Chevrolet Big Block Trivia or : Where were they hiding them Horses!?

[SammyChevelleTypeS3]

Now it's "Cowboy Cadillacs". Lifted Bro-Trucks, 40s, deleted Diesels, rolling coal and www.bullsballs.com

LoL.... I cringe sometimes when I think of what our parents must have thought at some of the music and stunts we pulled in our teen age years. I was lucky, the greatest semi-fight we had in my house over one of the sons was when he wanted an earing and a tatoo.

 

[wpod]

The old cars have a soul, a character all their own.

If someone dangled two sets of keys in front me, a new Hellcat or a '70-'71 Challenger 440, it would be a tough choice but I think I would rather have the '70.

The Hell cat has much better performance, the Challenger would be much simpler.

 

[SammyChevelleTypeS3]

My step dad was shopping for a new chevelle in 1977, I tried to convince him to get the 350 but he settled for the 305.
This ended up being my first car in 1985. Except for the cam going bad early it was a reliable car. GM paid for the cam, I think there was a recall for it.

I bet once you were driving and had to fuel the car up you may have been happy you only had that low , around ?135Hp? 305 that likely did decent on gas mpg.

 

[wpod]

The +.030 396 was a 402, but marketed as a 396.
Other small BBCs were the 366 and 427 tall deck (10.2" vs 9.8") truck engines found in school busses and whatnot.

That was quite the interesting engine. In 1975 I bought my friends 1974 Hondo sprint drag boat that he blew up his brand new engine first time out on the lake . My other friend had a 402 engine that was blueprinted had higher compression head work etc he removed from a car he wanted to sell. I bought the engine and put it in the Hondo. It was an 8,500 RPM engine and impressed the other guys I raced when they found out is was a [396] in a drag boat a 396 can not beat a 454+ ci engine though. Those big block engines were easy to build very durable and high quality parts were lower cost that any other brand. Quite the deal .

 

[userfriendly]

Lets pick a vehicle weight. I got into trouble about running 10's in old Camaros with another poster. Pick a weight and we can calculate how much HP is required for 9.9. I would guess you can strip down a 3500 lb car to 3200 lbs. A 9.9 would required about 650 dyno horsepower according to some of the ET calculators.

Here is a normally aspirated 441 ci LS engine that can do that, revving to 6500 rpm.

MEDIA=youtube]UM3H-HPAKIA[/MEDIA]

Minimum weight for Super Gas is 2,100 lbs. Usually V8 roadsters. 4/10ths tree

www.nhra.com

The stock L8T has enough power at 401, but it's not flexible enough because the rpm is too low.
A super gas car needs a 5,500 minimum stall torque converter (imo) for a proper launch, reaction time and 60 foot.

 

[Chris142]

I bet once you were driving and had to fuel the car up you may have been happy you only had that low , around ?135Hp? 305 that likely did decent on gas mpg.

Actully the 305 was known for v6 power with v8 economy. Low compression ,retarded cam and ignition timing etc.

 

[DriveHard]

Was that the same engine as the 8.1? (It works out to be close.)

The 8.1 was a well-regarded truck engine with lots of torque.

Yup, and used by Mercury Marine as well... 496 MAG and 496 MAG HO

 

[Number_35]

Actully the 305 was known for v6 power with v8 economy. Low compression ,retarded cam and ignition timing etc.

I knew a couple of people with 305-powered cars back around 1978 - a Camaro and a Nova. Both were pleased with 26 MPG (Imperial) on the highway.

By comparison, my '68 Impala (307) typically did 19 MPG (Imperial) on the highway.

The 305 was limited, though, by its small bore (3.736") which limited the size of the valves.

If they'd destroked the 350 instead, say from 3.48" down to 3.25", and kept the 4.00" bore ... they'd have reinvented the 307.

 

[SammyChevelleTypeS3]

I knew a couple of people with 305-powered cars back around 1978 - a Camaro and a Nova. Both were pleased with 26 MPG (Imperial) on the highway.

By comparison, my '68 Impala (307) typically did 19 MPG (Imperial) on the highway.

