FlatBlackZ28

So, I have my LT1 out of my car and torn apart. The car ran fairly well last year. First, I'll give you some background on the car.

Combo was:
Stock LT1 heads with stock valves and light porting.
CC306 cam, beehives and stamped 1.6 roller tip rockers
Pacesetter longtubes to 3 inch exhaust, no cats
52mm TB, 36# injectors, Walbro 255, 373's, 3200 stall. etc etc etc

The car put down about 350rwhp revving to 6500 (power was not yet falling off when we shut it down, but I didn't want to pop the stock bottom end) through a performabuilt auto and a 10 bolt.
Ran a best of 12.4 and a best mph of 110 in around 3000 DA

This takes us to the question portion.
The shop that put this engine together a couple of years ago for me did a pretty shitty job. The car ran strong, but upon taking it apart, they half-arsed everything.

The header bolts weren't all in completely, and you could tell that the headers were leaking, some ports more than others.
The gaskets used between the intake manifold and the heads actually had slightly smaller ports than the heads did. Yes, smaller, lol.

SO given these two variables, combined with the fact that I will be giving myself a fresh shortblock boring the block .030 over and adding forged internals, an LTCC ignition, and revving at least another few hunder rpms or so, should I see a decent increase in power? How much were these screwups holding me back? I was amazed that my car hadn't fallen apart. These were not the only shortcuts found on the car, but I won't even get into the rest.

05HD

Intake gaskets the right size may help a bit, depending on why the ones they used were too small. Exhaust leaks aren't going to affect power. If the added RPM puts you in a better place when you upshift, it will be your best gain, probably a couple tenths at the track.

RamAir95TA

iTrader: (2)

Unless the new rotating assembly is substantially lighter gains will be very minimal. The LTCC won't provide any power over stock and can actually complicate what a perfectly good optispark is capable of doing. The header bolts may not have been the shop's fault - all header bolts should be retightened after a few heat cycles. Depending on the size of the leak they could have been throwing off the O2s.

I'd say you'd gain some, but not much more than 10HP or so. Considering the numbers you were putting down were pretty good for what you've got done you weren't losing much. Most of the gains will come from shifting higher - not necessarily a HP gain, just using what you couldn't last time.

FlatBlackZ28

I was having ignition problems, ignition low voltage code accompanied by sputtering and backfiring and no power whatsoever. That's why I decided to go coil per cylinder, as it was hardly going to cost anymore than a new opti. $359 for the LTCC box and harness. Plus, it retards timing and gives me a rev limiter for my nitrous kit. So it was actually cheaper for me to go coil per cylinder than it would have been to buy a new opti and then by something like a Mallory 685.

How much do people usually see from a freshened up bottom end? I'm hoping to be able to hit 11's on motor in the same 3000-ish DA that we usually see at Thompson Raceway Park. Hopefully the extra RPM's I can now turn plus the few other little changes will net me enough to see 11.9 on motor so I can go for 10's on spray. The biggest reason for the new bottom end was to be able to hold up to my 150 shot.

ahritchie

iTrader: (1)

What are your plans for the "freshened up bottom end"? Do you mean just a basic stock rebuild with new bearings/rings? Or forged pistons, rods, and stock or forged crank? Stroker crank? You probably need both forged pistons and rods minimum to safely run a 150 shot on top of a 350 RWHP motor. I would just go with an all forged 383 stroker bottom end and you will definitely pick up a few tenths and have plenty of room to grow and not worry about blowing it up with nitrous.

FlatBlackZ28

I'm having the block bored .030 over. Reusing the stock crank, because its more than strong enough for my needs, and even leaves me some room to grow in the power department. The car on spray will have more than enough grunt, and I'd prefer a higher/faster revving engine to a spending the extra money on a forged crank and then having the crank prepped. I will be using forged I-beam rods (because of the weight savings over H-beams and they will support much more power than I will be making) and forged CP pistons.

96capricemgr

iTrader: (1)

I replied on CamaroZ28 to this. Now what do the rest of you think about "light porting" and "intake gasket too small"

Couple things I asked and was not answered on was if the gasket could have been a gen 1 gasket, and if the manifold was ported.

If the manifold was not ported and it was an LT1 gasket, then the heads were wildly hogged out and the gasket being in the port a little would not have hurt power since it would not have blocked the manifold port.

FlatBlackZ28

I don't think it could have been a gen 1 gasket, could it? If it was, wouldn't it have blocked the coolant passages on my engine?

No, the intake was not ported. When I took the intake off, the gaskets stuck to the heads and I could tell there was a little lip. Upon further inspection, it kinda looked lick the gaskets may not have been matched up to the ports very well. At least this time I'll know that everything is going together the way it should be, and the car can only get faster from here.

96capricemgr

iTrader: (1)

There are no water ports at the intake surface of LT1 heads or intake so nothing to block, and LT1 intake gaskets have plastic pins to locate them so they should not be misaligned.

Again if the gasket was still larger than the manifold port this was not costing any power. And if the head port is larger than the gasket the heads had a LOT of material taken out.