Indy_68_S

Looking for opinions, guidance, critiques, recommendations, etc...for my street '68 350 build...

So far I have....

350 + .030
stock crank & rods
Flat tops (1.612 comp dist)
#5 heads (untouched at this point) - will prolly get BBO valves -2.000/1.625 & maybe very mild polish/teardrop
Intake - undecided -will be either orig iron, 3711, or 7111
Orig rebuilt Q-jet (adj'd to build & + elec choke if using 3711/7111)
Logs, Thornton logs, or maybe Sanderson shorty rear dumps - don't want the hassle of full lengths...
M20 & 3.42 anti-spin

My thoughts/questions...

1. Flat tops + polished chambers(68-70cc chambers) + proper headgasket (which is?) puts me in high 9's or 10-ish for C/R ? Or ?

2. Have head exhaust dividers welded up ?

3. Fill crossovers ? (Car will not be a year round daily driver....I hope!)

Am I on the right track here ? If so, the next round of questions is cam/valvetrain....

Thanks...!

cutlassefi

Depending on the deck you'll have about 9.5:1 with 68-70cc chambers.

Fill the crossovers and weld the center divider if going with headers, if not there's no use in welding it if using manifolds.

A 650-700 carb, Performer RPM and you're good to go. If using a stock valvetrain I have some cams that are very friendly to that setup. If you're going to go aftermarket then I can either grind you one or I have something that will work well off the shelf.

Jmo. Good luck in your build.

Mark

Indy_68_S

Thanks, Mark. I appreciate the input....

Any others out there want to chime in ?? Don't be shy !

I'm now wondering how much I really need to mod the heads...

How much do I gain from just the BBO valves ?

I'm sure a full port/polish/teardrop/fill x over setup would be nice, but I'd be doing it myself as it wouldn't be worth it to pay someone. I'm a bit anxious about modding my virginal factory heads. If the BBO valves give me something..then I may just stick with the upsized valves and a stock valvetrain.

If I go with a lower perf setup like a non-RPM Performer (w/ the name ground off & sprayed gold!) and logs (trying to keep it visually close to stock), would extensive head work even pay off ?

My target is just a nice, stock appearing engine with some added performance internally. Maybe somewhere in the 325-350HP range. A 375-400+HP 350 would be awesome, but at that level I'd really be drifting from my original intent of 'restoration'. Something with reasonably wide powerband as the M20 & 3.42 should take care of the really low end.

This will be the first engine I've planned from scratch and balancing the variables can get a bit overwhelming. Decades ago I helped buddies rebuild various SBCs/SBMs, but there wasn't any real planning involved. It was just stick these new parts in, hope for the best, and butt dyno it (which always showed an improvement!). There also wasn't much concern for durability as the cars themselves were rarely kept very long.

With this one I want to make sure that the whole package works together properly, is cost effective, and durable..... so I'm going to ask a million questions..!

coppercutlass

your build sounds alot like mine but my efforts went with racing instead of stock but used alot of the same components. imo i would go with the performer instead of the rpm it cost less and will look close to o.e since it sounds like you want a strong street runner that intake will work good the rpm is great i have one on my 350 but unless your racing id go with the performer. as far as the heads go its money well spent i had rocket racing do mine .,had the big valves installed sligthly bigger than the big block valve but it breathes so much better than the heads on my old combo. as far as the crossover and divider go its preference i didnt do it to mine i personally think its not worth the work or paying someone to do for not that much of an improvement that money is better spent elsewhere. now comes the part everyone has truly a diffrent view on things the cam since it sounds like you are building a nice street bruiser id go with some thing that builds good tourqe my last motor had a towing cam it would shred tires but with my new combo i gave some of that up for the higher rpm performance so pick the cam for your needs or get one custom ground. i run a 280h from comp in my 350 a re pro of the w31 with modern design and according to the numbers from my last time at the track its putting 305 hp to the rear wheels not bad for a motor i built with 2800 bucks carb to oil pan

captjim

Mark, I think you are a tad low on Cr. With that p/h and a .015 clean-up cut, he will be pretty close to zero deck. With 70 cc heads, I get a little over 10 to 1

I have a very similar build in my 71 Skylark. Speed Pro flat tops sitting .015 down with a .027 gasket, 2.02 intakes and stock exhaust valves, port work in the bowl area, RPM intake, Sanderson shorty headers, 60803 Voodoo cam (.510/.522 227/233) Holley 750 vac sec carb. Car starts right up, runs great, very responsive and fun to drive. No ET or dyno numbers, but it should be an easy low 13 second car with the 3.73 gears.

