Hello all -

Currently working on a 1968 F85 - survivor, never been modified. 350 2bbl, automatic, 2 door post coupe. 198k on the original drivetrain, with regular maintenance along the way.

Following a build sheet, I purchased this cam to install, along with some other parts:

COMP Cams CL42-600-5 - Hydraulic Flat Tappet, Advertised Duration 278/296, Lift .491/.476 https://www.summitracing.com/parts/cca-cl42-600-5

I'm curious if stock valve springs will work with the increased duration - if possible, I would prefer to install the cam and not do springs, as I want to leave them on the engine. But I can't seem to find any specs on OEM valve travel, and whether the stock 1968 valve springs will accommodate the new cam.

I have searched relatively thoroughly, and seen a lot of cam recommendations, but no mention of the use of stock valves versus the simple "just put a new spring kit on it."

Anybody re-use stock valve springs, or have specs to show me these will work before I install this cam?

Excited to be a part of this community - thank you in advance.

Paul

 

First of all, you have valve springs with 198k miles on them. They have undoubtedly lost a lot of their tension over the years. They can also break and cause major engine problems. The valves will also float easier with worn out springs. There is a difference between re-using springs and re-using worn out springs.
Your cam isn't bad, but you'll be better of getting new springs that would work well.
Call CompCams and see what NEW valve springs they suggest.

 

I agree. When I rebuilt the engine on my car in 1982 (100k miles and 12 years old) I used the original valve springs and they would float at 5000 RPM and the engine would fall flat. After installing new springs, the engine would pull to 5800 RPM without a hiccup.

Buy some new springs.

 

I once lost a 454 BBC to valve float. Springs were not stiff enough to handle the lift and going up a hill one day the motor started making HORRIBLE sounds. The number one intake valve hit the piston hard enough to break off the head of the valve which after banging around in the cylinder for a few revolutions broke the piston in half and sent the wrist pin through the cylinder wall into the water jacket. When I tore the motor down, I could see marks on top of the pistons where the other valves were hitting as well. I had the block sleeved, rebuilt it with the correct springs and it ran great. As others have said, buy the recommended springs for the cam. If you are trying to avoid pulling the heads, you can change valve springs by putting air into the cylinders, however at 198K pulling the motor completely apart to at least inspect and clean everything is a good idea.

 

Paul,
The duration is not really what will cause a problem, its the lift. I dont think the stock springs and retainers will work with .491 lift. The retainers are liable to hit the top of the valve guide.

 

I'm certainly not a cam expert, but that cam will be very disappointing in a low compression 350. I'm sure others more experienced than me can offer a better choice.

 

^^^^^^^
Not the best choice of cams for your build. Plus they’re designed to be installed with a fair amount of advance. Did you degree it? I’ll bet no. Scrap the idea of trying to use 53 year old springs. You’re asking for trouble.

 

As said, a very big cam for a 9 to 1 compression at best 350. Even the generic 204/214 cam will work better with your combo. I ran two different brands, both worked fine. I used a 214/214 .472/.472 110 LSA that worked really well in my 9 to 1 350. It lost a couple of lobes a couple of years later. The rebuilt heads I picked up had supposed upgraded BBC springs, not stock for sure that very well could have been too stiff. Easily pulled past 5000 rpm. My current 9.5 to 1 358 build is getting a 218/218 roller cam with matching springs. No chance of a flat cam. As said, always degree your cam. I assume you are going to a 4 bbl intake and carb? Also seriously consider a TH350 or TH2004R swap. Good luck.

 

Thanks for the advice, everyone. Looks like I'm pulling the heads and replacing valve springs, along with returning this cam and getting a different one. I've seen a myriad of threads on cam suggestion, but I'll ask in here - any recommendations? Plans for the car are to be a cruiser, so low range RPM around town usage. I'll be upgrading from the factory manifold and 2bbl setup to the Edelbrock #3711 and a Brawler 650 (it was a package deal, used, but got a great deal on low usage parts), with Headman headers and a 2.5 Summit Turbo exhaust (I liked the sound, and it was pretty affordable for both exhaust and headers). Trying to do this on a relatively low budget (which is why bodywork is later on the list) so I can drive sooner with a car that sounds good, but park anywhere I have to haul the kids.

 

You might not be ready for a different cam or "Go Fast" goodies with an engine that has high miles (198k).

 

Your situation is not that different from mine. I have a '68 Cutlass Convertible with an unknown mileage 9 to 1 2bbl 350. I have no plans to race it, but I want it to be fun to drive. The 2bbl was garbage, and the car ran poorly even after a full professional rebuild of the 2bbl.

I swapped the intake and carb for an Edelbrock 2711 and a Holley Street Warrior 600 CFM 4bbl, and converted the car to dual exhaust with turbo mufflers, keeping the factory exhaust manifolds. After a basic tuneup, you would not believe the difference these changes made in both drivability and performance. It will burn the tires with ease and pulls hard to the redline.

My advice to you is to do things incrementally. Go ahead and install your 3711 and Brawler 650 and covert it to dual exhaust as you said you planned to do. If you haven't already done so, refresh your distributor components, plugs and wires, too.

Do these things, and see how it drives. You might just find that the car is a blast to drive, and you will not have to sink that much money into it at this time. Save up for a full rebuild for when the engine finally needs it, and invest in a better cam and the new Edelbrock aluminum heads at that time.

Good luck!

 

The generic 204/214 cam is a cheap upgrade, pulls like 19" of vacuum and idles nice and smooth. You don't need to pull the heads to change valve springs and seals with compressed air, I have done it before in vehicle. The cam is trickier, getting the front cover in place and tearing apart the front end. You can get away without valve with a very mild cam like that but expect valve float. What trans and gearing is in this car? If it is the 2 speed, spend the cam money on a 3 or 4 spd auto to replace it first.