71 350 Rebuild advice needed - Head and Cam Suggestions

[72SB]

OP you might just want to put the 4 brl on now and see what its like. It should certainly wake it up but IIRC the heads were different on 2 brl vs 4 brl cars also so published 4 brl HP would be less with the smaller heads

With that said when I put a 4 brl on my 327 210 hp 2 brl motor it really woke it up.

If you do go cam, lifters, new heads at that point you would want to hone, re-bearing and ring the motor. That total cost is likely as much if not more than a new crate motor with modern heads, 1 piece RMS and full hydraulic roller cam....and a warranty. I found this to be the case when I needed to rebuild my 327.

Check out Blueprint Engines. What I got. The 411hp/413tq REALLY makes a difference over mid 200hp motor.

[SCOTI]

Larger valves in the heads doesn't automatically equate to better just like a larger cam doesn't automatically equal better performance.

The right cam & heads (or re-worked heads) w/the right pistons (compression) are what will make power.

A plain-jane early 70's 350 would likely have 17-18cc dished pistons. Couple that w/the 76cc chamber heads & you have your basic low compression no frills sbc. Larger valves won't help compression nor will they help increase power much when there's minimal pressure supplying the mix. A larger cam w/more aggressive timing events would help things sound better (like it has power) but not boost perf by much if any. Too big of a cam w/low compression can actually hurt things when below the upper rpm range as low speed cylinder pressure is in the basement.

You want/need flat-top pistons & smaller chamber heads. Later model Vortecs offer superior flow + velocity vs any previous cast iron head & their smaller 64cc chambers help compression. You can spend money on the old 76cc heads but won't get the same results as you could swapping to better flowing heads.

It's all about the combo of parts. We did several 350ci motors years/years ago (pre-Vortec era) w/flat-top pistons & iron 76cc GM 882 heads (milled for true flat surface & to help compression). Each had a mild cam (~222° int duration was the largest cam) & made just over 300hp on the dyno (so 240-ish HP to the ground).

All worked well but I don't see you hitting a 300hp number w/o pistons & spending $$ on the heads. There are aftermarket alum heads that now offer much more bang for the buck & don't require the Vortec specific intake & related parts (which adds to their overall cost to use).

I recently picked-up a 69 350 that was plucked out of a fellow board members C10. It will get the same treatment & be the replacement for my '78 Malibu's low compression 305sbc. The dished pistons will be swapped out for flat-tops; some aftermarket/better flowing alum 64cc heads will replace the small valve iron units, & a mild hyd roller cam (basically the GEN2 sbc GM LT4 Hot-Cam) to upgrade the timing events. I'm estimating 300hp to the ground.

[54blackhornet]

Scoti your last post explained more about building a SBC than anything I have ever read ! Thanks

[SCOTI]

Originally Posted by 54blackhornet

Scoti your last post explained more about building a SBC than anything I have ever read ! Thanks

Thanks.

Constantly reading everything I can on the subject & doing things the wrong way will teach you a thing or two.

Case in point... 2 1974 Z/28's. Both had 350sbc's; 4spd Muncies; full length headers/true 2.5" dual exhaust; & 8.5" 10-bolt rear ends.

Z/28 No.1
* Dished pistons swapped to flat-tops
* Old school 462/Fuelie/Cammel-Hump heads w/2.02INT valves; w/porting + milled for straightness & compression bump
* CompCams 230/280/.480" lift hydraulic flat tappet cam
* Victor Jr & 750 mech secondary Holley
* 27.4" rear tire & 4.11's

Z/28 No.2
* OE dished pistons
* 70's era 993 76cc iron heads w/2.02INT valves machined/added
* CompCams 244/292/.501" lift hydraulic flat tappet cam
* Victor Jr & 750 mech secondary Holley
* 26.5" rear tire & 3.08's

Z/28 #1 would snap your neck back & pin you to the seat accelerating.
Z/28 #2 was a dog off the line & generally had no power but sounded like it had more balls vs #1. It did not.....