INDY, if you are keeping the stock manifolds, don't bother with much head work, IMO. I would use the RPM over the Performer in this application. Watch the CR, you will need a bit of cam ot it will detonate. Measure everything before and during assembly. You might be better cutting a dish into the pistons and lowering compression, then going with a mild cam, especially with stock manifolds.

jensenracing77

you should come take my Rallye 350 for a drive. it is along the lines of your build, i have the stock intake and exhaust manifolds but i am very pleased with it. i went with the 2.0 intakes and he cut the bowls to match but zero port or polish. i have flat tops and if i remember right i think it came to 9.80 compression with 6 heads. i would have to look it up but i think the cam was jm18-20? i want to believe it is close to 350 HP but i feel sure it is not over that. i also have 3.42 gears. if you want to come drive it let me know.

oldcutlass

Any aggressive cam works better with headers or some sort of upgraded exhaust. He can lower his CR if he uses the standard head gasket from felpro. I would not go more than .500 on the cam with stock rocker assy's.

Do not use a hi output oilpump, and clean all the oil returns so the oil returns to the pan easily!

captjim

All due respect, no way you are close to 350 Hp with zero port work and stock manifolds. However, I'm sure you are making a bunch of torque, and that is what makes a car fun to drive.

coppercutlass

Stock w31's had 325 hp. 350 hp. with no port work is possible

jensenracing77

may be, i have no idea really. but i sure like it. i just figured stock claimed to be 310. with everything i have together, i figured it added at least another 30 HP but again, i have no idea. i agree on the torque, that is what i wanted when i built it. i will build a big block for my next engine.

sorry, didn't mean to derail the thread.

captjim

Your opinion, I respectfully disagree. Please explain how a 10% gain is realized with less compression and cam. Published numbers are relatively worthless, IMO. Nobody disregards HP numbers more than I do, it is all about torque and throttle response on a street car, IMHO.

captjim

Please expand on this? You have less compression, less cam, stock heads and mannis, yet make an increase in HP? How?

jensenracing77

good lord, it is his thread. i didn't dyno the engine and i built it to be torquey. maybe i am off on my figures. stock was not flat tops in the 310 engine the valves are bigger than stock 310 engine the outlets of my manifolds are bored (not that i can even prove that helped), bigger exhaust, somewhat better cam than the 310 engine. lets move on and find good info for indy 68 s. i was just offering him to drive my car and i could give him better specs of my engine if he drove it to see if it was anything like what he wants. i am pleased with the engine and with not much more work and a more proper cam he could do better than what i have.

captjim

No, the factory cam had a lot more duration. Flat tops and a .040 gasket vs 6cc and a shim gasket, stock had more compression. I am trying to help the OP, you are the one tossing random numbers around.

IMO in this application if the OP wants to retain stock manifolds, a Cr around 9 to 1 and a mild cam will make for a better combination. If he is willing to upgrade both induction and exhaust, then that will provide options for performance upgrades. IMO, SBO exhaust manifolds are TERRIBLE. Headers alone make a significant difference.

jensenracing77

the 310 engine did not have flat tops. and i did not list all the details of my engine. i am done here.

captjim

You are correct, it did not have flat tops, it had 6 cc dished pistons. It did, however, have a shim gasket and more p/h, resulting in a HIGHER Cr with a dish than most engines will with flat tops.

I am not sure what details you could list that would account for the increase in power, but please feel free to share.

My 9 to 1 355 ran 13.9 in a 3800 lb wagon. RWHP was 240, figure crank HP at 300. Race valve job, zero deck, blueprinted, bowl work, headers, Holley. Performer intake. Most guys over estimate their true HP.

coppercutlass

my last 9to1 motor in my 72 cutlass with a towing cam edelbrock performer intake and 1405 carb headers and 3.42 gears ran 13.9 then with an x pipe and 3.73 gears and other minor mods went 13.71 my new build is a 350 9.75to1 ,bigger cam, little bit of head work and rpm intake same carb as my old engine it went 13.4 first time out with out turning a wrench ., a 10 percent increase can be fond in a better intake ignition and better mufflers ,hei etc etc thats how , how is that my 350 with a towing cam had a faster e.t. than a w31 from 1969

Indy_68_S

Well, I'm leaning toward the Sanderson shortys now.... I need something as my original logs are pretty far gone....and the Thorntons, while pretty, don't seem to offer as much as the shortys...

