[Richard/SIA]

According to the numbers I decoded from the 1970 350 I just bought it should be "300 HP" and 10.25-1 compression.

It appears to have been rebuilt once, but the block was not decked.

Came out of a Nova that had a few goodies, headers, "Thunder series" double pumper, Torker II manifold, vacuum can, MSD pro-billet distributor & MSD "Blaster SS" Coil.

Since I never took the heads off I have to wonder if the compression might be even higher?
Disappointed I was not able to spec out the cam too.
Looked at the lobes as best I could while the pan was off, looks fairly mild to me.
From what I could see the pistons look very clean, cross-hatch still visible in the lower cylinders.
Only reason I had anything off was to fix oil leaks.

The guy I got the engine from is not the guy who rebuilt it.

I did hear it run briefly before purchase, sounded fairly mild, maybe a little lope.

My main concern now is what ignition timing to start with, and what octane fuel to use?

Putting an Edelbrock Performer and Q-Jet on in place of the Torker II and double pumper.
Trans is a built Turbo 400 with shift kit, 3:73 rear as I recall.

Anything else I am missing and should be concerned with here?

 

[Tom Mobley]

in 1970 that was a premium fuel engine, around 100 octane. there's not some kind of magic here, it's still a 100 octane engine. I've built a number of these engines for guys who demanded factory specs for restored cars, they are horrible pingers. I won't build them anymore.

You can probably make it work by retarding the timing a bunch. Poor power output, horrible gas mileage and running hot are expected.

best thing: 76cc large chamber heads or 12cc dish pistons.

 

[Aaron]

in 1970 that was a premium fuel engine, around 100 octane. there's not some kind of magic here, it's still a 100 octane engine. I've built a number of these engines for guys who demanded factory specs for restored cars, they are horrible pingers. I won't build them anymore.

You can probably make it work by retarding the timing a bunch. Poor power output, horrible gas mileage and running hot are expected.

best thing: 76cc large chamber heads or 12cc dish pistons.

Tom

What is the quench on that stock motor?

Are the pistons like down in the hole .025 with a big thick headgasket making quench like .067 or something.

What would happen if you got the quench down to around .035 to .040?

Would that make it friendly to 93 octane?

 

[bracketchev1221]

Mine ran fine on 93 octane gas and 12 degrees advance initial with a mild rebuilder cam in it. BUT it was a stick with 4.10 gears.

 

[Aaron]

Mine ran fine on 93 octane gas and 12 degrees advance initial with a mild rebuilder cam in it. BUT it was a stick with 4.10 gears.

Do you know what kind of total timing you had in it and when it was all in?

How about vacuum advance? Did you run any of that?

That had to be fun to drive on the street. Lots of bottom end with a 4 speed and 4:10 gears.

 

[bracketchev1221]

That distributor would advance to over 40 degrees at like 4000 rpm. I did not have the vacuum advance hooked up to it.

 

[Aaron]

Oh wow!

Im very surprised it did not ping at 4000 to 5000 rpms at part throttle.

 

[Richard/SIA]

Re: 1970 350 300 HP = Stock 10.25-1 compression.

Thanks for the hints guys.

Once it's back in a car I will check the cranking compression.
Did not want to tear it down to spec everything as I already have plenty of project engines.

I have made an attempt to reach the former owner to see what he did to it during the rebuild.
He was certainly trying to go faster from what I saw of the Nova.
So I have no idea if he lowered compression or increased it.

With his having put on a Torker II and no-choke double pumper I would be surprised if he lowered compression.

Block is NOT decked so pistons may indeed be down the hole a bit.

Now I wonder if some thin head gaskets might help if I run into ping issues?
Would actually increase compression, but decrease the quench a little.
At just below 5000' elevation a lot of guys here run 11-1 without issue on zero decked blocks.

I have an MSD 6A and tunable advance setup I can put on if necessary.
Probably will need it for the 327 anyway.

EDIT: Looked up the heads, supposed to be 64cc with 2.02 intakes.
They have not been ported but should still be fun.
How much toluene do I add per gallon to get 100 octane?

 

[Highway Star]

I don't think you will know what the compression ratio is until you see the pistons. I also think speculating isn't a great idea. Cranking compression might give you some idea, but if you aren't taking the heads off, you won't know for sure until you start driving it.

 

[mfret1970]

If cr is in question and cam is unknown, I'd be tempted to change the cam just so I knew what was in there. 5000' of elevation will handle more cr, but it may want a bit more cam to further bleed off cyl pressure at lower rpms.


Sent from AutoGuide.com App

 

[Richard/SIA]

Hoping to get it switched in this coming weekend.

Will start with factory spec of 4º advance and experiment from there.

 

[Jerry70]

Unless you're going back to an original spec distributor, the factory specs are meaningless. Start by setting total to around 36º or so and then check initial. Typically, MSD's come with a 21º bushing installed but include a smaller and larger bushing in the parts bag. 4º initial with the standard bushing will result in only 25º total.

 

[von]

If it was rebuilt it's possible that dished pistons were installed (stock 300 hp pistons are flat tops). Also I believe some "rebuilder" pistons have a lower compression height than stock (distance from pin to top), which would increase the deck height and lower the CR. If it has an aftermarket performance cam, it could have a little more duration than stock, which due to the intake valve closing later, could lower the DYNAMIC compression ratio, thus lowering the detonation threshold. Then there's your local altitude. My advice is to put premium gas in it, adjust total timing (mech plus initial) to 36 degrees and drive it to see if you detect any ping. If so I'd start with a longer and slower mech advance curve in the dist with less initial advance, closer to stock specs.

