De-stroke a motor for a daily driver. Any advantage other than fuel mileage?

[cardo0]

Cleaning up my GEN II sbc block before machine work. Planning on stroking it for some fun time drag racing but the camaro has 270,000mi and will continue to be my daily driver. Got ahead of my self and had the heads rebuilt and milled 0.010" already. Now I'm thinking I can't run the cheap pistons I want w/o compression ratio getting out of hand.

Thinking maybe use a 3.00" stroke instead of 3.5625" as planned so I don't have to use a huge cam and pistons with a huge dish.

Modest cam and reworked heads with bigger valves could make 310" more fun than with the stock 350 heads and cam I'm guessing? And a whole lot easier on the stock 7.625" rear end - easier on the 4L60E too.

I guess what I really want is throttle response and pulls to 6,800rpm more so than torque spinning me sideways. Just want a fun driving car that I can still be racing at the strip w/o getting embarrassed by family cars.

I think now what I'm asking is will I be happy with 310 cubes as using 370 cubes with same cam and heads? Is there that much difference?

[BigBro74]

.010 will not be a big deal.
Just use a 350 crank- it will work better than a 3” stroke and have tons more “cheap” piston options than either of the stroke options you have mentioned. I have many questions——-
Has the block been decked?
What body Camaro?
What size chambers in the heads?
What compression ratio?

Please post all details for more input

[Ericnova]

Everything about your plan to go to a smaller engine is just wrong.

The .010" milled from the head is just barely 1.5cc on the SBC head....not enough to make any kind of drastic change in compression ratio.

Smaller engine will have to work harder to move as heavy a car as a Camaro....you'll more likely to get worse gas mileage than the bigger engine would, as the bigger engine could just loaf along instead of straining like the small engine will.

Don't even dork around with 3.562" stroke, go right to 3.75"....only reason to use the somewhat unconventional 3.562" stroke is you have a cubic inch rule you have to fit under, otherwise forget it.

Go to that little 3.0" stroke without setting the entire engine and valvetrain/heads up to spin 8000 rpm so it makes real power, and go mild setting it up for 6800 rpm and you'll get beat by every Honda Accord or Kia Sorrento on the road. The 3.75" stroke has no problem turning 6800 rpm, and unless the heads are a cork you'll have 75+ more HP there than the 310" engine will have.

Throttle response in gear is entirely related to TORQUE, as torque is what gets things moving.....how snappy that short stroke is in neutral is absolutely meaningless....and TORQUE at ow rpms in a naturally aspirated engine is entirely related to how big the engine is.

[plovett]

Certainly more details will help. In general though, are you willing to and is it practical to, run a lower rear gear with the smaller engine?

In general, a 20% smaller engine will want 20% more gearing.

JMO,

paulie

[plovett]

Torque is a meaningless value for a running engine. Horsepower, gearing, and weight, mean something. NOT trying to start that discussion.

So, if you change the displacement, the gearing and rpm needed change to get to the same final result. The question is, is it practical in your particular situation? Most of the time, more displacement is more practical. Not always, though.

JMO,

paulie

[PackardV8]

I guess what I really want is throttle response and pulls to 6,800rpm

This idea of the 3.00" stroke comes along at least once a week. RPMs are the most expensive motive power in a SBC.

more so than torque spinning me sideways.

So noise rather than power?

Just want a fun driving car that I can still be racing at the strip w/o getting embarrassed by family cars.

A 3.00" stroke in a 3800# car is the guarantee of being embarassed by Camrys.

I think now what I'm asking is will I be happy with 310 cubes as using 370 cubes with same cam and heads? Is there that much difference?

So spend more money to build less power? (We obsolete engine guys do that every time; not a rational decision, but there you have it.)

[lefty o]

Torque is a meaningless value for a running engine. Horsepower, gearing, and weight, mean something. NOT trying to start that discussion.

So, if you change the displacement, the gearing and rpm needed change to get to the same final result. The question is, is it practical in your particular situation? Most of the time, more displacement is more practical. Not always, though.

JMO,

paulie

if torque is meaningless, then so is hp, since hp is just a figure that is mathmatically derived from... surprise TORQUE.

