Z06CE

They are chrome stamped steel but a lot of interference. Looks like original.
But that's what I was thinking. Rockers binding on the valve covers. Makes sense to me.

CanadaGrant

I found that using stock type valve covers and aftermarket rockers, even the stock stamped steel non-roller ones that Comp makes, the tip of the rocker right at the pushrod will just touch the tin oil shielding that covers the pcv port on the left side and the port to the air filter on the right. I put the covers on without gaskets and moved them around to see where they touched and had to dimple the shielding in about 1/16" right where the top tip of the rocker was rubbing. And this was with Comp's "stock" rockers. It was only on the tin oil shielding which is pretty flimsy stuff and not the cover itself. If the rockers are not stock or even really close to stock you have to make modifications or use different covers. I believe it was on #3 and #6 exhaust valve rockers which are just below the inside tin oil shielding and if you remove the shielding instead of just dimpling it, you will then use a ton of oil.

jackson

Just my opinion: I really like quality beehive springs.

But (also just my opinion) I don't think every application warrants the additional expense of quality beehive springs.

I question if OP's application warrants quality beehives; particularly if this plays out as simply a replace-repair rather than an upgrade.

If OP's does turn into an all-out Roller cam & lifter retro-fit/upgrade, and depending how large the new cam, then (IMO) quality beehives become much more practical.

But 'til then, a good quality (eg PAC), correctly speced conventional single w/ damper seems a practical choice.

If PAC 1900's seat pressure seems too weak for some ... then how about PAC 1931 ?

PAC 1931 costs about $13 more & has about 30 lbs more seat pressure than 1900... PAC 1931-16 about $72 / set (roughly $20 less than comp 911)


https://www.racingsprings.com/index..../category/399/

https://www.jegs.com/i/PAC-Racing-Sp...31-16/10002/-1

https://www.summitracing.com/parts/rsc-pac-1931-16

ctmccloskey

Hello all,
I have a 1968 Corvette with the 427 (originally an L-71) and I wanted to make some real power so I actually sought out the 3931063 Cast Iron Cylinder heads for my power build. The heads were then ported professionally and all new valves, springs and everything. When my Builder and I started this project I had a budget (of sorts) and we bought a Comp Cam Complete kit including the timing chain, valve springs, lifters and other top end parts. My engine uses the same pistons that the L-88 used and is currently set up to run 12.25-1 Compression ratio using the GM cast Iron heads. We put clay in the cylinders to be absolutely sure there was sufficient room for both parts as they spun around. I used the same Gold Roller TIP Rocker arms. We measured the push rod lengths and ordered a set of one piece units that are virtually the stock length. My engine was balanced at 7000 rpm and I have driven this car on several hundred mile trips with no ill effects of the compression. In fact I really like the power that a 427 can make with those cast iron heads. I can't ever go back to the race track because I can drop into the 11's with a 3.36 rear end. The GtechPro I have said that it is way more that the 435 hp they claimed the car had when new.

The heads off the later model 454 might have had issues to start with if they were from a truck 454. Your pistons are correct for the 3931063 heads and those heads are not a bad design. I chose them primarily because they have a "Closed Chamber" design over the newer heads going towards "Open Chambered" heads. After doing some homework I learned that the closed chamber heads have a much smaller problem with detonation. All my homework was done in 1992,93 for this engine and Compression was the cheapest way of making lots of power. I would love to have a set of aluminum heads to use but they just started making closed chamber Aluminum heads!

Z06CE, If you have the old heads get them cleaned up, grind the valves again and install new seals. Since the other parts of the engine (Hopefully) were designed to use the 063 heads, it would be basically close to a stock rebuild. When my pistons are at top dead center the piston has parts that stick out above the engine block by over 1/2". Those parts match the indents in the heads and boy do they compress some air. Using lower compression like 10-1 or 10.5-1 would probably allow you to use pump gas without any noise or rattling. The original design was worthwhile, that is why I would switch back to 427 heads or switch blocks so you have a real 454. I would go back to the 427 heads and use them as they were designed as a system by GM.

Using high compression is easier to do now with the newer technologies helping us. I have a Snow Performance Water/Methanol injection system that gets activated by a vacuum line and gives my car the equivalent of 115 Octane gasoline while putting regular gas in the tank. I used a MSD ignition system with their Billet tach drive distributor to light the fire and a set of long tube headers that flow into a "Chambered Exhaust" and out the back. I have a Pulse width Modulation Cooling Fan controller and another PWM Electric Fuel pump Control system so my car does't sound like an F-15 taking off in car. Next is the J&S Safeguard system that will retard the specific cylinder if knocking is actually happening, it can retard any cylinder up to 20* and will return the timing if the knocking stops. I also want to install a Pro Flow EFI system from Edlebrock as soon as I can afford.

I love my 51 year old C3 Convertible and the BB helps me keep that big smile on my face. I hope that your car can do the same for you before the weather gets nice! I have had my 1968 C3 since July of 1991, I also have a 1988 C4 Corvette but that was for the women of my family. With all the stuff on my engine I can still reach all eight spark plugs from the top. These car may be money pits but mine has increased in value several times over since I bought it. I love the torque the BB makes, I can slow to 20-25 mph in 4th and accelerate away without any issues.
This engine built by a Speed Shop Owner and I and we had a great time building my motor over about 6-9 months. He had it on display at his shop for his annual Customer Christmas Party to show off his handiwork, the man sold a lot of engines after that.