I was going to try to keep it as original appearing as possible....logs,heat shields, factory aircleaner, divorced choke,etc....but that idea seems to be fading...

I'm now looking at some 3cc dish Probes that Mark suggested as they're available and seem to be a better product. My builder agreed and mentioned that that 3cc might come in handy once all the deck cleanup etc is done. We will cc the heads once the new valves are in, decide if the Probes are the ones, and fine tune the C/R with the HG.

coppercutlass

the probes are a tad bit expensive why not go with flat tops and just get a thicker gasket from corteco im always looking for ways to save money but if the funds are there for the probes go for it

Indy_68_S

Thanks for that offer...I may take you up on that if I'm headed west anytime soon ! I can't remember...Is yours AT or MT ?

The bowl work is the one thing that I think would most benefit the heads. The hitch is do I have the new (2.000/1.625) valves installed first , pull 'em out, and then worry about nicking a seat ? Or do I do the bowls prior to the new valve installation & not worry too much about getting the edges right up to the seat ? ...and there's still still me being nervous about taking a burr to my pristine heads !

Head pics as I so happy they cleaned up and checked out OK...


clicky pics for big

Indy_68_S

My builder quoted ~ $20 diff between the Probes & the SP flatops...& he was cheaper than online $$ I found for the Probes... The expense increase comes in the rings....

coppercutlass

oh then yeah thats always a good deal., sp with rings are closer to 500

jensenracing77

it was a 4 speed till about a month ago. i just had Vedders rebuild a TH350 and i put it in with a dual gate shifter setup. the guy that did my valves did the bowls also. it didn't cost that much if i remember right.

oldzy

Just curious why a 4-spd -> auto?

jensenracing77

lol, i get that alot. i just don't like driving manuals anymore. if this was't my first car from 1990 i would have just sold it and found one that was an automatic. i can always put the original parts back in some day.

captjim

Good advice. I have always thought that the $ spent on a good valve job with bowl work was worth it.

FWIW, every engine I built with Speed Pros ended up with the pistons .025 down +/-

coppercutlass

bowl work is worth it i got lucky and my machine shop did it for free. also i found alot of small blocks are usually .025 in the hole i got cast flat tops from a 68 w31 they where .025 in the hole also my 14cc pistons where .025 in the hole. dont know about 73 and later years i usually stick to 72 and earlier

Indy_68_S

And, that's about where we are now!

So far...

Car
M-20,3.42, & PB

stock iron intake
7028250 Q-jet setup to W-31 specs
stock exh logs

#5 heads
2.000/1.625 valves
stock valve train
light bowl work
chambers cc'd to just under 68

.030 block
stock crank & rods
3 cc Probes

The plan now is to determine the deck height & therefore the piston install depth (clearance), but we're using ~ .020 for figuring.

With the numbers above & a .030 head gasket (Head gasket can be changed to accomodate final clearance)

CR will be ~ 9.8/9.9:1.

Sooo, what say CO as far as flat tappet hydraulic cams go ?
Or does anyone see anything weird with the numbers above ?

Jharken

68 355 with Probe piston looked like this.

70 cc chamber #5

3.0 cc valve relief

.022 deck clearance at TDC

.027 Cometic head gasket

4.125 head gasket bore

.049 quench

9.70 static compression

Indy_68_S

Thanks ! That looks pretty close to what I have except for the chamber size. Mine measured out to just under 68cc w/ the new valves.

Cylinder Bore Size : 4.087
Piston Stroke Length : 3.385
Head Gasket Bore Diameter : 4.125
Compressed Head Gasket Thickness: .027
Combustion Chamber Volume : 68
Piston Dome Volume In CCs : -3
Piston Deck Clearance : .022
Static CR = 9.91 : 1

Deck clearance is the only unknown at this point. I should have that in the next day or so.....

captjim

I know that there are more modern grinds, but IMO the Engle 20-22 is an awsome old-school cam for a 10 to 1 355 , especially with a 4 speed. Sounds good, runs good, will work with stock rockers, specs as I recall them are 226/230 .496/.512 on a 110??

cutlassefi

Imo you should wait for your cam choice until the rest of the combo is finalized.

Rickman48

And if you're sticking with the automatic, use a Holeshot converter - really helps outa the gates!

Indy_68_S

Good to know. Thanks...

That's the plan....Just waiting on the next round of numbers....

