mike623

I am going to be installing number 6 heads on my 1972 cutlass 350. Does any one have any advice on what I should have done on them? I am leaving the bottom end stock. I will be adding a stock 4 barrel manifold and q-jet. I was going to deafinately have a valve job done on the heads. I was wondering about having the bigger valves installed in them? If I do what size? I have a 1970 cutlass supreme convertible with the 6 heads and that car runs like a champ even with the 2-barrel.

Warhead

First off-guides. If they are out of spec, have new ones installed.
Vat (clean), magnaflux (check for cracks), and Surface the combustion side of the head. Do it all. If you want more compression, you can shave more off, it will just cost more to do it.
.030" cut, will always be a safe number if there have been no previous cuts. Some people cut more with no issues. Otherwise, plan to shave them at least .005" just to make them flat.
It is not too difficult to install larger valves. 2 inch intake valves will pick up about 20 hp on the top end above 4500 rpm. If you do not wind up the engine that tight ever, don't bother with it. Figure $100, plus the price of the valves.
You can do the exhaust valves, but do not expect to see or feel much in the seat of your pants from doing those.
Keep the 1.56's.
At the the very least, if you use the stock 1.88 intakes, have your machinist do a 30 degree back cut behind the 45 angle on the valve. Along with a 3-4 angle valve seat (15/30/45/60), you will be able to pick up a bit of flow from those 1.88's. You can also do this with the 2 inch valves, if you decide to go that route.
If your machinist can not/will not do this, find a new machinist, or send me a PM and I will do the valves, for $2 per valve, plus shipping. If you and I can safely stuff 200 valves in a USPS flat rate box, the shipping will be the same as 16.

Throw the umbrella seals in the trash can, and get a set of Viton positive rubber seals. This will require the machinist to cut the OD of the guides to .500". Go to Goodson.com for the seals. He can tell you more about them.

I really love those 2 bbl carbs. I always wished they made a 2X2 manifold for these things just because they are such good, reliable carburetors.

Jim

mike623

If I do go with 2in. valves do I need to changes cams or will the stock cam be ok?

Warhead

You can run either camshaft.
You will definitely optimize your engines performance by going to a custom cam, that maximizes the breathing capabilities of the heads with the larger valves, even if you want to keep a smooth idle.
The factory had numerous cam grinds for either 2, and especially 4 barrel engines.
If the camshaft is in good condition, you can still run it. There is better units available to you, though.
Jim

mike623

What was the stock cam in the w-31? Were they high horsepower 350 with big valve number 6 heads?

cutlassefi

I think it was the 308/308, 233/233, .474/.474 on a 113. No you don't HAVE to change the cam if you modify your heads, but that cam is too much for your compression ratio.

If you're going to change it let me know. I do custom grinds or help shed light on what else is correct for your application.

mike623

I think I am going to stick with the stock valve size. So i need to have a 3 or 4 angle valve job, have my machinist do a 30 degree back cut behind the 45 angle on the intake valves. Along with a 3-4 angle valve seat (15/30/45/60), put a set of positive viton rubber seals, have the machinist cut the OD of the guides to .500". Have the guides replaced. Have the heads shaved .030". And surface the combustion side of the heads. Is there anything else that should be done or any other specs? I would like to print something of here and take it to the machinist and say this is what I want so any other input or ideas would be cool. And I guess I will be keeping the stock cam for now to keep thing a little simpler.
Thanks, Mike

mike623

Also, Is the cam different in the 2-barrel motors and 4-barrel motors? Because this motor has a 2-barrel on it right now but when I swap heads I am putting an original 4-barrel cast iron intake with a original 4-barrel q-jet. Of course the carb will be rebuilt before it goes on. Sorry for all of the questions, they just come to me and I feel like if I dont ask then I might miss something important .
I love learning what all i can do to my cars. Thanks for all of the advice.

Warhead

The cam for a 2 bbl engine is usually smaller than your typical 4 bbl engine.
If you change cams, I would also invest in a NEW set of valve springs for it also. Just me, I like new springs.
As for the camshaft, I would be looking for something in the 210-215 degrees @ .050 lift (intake), with about .475-.500" lift at the valve..... but no more duration than that. Anymore than that would cause driveability to suffer. You may get by with a little bit more lift, but not much.
Mark (cutlassefi) would be better at a cam recommendation than me.
Jim

highlander

if i were to have the heads shaved down a little, would i then have issues on installing my edelbrock alum. intake on? I have been thinking of doing the same as this tread but was warned about the intake fitment? I have about the same build as the thread starter 350 originaly 2 barrel that is now a four barrel holley 670.

