I was wrong!

Once I started in on her I found one thing after another plus the “I should probably replace that too” while it’s torn apart ramped up. Since I had removed the water pump, the cam was calling to me to be replaced! I’ve always wanted to do a cam so I decided it’s now or never. My Corvette’s stock except for the cat back exhaust, which is why I decided on the TPIS cam. I didn’t want drivability issues & since I’m still a green mechanic I didn’t want issues that would be way over my head. So on it’s way to me is the mild cam, springs & timing chain & gear set. As I said, I’m so close to being able to pull the heads it was becoming very very tempting. But knowing myself I’d need to do some cleaning up porting on the heads similar as I just did to the intake base, plus a valve job, etc, etc. Having read many threads & excellent advice from this forum, I knew it was time to join.

My goal is to have a fun street car & hopefully get back into some occasional autocrossing. I know there are a lot of restrictions with the TPI & heads but I also know it made a lot of fun torque too. For now I’m just trying to improve a little on what it’s good at then maybe in the future do a 383 or even an LS swap. Thanks for the welcome & help as I journey along with these repairs!



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Im sure many of us are waiting to find out how far you want to go in modifying, up-grading and repairing your corvette.
personally I really like the c4 corvette design, especially the later version like the 1996,
I just wish the factory had installed an injected, big block engine and a 4l80e trans with a much more robust differential as an option.

installing a BIG BLOCK CHEVY IN A C4

theres no way a c-4 will exactly match the weight distribution and handling of a C6, BUT the strait line acceleration CAN be equaled or exceeded with a decent well thought thru and executed BBC swap,and you might be amazed at how well a properly set-up C4 with a big block engine handles in the...
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the c4-bbc engine swap

no its not a TRUE drop in,and drive engine swap, it will require some fabrication skills to do correctly, but its not that difficult either! and its a reasonable way to get 500-600 hp, and 500-600 ft lbs of torque PLUS in a c4 corvette. Ive built engines for . and helped work on, some of the...
garage.grumpysperformance.com

 
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Are there certain things that are prone to failure like old Ford engines & their timing chains failing. While it would be a blast in the end, I’m not going to pulling the engine for rebuild or replacement at this time. I’ve got too many old cars in need of repairs to get them back on the road.

The stock engine is a great torque engine & I love that about it. The components it came with are matched well. The flow rates of the TPI intake is matched to the heads & the cam to those as well. When looking at the cfm flow of the stock heads intake to exhaust ports are well matched, from 80-90% all the way up to .500 lift (intake port cfm divided into exhaust port cfm). Since one doesn’t need to make up for poorly flowing head exhaust ports a mild single pattern cam is a good upgrade for the stock engine. I definitely don’t want to throw a better flowing intake on to be choked by the heads or vise versa. As they say the system has to work well together.

I’ve cleaned up the intake manifold a little bit & may also clean up the plenum. Without a flow bench I’d be guessing at the porting changes that help vs hurt cfm & velocity. Thus I don’t want to go crazy porting, kill velocity of the incoming air & lose low end torque. So my “plan” is to keep it close to stock with a few tweaks here & there. Putting on a thinner head gasket to get a better quench height & a slight bump in compression is one of those I’m still considering. Only problem is I know myself well enough to know I couldn’t just stop with a gasket change, I’d need to refreshed the heads. So then comes 1.6 roller rockers, high performance valves w/narrower stems, new guides & a precise valve job, etc. The rough casting ports would be too much to not touch so then comes a clean up of those too. Then the short block would be calling me to just pull it & stroke it…. Which is why I’m questioning even unbolting the heads!
 
the factory heads are really flow restrictive, even if in great original condition,
and by now the OEM valve springs are surely well worn and in need of replacement
 
From what I’ve seen the heads & intake system are pretty closely matched in the flow restrictiveness. Naturally those are other peoples flow bench findings which may vary person to person & equipment to equipment doing the testing. One good thing that comes with age is knowing one’s self & that’s why I’m trying to “not” swap to different heads… I know then the chase begins for me to fix everything else causing flow restrictions compared to the last one I fixed. It’s hard for me to say “when” & not want to keep changing things to make it the absolute best it can be! Heck, just dismantling the vette this far has lead me to not only clean every single part, nut & bolt removed but to clean all the aluminum suspension & driveline. Actually in hind sight that was a good thing since I found a nut on the rear end batwing to frame just about completely off!

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This is one of the informational images I’ve used when doing my evaluations. Which I probably got from one of your threads.

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I’m guessing here but if the heads are more restrictive than the intake, I would think I could do a clean up porting and installing new high performance valves would get even the stock heads flowing for a better match to the stock TPIS if not surpassing it. Again, I’m just guessing here.

I completely agree with your statement on the valve springs. As it sat for almost the last 10 years I certainly didn’t start it more than a couple times, so I know some springs have sat compressed for years. That isn’t good especially since I know once fixed I wont drive like a little old lady! With the new cam I have coming is also a new set of springs & a new timing chain set, in case the factory one has stretched some over time.

