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Quick question about SBC rotocaps and valve springs

9K views 31 replies 4 participants last post by  MouseFink 
#1 ·
I've got a set of 487X heads with rotocaps. Are the exhaust springs shorter than the intake springs? Can't seem to find anything on this.
 
#3 ·
Chevrolet engines, primarily industrial engines, with valve rotators on the exhaust valves use the same valve springs on both the intake and exhaust valves. The exhaust valve spring pockets on the on those heads are machined .090" deeper to compensate for the thicker exhaust valve rotators. If you choose not the use exhaust valve rotators, you must change the heads to some that are not equipped with valve rotators.

You should not shim the exhaust valve springs more than .040" . There are aftermarket .130" shim cups made for BB Chevy valve springs that are on the base of the valve spring pockets and are designed to replace spring rotators but they are too large in diameter for SB Chevy heads. If you enlarge the SB Chevy spring pockets enough to fit BB Chevy spring rotator/spacers, you risk breaking into the water jacket.
 
#4 ·
Shim the spring seat .040" and then use -.050" reduced height valve locks and you're right back to stock height.

Common deal, Competition Products is one place that has a real good price on the valve locks.
#4333 is -.030" in stock 7° angle.

You may have to go to 10°, but stock diameter 10° spring retainers are fairly cheap so it isn't a big deal.
#3811, for 1.250" stock spring, $19.95/set
#86110x2-16 Crower -.050" 10° valve locks.
 
#5 · (Edited)
The best solution is to get rid of the 487X heads. Locate some good heads without rotators and keep the valve spring seat pressure below 120 lb. The 487X heads had induction hardened exhaust valve seats when new. GM was experimenting with induction hardened exhaust valve seats in the early 70s. GM used heads with induction hardened exhaust valve seats primarily on engines that spent most of the time at idle and low RPM such as police, taxi and truck engines.
 
#7 ·
Thing is this is the from the numbers matching engine out of my '72 Corvette. Not looking to make a 1/4 mile warrior, this is a restoration...With the exception of flat top, forged pistons and a really mild 260 Comp Cam to keep intake vacuum to run all the vacuum stuff...There's a lot of vacuum controlled stuff on this car..Headlight doors etc. Just a little something extra for the shifts between the wide ration M20.
 
#10 · (Edited)
Ah so...Numbers matching heads . I am glad to see someone else is trying to keep the numbers matching, even if you must sacrifice some top end power. .

. I have the original 3782461 double hump heads with 1.94"/1.50" valves on my l1962 Chevrolet Bel Air 2-door sedan, 327/300 engine. I recently purchased a another pair
of those heads with the "X" code on e-bay that were factory equipped with 2.02"/1.60" valves and were used on 1962 Corvettes. Only the .date codes are incorrect . In my case, I will gain top end power with the larger valves when I replace the OE 3782461 heads with th "X" code heads.

Chevrolet head casting numbers and casting dates are not as important as most other GM cars because the casting numbers are hidden under the valve covers..
 
#8 ·
The reason for my question is when I disassembled the heads I pitched the valve springs and bought new ones..And they're all the same part number. I plan on using the rotocaps because, as I understand it, the exhaust valve has a chance to run a little cooler if they can turn and that makes a difference here in Arizona. I'm not concerned with the extra weight of them. This engine will probably never see 5,500 RPM.
 
#9 ·
The exhaust rotators have nothing to do with heat, whomever told you that was badly mis-informed.

Rotators were an attempt to even out exhaust seat wear and prolong valve seat life, as at this early time in the mandated emissions legal era they were unsure how induction hardened seats and lack of leaded gasoline were going to impact valve seat life.
It has been proven the rotators were unnecessary and they were discontinued within about 5-6 years time.

I should have said there were no post '71 heads worth rebuilding, unless you have a numbers matching resto need for them, Corvette and Z28 Camaro are about it. Otherwise, the only use for them is entry level circle track rules where they mandate the use of them to limit power.

As long as you have room to fit the taller spring without coil bind, the taller spring can be used. Spring seat and open pressure will be higher, but that's a plus, it will help counter the added weight of the rotators.
 