The #2 car was mine. The motor was already built/car was set-up when I bought it. Car #1 was a buddys build. I was hoping mine would be as stout or more w/fresh tune-up stuff but you can't overcome that cylinder pressure difference & the heads ability to move air. Mine got totaled before I could re-work the motor. The drivetrain was plucked & certain parts were re-used. The rebuilt motor was the 1st of the several mentioned in my previous post. The much milder combo w/compression had 100% more seat of the pants power.

[Accelo]

It is very difficulty to rework head for the price of new these days. The power of mass production is just difficult to make up. Especially true with pre-70/s heads without hardened seats. Even the early valve stems were soft and are likely badly worn if run on no lead fuel.

Newer heads have;
Better flow, Stellite valve stems, larger valves, hardened seats, better swirl and higher compression.
Personally I can see no reason to go back to the 70's technology unless you are restoring a truck.

[jimijam00]

Originally Posted by SCOTI

Z/28 #1 would snap your neck back & pin you to the seat accelerating
Z/28 #2 was a dog off the line

Final gear ratio

[Yamariv]

Originally Posted by SCOTI

Thanks.

Constantly reading everything I can on the subject & doing things the wrong way will teach you a thing or two.

Case in point... 2 1974 Z/28's. Both had 350sbc's; 4spd Muncies; full length headers/true 2.5" dual exhaust; & 8.5" 10-bolt rear ends.

Z/28 No.1
* Dished pistons swapped to flat-tops
* Old school 462/Fuelie/Cammel-Hump heads w/2.02INT valves; w/porting + milled for straightness & compression bump
* CompCams 230/280/.480" lift hydraulic flat tappet cam
* Victor Jr & 750 mech secondary Holley
* 27.4" rear tire & 4.11's

Z/28 No.2
* OE dished pistons
* 70's era 993 76cc iron heads w/2.02INT valves machined/added
* CompCams 244/292/.501" lift hydraulic flat tappet cam
* Victor Jr & 750 mech secondary Holley
* 26.5" rear tire & 3.08's

Z/28 #1 would snap your neck back & pin you to the seat accelerating.
Z/28 #2 was a dog off the line & generally had no power but sounded like it had more balls vs #1. It did not.....

The #2 car was mine. The motor was already built/car was set-up when I bought it. Car #1 was a buddys build. I was hoping mine would be as stout or more w/fresh tune-up stuff but you can't overcome that cylinder pressure difference & the heads ability to move air. Mine got totaled before I could re-work the motor. The drivetrain was plucked & certain parts were re-used. The rebuilt motor was the 1st of the several mentioned in my previous post. The much milder combo w/compression had 100% more seat of the pants power.

I appreciate all the info! Just to clarify, my engine has flat top pistons which should help with my specs

[SCOTI]

Originally Posted by jimijam00

Final gear ratio

Absolutely a contributing factor.

But that 10:1 vs 8:1 & the flow of those 462's vs smog version 76cc heads was worth more from my perspective. That rebuilt/updated 350 went into a g-body elcamino w/less gearing (26" tall tires/2.73's). It had more guts off the line & enough low-end to twist the d-shaft in half like a twisting a coke-can.

[SCOTI]

Originally Posted by Yamariv

I appreciate all the info! Just to clarify, my engine has flat top pistons which should help with my specs

I was told mine had flat-tops but learned it wasn't so. How was the piston type verified on your engine?

[Yamariv]

Originally Posted by SCOTI

I was told mine had flat-tops but learned it wasn't so. How was the piston type verified on your engine?

....

[SCOTI]

Originally Posted by Yamariv

....

Gotcha. Wasn't sure how far apart you had inspected things.

[Already Gone]

Originally Posted by Yamariv

Hey Greg, thanks for the suggestions! That's the kind of info I was hoping for So no issues running the same set up on your 400 SBC vs a 350?

Summit sells these head individually correct? My local machine shop gave an estimate of $400 per head to fully rebuild..wish shipping across the border wasn't soo expensive through Summit though..

What kind of HP do you think your buddy is getting with this setup on his 350?

