Bottom line up front. I am shooting for low 11 sec timeslips, 120 MPH traps and over 400 RWHP. I have mods and car set up in sig.

Just before I was deployed, I was in the process of installing a heads and cam kit on my stock shortblock 1996 Z28 when the hub bolt broke off in the crank. So now I am in need of a new bottom end. I did not have the time to fix this before I stepped on the plane.

Now that I am over here I am putting away some cash for a new bottom end when I get back. I plan to use the LE heads on the new motor wether it be 383 or 350/355.

I have a custom cam that was done for me to do those goals on a stock bottom end. I do have a fresh set of nice flowing LE heads/intake that are bolted on my engine now. I have all supporting mods covered. I do planning on buying some more odds and ends while I am overhere such as tubular K member, Racetronix fuel pump ect., but first I need to know which route to take.

I am having a hard time deciding on what to do for a bottom end. Here is what I am looking at:

1. Stock short/longblock from GM, maybe a 4-bolt version. I figure I could go this route and have a fresh engine that performs and have cash left over for a paintjob (it could use one). I just wonder how long one of these would last spinning it to meet my goals...

2. 355. Take my bottom end, source another stock crank and put it back together with some good pistons and drill it for 4-bolt mains. I could use my current set up with now changes.


3. Forged 383. Since I am going to need a new crank anyway, 383 is appealing, just costs more. Then I would also need to get another cam ground to get max performance. More expensive as well, but I could spin it and throw about anything at it and feel safe and the extra torque would be nice.


Any other sugestions are welcome. I wanted to hear from guys who have had past experiences with this and can offer me some hindsight. I figure I can spend about $5-6K in that ball park. I do not get back stateside to December so I got time to buy stuff.

Thanks!

Jeff

 

i'd say forged 383...get to 450 NA and then you can toss all sorts of spray at it

 

I would buy a good used stock crank. Splayed mains, forged rods and some nitrous friendly pistons. That way if you don't hit low 11's, you can throw some spray at it. Don't forget a strong DS in your plans. That and a roll bar if you plan on hitting the track often.
Until then, stay safe and thanks.

 

Only right way to do it. took me 3 months to build mine up and get it in car. remember, you really need to pay attention to details, get a machine shop to align bore, and clearance check EVERYTHING! I went with eagle 4340 crank, eagle 4340 rods, JE -16cc pistons for 11.5:1 compression. the rods from eagle had to be reconditioned for clearance, that i woulnt have been able to check myself. The shop that did it has been making drag/flat bottom boat motors since the mid 60's. find a good shop!

I'm getting it tuned in a week or 2 by bryan herter. should put around 450 to the wheels.

do it right, in the end you'll be glad you spent the $.

 

You can't drill the broken bolt out and helicoil the crank?
That alone shouldn't be a reason to build a whole new motor.
It's not even a reason to pull the motor out of the car.
You can clear 400rwhp with LE-ported stock heads and a 230ish duration cam.

Having said that, if you still want to build a motor;

4-bolt splayed are not a cheap install. You're looking at parts (caps, and studs) + $350-500 in machine shop labor.
It is however a very wise investment if you're going to run any decent amount of N20.
Don't waste your time with a 4-bolt GM block, the costs are outrageous and they have a
tendency to crack under pressure.

The cost of doing a 383 VS a 355 shortblock is similar.
- You need a longer stroke crank and matching pistons (similar cost to what you'd have bought for the 355)
- You will have to machine for the larger bore either way
- Depending on the rod choice, you may have to clearance the blockto keep the rods from hitting the casting with a 383.

The 383 will compress the torque curve, allowing the use of a larger duration cam
and should have a lot more grunt off the line. But as you said, there's a cost involved
in having a new cam designed. Although, you could always sell the old one to make
part of that back. (that's what I did)
Don't forget, you will need larger injectors (unless you already had 36 or 42#) and a 255lph fuel pump.

Both options give you the opportunity to go with a lighter-weight rotating assembly
and balance internally, which should allow you to rev quicker and reduce the amount
of power lost to simply turning the assembly. Depending what you buy, balancing
could be very inexpensive ($125) or very expensive (needing several mallory slugs @ $50 each).
Either way, I suggest a forged assembly. If you're going that deep, you should do it right,
you don't want to be rebuilding the bottom end again later.