Warhead

NOT A PROBLEM IF THE HEADS HAVE NOT BEEN CUT OVER .030".
Jim

captjim

Keep in mind that engine had the big dish pistons. With the heads cut to 64 cc and a stock .040 gasket, Cr is like 8.1 to 1. With a .028 head gasket 8.4 to 1. So don't go nuts with the cam or you will not be happy. Small cam, 4 bbl intake, exhaust upgrade (if not already done) and a gear swap to 3.23-3.42 and you have a fun, responsive cruiser.

highlander

^^^so, suggest a cam for me if you could. Assuming i have the head work done, I also have true duals through hooker headers and 2" flow masters. 4 barrel carb and edelbrock performer intake. I am in the progress of have the rear end done to a 3.73 posi. Not real sure of tire size right of hand.

captjim

I can't for sure, unlit everything is measured and you know the true Cr. But, something like this,
http://www.lunatipower.com/Product.aspx?id=1720&gid=287

• Advertised Duration (Int/Exh): 250/256
• Duration @ .050 (Int/Exh): 207/213
• Gross Valve Lift (Int/Exh): .466/.485
• LSA/ICL: 112/108
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 800-5000

Would work well with an 8.3-8.4 engine, IMO.
Also, IMO, you don't need that much gear. The engine will have good off-idle torque and you won't need to see anything over 4800 rpm, so unless you have OD trans, I would go 3.23.

cutlassefi

I agree with Jim, 3.23 might be a bit better. I know he likes the VooDoo stuff and with good reason but you might want to look at an Erson RV12 or the Lunati 06185 single pattern cam (210/210 on a 110, .470 lift on both). They will give you a bit more midrange and don't require much more spring pressure over stock.

highlander

taking notes..... i am not sure if i want to stay with a nice numbers matching original small block or cave in and go to a 455..........one or the other will happen once the weather changes here in micheeegan.

tonycpe

Please note on a early 350 2 -barrel motor , you may have to switch push rods when changeing cams. Gm parts book will show different #s for a 2- barrel and 4 - barrel motor. the 4 -barrel push rods will be slightly longer.

Warhead

Factory length should be 8.234" for both 2 & 4 barrel engines.
CSK shows them for $1.99 each, Autozone will sell MPR307 for .89 each.
The 8.280 pushrod is for the earlier 330 engines with 45 degree lifter.
Tony, if your book has some other info, please share all details/measurements.
Jim

tonycpe

no book , first hand info. When i changed the cam in 1969 on my still pretty new 1968 cutlass , that is what I had to do . I remember having to go to 3 different dealers to get 16 of them
I think i still have the originals , they had a green stripe on them.
I thought is was because of the cam core. but that is all i know.
I wish i had some 10" calipers so i could dig em out and measure.
It was a long time ago, but my first big cam was kinda big deal and i thought i remembered it pretty well.
I know i'm getting old but hope i 'm not losing my memory.
Now i would really like to know if this is true. Anyone?

highlander

I decided to go with the cam you sugjested:

• Advertised Duration (Int/Exh): 250/256
• Duration @ .050 (Int/Exh): 207/213
• Gross Valve Lift (Int/Exh): .466/.485
• LSA/ICL: 112/108
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 800-5000

Using my stock 7A heads with out having them decked or taken off for that matter as it would cost 500 dollars to have them redone and as far as i can tell there is nothing wrong with them.

I chose a set of 3.42 gears that a re being done already. my question is about push rods, i have a Tech from the service dept here at the dealership i work at helping me, but want to know from any one her if i do or dont need longer push rods? Also i need a new valey pan ,timeing cover, water pump and thermostat gasket any thing else?

jpaulwhite

Nice car Highlander. I plan on getting my heads redone and slapping a cam in my 71 eventually. Good to see other 350 folks out there doing it. Good luck and post some results :-)

highlander

I have a question about installing that cam. The wrech from work is planing on installing it straight up. Meaning finding tdc and installing the cam. I have a stock replacement chain set in the car right now and am not planing on changing it. I have read about degreeing a cam. It is it nessary for me on my application?

captjim

I ALWAYS do it, half an hours work and it can make a world of a difference. It is easier with the heads off.
http://www.oldspower.com/vb/showthread.php?t=39723

Warhead

Wiggle the valve springs at the tops.
You need new guides.
I never see 2 Oldsmobile cylinder heads hold all 16 guides within tolerance over 100 K miles.
Usually 50%, always at least 3 or 4, sometimes EVERY ONE.
The result is reduced compression, and blowing power out the exhaust pipe.
BTW, all that oil that comes down from those loose guides hardens on the valve head and blocks airflow.

Just sooo you know.

Ask the cam manufacturer if you need the longer pushrods. They will be the first, most informed people at telling you if it was manufactured on a reduced base circle, or if they supply short lifters. Since you do not plan on pulling the heads, there would be no other reason for them.

My opinions
Jim

highlander

can those guides be replaced with out pulling the heads?

captjim

Nope.

highlander

rats didnt think so....

michael hilsabeck

in early 350 pushrods were differnt 2 bar to 4 bar