Headers! Good choice. #1 compression, #2 breathing

Even with smaller runners your intake flow should be adequate for RV power settings. Runners are usually fairly well balanced for flow between cylinders. Cast exhaust manifolds are another story. Usually pretty bad for both flow and cylinder balance. Headers are lighter, easier to install. You will have much better power balance between cylinders. Way less heat soak under the doghouse after shutdown, too.

I have always been satisfied with any headers I have installed. No magic bullet but always smoother.

Keep us posted, you gearhead, you.

Got the kid up the street to help lift the heads on to the engine, what a hassle he is tough to get pointed in a workable direction wants to do it his way, very "head" strong! (Pun intended) Broke about every sensor there is so more expense!

My torque wrench is busted, tomorrow will go get a loaner and finish the job with new bolts!!! Hope to get all the lifters adjusted too. Headers should be here Monday. Headers will let me temperature check each cylinder, no more non-burning holes! But will take some exhaust mods!

"gonna use the 305 heads"

Duane! I am thinking that these might be good. These seem to be "truck" heads, and though the port volume is low, this is a desirable characteristic in truck heads. This facilitates a higher velocity of the intake air charge, to the combustion chamber. That is good for better ignition of the fuel/air mixture. Truck engines will be really concerned about the torque at the low end, say from 1500 to 3000 RPM. That is where the RV engines live, get the rig up to speed and stay there. You aren't concerned with the 4000 RPM plus drag strip passes.

You were also concerned with your compression ratio. Well the other factor in that is "volumetric efficiency". You won't be running wide open throttle all that much, so generally you are at part throttle. The cylinder will fill with lower pressure intake air, so you won't be compressing 350 cubic inches of air at standard pressure.

So that works to your favor for avoiding the pinging of a high compression engine.

I was also thinking about the idea that some chevy engine builders use, going with 1.6:1 rocker arm ratios, instead of the usual 1.5:1. This will allow for greater air flow in. You can do that at a later time too.

Some guys worry about freshening up the top end of an engine, without also doing the lower end. You have a chevy 350 truck motor, so you will have the 4 bolt main caps, not the 2 bolt caps.

Oh by the way, is this a 4 barrel carburetor on your engine?

Happy Motoring!
Matt

It is a fine 4bbl on the engine;-))!

quote:

Originally posted by ccctimtation:
It is a fine 4bbl on the engine;-))!

'

Yes Matt, it has an almost new Rochester Quadrajet, a gift from Tim!!! Thanks for the research, got the heads in place and the new bolts snugged up.

Hope to be running in a couple of days~~

quote:

almost new Rochester Quadrajet

Hi Duane,
I am sure that if you have a Quadrajet on a 1971 Chevy 350, that the engine will have a forged crankshaft. That lower end is going to handle any of the power increase you are making at that top end.

It took me some time to learn to tune the quadrajet, to get the secondary doors opening up and letting more air in.

It is really smart to get the new head bolts.

Happy motoring!
Matt

The new headers did not show up yet. Did get the heads through all three stages of torque. Decided to let it sit over night and recheck tomorrow. Could not find a thicker head gasket so had to stack two regular .041 thick ones. Gonna take extra care with this tightening process. Will put the rocker arms and push rods in and adjust them too.

The hot rod shop guy told me there is a new method of making the lifter adjustment.

1 Set the piston on top center, combustion stroke
2 Remove each lifter and lube with start up lube and replace
3 Tighten each rocker arm and push rod until it will just spin, no play
4 Back off 1/4 turn. Check cylinder for compression
5 Done

Anyone ever tried it this way???

quote:

stack two regular .041 thick ones

Duane,
Talk to your hot rod shop guy, see what he recommends for intake manifold gaskets in this situation. Thicker head gaskets move the heads further apart from each other, so you will want a compatible thickness on the intake manifold gasket to best seal the intake runners and the coolant passages.