 

[Richard/SIA]

Pop-Up's! Looks like I lucked into a serious engine?

Not sure if it's good or bad luck, yet. :thumbsup: :clonk:

I had an idea, thought I might get a clue on compression by looking through a spark plug hole.
64cc strait plug heads.

So I pulled No. 1 with the engine at No. 1 TDC.

I was looking at the SIDE of the piston dome!

No flat tops here, and no dish either.

Now I know why this engine had a Torker II and double pumper on it.
Still curious how rad the cam will be, and what compression I really have.
But it's got to be around 11-1 or more.
Premium fuel for sure, I might need to buy an airplane title to get access to real gasoline.

Now I wonder if maybe I should have gone ahead and put my Victor Jr. on it?
Buttoned up the Performer last night, thinking of taking it off for the Jr. now.

I did hear this engine run at a semi-fast idle, but did not get to mash it.
Now I wonder if that faster idle might have been for streetability?

I guess I will try it with the performer and change it out if the engine feels choked.

 

[von]

Domed pistons. Since it's obviously been modified the question now is which heads it actually has now (could have a larger combustion chamber than stock). What is the casting number?

 

[Aaron]

To me, judging by what you said, 300 horse motor with maybe the stock cam in it with domed pistons is nothing but a 110 octane motor. No desirable at all for the street.

What do you plan to do with this thing?

I would not put that back in the car. To much work.

I would do a compression test on a stand somewhere. This will tell you alot!

I would see what that test tells you then make a plan.

Shoot for cranking compression of around 180 to 190 psi.

Depending on what you find out on the test will tell you what you need to do. I would leave the cam alone more than likely and swap the pistons out. Get a light hone and put in a set of pistons that will give you 9.5 to 9.8 compression. The run it.

 

[Richard/SIA]

Re: 1970 350 300 HP = Stock 10.25-1 compression.

Engine nearly in at last, just have to bolt up the accessories.
Would go faster if I were capable of just bolting dirty parts back on.
Everything is cleaned and repainted, it's just the way I am.
When I was younger this sort of swap took hours, now it's DAYS!

Got the headers to fit, saved some bucks since I got them with this engine!
Have to fab the rest of the exhaust, dumping ahead of the wheels for simplicity and nostalgia.

Car is now about 150 lb's lighter.
Headers, aluminum intake manifold, and 40 lb. off the driver over the last few months! :hurray:
Another 20 lb. off the driver and it should all be good. :thumbsup:

Need to figure out what number spark plugs to run, not sure I trust what was in there as it seems the car may have been running rich.

Not certain of the compression yet.
I looked up the head casting numbers, 64cc, so definitely very high compression.

I doubt the cam is stock, former owner found it necessary to fit a vacuum can on his '70 Nova with this engine.
Maybe he needed extra vacuum with his drum brakes?
I will also fit the vacuum can just to be sure.
References I see here and elsewhere indicate a vacuum can should only be needed with radical cams?

Use is daily driver and the occasional blast past slow-pokes, night time flying on our long desert roads.

This is a temporary engine until I can get my 327 completed.
Funny thing is, this is the sort of 350 engine guys keep telling me to build instead of the 327 I have been gathering parts for.

The 327 will be pretty radical, at least 10.5-1 compression, aluminum heads, Victor Jr., light rods, etc.

 

[Aaron]

If this 300 horse 350 is just temporary. Just de tune it for daily driving or whatever your doing with it.

The 327 you described is not radical, unless it has a huge cam or exotic valvetrain. The motor is going to run at 180* really easy. Alum. heads at 10.5 compression is nothing for 93 octane these days. Unless the quench is some god awful sign of like .051 or higher.

 

[Richard/SIA]

It lives! :hurray:
Finally got to fire it up in it's new home tonight, open headers and all. :thumbsup:

Seems like it's been forever getting this engine in.
Would have been a lot faster if I had just slapped it in, old grease and all.
But no, I had to replace all the possibly leaky gaskets, front seal, clean and paint the engine, all the brackets and pulleys, etc.

Swapped out the Torker II for my Performer and quadrajet.

Engine came with an MSD distributor and I kept that on it.

Have not driven it, or dialed in the timing yet, but it sounds very healthy and definitely has either a fairly radical cam or one of those "Mutha-Thumpa" types in it.

Since the old owner found it necessary to fit a vacuum can and I got it with the engine I went ahead and mounted it up.
Perusing some on-line discussion it seems the trans may be happier with the vacuum canister too.

Tomorrow is exhaust system day, looks like I will put on some big old Glass Packs I have laying around!
Regular mufflers are too thick, no ground clearance at all.
Angled exits, just ahead of the rear wheels, and the whole thing is massive 3" Dia. overkill.

Even with this setup the rule is going to be that if a company has "Speed bumps" in their parking lot, I'm not shopping there!

It's just a temporary system until I can find some slim profile street mufflers.
Not sure the local cops / judge will have much humor about it though, so I will have to take it very easy around town.
SOME people here can run anything they like, but they tend to be the sons of big-shot lawyers or from "Old Founding Families".

 

[Richard/SIA]

Update for the curious.

Dumped the Q-Jet and put the Holley 700 CFM? double pumper back on it.
Runs MUCH better!

Ignition at about 20º static, have to get a better timing light ASAP.

Engine wants a looser converter so it can get on the cam before the T400 shifts.
Still some issue with getting it to stay running in gear, manual shifting it helps.

Got one good test drive, can peg the speedo pretty easy, and still pullng strong.