The LE2 heads will work on a 383, although a set of LE-ported Dart or TFS heads would
likely unlock an additional 10-15rwhp at peak depending on the cam you select.

FWIW, I paid $1850 for an undercut, lightweight eagle forged 383 assembly.
I ordered the "unbalanced" version and got it to balance without mallory slugs.
I paid $1600 to the machine shop to deck, bore, clearance, 1/2fill, 4-bolt and fully assemble the motor.
Add the cost of gaskets, studs, main caps and anything else you need and see where how it fits your budget.

Oh, and don't forget the tune.

 

I pretty much have everything needed to run a 383. I do have 42lb injectors. I have a strange chromoly DS with a loop, Moser 12-bolt with 4.10s. The car is pretty much ready for 11's. No cage though, its a street car

We did try drilling the bolt out, with no luck. That sucker was in there. Actually it still is. lol

Anyways, I see what you are saying about the 383 route. Its what I was kind of leaning towards. I was looking at the Victory Racing racer 383. ($3600-ish) Its got compstar internals and I know they are pretty nice pieces. They said I could send them my heads and a cam and they can set it all up and get it ready to fire. I think for the money thats a pretty good deal. I am thinking it is a splayed 4-bolt... Anyone have any experience with Victory?

I would have to sell my custom cam, get one made for the 383 and my goals. I would also need another base tune. Those are the main costs for the supporting parts I would have to make up going 383 over 350/355.

I also like the idea of the lighter weight rotating assembly. Its hard for me to do alot of the shopping over here. I will have to wait till I get back till I really get started unless I go with a Vendor like Victory or Golen.

Thank you all for your help. You are helping me put everything in perspective.

Jeff

 

my96z. i just got done my project (in sig) and it involved everything that james said. if your thinking you want to go 383. save up. and do it. i have a 4 bolt forged bottom end, and le2 heads with a XFI280 cam (230/236). http://www.compcams.com/Cam_Specs/Ca...csid=1111&sb=0
getting a tune in 2 weeks.

shes like a bet outta hell... Est. 425+ rwhp
If you have any questions if you go this route shoot me a pm..

 

Creative2, that cam is a hair smaller than the custom one that was ground for my stock shortblock. If that cam can put a 383 at 425RWHP+ then I might be o.k with the cam I have. I just would feel more comfortable having another one ground for a 383 as opposed to one ground for a 350.

Jeff

 

i agree. my first cam was the cc 503 for my h/c swap. once i went to the 383 project i had to sell it for a better matched cam. talk to whoever ground it, see if the grind would be ok in a 383 setup. however, what james was saying about 383 flattening the tq curve, the larger duration cams will get you more power in the end. what are the cam specs?

 

It was ground for me by Brett. I told him I wanted 400rwhp, 11 sec timeslips and 120 MPH traps in my stock bottom end. He said it would work well in a 383 but I would rather get one custom made for the 383 and I am sure I can go bigger with the extra cubes.

Brett doesnt like the specs on his cams posted, but its real similar, just more lift and less LSA.

 

;D sounds like a pretty sexy cam... would most likely perform GREAT in a 383, however anything ground custom to match an engine will always net higher numbers, just due to the combination. i learned its not always "bigger badder more hp"

 

I don't want to steal the thread here but... I'm starting my cam, timing chain, opti swap tomorrow on my 95 LT1. How can I prevent from breaking the bolt off? How did this happen? I don't want to make the same mistake.

Thanks

 

get a grade 8 bolt, and Tq to NO MORE than 60 ft/Lbs.

ARB SBC balancer bolt

From Brent Frankers website
Crankshaft Balancer Bolt
60 Ft/Lbs
OR
720Inch/lbs

 

Well after doing some research I am kind of leaning towards Victory Racing's 383 Racer shortblock. I like that it has Compstar guts in it compared to most builders using Eagle for about the same price.

 

just remember if you have to get a new crank, a balanced 383 kit can save you some decent money and hassle vs piecing together a 355 and paying a shop to balance it