On the head bolts, did you use something like "Permatex Aviation Sealant"? Those bolts hit the water jacket of the block so you need that. Some/all of the 350 intake manifold bolts will need that too.

Your guy is telling you good info about the valve lash adjustment. I hadn't seen the steps involving the start up lube and the compression check. With new lifters, I have seen it done with a step of "pumping" up the lifters to get the air out, and get motor oil in.

The key to the activity is knowing when you have both valves closed. The timing mark is in place for #1. When that is aligned with the timing tab, you can adjust the valves for cylinder #1, and a few others.

I looked up a reference: https://www.jalopyjournal.com/...djust-valves.168345/

That lists it as "adding a quarter turn" after the pushrod loses the end to end play. I think I've done it that way.

But it might depend on your gaskets and your lifters as well.

When I worked on the 454 recently, I must have not had one of the valves in the right position, I needed to remove a valve cover a couple times to get it right.

Are you sticking with the stock intake manifold? You can be assured that the geometries of the other parts will work right. On my 454, I had to add a 2" lift to the doghouse because of the intake manifold change.

Talk to your hot rod guy, he probably has "drag racer" thermostats in stock. Those allow for greater flow rates, I think it has cooled down my 454.

I am pleased to read of your progress.
Happy Motoring,
Matt

Matt: the head bolts were precoated with a sealant, not sure what it was.

Thanks for the tip on the intake manifolds and thermostat.!!

Got my new headers today, the one on the drivers side does not fit, hits the frame! Guess the thing could be dented on two of the runner tubes, but afraid the dents will have to be deep and might affect flow. Thinking!!!

Got all the valves adjusted as the hot rod guy told me, next install the intake manifold and carburetor. Figure out what to do about the exhaust and get this Barth on the road!

Hmmm. Them headers hit the frame? Sounds simple, just notch the frame, weld a sister frame patch from an old spring, etc. hillbilly easy! Torch time!

Hopefully you can get them to fit.

quote:

new headers today, the one on the drivers side does not fit, hits the frame!

So I am still stuck in the '80s. I have a 1988 IROC. Yes, another project. The headers did not fit. I didn't think of cutting the frame, and I don't know that I would, if I did think of it.

What I did: I positioned the header loosely on the bolts holding to the cylinder head, a 350 in fact. I saw that if I had about a 10 or 15 degree angle on the headers, I would clear the frame with half an inch. I didn't want to go closer, thinking that the engine vibration could cause an annoying noise if the header vibrated.

So, with "hillbilly engineering" in mind, I used a grinder to put the bevel on the header flange that I wanted. I used an iron top for a vintage table saw as my reference for what was true and flat. Seems to fit great now. With what I learned about exhaust manifold gaskets on the 454 in the Barth recently, I will probably need to try the same brand, the name of which presently escapes me!

Happy Motoring, right?
Matt

Have come to grips with the header situation for now anyway. Gonna go back to manifolds, no exhaust pipe changes required and gives me time to determine if I am pleased with this whole set-up. Will keep the headers and probably make the change later.

Checked the intake manifold situation, looks like one gasket will work out fine. Per-side that is!!

Just have not put the time into this job to finish it in a expedient manner. Maybe some spark of ambition will strike me!!

Figured out why the valve seat guy said the compression changed from 8.7 to 9.1 when he did the hardened seat change, he used a .020 steel gasket not the standard .041. Wonder if did that for more power or just liked the thinner steel head gaskets. Broke my compression test gage or would get the pressure now and figure the ratio out.

Been rainy and I have been a bit lazy!! Did get the exhaust manifolds and pipes replaced, the intake manifold installed and the valves adjusted.

Providing the weather holds, should get the timing set and checked, spark plugs installed and wires connected, reinstall the carburetor, connect all the cooling and vacuum lines and refill the radiator.

Might get ole 71 back on the road this week!!! At least get back to the initial job of repairing the brake line leak!

This repair has taken its toll on the new carpet and again there are tools spread all over, such a slob!!

Sounds like you have been busy