[jeff swisher]

My vehicle for a comparison 3380 pounds with driver and fuel.
3.25 rear gear 2500 stall TH 350.
I have had 4 engines in it. All ran fine and dandy on 91 octane and would pull my 20 foot pontoon to the lake just fine.
First up was a real runner that hooked up to the pavement pretty good if i drove it correctly.
10.87 compression 350" with 268H comp high energy 218@ .050 ground on a 106LSA 225 psi cranking pressure.
Ported 601 heads 1.84-1.50 valves It would rev to 7200 rpm then valve float set in I ran Z28 springs with heavy stock retainers and 110 seat pressure.

Next up was a 385" stroker with the same heads and a 280H cam 230@ .050. 11.94 compression.

I could not get that thing to hook to the pavement in any gear even at 55 mph on the highway it would blow the tires off.
1947 dodge truck is a bit light in the bed i suppose. 7000 rpm

Next up was an over bored 327" SBC with the same heads and the same 280H cam.
Wow it had been a long time since I built a small cube deal 30+ years.
It was such a slow turd I only kept it in for 2 days and pulled it out. Yea it hooked up solid to the road.. In fact It did not want to spin a tire.
At 4500rpm it started really pulling but it still did not have the umph that the 350 or 385 had not at any RPM.

It still sits on the floor of my garage. Buddy has a 1933 Ford it will go into but the 327 will get a smaller cam like the 268H on a 106LSA.

My truck currently has a 357" with Ported 906 heads and Roller cam 228@ .050 and .492" lift on a 110 LSA.
20 TQ less than the 385" and only 3 or 4 HP less this hooks up well runs well to 7200rpm and sips the fuel.

I will not build another under 350" deal again for my cars. Turdish in my mind.
30 years ago in a 4 speed camaro launching at 4500rpm the little 327" engines felt really strong.
Heck in 1980's the Iroc 305 and 5.0 mustangs felt strong but they will get beat today by most 4 cylinder cars.

[engineguyBill]

Cardo,
You won't necessarily gain fuel mileage by destroking an engine. The only time that I would recommend destroking an engine is to meet class rules (weight to cubic inches) or if the goal is to build a very high RPM maximum-effort engine combination.

[cardo0]

Thanks for all the input and sharing your builds.

Car is 4th Gen camaro less than 3,300lbs but becomes over 4000lbs with me in it. 4L60E turning 3.23 gears for now. And that's kinda the issue as I drive it over 20k mi a year turning mostly below 2,200rpm.

So my Gen II LT1 heads measured 54.5cc - 55cc before milling. Now the edge of the 2.00" intake valve sticks out enough of the chamber I need to grove my plexiglass plate to measure chambers. Yes I'll get around to it but not in a hurry now.

I had planned on doing a 9/16 stroker because the stock crank turns nicely by hand and has 'bout 110k mi on it - rod bearings and journals look excellent. Piston shopping for the compression ratio I want found 12.3cc dish is all I find for the c.r. I want. I mean cheap pistons less than $150.

I'll share my thoughts here in that I can use crank and rods from a L99 to make it a 310" motor. I already tore up my 4L60E once with the stock 350". I trans shop told me the rear end has too much play and I think it makes some noise. Going to stronger entire rear end gonna be over $3000 doing it myself. Rebuild the stock 7.625 ten bolt less than $1000.
Car has shorty 1&5/8" headers now which would be a good match for 310 cubes.

I'm thinking since the reworked heads with bigger valves and a bigger cam should pull harder than the stock cammed 350". But maybe I should just stay with the stock stroke 3.48" and keep rebuilding the transmission and rear end as needed. Going to 3.75" stroker should get better rear end and bigger header tubes also.

Anyways that's where I'm at folks. Trying to keep it fun more so than expensive.

[lefty o]

Thanks for all the input and sharing your builds.

Car is 4th Gen camaro less than 3,300lbs but becomes over 4000lbs with me in it. 4L60E turning 3.23 gears for now. And that's kinda the issue as I drive it over 20k mi a year turning mostly below 2,200rpm.