The 305 was limited, though, by its small bore (3.736") which limited the size of the valves.

If they'd destroked the 350 instead, say from 3.48" down to 3.25", and kept the 4.00" bore ... they'd have reinvented the 307.

One of my Chevelles, a 1972 Malibu had the 307cui 2bb engine. It was a really low hp motor but it ran very well and the great thing was it did really good at the gas pumps.

 

[userfriendly]

I knew a couple of people with 305-powered cars back around 1978 - a Camaro and a Nova. Both were pleased with 26 MPG (Imperial) on the highway.

By comparison, my '68 Impala (307) typically did 19 MPG (Imperial) on the highway.

The 305 was limited, though, by its small bore (3.736") which limited the size of the valves.

If they'd destroked the 350 instead, say from 3.48" down to 3.25", and kept the 4.00" bore ... they'd have reinvented the 307.

I thought the 327 was a 4" bore and 3.25" stroke.

 

[DriveHard]

I knew a couple of people with 305-powered cars back around 1978 - a Camaro and a Nova. Both were pleased with 26 MPG (Imperial) on the highway.

By comparison, my '68 Impala (307) typically did 19 MPG (Imperial) on the highway.

The 305 was limited, though, by its small bore (3.736") which limited the size of the valves.

If they'd destroked the 350 instead, say from 3.48" down to 3.25", and kept the 4.00" bore ... they'd have reinvented the 307.

If they would have done what you suggest to get a revamped 307, it would have had worse efficiency than the 305 due to the shorter stroke.

 

[ARCOgraphite]

R. Holdener recently combo'd a wrecking yard Gen 5 BBC peanut-port TBI truck engine - usually passed over for the small ports,
But it made fantastic torque - great for excellent street perfomance in say a B-body GM platform or truck with a THM400.

I think he used a 750 CFM 4bbl, Weiand dual plane, a quite mild XE268 cam and long tube headers. Also pop-up dome pistons to get the compression back up into the high 9's.

I was not aware those small port heads would support this much mid rpm torque! Very impressive.

 

[Number_35]

I thought the 327 was a 4" bore and 3.25" stroke.

Arg, you're correct - the 327 was stroked from 3.25" to 3.48" to create the 350. The 307 had the same 3.25" stroke, but the 283's bore of 3.875".

 

[Number_35]

If they would have done what you suggest to get a revamped 307, it would have had worse efficiency than the 305 due to the shorter stroke.

Agreed, but would have breathed better, and so perhaps avoided the scorn poured on the 305. It's a trade-off for sure.

In general, for engines of the same displacement, oversquare (i.e. bore > stroke) results in slower piston speed, and thus greater ability to rev higher. The undersquare engine would have more low-end torque, but be limited in the upper RPM range, and generally turn in better (lower) fuel consumption.

It's hard to find real-life examples, as there are so many confounding variables - camshaft, compression ratio, carburetion, etc.

However, I would have loved to see the 305 tested vs. the 307 with all the variables controlled.

 

[userfriendly]

R. Holdener recently combo'd a wrecking yard Gen 5 BBC peanut-port TBI truck engine - usually passed over for the small ports,
But it made fantastic torque - great for excellent street perfomance in say a B-body GM platform or truck with a THM400.

I think he used a 750 CFM 4bbl, Weiand dual plane, a quite mild XE268 cam and long tube headers. Also pop-up dome pistons to get the compression back up into the high 9's.

I was not aware those small port heads would support this much mid rpm torque! Very impressive.

View attachment 220892

View attachment 220893

Now overlay a 2024 6.6L Duramax L5P on the dyno graph.

IMO, the BBC oval peanut port heads can go into the same recycle bin as the 366 truck blocks.

 

[userfriendly]

Agreed, but would have breathed better, and so perhaps avoided the scorn poured on the 305. It's a trade-off for sure.

In general, for engines of the same displacement, oversquare (i.e. bore > stroke) results in slower piston speed, and thus greater ability to rev higher. The undersquare engine would have more low-end torque, but be limited in the upper RPM range, and generally turn in better (lower) fuel consumption.