#15 ·
I had to fork over $750 for the 3782461X heads. They were bare castings, no valves, and no valve springs.

The valve seats and combustion chamber walls
on the 461 "X" code heads are machined for 2.02"I and 1.72" E valves from the factory. The intake valve pockets on the "X" code heads are also larger to accommodate the larger valves.

I will up grade to the "X" code heads in the spring when I replace the GM 151 Camshaft. I plan on replacing the GM "151" L79 camshaft with a Comp Cams Nostalgia duplicate of that camshaft and a fresh set
of valve springs. The 327 engine in my 1962 Bel Aie was rebuilt in 1986 and it has about 65k miles on it today. A newly rebuilt 1967 Rochester Q-jet and air cleaner will replace the original 1962 Carter AFB and air cleaner. If I can secure a 4.11 Positraction on e-bay (or anywhere) in good condition, I will replace the 3.36 Posi that is in there now.

I found a rebuilt 4.56 Positraction on e-bay for $775 but that would be too stiff for my hydraulic lifter camshaft., I had a 4.56 P-track in my 1959 Impala and driving at 40 MPH along with the trucks and busses was tiresome, even with the GM 30-30 solid lifter cam in a new ..1964 GM 327 crate. motor.
,
It is about time for a new radiator from Show Cbars. Inc. along with the correct no by-pass water pump
 
#16 ·
Easy to tell if that car you saw was a 72 or 74. The last year for chrome bumpers, front and rear was 72. Quite a difference in price with the chrome bumper cars.
hcompton have you had any experience with the tach drive distributors? The gears in mine are chewed up so the tach doesn't work. I've looked at the shaft and crossgear kits in the catalogs but others have had bad experiences with them getting chewed up in a short time. Seems they're made "off-shore" of chineseium and most say OEM NOS is the only way to go but those are rare as hen's teeth now.
 
#17 ·
Use a Mother's Clay Bar kit on the original paint after hand washing. You will be amazed on what you will get. It is time consuming to use a clay bar kit but it is worth it. The clay bar application only needs to be done once every three or four years. The paint looks like glass.

I used a Mother's Clay Bar kit on my 1962 Bel Air Surf Green paint and it really shines. Use clay bar before hand waxing. My 1962 Bel Air 2-door sedan was repainted the original Surf Green lacquer in 1995 and it looks new with no chips or scratches.

I will take some straight GM original bumpers I purchased on e-bay to North Texas chrome shop in Wichita Falls Texas next year for the finishing touch. My Bel Air has a new Ciadella factory duplicate interior, which was only available in green for Surf Green body paint.
 
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#19 · (Edited)
You must have a feel for using clay bar. You can feel the resistance to the rubbing action as the clay and spray bottle solution picks up the imperfections in the paint and the resistance to the rubbing action diminishes. It takes about an hour to rub out the hood of my 62 Bel Air. Plan on spending about six hours from body wash and dry to the clay bar finish. You must keep a clean face on the clay bar as it picks up imperfections and the spray solution keeps the clay lubricated, That will require that you knead the clay as often as required. After the clay bar, I use Turtle Wax Liquid Spray Wax and Mothers Spray Quick Detailer to maintain a glossy finish. Turtle Wax Liquid Spray is great for door jambs where you cannot get good rubbing action.

My 1962 Chevrolet was painted with Surf Green lacquer and hand rubbed with no clear coat by the previous owner in Oklahoma City. That was before the commercial use of lacquer paint was banned by the EPA . According to the previous owner, my 62 Bel Air was in two episodes of the TV series "Route 66" and were the only two episodes filmed in Oklahoma.
 
#18 ·
I'm afraid mine's beyond clay bars and rubbing compound. If you look at the front between the headlight doors you can see the paint's faded clean through. From the doors back it's not bad until you get about a foot away you can see tiny square cracks in the lacquer paint. I plan on having it painted when all the mechanical work is done.
 
#20 · (Edited)
I have a good friend that owns a shop that specializes in fiberglass. He's done a lot of Vettes, he's really good so he'll be doing the paint. It won't be a color change. Same Targa Blue as original.
We've bartered work back and forth before and it's always worked out well.
Don't live near any beach. Car's lived it's whole life here in Az. The former owner had a bra on it. That's what caused the paint to rub away. I'm not going to put a bra on it. They're the ugliest thing anyone could put on a car IMO.
 