BTW, I found my 350 in your fair city! Drove the old girl up there and back in an afternoon and she didn't miss a beat. Calculated my US MPG for the trip and I got 15.8! Not too bad for the old girl..

Don't know what his HP is with the 350 and its in a 39 Ford Coupe as same as my engine as the builder figures 325/350 HP with about 400 ft lbs of torque. Just wanted a streetable and reliable engine with a bit of oomph.

[Yamariv]

Originally Posted by SCOTI

Gotcha. Wasn't sure how far apart you had inspected things.

Yeah I pulled the heads before we loaded it up and since I've brought it home, I've pulled all the rods and crank bearings. Wanted to have a good idea of where I'm at before I decide what or how to build it.

Since it's a flat top pistons, what would you recommend for a head and cam? From my research, the 76cc heads with flat pistons should bring me to 9.0-1 compression which is pretty much where I'd like to stay since I want to run it on regular gas. Maybe mid grade 89 octane at the most.

[Yamariv]

Originally Posted by Already Gone

Don't know what his HP is with the 350 and its in a 39 Ford Coupe as same as my engine as the builder figures 325/350 HP with about 400 ft lbs of torque. Just wanted a streetable and reliable engine with a bit of oomph.

Those are nice HP and Torque numbers Greg! I'm jealous!

[MARKDTN]

Originally Posted by Yamariv

Thank you guys for all the advice to switch to Vortec but I'm going to have to stick with and work with what I've already have. Yes fuel injection would be way better but I don't have that budget and I want to keep the truck the way it came, with an old school engine.

Wouldn't these heads breathe a little better if the machine shop puts a little bit larger valves in? Are there decent quality affordable aluminum heads that might be a better fit? I've checked Summit and I have about 700 different head options..I have no clue how to choose.

Maybe I missed it but what is the casting number of the heads you have? The '72 Z28 and the 400 mentioned very likely have a different casting than you so it is an apples and oranges kind of thing.

[tutone]

15 years ago, I built a 327. I know it wasn't a 350 but for what it's worth, this was the set up. Absolutely the best pulling little engine I ever had.
327 large journal crank
Flat top pistons
1970 pickup truck heads with 2.02s (enlarged valves but open chamber)
New valve springs
Edelbrock performer and 750 carb
Headers
Crane cam (card pictured)
Your results may vary, but I had it in front of a muncie m20
Good off throttle reponse, decent idle, hard pulling little engine.
I sold the car to a friend in 2011 and it still runs great.

[ghackett1]

Originally Posted by ghackett1

I have an original 72 Z28 and it has from the factory an 010 block and 487 heads. The heads are 202 valves and the bottom end is a 4 bolt, steel crank, pink rods and a gm solid lifter cam. My point being the combo you have can be made to GOOOOOO!
It would be costly but very doable. Good luck.

Here’s the 72 Z28 I was referring to, I’ve owned it for 28 years—the Original LT1 350 is the same foundation you are starting with. Good luck with your build, in my truck I dropped in a 355/390HP crate engine and love it—so your options are unlimited!

[SCOTI]

Originally Posted by tutone

15 years ago, I built a 327. I know it wasn't a 350 but for what it's worth, this was the set up. Absolutely the best pulling little engine I ever had.
327 large journal crank
Flat top pistons
1970 pickup truck heads with 2.02s (enlarged valves but open chamber)
New valve springs
Edelbrock performer and 750 carb
Headers
Crane cam (card pictured)
Your results may vary, but I had it in front of a muncie m20
Good off throttle reponse, decent idle, hard pulling little engine.
I sold the car to a friend in 2011 and it still runs great.

That cam's very close to what I used in my mild 350 re-build. I believe mine was the Crane Cam w/the split duration just under that one (212/218 comes to mind). I prob used the 266-2 as the likely grind. I recall the builder/dyno guy helping me agreeing the extra exhaust duration would help the weaker exhaust side. Non-stock/noticeable idle w/o being non-daily friendly.

[Yamariv]

Originally Posted by MARKDTN

Maybe I missed it but what is the casting number of the heads you have? The '72 Z28 and the 400 mentioned very likely have a different casting than you so it is an apples and oranges kind of thing.