It's hard to find real-life examples, as there are so many confounding variables - camshaft, compression ratio, carburetion, etc.

However, I would have loved to see the 305 tested vs. the 307 with all the variables controlled.

Been there done that. I rebuilt a 307, the block was a newer example with a spin-on filter and installed 305 heads with 1.94/1.6" valves.
I spent hours cleaning up the intake ports. With flat top pistons it ended up about 10:1 compression ratio.
The camshaft was Erson 208/214 109 LSA, intake CL @ 107, 1.6/1.5 roller tip rockers, better springs & moly retainers.
Edelbrock dual plane and 600 cfm, shorty headers, 2 1/2 exhaust.
It went into my son's 87 3/4 ton GMC, 7 inch lift and 40/13.50R17 Goodyear MTRs, 4.10 gears and 400 turbo.
Other bro-truckers couldn't believe it was only 311 cid.

Why 305 heads on a 307 block? Let's see if anybody knows the answer.

Crykie,,,, 4500 posts/21 years!

 

[Number_35]

Been there done that. I rebuilt a 307, the block was a newer example with a spin-on filter and installed 305 heads with 1.94/1.6" valves.
I spent hours cleaning up the intake ports. With flat top pistons it ended up about 10:1 compression ratio.
The camshaft was Erson 208/214 109 LSA, intake CL @ 107, 1.6/1.5 roller tip rockers, better springs & moly retainers.
Edelbrock dual plane and 600 cfm, shorty headers, 2 1/2 exhaust.
It went into my son's 87 3/4 ton GMC, 7 inch lift and 40/13.50R17 Goodyear MTRs, 4.10 gears and 400 turbo.
Other bro-truckers couldn't believe it was only 311 cid.

Why 305 heads on a 307 block? Let's see if anybody knows the answer.

Crykie,,,, 4500 posts/21 years!

I give up! Why?

(Edit: Neat project, by the way, even if I don't understand the advantages of the head/block mismatch.)

 

[userfriendly]

I give up! Why?

(Edit: Neat project, by the way, even if I don't understand the advantages of the head/block mismatch.)

Valve spacing. 350 heads would likely require the block to be notched to clear the intake valves, especially if 2.02"s or 2.05's were installed.
Plus the 305s have a twist that directs the flow more towards the middle with added swirl.

Not your run of the mill B6 ( bad built butch body big block).

 

[paulo57509]

Been there done that. I rebuilt a 307, the block was a newer example with a spin-on filter and installed 305 heads with 1.94/1.6" valves.
I spent hours cleaning up the intake ports. With flat top pistons it ended up about 10:1 compression ratio.
The camshaft was Erson 208/214 109 LSA, intake CL @ 107, 1.6/1.5 roller tip rockers, better springs & moly retainers.
Edelbrock dual plane and 600 cfm, shorty headers, 2 1/2 exhaust.
It went into my son's 87 3/4 ton GMC, 7 inch lift and 40/13.50R17 Goodyear MTRs, 4.10 gears and 400 turbo.
Other bro-truckers couldn't believe it was only 311 cid.

Why 305 heads on a 307 block? Let's see if anybody knows the answer.

Crykie,,,, 4500 posts/21 years!

Smaller chamber volume = increased compression. Lousy flow because of the smaller diameter valves?

 

[userfriendly]

Smaller chamber volume = increased compression. Lousy flow because of the smaller diameter valves?

Typically yes, but I installed hard exhaust seats for future LPG, 1.94" intake and 1.6" exhaust valves.
Good enough flow for 311 cid, but would probably suck on a 350 over 4,000 rpm.
305 heads are 58cc and flat top 307 pistons is good as it gets.
Forged crank from a 327, the block was a throw in at an auction, it was already freshly bored +.030" decked and align honed.
.0025" rods & mains, pinned oil pump drive, HV Melling oil pump 60 psi spring, long PH373 filter and 10w30 Duron P1,200 Zn 1,300.