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#25 · (Edited)
My associate in Seattle WA bought a 1967 Corvette L88 that was ordered for Dick Clark. It was one of 20 1967 L88 Corvettes produced. Dick Clark refused to accept delivery of tht Corvette when he found out it did not have a radio. It was then put on the used car lot. It was a 1967 Corvette L88 convertible, white paint, black interior and Side pipes. One of 20 produced with the L88 engine.


He paid $7000 for that 1967 Corvette in 1968.i don't know where the car is today. I believe it was converted into a race car and has been destroyed. Current price for those cars is about $3,000,000.00
 
#26 · (Edited)
My associate's 1967 Corvette L88 was the fastest car I have ever driven. It was equipped-with a Muncie 4-speed and a 4.56 rear end gear ratio. He has owned several muscle cars and I have driven all of them. For example:

He has owned a new 1967 Pontiac Firebird 400 convertible, a 1969 Dodge Charger 426 Street Hemi, 1969 Z28 Camaro, 1969 Mustang 429, 1970 Chevrolet Chevelle SS LS6 454. All had 4-speed manual transmissions. He raced his 454 Chevelle LS6 at dragstrips on the west coast. The Chevelle was being towed on a trailer to a drag strip near Los Angeles when the trailer came loose. The trailer rolled to a stop without any damage done. Fortunatly, he was not going but 40 MPH. He now owns a Mercedes-Benz and lives in assisted living community in Oregon. He had a mild stroke about six months ago.
 
#29 · (Edited)
There are four part numbers for the valve springs used on SB Chevy engines but they are all the same rate and fit. GM followed this practice with the various camshafts as long as there was leaded gasoline available at the pump. When leaded gasoline was eliminated GM had from 1970 to 1975 to use induction hardened valve seats, milder camshafts with less valve lift or finally, roller camshafts that were introduced in 1992 and was the most expensive to the consumer but the only solution to the problems associated with no lead gasoline.

All SB Chevrolet valve springs were rated at 80 to 90 lb @ 1.700" assembled height.
Single without damper ... 16 quantity in package
Single with damper........ 8
Single without damper... 8
Single with damper ...... 16
 
#30 ·
Roller camshafts had nothing to do with with no-lead gasoline. They were used to deal with the lack of adequate amounts of ZDDP (Zinc Dialkyl DithioPhosphate) in today's oil. Back in the 1980s, motor oils usually contained around 1500 parts per million (ppm) of ZDDP.

This is from an article that explains it:

"In the 1990s, the American Petroleum Institute (API) reduced the amount of phosphorus allowed in motor oils to 1200 ppm. This was done to help prolong the life of the catalytic converter and oxygen sensors, both of which can become contaminated over time by exposure to phosphorus in the exhaust. All engines use a small amount of oil between oil changes, so reducing the phosphorus content was seen as a necessary move to prevent emissions failures as vehicles aged.

In 2005, API cut the amount of ZDDP again, this time lowering it to 800 ppm. This includes the current API 'SN' category as well as ILSAC GF-5 motor oils. Their reason for making the change is that modern engines with roller cams or OHC cam followers do not experience the same levels of friction and pressure as flat tapped cams in older pushrod engines. Consequently, today's engines can get by with less anti-wear additive -- which is true.

The trouble is, there are still a lot of older vehicles on the road that have flat tappet cam pushrod engines. What's more, flat tappet cams are still the most economical choice for many performance engines, including classic muscle cars, vintage sports cars, street rods, hot rods, circle track racers, drag racers and even NASCAR. Most of these engines are using high lift performance cams with stiffer than stock valve springs. If conventional motor oils (including synthetic oils and synthetic blends) are used in these engines, cam wear and cam failure can occur."
 
#31 · (Edited)
Sure is a lot of difference in the fuel, oils, antifreeze, brake fluids etc. that are used today in newer cars compared to what the the older cars used. You can spend a fortune on fuel and oil additives every time you refuel or change oil in older cars just to make them compatible. ... I'm now down to doing research on the changes in blinker fluids.
 
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