The head casting #'s are 3986336 = 76CC 1.94/1.50 Valves

[Yamariv]

Originally Posted by ghackett1

Here’s the 72 Z28 I was referring to, I’ve owned it for 28 years—the Original LT1 350 is the same foundation you are starting with. Good luck with your build, in my truck I dropped in a 355/390HP crate engine and love it—so your options are unlimited!

Wow, that's a gorgeous car!! Lifes not fair

[Yamariv]

Originally Posted by tutone

15 years ago, I built a 327. I know it wasn't a 350 but for what it's worth, this was the set up. Absolutely the best pulling little engine I ever had.
327 large journal crank
Flat top pistons
1970 pickup truck heads with 2.02s (enlarged valves but open chamber)
New valve springs
Edelbrock performer and 750 carb
Headers
Crane cam (card pictured)
Your results may vary, but I had it in front of a muncie m20
Good off throttle reponse, decent idle, hard pulling little engine.
I sold the car to a friend in 2011 and it still runs great.

Awesome info, thank you!

[MARKDTN]

Originally Posted by ghackett1

Here’s the 72 Z28 I was referring to, I’ve owned it for 28 years—the Original LT1 350 is the same foundation you are starting with. Good luck with your build, in my truck I dropped in a 355/390HP crate engine and love it—so your options are unlimited!

That is a beautiful car!

FYI-But same foundation is only if you squint really hard. Might both have an 010 casting 350 block but that is where the similarities start to fade. A 1972 LT1 is 9:1 compression (in '70 it was 11:1), 4 bolt mains, steel crank shaft, solid lifter engine. A 1972 Biscane 350 is 8.5:1 compression, 2 -bolt mains, Cast crank, hydraulic lifter engine. All those things interchange for the most part, but are much more heavy duty and/or performance oriented for the LT1. LT1 also had a bigger oil pan, windage tray, different timing chain, better connecting rods, and so forth than the low HP 350s that year.

[Mid-Pack]

I suggest you call the cam manufacturer for recommendations, like Comp Cams. Tell them what you got and what your expectations are. With your current motor and stock rebuilt heads I would probably stick with something like the Comp Cam XE250H or XE256H cam.

Here`s some of their dyno charts: https://www.compcams.com/dyno-graphs

Just my .02

[Yamariv]

Originally Posted by Mid-Pack

I suggest you call the cam manufacturer for recommendations, like Comp Cams. Tell them what you got and what your expectations are. With your current motor and stock rebuilt heads I would probably stick with something like the Comp Cam XE250H or XE256H cam.

Here`s some of their dyno charts: https://www.compcams.com/dyno-graphs

Just my .02

Very cool info on those graphs, thank you for that! I didn't realize Comp cams would give advice, I'll have to try and give them a call

[ghackett1]

Originally Posted by MARKDTN

That is a beautiful car!

FYI-But same foundation is only if you squint really hard. Might both have an 010 casting 350 block but that is where the similarities start to fade. A 1972 LT1 is 9:1 compression (in '71 it was 11:1), 4 bolt mains, steel crank shaft, solid lifter engine. A 1972 Biscane 350 is 8.5:1 compression, 2 -bolt mains, Cast crank, hydraulic lifter engine. All those things interchange for the most part, but are much more heavy duty and/or performance oriented for the LT1. LT1 also had a bigger oil pan, windage tray, different timing chain, better connecting rods, and so forth than the low HP 350s that year.

Thx, but if he has 487 heads he does not have 11:1 compression with 76cc heads, basically the same foundation as the 72. 1970 had 64cc heads and 11:1 compression with the LT1 either corvette or Z28. The difference lies there. Basically the 71& 72 were the same. Also in 72 they changed how they rated the hp from the crankshaft to the rear wheels so the 72 numbers looked much lower but were basically the same as 71.

Here are the head specs for 71 & 72 Z28: 3973487 comes up as s good for '71 or '72 Z/28 head at 2.02/1,6 valves and a 75.47 cc chamber.