When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I started working on vettes about 1980. Since I had a big garage friends would bring over side jobs. Originally wasn't a big deal back then and the 390 hp 427s were really low on the performance scale. It was very common to replace 427s with the more common and powerful 454s
Because of your casting numbers it is very possible that you have a lower budget rebuild 454
Those valve springs might be 40 year old truck springs. Low lift low rpm soft when new. 85 to 100 lbs seat pressure. And worn down from there. They might be brand new and too high a spring rate for the valvetrain. You have the top end pretty much apart. Pull couple of springs and get them ID'd any cyl head shop can tell you what spring pressure at seat and fully open and how far from seat to coil bind. I forgot this was a roller lifter setup. Now we don't know if they are solids or hydraulics. Shine flashlight down pushrod hole and get a look at the top of a couple lifters. Pic is a solid roller lifter. A hyd lifter will have a snap ring showing on top.
Last edited by derekderek; 03-10-2019 at 10:29 AM.
The 3963512 block used in the 69 427 was also used for 70 454's. Exact same block right down to the casting number. Different crankshaft gave it the additional cubes.
Those valve springs might be 40 year old truck springs. Low lift low rpm soft when new. 85 to 100 lbs seat pressure. And worn down from there. They might be brand new and too high a spring rate for the valvetrain. You have the top end pretty much apart. Pull couple of springs and get them ID'd any cyl head shop can tell you what spring pressure at seat and fully open and how far from seat to coil bind. I forgot this was a roller lifter setup. Now we don't know if they are solids or hydraulics. Shine flashlight down pushrod hole and get a look at the top of a couple lifters. Pic is a solid roller lifter. A hyd lifter will have a snap ring showing on top.
The lifters are hydraulic. I can see the snap ring retainers.
The C retainers that hold the springs can hit? Wow.
I know what the crap push rods were used...
They are Sealed Power
Exhaust part# RP 3103. 9.2540"
Intake part # RP 3104. 8,2810"
3/8 dia. .060. Wall
It might have been a blessing that the PR's bent before anything else!
Notably, they're not listed as "hi-performance", but those "crap" 3-piece PRs are correct "OE replacement" for BBC.
In my estimation and given the harsh conditions, seems those "crap" sealed power PRs comported themselves admirably.
And while they're correct OE replacements, their lengths may or may not be correct for a modified build-combo; perhaps length/geometry wasn't even considered during the "freshening."
So far anything's possible, but I doubt PR length was a significant factor here.
Once the valvetrain problems are diagnosed, and as they're sorted, suggest pushrod length/geometry should be checked before ordering new PRs.
Seems, I've seen where another poster suggests OP's Cam is a roller.
? Does it have roller lifters ? ... I doubt it, as those replacement PRs are far too long for any typical aftermarket BBC roller setup.
Ok hyd lifters. Valve springs. Are there big steel umbrellas on outside of springs that cover the top half of the springs? If so orig truck springs. Got a pic of the valve springs as they sit?
haha
Pushrods are kind of a fusible link, op you are probably fine put some good ones in and motor on.
I bent a few on a brand new motor somehow got ahold of some knockoff Manley pieces it screwed teh valvetrain up (ALL of it) in 60 mi
Guy overat Manley sent me the real deal no issues since.
Gearheads sometimes convince themselves pushrods and old springs "are fine"
two things put GM to there stock worth 85 cents at the time they took bank ruptcy. They paid there high ups rediculous money and with there regular assembline workers inculding all there benefits were equal to $70.00 an hour. By comparison toyota with no unions paying there regular assembly line works $46.00 an hour. Has gm learned anythimg nope. I just read the ceo of gm is paid 5 times as much as the ceo of toyota. The second thing did them in lousy products for many years the pickup i mentioned as just one example , while toyota and honda just kept making better and better products. They put a company that up to 1960 had 52 percent of the entire world market completely out of business. Government took ot completely over run it and finance it.
All bent push rods are intake push rods so issue should be found there. Pull an intake valve spring off and inspect bottom of retainer and top of valve guide. Look for any witness marks showing contact between those points. If the seals are aftermarket, they can get hammered and that will confirm the interference. Could be coil bind. This push rod bending happened very recently after some kind of change in the valve train or over revving the engine. Too much lift for the intake valve train happened somewhere. If compression is good the valve head is not bent.
Maybe rotate engine with a checking spring on an intake valve to see if you can see (or feel) the binding.
To the OP all it takes with a hydraulic is a couple of times well over reved and lifters pumped up from it and the valve springs are no good. While you have it apart toss the valve springs in the trash and start over. Any good chrome molly .080 thick 3/8 pushrod what you need, check tour cam and lifters. Any stick shift hydraulic lifter car should have a rev limiter put on it.
Ok hyd lifters. Valve springs. Are there big steel umbrellas on outside of springs that cover the top half of the springs? If so orig truck springs. Got a pic of the valve springs as they sit?
Could anyone tell me how to work this leak down gauge? Is says set to set on the gauge with the regulator then what? The air is flowing into the cylinder and stays on set. What next?
Could anyone tell me how to work this leak down gauge? Is says set to set on the gauge with the regulator then what? The air is flowing into the cylinder and stays on set. What next?
Ok, those are aftermarket, not 40 year old orig springs. Still need to pull them, get tension checked and see if they have enough travel to live with that cam.
Clean in there. No wear marks on the valve stem tips. This is a fresh top end. Time to remove an intake retainer and spring to inspect the top of the seals. Careful not to drop in the intake valve.
03-10-2019, 09:36 AM
