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Old 12-29-2017, 10:27 PM   #1
Alex V.
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Cooling down a 350: heads/cam, just for kicks

So I traded some Jeep parts for cash and a fully dressed 350. Top to bottom: Weiand Xcelerator intake, 461 camel hump heads (dated K164) w/1.94 intake valves (originally 62 CC chambers but may have been shaved), TRW cast flat-top double eyebrow pistons in bores .010" over. It has a flat-tappet cam that I've not ID'd yet (assuming it's pretty hot given the rest of the build and that it was in a S10 that was raced), and haven't pulled the pan to ID the crank but it is 3.48" stroke. All this in a '70 010 block stamped as a 255HP truck application. HOWEVER, the rear of the block is chipped off right in the casting for the oil filter and it has been rigged for a remote setup. The epoxy or whatever they used doesn't appear to be leaking (though it has grease and stuff on it that indicates it has been run) so I'm casually considering selling the stock 2-bolt, cast crank '78 350 out of the Suburban (figuring the long block is worth $350-400) and doing something cheap but usable with this engine (valued at $250 in the trade) to keep the Suburban mobile but get some money out of the deal easier than parting this one out.

Taking the pistons as a constant, I have either the camel humps (putting compression north of 10.5:1) or a set of the original heads for the 'Burb's 220 HP 327 (1.76 valves and 68CC chambers, IIRC) that I might have redone and stick on it which would get the compression down to around 9.5:1. I don't expect perfection because I'm not building the engine from scratch, but with something like Summit's 1065 cam and a lower rise intake (maybe something for mid torque that my 4GC would bolt to) could this be an engine that doesn't drink fuel and performs well from about 1,500 RPM on up? Also, it doesn't need top end - the Suburban with its 4-speed and 3.73's is in its zone at 2,000-3,200 so if it runs up to 4 grand alright that's all it needs.

Is there any chance the small-valve heads with a mid-range cam and moderate compression would get enough air through above 2 grand to develop power (325 gross HP is high for my purposes) but retain enough smoothness not to jerk the 'Burb into pieces via the 4-speed? The current engine had a 3/4 cam in it when I got it and it was a bad combo if you didn't like whiplash.
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1967 C10 Suburban, 350/NP435, Green/Green, PS, PB, HD cooling, charging, shocks, and springs.

1985 GMC C3500 SRW, Sierra Classic, 454/TH400, white/blue.

Last edited by Alex V.; 12-29-2017 at 10:40 PM.
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Old 12-29-2017, 10:49 PM   #2
Alex V.
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Re: Cooling down a 350: heads/cam, just for kicks

Also, here are a few pics of the block damage. The lip where the filter gasket would seal is chipped - is there any remote adapter that would seal to the inner area of the casting and avoid that area altogether?
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1967 C10 Suburban, 350/NP435, Green/Green, PS, PB, HD cooling, charging, shocks, and springs.

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Old 12-29-2017, 11:41 PM   #3
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Re: Cooling down a 350: heads/cam, just for kicks

Wow.....well, you are moving in the right direction to get things in the 1500 rpm range in terms of performance.
One thing to check to get started...are the 461 heads. Do they have the extra/additional end tapped holes?....if not, and depending on what your alternator, a/c etc brackets are...they might not work, given that they usually don't have these needed holes for the truck stuff.

If there any info on the cam?....you are going to want lift...not duration (ie: lumpity, lumpity) for a heavier vehicle needing torque....like a truck.

all good
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Old 12-29-2017, 11:56 PM   #4
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Re: Cooling down a 350: heads/cam, just for kicks

I don't believe the 461's have accessory holes. However, I googled around a bit more and found some other discussion of small-valve heads potentially allowing equal or better low-end than the "benchmark" 1.94's. Also, the 461's are going to net no less than 10.5:1 compression with the pistons present, and I need it to be a mid-grade friendly engine. Supposedly the 68cc chambers of my 327 heads would put compression at 9.5 which which shouldn't require premium.

So duration is what causes rough idle? I thought it was lift... but that's why I'm asking.
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Old 12-30-2017, 12:16 AM   #5
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Re: Cooling down a 350: heads/cam, just for kicks

A tight LSA causes rough idle. Like 108 or 110.
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Old 12-31-2017, 05:26 PM   #6
Alex V.
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Re: Cooling down a 350: heads/cam, just for kicks

I've found someone interested in trading an Erson TQ20H cam for the Weiand high-rise intake I got with the trade. It's a square pattern 292 adv. duration/.449 lift, 111* LSA w/4* advance. Any input on how well that cam would run up to 3,500 RPM with a 9.5:1 comp. ratio and 1.72 intake valves?

Also, the engine has a Comp double roller timing set on it that can be moved 4 (crank)degrees either way, currently set at 0. With the cam having 4 degrees advance, for my purposes should I leave the crank gear at 0 or retard it 4 to put the cam at +2?

I pulled the pan off and took the cam out yesterday. It's a 4-bolt (too bad the block is messed up), cast crank, and had a Comp 4-224-12 Magnum solid lifter cam in it. This sucker was hot!
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1985 GMC C3500 SRW, Sierra Classic, 454/TH400, white/blue.
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Old 01-02-2018, 03:00 PM   #7
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Re: Cooling down a 350: heads/cam, just for kicks

1.72 valves wil choke the hell out of it.

Gary
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Old 01-02-2018, 11:53 PM   #8
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Re: Cooling down a 350: heads/cam, just for kicks

I am biased. I would not reuse that block. They are plentiful for one reason. When you have to line hone the crank the costs become counter productive instead of using something more like a L31 Vortec Block.

But thats just me, I can be somewhat of a perfectionist which kicks me in the arse from time to time.
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Old 01-03-2018, 12:02 AM   #9
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Re: Cooling down a 350: heads/cam, just for kicks

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Originally Posted by toolboxchev View Post
I am biased. I would not reuse that block. They are plentiful for one reason. When you have to line hone the crank the costs become counter productive instead of using something more like a L31 Vortec Block.

But thats just me, I can be somewhat of a perfectionist which kicks me in the arse from time to time.
I'm not removing the rotating assembly. The top end was clearly disassembled to replace a bent valve - fresh gaskets and squeaky clean chambers, but no apparent recent work to the bottom end. Given that I'm going to put some less aggressive heads and cam in it (total investment <$400, most of which will come from selling the other parts) and use it in my 'Burb for the time being because I believe the running engine in it will sell better than this one with the damaged block, while I see no indications the short block of this engine isn't still sound.
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1967 C10 Suburban, 350/NP435, Green/Green, PS, PB, HD cooling, charging, shocks, and springs.

1985 GMC C3500 SRW, Sierra Classic, 454/TH400, white/blue.
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Old 01-08-2018, 11:21 AM   #10
Alex V.
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Re: Cooling down a 350: heads/cam, just for kicks

For anyone that's curious, I got my numbers plugged into a dyno program.

This is with the 480 heads, flat-top pistons, 9.39:1 comp ratio, 500CFM carb., and small tube headers w/mufflers.

First one is with a TQ20H cam.
Second is with a Summit "1065".
Third is a Comp 12-238-2.

The curves aren't huge, but the torque is good and flat. It's so tempting to ditch the Erson and go for the Comp Xtreme Energy and that extra 60 lb-ft.
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Alex V.
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1967 C10 Suburban, 350/NP435, Green/Green, PS, PB, HD cooling, charging, shocks, and springs.

1985 GMC C3500 SRW, Sierra Classic, 454/TH400, white/blue.
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