368...should I, could I, would I

[Paul Workman]

Originally Posted by Hib Halverson

Well, I'm kinda fixated on the 368 because, if I did it, it'd have to be for under 10 grand and to go 385, I'd need a crankshaft which I bet costs $4000.

My 350 already makes about 500-hp via the port work and other engine mods I have already. I can easily spin the tires, which are F1 Supercars. A good 385 which is streetable, is going to make 580 or so and a good 415 is over 600. All that would do is spin the tires more, but not make the car that much quicker. Obviously, if I put slicks on the car, it'd be a different story...but then I'd be breaking driveline parts.

A comment was made about a 368 with different intake cams failing California's smog check. No doubt, the reason I'm still not sure about the cams is just that–the smog check. Actually the smog check is also why I may have to retain my ported stock exhaust manifolds and cats.



I'm not a drag racer (at least not a frequent one) and I think a 540-550-hp 368, coupled with the right suspension upgrades (right now, other than revalved SRC shocks, my suspension is stock) and a 3.73 axle (right now, the ratio is stock) would make a really fun car. It won't catch my 12 Z06 on a road course, but it will keep it in sight.

Frank is right - Lots of options:

You're going to buy sleeves, pistons, rings, bearings anyway, so bigger is possible for very little more $$ e.g., 385. And, you keep your stock crank and cams and get close to 600 CHP, provided the porting is increased to handle it.

somewhere above 385 you can transition to 402 via off-set grinding the crank. At 385 you should be able to get to close to 575 CHP, on stock cams (read: Kalifornia emmissions requirements in mind).

There's porting, and there's porting... A lot has changed since porting was done in the 90s. One of the often said ditties is, "If you port the intake, you'll give up low/mid range torque for top end". Well, apparently the LT5 was starving for air from the git-go (read: doesn't appear to apply in this case!). Have you seen Marc Haibecks office "wall paper"? It is becoming covered with dyno graphs that show many motors not only making substantial power improvements, but without sacrificing torque anywhere in the band! The point is, HOW your porting is done (dare I say by whom?), could be important. (Some of these gurus are porting LT5 stuff almost weekly. And, now there is a proven CNC head porting program in IL for the LT5 to consider (@ about $2500 inclucing taking the motor apart and putting it back together with the ported heads).

I guess the bottom line goes back to what I said earlier about the 368. Hib, you dropped a lot of big names around w/ regard to your project. But, truth is where you find it, and a lot of big names have refocused on other (e.g, LSx) projects - seldom do work on LT5s anymore. Yet, there are still some well known, dyed in the wool DOHC purists that are still dedicated to the LT5, that may have something to offer and won't cost you a fortune.

I'm just sayin...

P.

[XfireZ51]

Paul,

Well said. If the GVD heads I have are any indication, cylinder head work has evolved beyond it as an example.

540-550chp is available w a 5.7L

[Pete]

391ci Closed Deck (very reliable)
4.125 bore
3.66 stroke (stock crank)
Stock Cams 570-580 chp
Done
There's 4 of the closed deck engines out there 3 run 10's with mild cams.

My suggestion is if you go with a intake cam put in a small exhaust
.220 .425 or .224 .415

Paul your very right sir LT5 has come a long way since the '90's
Pete

[Hib Halverson]

Thanks for all of the input.

Three final questions to "Pete"....

What is the cost of converting a 350 to the four-and-an-eighth bore 391

What's the CR of that engine?

Finally, I don't care about running 10s, but I do care about getting 60,000 miles out of the engine with it running nearly as good at the end of that 60,000 miles as it did after the break-in. Can I do that?

[Hib Halverson]

Originally Posted by XfireZ51

Paul,

Well said. If the GVD heads I have are any indication, cylinder head work has evolved beyond it as an example.

540-550chp is available w a 5.7L

How did you arrive at the conclusion that head work as evolved past GVD heads?

Did you just look at the ports and decide that or did you do some flow and engine dyno testing?

[Pete]

Originally Posted by Hib Halverson

Thanks for all of the input.

Three final questions to "Pete"....

What is the cost of converting a 350 to the four-and-an-eighth bore 391

What's the CR of that engine?

Finally, I don't care about running 10s, but I do care about getting 60,000 miles out of the engine with it running nearly as good at the end of that 60,000 miles as it did after the break-in. Can I do that?

For complete rotating short block done ready for install $9500
New pistons,rings,rods,etc.
You need to supply a good short block/crank.

Compression is your choice 9.5-1 thru 13.0-1

The way this is done the sleeves are thicker and stronger then open deck 4" sleeves.
One of these already have 10-15k miles on them with alot of drag time
alot of Chicago traffic and has run 10.40's @ 133 this car runs just fine.

So if you won't drive it as hard as the above car then i would not worry about reliability.

Pete

[Polo-1]

putting in the 379ci in the AM.

Stock crank cut to 3.75
Bore LA sleeve 4.010

If it were for me....

Pete do the BIG Bore 4.125 and a stock crank cut to 3.75 come out to 401ci.

Best dollar spend for a big inch LT5 on the cheap. Great rod stroke 1.56 to 1.6 either 5.850 or 6.000 rod used.

[XfireZ51]

Originally Posted by Hib Halverson

How did you arrive at the conclusion that head work as evolved past GVD heads?

Did you just look at the ports and decide that or did you do some flow and engine dyno testing?

I have my own motor and dyno testing along w Marc Hs experience and work.

[Paul Workman]

Originally Posted by XfireZ51

I have my own motor and dyno testing along w Marc Hs experience and work.

Yeah, but Dom... You forgot to mention there's some FBI "nuances" to the porting too that we're sworn to secrecy to, under penalty of being violated by Marc or (worse) an angry Greek!!

P.

[tomtom72]

Originally Posted by Paul Workman

Frank is right - Lots of options: The point is, HOW your porting is done (dare I say by whom?), could be important. (Some of these gurus are porting LT5 stuff almost weekly. And, now there is a proven CNC head porting program in IL for the LT5 to consider (@ about $2500 inclucing taking the motor apart and putting it back together with the ported heads).

I'm just sayin...

P.

I have a question from left field, but first I apologize for invading Hib's thread with my question.

I took out all but what made me almost spit my coffee on my LCD....Paul the part of your post I isolated is indeed fact????? I have a lot of Q's related to this Q, but this is the most important to a person of blue collar means.

TIA

Tom