So my Gen II LT1 heads measured 54.5cc - 55cc before milling. Now the edge of the 2.00" intake valve sticks out enough of the chamber I need to grove my plexiglass plate to measure chambers. Yes I'll get around to it but not in a hurry now.

I had planned on doing a 9/16 stroker because the stock crank turns nicely by hand and has 'bout 110k mi on it - rod bearings and journals look excellent. Piston shopping for the compression ratio I want found 12.3cc dish is all I find for the c.r. I want. I mean cheap pistons less than $150.

I'll share my thoughts here in that I can use crank and rods from a L99 to make it a 310" motor. I already tore up my 4L60E once with the stock 350". I trans shop told me the rear end has too much play and I think it makes some noise. Going to stronger entire rear end gonna be over $3000 doing it myself. Rebuild the stock 7.625 ten bolt less than $1000.
Car has shorty 1&5/8" headers now which would be a good match for 310 cubes.

I'm thinking since the reworked heads with bigger valves and a bigger cam should pull harder than the stock cammed 350". But maybe I should just stay with the stock stroke 3.48" and keep rebuilding the transmission and rear end as needed. Going to 3.75" stroker should get better rear end and bigger header tubes also.

Anyways that's where I'm at folks. Trying to keep it fun more so than expensive.

so, 4000+#, you normally drive at low rpm, with a 3.23 gear. i cant think of a worse thing to do than shortening the stroke.

[BillK]

Cant help you as far as the all out power goes but if you want mileage I say stick with the larger engine.

25 years or so ago I had a 1985 K5 Blazer that I bought new. Came with a 305 in it and it was "ok" as far as a driver goes but got pretty terrible mileage, probably no better than 17 on the highway. I put about 170k on the 305 and then pulled it out and built a nice later model 350. Stockish hydraulic roller cam engine. Not only did I get more power but the mileage went up to almost 20mpg highway because the 350 was loafing compared to the poor 305.

I have one customer that builds nothing but LT1's and almost all of them are 383's. Mostly in Impala SS's and Camaros.

[plovett]

Torque is a meaningless value for a running engine. Horsepower, gearing, and weight, mean something. NOT trying to start that discussion.

So, if you change the displacement, the gearing and rpm needed change to get to the same final result. The question is, is it practical in your particular situation? Most of the time, more displacement is more practical. Not always, though.

JMO,

paulie

if torque is meaningless, then so is hp, since hp is just a figure that is mathmatically derived from... surprise TORQUE.

No. Hp incorporates rpm which is a condition the engine in a running vehicle is always operating in. It is moving. Torque, by itself, is meaninglingless in an operating vechicle. I do not want to start that debate again. My point was a smaller displacement engine, with similar parts, in the same vehicle, will want lower (higher numerically) gearing. Simple as that.

paulie

edit: hp and torque are NOT the same thing. If you don't get that then......you don't get that.

[77cruiser]

Cardo,
You won't necessarily gain fuel mileage by destroking an engine. The only time that I would recommend destroking an engine is to meet class rules (weight to cubic inches) or if the goal is to build a very high RPM maximum-effort engine combination.

My 421 gets about 19 mpg @ 65-70 mph in a 77 Monte.

[lefty o]

Torque is a meaningless value for a running engine. Horsepower, gearing, and weight, mean something. NOT trying to start that discussion.

So, if you change the displacement, the gearing and rpm needed change to get to the same final result. The question is, is it practical in your particular situation? Most of the time, more displacement is more practical. Not always, though.

JMO,

paulie

if torque is meaningless, then so is hp, since hp is just a figure that is mathmatically derived from... surprise TORQUE.

No. Hp incorporates rpm which is a condition the engine in a running vehicle is always operating in. It is moving. Torque, by itself, is meaninglingless in an operating vechicle. I do not want to start that debate again. My point was a smaller displacement engine, with similar parts, in the same vehicle, will want lower (higher numerically) gearing. Simple as that.

paulie

edit: hp and torque are NOT the same thing. If you don't get that then......you don't get that.

i did not say they are the same thing, did I? you are wrong though.