355ci Horsepower Estimate?

[FastLT1]

So my project is on hold for a little bit while my builder is out of town. In the meantime, I'm trying to keep everything fresh on my mind so we can jump in and get this thing running when he gets back.

I do have high hopes for this motor at the track but since it's not running yet I'd just like to know what kind of power you guys think it could make with a PCMForless tune. Flywheel and rear wheel. It will have a Dyno tune some day but not any time soon. My builder ported the heads very well in my opinion. He isn't an old school small block kinda guy and is very experienced with LT1s so he knows what he's doing (in other words he didn't just jump in with a grinder and take out as much material as he possibly could lol). but these heads will have to get me by until I can afford LE2 heads later on down the road.

Mods here for those who haven't seen my build thread:
355ci 11.5:1cr
Speed-Pro Hyper pistons
Scat Forged I beams
Ported heads
LE cam 232/240 .578/.574 110 LSA 107ICL
Scorpion 1.6 roller rockers
Lunati dual valve spring kit
Single roller timing chain
CSR electric waterpump
Pacesetter longtubes
TSP Rumbler cat back
K&N cold air intake
3600 stall
160* tstat
Free mods
Sure I'm forgetting something lol

So what do you guys think?

[BOLO]

HEADS is where it determines horsepower.

[FastLT1]

Well he pretty much just cleaned up all the rough spots and smoothed them out very well and is doing a valve job. So I would assume they will flow a little better than stock heads.

[zooguy]

325 to the tires

[RamAir95TA]

It ALWAYS pays to do it right the first time. I would wait a few more weeks and get the right heads.

[FastLT1]

I do agree with that, but it will be quite a bit longer before I can get better heads. I mean I still have to buy a torque converter, gears and an install kit, a new opti because mine is crap and my builder is letting me borrow one of his to get my car running.

[Paulster2]

That's a pretty large cam for (a little better than) stock heads ... I'm thinking it's really going to be a dog (just being real). I'm with the other guys in that you need some better heads, or at a bare minimum, get these hogged out by a reputable porter. 325 to the wheels is probably a good estimate.

EDIT: I'm seeing flow numbers on stock LT1 heads to be in the 206cfm range. With that in mind, you are only going to see a max of somewhere around 400 flywheel HP and that's with all the other supporting mods being right.

[HellTeeOne]

If everything is right, I'd say you will see somewhere in the range of 325-370 rwhp. Hard to get much more specific than that. This is assuming the heads are barely better than stock. I made over 350rwhp with stock untouched heads, stock compression and a cam quite a bit smaller than that. Might pay to put the heads on a flowbench and see how they do. That cam is a bit bigly, but it should do ok if the tuning is good.

[FastLT1]

I do understand that the heads will be holding me back, but I plan on running this set up for a LONG time so it will definitely see a better set of heads in the future. With all the LT1 guys that make 325+rwhp on stock heads and a hotcam kit, I really hope I make more than that before the head swap

[94ndta]

Too big of a cam can kill your power too. In fact there is a guy on ls1 tech right now running 13.8 with basically the same set up as you, only the cam is slightly larger. He cannot figure out why he is slow as well.

[zooguy]

Too big of a cam can kill your power too. In fact there is a guy on ls1 tech right now running 13.8 with basically the same set up as you, only the cam is slightly larger. He cannot figure out why he is slow as well.


^ this

[FastLT1]

I remember reading that guys thread. I just never understood problems like that because even my engine builder, him and his dad have a old Malibu with a stock shortblock 350 from a 80's monte Carlo with a 246/246 duration cam and stock ported heads that runs mid 7's in the 1/8th. Which is what my goal is.

[FastLT1]

Also the reason I went with a larger cam (besides the fact that LE2 heads are coming later on), was because I bought better pistons and rods (with ARP rod bolts) with the intention of spinning the motor around 6500-6600rpms or so

[RamAir95TA]

Ugh...