This is the information from TPIS on the Super L98 cam I’ve bought, I like the sleeper nature of this cam. While I thought about doing the 1.6 roller rockers as well I know that would add almost another $550 & I’m not sure how much of an improvement it would make or if I really need it at this point.

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sellecting valve springs, and setting up the valve train

How do you determine the spring pressure needed to keep the valves under control for a given lift, duration, and max rpm. It might take you several hours to read thru all the links and sub links but its time very well spent as it could save your engine from destruction and save you thousands of...
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valve train clearances and problems

you might want to read thru these links and sub links it will help you avoid costly mistakes http://www.summitracing.com/parts/pro-66830/overview/ https://www.harborfreight.com/multipositional-magnetic-base-with-fine-adjustment-5645.html...
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checking piston to valve clearances

this is an old post I got asked to repost, naturally the first step is to install and correctly degree in your cam, http://garage.grumpysperformance.com/index.php?threads/measuring-piston-dome-volume.17255/...
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louis tool/swapping to 1.6:1 ratio rockers

Grumpy? can i install a set of roller rockers,1.6 ratio in my l79 engine with having my pushrod holes elongated to accept the 1.6 ratio? https://www.hotrod.com/articles/roller-rocker-ratio-test/...
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yeah, but once you wade through it you'll be far better equipped to make smarter choices
 
I’ve been doing re-assembly of my 89 Corvette’s engine; cams in, timing chain, oil pan, etc. My question today is this, the stock aluminum heads (113’s) came with self aligning rocker arms & what looks like a pushrod guide plate. I’ve read that it’s not a true guide plate but was an assembly plate when built. So do I keep them all in place or do I pull them? If they were true guide plates I know I’d need to pull them with self aligning rockers, but it looks like it can go either way.

I’ve installed new valve springs & seals. I have new ARP rocker studs ready to install but need to decide on the plates before I locktite them in place. Then I can install the 1.6 full roller rocker arms adjust the lash & see if the OEM valve covers will fit since that’s my goal.

I’ve read it both ways on cutting off the drippers on the inside of the valve covers. Some say cut them off, others say you don’t need to. Any advice here too?

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Its been my experience that you don't need valve cover drippers with roller rockers, as they get enough oil to function reliably without them.
you can either use the guide plates with standard roller rockers or eliminate the guide plates and use the self aligning style rockers
personally Ive usually preferred the self aligning roller rocker and no guide plate option but either route works, you might need spacer washers under the studs if the plates are removed
 
I agree, if they were traditional guide plates & that’s where it’s gotten confusing for me. Knowing how GM doesn’t spend a nickel unless they absolutely have to do so, I find it odd they’d add something that wasn’t needed. Since the plates were there before with the stamped steel self aligning rockers, I’m inclined to leave them as GM built it with the new rocker arm change.

If the drippers were an issue wouldn’t I feel that interfering when installing the valve covers?
 
I should back up & fill in what happened over the last few months. After pulling the timing cover I found the chain was quite stretched, way too much for a performance engine! Good thing a replacement was on the way.
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After the cam was pulled out I found wear on the front most bearing & marks on all the cam journals, oddly enough wear was on the top of the bearing approx 12 to 1pm. I would have expected it at 6pm from the timing chain pulling down & all the springs force down on the cam too.
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Figuring all the cam bearings had issues from the cam journal scratches & imagining the rod & mains looked the same, I decided to pull the engine & rebuild it to 383. After getting all bolts out but one, I realized if I pull the engine I’d have to support the 6spd manual trans with a jack stand (no cross member to support it) until it was completed & together again. I eventually decided that wasn’t feasible to do & would probably take over a year to do. The front bearing measured in spec on X & Y axis, plus since it ran fine before it surely will when back together & I can always bump up to 10w40 synthetic from the 5w30 synthetic I use. This way I can plan my engine build or LS swap & limit down time. Finally I’ve got too many other broken old cars & this one is physically blocking those in the garage from ever getting out.
So in went the TPIS Super L98 camshaft & re-assembly began. Naturally I got side tracked painting the front of the block, cleaning aluminum brackets, trying to find decent motor mount replacements, etc, etc. Pulled the oil pan, cleaning everything & reinstalled with a new gasket. Also fixed the pan draining since it’s shape was holding used oil even with raising the front end to try to get it all out.
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Next came replacing the valve springs & valve seals. Naturally I bent a couple rocker arm studs as I taught myself to do this so I ordered new set of ARP’s. I decided to pick up a set of inexpensive full roller rockers too, finally found an inexpensive set of 1.6’s. Naturally everything takes forever to get shipped to me as does trying to learn how to do all these things. Life would be so much simpler if I knew what I was doing or had a mentor. Oh well…

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Valve covers painted after searching forever to find a paint that I thought was close to the original color. (Duplicolor DE1650 cast coat aluminum) Match or not, it looks good to me.
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