Nope. M-20... w/3.42 anti-spin. Not a race car, but oughtta be fun around town & tolerable on the highway...

Indy_68_S

Cam Time!

Car
M-20 4 speed
3.42 anti-spin
PB (will need some vac)
No A/C

stock iron intake
7028250 Q-jet setup to W-31 specs
shortie headers

#5 heads
2.000/1.625 valves
stock type valve train (new parts)
light bowl work
chambers cc'd 67.5
.030 block
stock crank & rods
3 cc Probes
9.95:1 CR

Car will be a fun driver, not a race car, so I'm looking for something that makes decent power, but doesn't hammer the engine (i.e. easy on the stock-type valvetrain, etc...)

Here's a few cams I'm looking at now (in no particular order)...
CamPics1.jpg

I'm still learning about the effects of the timing, LSA, slow/fast ramp,etc...So, some (or all!) may seem goofy. The last 2 columns were an attempt to determine fast/slow ramp...& may be meaningless.

Talk 'em up / shoot 'em down. Share experiences. Argue pros/cons

Please let me know if I'm on the right track..

cutlassefi

Had that exact crane, it was ok.
Had the jm-18-20, not impressed.
I'd do an Erson hiFlow AH, 284/284, 220/220@.050, on a 110, .504/.504 lift or one of my custom 220/223@.050 cams, they'll be easy on the valvetrain and give awesome midrange, will work with a stock converter too.
With a stock intake and shorty headers I'd do something with little or no stagger. But with almost 10.0:1 you'll need decent off the seat time to keep things in check.
Jmo

Indy_68_S

Thanks for the input Mark & Joe!

How about the 20-22 ? Too much for this combo?

No converter.... M-20. Curious about your custom 220/223.. On a 110 ? Lift ?

Ahh, because of the limitations of both the OE intake and the shorties make it uneccessary to favor the intake or exhaust side ?

Can you elaborate ?



I couldn't find either of those in the current Comp catalog...both look discontinued on their website (or maybe custom?). I'm trying to keep the stock type non-adj valvetrain just because I don't want to further machine the heads for studs & I have a whole new set of pedestals/bridges/rockers already...


OK... Other ideas ??!!

71 Cutlass

A lot of mixed up info in this thread. Everything from people not understanding the old horsepower ratings of the 1960s -through 1971, and the CR. that flat top pistons bring to the table. The only post I thought that addressed the CR issue was Capt. Jim who said the CR of the car was at least 10:1. The W-31 had 10.25:1. My rebuild which is virtually the same as the OP is 10.5:1. In reference to HP numbers of the W-31...those numbers are the Gross Brake HP, not Net HP. Net is the standard used today. To give an example of the difference: a 1971 Cutlass (my car) when stock, was rated at 260 HP...that was using the old HP rating system of GBHP. The following year, a 1972 Cutlass with the same motor as the 1971 was rated at 180HP, using the new net HP rating system. That's a drop of 80 HP using the modern day HP rating system. So when someone argues that the W-31 made 325 HP, remember that was on the old HP rating system not the new system. On the new system, the W-31 will be a lot lower than 325 HP just like the 1972 Cutlass and 1971 Cutlass have much different numbers.

Indy_68_S

I'm not sure how the SAE Net vs. Gross HP difference applies to this thread.
Car is a '68 so any HP discussions would reference Gross (old method) when comparing to published factory numbers.

I'm simply trying to build a decent & reliable 350 & stay somewhat true to its roots (ex. stock valve train). I needed a CR that will tolerate today's crappy gas (10:1) and using proven tricks/methods such as BBO valves & different cam similar to one from the W-31 program will allow me to squeeze as much as possible from it.

cutlassefi

You've gone back and forth on your combo so it's a bit difficult to nail some of this down, i.e. stock intake, 3711, or a 7111, big differences there.
But if I had to recommend something right now I'd do either the 220/220 on a 110, lift is .504/.504 or the 220/223, lift would be .504/.510 on that with the advertise duration would be 284/289. I'd only do something a little different if you stuck with exhaust manifolds, 220/228, still on a 110. All three cams would work with a stock valvetrain with no issues.
I don't recommend any fast ramp cam for 60's-70's iron headed V-8's, they can use the off the seat time of a slightly slower profile. Plus it's easier on the stock stuff.
If you shoot for 9.5:1 or so along with some minor bowl work in the heads, based on the rest of your proposed combo you'd have a very driveable, nice ride.

Jmo.