I wish you the very best in solving your Corvettes Dilemma, if you have any specific questions please feel free. Valve covers are an easy fix, summit sells chrome Mr. Gasket for less than $100 in Chrome that fit around the brake booster on a BB Corvette!
Chris a.k.a. ctmccloskey

Z06CE

The heads are 336781 Date code 1973, Oval intake runners. Open chamber design.

jim2527

IIRC lobes also have a slight cant/angle that keeps the pushed back? in the block.

suprspooky

Did you decide to do the easy fix (Springs and Pushrods, taller valve covers/gasket stack) or are you biting the bullet and pulling the Heads?

Z06CE

I'm pulling the heads,
If the lifters are solid I'm pulling the cam

derekderek

Do you have a block casting number? Are you even sure it is a 427 and not a 454? Or a 396? So, once the heads are off get one piston all the way at top dead center and measure the 2 lowest down. And see if they are 3 and 3/4 or 4" down in the Bore. And if 4-1/8th or 4-1/4 dia. And we're going to want some pictures of a piston tops in numbers on the pistons to see what you have for pistons etc. Then some decisions may need to be made depending on the condition of these heads whether you want to move forward with them or some other head that might be better suited to this engine.

CanadaGrant

If the lifters are solid or hydraulic you will be pulling the cam. Lifters with that much damage or any damage for that matter, your cam is gone. The cam goes before the lifters do.

jackson

Also ... that internal snap ring ... can be found in some Hi-Rev aka Anti-Pump-up Hydraulic lifters

pull one apart ... post pics

stingr69

The lifter side view pictures looked like they were not all moving the same lift by a considerable amount. Might just be the pix so it is hard to see from here. Maybe just the bent pushrods????

Gale Banks 80'

I might be a little off topic here but oh well. I'm getting close to doing my L-88 project and I may or may not be in the same field as this subject. The engines date codes and parts numbers are on par with an L-88 and I intend to restore the engine and car. I havn't been into the engine yet it sounds as though it doesn't have much of a cam in it. A bit surprising since its got an Offenhauser Cross Ram, Hooker side pipes and Crane Roller Rockers. I realize the X Rams are hard to tune and maybe somebody didn't put much of a cam it for that reason. Anyway I will be using the L-88 Intake with the 2196 Carb. Stock Valve Covers and gaskets. I would like to run a Hyd Roller. OK so here is the question. Anybody know of a Rocker that will work under the Stock Valve Covers ? I'd like to use the Crower. I intend to have it Judged. I have used the Crower's under stock SBC covers with a Roller.

Z06CE

Block Casting # 3963512 MH VIn matches Block

Z06CE

I dont know at this time if the lifters are damaged. I was able to get the intake pulled... i eyeballed 2 lifters... they looked ok, I tried to push on the lifter to see if they are hydraulic, but could not budge them. I'll be disassembling one like Jackson had mentioned to verify solid or hydraulic. My work schedule is not allowing me to work on the car until Friday.

I have a question with the Carburetor. Its a Holley 4165 800 CFM. Since its off the intake right now and there's gas in it, should I drain the gas out from it and how should I drain it?

HeadsU.P.

Please start your own thread. Your high jacking this thread makes it confusing which person posters are responding to.

Z06CE

I don't want a solid lifter-cam set up. I don't want to be adjusting valve lash every few months. I don't think I want to go the hydraulic roller route. I'm not going to put many miles on the car. Its not a daily driver. Just want to get a good Flat tappet cam setup with matching components. I am not racing the car to get into the 10s.
I want a cam with some good power, low end torque, and streetable.

Gale Banks 80'

Good Power, Low end Torque, and Streetable = Hyd Roller Cam. ( and little or no break in ) There's a reason GM started putting them in Corvettes back in 1986 and has never looked back. Disadvantages = Cost.

derekderek

Not just in Corvettes. Not just in V8's. Roller lifters are now in everything with a lifter.

jackson

OP
Not that I think you need new heads; I don't.
But If you are considering a major expenditure on your 781 heads ... perhaps you might then consider another pair of heads.

Before you jump in, take a look at this NEW thread by DV about working with EQ BBC iron heads.
https://speedtalk.com/forum/viewtopic.php?f=1&t=56033


-edit-
yes, rollers are everywhere and there's a primary reason; albeit convoluted: EPA & Emissions System.
EPA requires automakers to warranty all components of Emission system for 100K miles. Automakers could not comply because existing motor oils' wear package contains elements which destroy catalysts. EPA requires oil formulators to reduce those catalyst-destroying elements (e.g. zinc, phosphorus). Newer EPA-approved oil formulations' wear packages don't provide adequate lubrication for flat tappet valve trains but are adequate for roller tappets. Automakers redesign older motors and design new motors so all now have roller lifters/roller followers. Roller lifters so their oil doesn't wreck the catalytic convertor and pollute the atmosphere.