[94ndta]

I remember reading that guys thread. I just never understood problems like that because even my engine builder, him and his dad have a old Malibu with a stock shortblock 350 from a 80's monte Carlo with a 246/246 duration cam and STOCK PORTED HEADS that runs mid 7's in the 1/8th. Which is what my goal is.

Read the bold in that type.

[94ndta]

Ugh...
If I remember correctly, you ran a cam about that size on stock heads that did not work out too well.

[Paulster2]

I completely understand where you are going. Building the bottom end good in the first place is the right way to go. Only thing I might have done differently is gone with some forged pistons instead of hyper-U, but as long as you are not shooting 100+ shots of N20, you should be okay (IMHO). One of the things about "spinning the motor around 6500-6600rpms or so" is that heads can limit the top end. If you don't have the flow to support it, the engine will fall on it's face, even with a big cam. In fact, the big cam can cause it to fall on it's face off the line, then the heads not flowing on the top end will be death up there. Death on both ends. This is where putting the correct engine together with a plan and the right parts really comes into play. If you know this going into it and planning on the better heads down the road, then so be it. Just don't be surprised by it and say something like, "I just rebuilt it ... I don't understand!" (Like was said about the guy above in post #10 by 94ndta.) Remember too, we're not trying to beat you up ... just trying to be realistic because you asked for an assessment.

[FastLT1]

Read the bold in that type.
Yes I know. He has stock ported heads on his 350 done by himself, just like my stock heads are ported by him as well lol.

[FastLT1]

I completely understand where you are going. Building the bottom end good in the first place is the right way to go. Only thing I might have done differently is gone with some forged pistons instead of hyper-U, but as long as you are not shooting 100+ shots of N20, you should be okay (IMHO). One of the things about "spinning the motor around 6500-6600rpms or so" is that heads can limit the top end. If you don't have the flow to support it, the engine will fall on it's face, even with a big cam. In fact, the big cam can cause it to fall on it's face off the line, then the heads not flowing on the top end will be death up there. Death on both ends. This is where putting the correct engine together with a plan and the right parts really comes into play. If you know this going into it and planning on the better heads down the road, then so be it. Just don't be surprised by it and say something like, "I just rebuilt it ... I don't understand!" (Like was said about the guy above in post #10 by 94ndta.) Remember too, we're not trying to beat you up ... just trying to be realistic because you asked for an assessment.

Thank you for understanding. The stronger foundation was more important to me than buying an expensive set of heads right now. Remember, this set up is going to be my daily driver for a little while but it hasn't been running since a month after I bought it which was 14 months ago. So I really just want it running so I can enjoy it. Even though my builder isn't famous, he's very experienced and knows what he's doing when it comes to head work so there's no reason to compare my (not permanent) head set up to a stock untouched head set up. I really can't wait to see her running

[englundjd]

if you really want to see how good your heads are you should put them on a flow bench... but beware, you could be very happy or very disappointed by doing that.... head flow number would also help us give a better hp estimate

[KWBaraka]

Too big of a cam can kill your power too. In fact there is a guy on ls1 tech right now running 13.8 with basically the same set up as you, only the cam is slightly larger. He cannot figure out why he is slow as well.

He's probably slow because his static compression is too low for the cam. A low dynamic compression ratio due to a overly large cam is a power killer.


That's a pretty large cam for (a little better than) stock heads.......

The lift is a bit high.....but the heads, ain't really stock. So much will depend on the quality of the port job and whether they will continue to build flow into the uper .5xx" range.

The cam's duration is pretty spot on for the compression ratio, though......that's a big plus.

I'm gonna say HP/TQ in the neighborhood of 360HP/350TQ at the wheels.

KW

[FastLT1]

Thanks for the replies everyone. I've decided as soon as its running, I'm trailering it 2 hours to the nearest dyno (which is a Super Flow dyno), to be tuned. A friend of mine claims he's done his research on LT1s and made a $50 bet with me that it won't reach 300rwhp lol. So we're going to find out

[adam85]

I would bet more than 50$ because your friend sounds like a moron.

[FastLT1]

That's what I was thinking lol. He's just a new guy in the shop and I figured it would be easy money