View Full Version : 370 vs 408


Tunink
10-29-2009, 09:43 AM
I am having somewhat of a dilemma. I'm getting mixed answers to this question every time I ask.

My block is sitting at the machine shop waiting for me to figure out what I want to do as far as a short block. My top end for the time being will be an L92 head, Vic Jr Carb intake, and a custom ground cam for which ever combination I chose. I will most likely have a plate kit on the car with a shot ranging from 150 to 200.

This motor will be going into a Notchback mustang that will weigh about 2800 lbs with me in it. It will most likely be backed by a manual valve bodied 4L65e. It will be street driven.

Ok now down to the options:

High revving 370 with built valve train. Rev limiter set to 7800 shift at 7600. 11:1 compression ratio. Stall will be somewhere in the 4000 range.

or

408. Callies compstar crank & rods. Forged Pistons (Diamond). Probably only revving to 6600 or so. Stall around 3200-3500.

Now the issue is the fact that the car is so light (relatively speaking) that I don't need tons and tons of torque and that the 370 would probably benefit me more at the track, but for a mostly street car I figured the 408 would be more fun to lug around.

If you need any other information let me know.

Tunink
10-29-2009, 11:10 AM
No one?

MelScrilla
10-29-2009, 11:22 AM
I would do the 408 as you can't beat the cubes, plus less rpm's will be easier on the motor. I would think a 408 would do better at the track too.

And with the same parts it takes in the valve train to turn the 370 to 7200 you could do the same thing with the 408 if you wanted to.

ViaBellator
10-29-2009, 11:56 AM
I agree with MelScrilla

You could talk all day about piston speed, and safe RPM ranges, but for most applications, a 408 can spin as fast as a 370 with only a marginal increase in risk.

Trevor @ Texas Speed & Perf.
10-29-2009, 06:12 PM
I'd definitely go with a 408. It'll definitely be more fun on the street, but I would be VERY concerned with backing up a high-revving engine with a 4L65. Honestly, for all of the additional valvetrain upgrades you'll need to turn the added RPM with the 370, the 408 will probably work out to the same overall price, if not cheaper!

We have quite a few 408 cid iron short-blocks in stock and ready to ship, so let us know if we can help you out! We also have all of our strokers on special with free truck freight shipping in the continental US through Thanksgiving! :cheers:

Trevor
Texas Speed & Performance

Bader-X
10-30-2009, 12:52 AM
if the heads and intake are the same on both set ups then I say 408 ....

if by going with the 370 you`ll use better heads or say all pro then the 370

and the the 408 you`ll get more hp and tq all over the rpm and maybe 20-30 hp at the top

FMS_FTW
10-30-2009, 12:56 AM
Always go for more cubes when possible.

Tunink
10-30-2009, 10:11 AM
Still can't make up my mind. Engine builder wants me to build the 370 with closer to 12:1 comp ratio and mechanical roller cam. He says that the hyd. lifters will have trouble spinning up to where I want to be with the 370.

We'll see.

Any real suggestions. I haven't committed to anything yet, other than the L92 heads, so a 408 is still in it, even though 90% of the people I talk to around here are saying that a higher spinning 370 will do better in a light weight car.

cam75w/ls1
10-31-2009, 10:12 AM
I've had good luck w/ the 370 combo since the rod length/stroke ratio is better for high revving. Works good in lightweight car.

XtraCajunSS
10-31-2009, 12:04 PM
A properly setup hyd roller valvetrain will have no problems turning 8K+ you just have to know what you're doing. If you have the means, a 408 would definitely be the way to go. You could always upgrade to a SR valvetrain later for even more power.

There is no substitute for cubic inches... besides a power adder...

Shane

flatchat
10-31-2009, 01:13 PM
iwould go 408 for sure.

00CAMARO408
10-31-2009, 03:00 PM
408 ALL THE WAY:cool:...I JUST FINISHED PUTTING MINE IN MY CAR

mygto
11-01-2009, 12:14 PM
408!:d

99blancoSS
11-01-2009, 12:40 PM
A properly setup hyd roller valvetrain will have no problems turning 8K+ you just have to know what you're doing. If you have the means, a 408 would definitely be the way to go. You could always upgrade to a SR valvetrain later for even more power.

There is no substitute for cubic inches... besides a power adder...

Shane

+1 for Shane and Melscrilla

Tunink
11-02-2009, 03:27 PM
Well. I made my purchase today. I post results when I get them.

Thanks for the input.

fatmat80
11-05-2009, 01:57 PM
another vote for the 408!!!

OH2LE
11-05-2009, 03:30 PM
:nod:my vote. 408

MNR-0
11-09-2009, 04:22 AM
Same bore, just different strokes?

If same bore, my preference would be the 370

MAC4264
11-15-2009, 01:43 PM
built a 402 steel 6.0L block, ET 5.3Lcnc heads, 238/240 cam, Fast 90
made 555/525 flywheel

built a 366 LS2 block, out of the box 225cc Darts, 227/235 cam, Fast 90
made 526/492 flywheel

The 402 above in my opinion was a disappointment it was removed from the car in less than 350 miles for oil cunsumption. The 366 shows more potential in my opinion as if it had some more cam and alittle more head it would be on that 402's back door. Steel block has also shown more power in the past in back to back comparisons.

370 all the way for me! 4.00 stroke dissapointments me everytime I use it in someway form and fashion.

LSX350Z
11-15-2009, 02:08 PM
I am having somewhat of a dilemma. I'm getting mixed answers to this question every time I ask.

My block is sitting at the machine shop waiting for me to figure out what I want to do as far as a short block. My top end for the time being will be an L92 head, Vic Jr Carb intake, and a custom ground cam for which ever combination I chose. I will most likely have a plate kit on the car with a shot ranging from 150 to 200.

This motor will be going into a Notchback mustang that will weigh about 2800 lbs with me in it. It will most likely be backed by a manual valve bodied 4L65e. It will be street driven.

Ok now down to the options:

High revving 370 with built valve train. Rev limiter set to 7800 shift at 7600. 11:1 compression ratio. Stall will be somewhere in the 4000 range.

or

408. Callies compstar crank & rods. Forged Pistons (Diamond). Probably only revving to 6600 or so. Stall around 3200-3500.

Now the issue is the fact that the car is so light (relatively speaking) that I don't need tons and tons of torque and that the 370 would probably benefit me more at the track, but for a mostly street car I figured the 408 would be more fun to lug around.

If you need any other information let me know.

There is no replacement for displacement! I would go with the 408!

JayplaySS2
11-15-2009, 05:10 PM
4 0 8 :cool:

1lejohn
11-15-2009, 06:29 PM
408 for me. Why make a high reving engine with the 92 heads they make great torque use them to ur advantage. I would watch how much compression you run with the 92's. There are debates on some sites about them being sensitive to comp. and detonation. I think you can get there with a hyd roller. The heads won't support real high lifts ,again debated on other sites. These are truck heads after all.
I believe them. Why would GM go with the LS7 heads if these would have done the job. I'm just a saying.
Then again why not try a high comp., high rev, soild roller and prove them wrong. Do you think the Vic jr will support this build? I would use a flat plate type t. body with a large elbow and have it run like a 5.0 with the filter pick up by the fender. Good luck keep use informed.
I wanted to go this way but backed off and went more street oriented. My cam is in the 240-250 range at .620 ish lift hyd roller.

1badA3Z
12-12-2009, 08:45 AM
408!!