1SloLQ9

Alright, If I did find a way to do an h pipe, I know its not going to gain me much if any, Does it just equal out the motor better? I have heard it helps all around and the h pipe was more geared toward low end vs high end like an x pipe would help with. Also do those shorty jba headers bolt up to stock down pipe? Have any dyno sheets on a stock 8.1 to see what and where they gain there power at? Thanks.

I was thinking of tossing some full roller rockers on there as well, I know they only add like 10hp tops, but i figured they would free up drive train a little and possibly help with tuning for timing purposes. I know the old style Big block rockers fit with those adaptors. I may have to raise the valve covers. Not to sure yet on that option. I believe Your company makes Full rollers as well correct? Any dyno gains or gains from tuning that you have seen?

I would assume freeing up the valve train would have to do something somewhere along the line.

Raylar Engineering

H-pipes and X-pipes even out the exhaust flow down stream. They both add a few HP/TRQ - but in a 5000lb truck, you'd never feel a difference between them (maybe 5 horsepower/torque difference). I would tend to steer you toward camshaft choices if you want to change the powerband of the engine.

The JBA headers work great. If you have an 01-03 truck, the headers are 3/4 length and require downpipes for either the Allison or 4L80E transmissions. 04-06 trucks do not require downpipes. We don't have any dynos of the JBA headers, but JBA does show gains of 28hp/29trq in the 5.3 small block:



I would expect 25hp/30trq (with tuning) out of short tube headers in an 8.1L application. Long tubes are generally another 10-15hp more.

Roller rockers actually end up being 18hp in the 8.1L. Our stainless steel roller rockers fit under the stock valve covers. They use our special AFN nuts which allow you to use the stock head studs.

If you're looking for a simple way to pick up about 100hp, you'll want a camshaft, roller rockers, valve spring kit and a set of shorty headers. Here's a video of our iron head valve spring kit.

Raylar Vortec Iron Head Camshaft & Valvetrain Kit - YouTube

If you're looking for torque the 202 is our towing camshaft. If you want more horsepower and a hot rod sound, the 203 camshaft is a great fit. The real wheel dynos below include our cylinder heads, but it gives you an idea of where the power would come on depending on the aggressiveness of the camshaft (and the benefit of a free flowing intake manifold for that matter).

1SloLQ9

That's not too terrible for roller rockers, I know its not a lot, I just figured since these engines tend to ping a lot with barely any timing, maybe the roller rockers would help that out, I've read It may also bring the power band up a little bit which may not be bad either, I'm probably going to stay away from cams or heads for now,

I would possibly be interested in the shorty's It would just be nice to see some real results on a 8.1 not a 5.3. As for the h pipe, I have a buddy with a lift and good welding skills I may just do it to say I did it, Then do the rockers and tune engine and see what I can get.

I was more or less thrilled it pulled 14mpg with a stuck clutch fan and 4.10 gears. lol. I figure a good tune, full synthetic in everything and maybe even the roller rockers could bump it up to around 16 on a trip someday. It has some sort of exhaust. Just a different then stock muffler, It would be nice to run dual 2.5 in and 2.5 out, but i'd want an x or h pipe before I did that. Or if they made a dual 3in and single 4 out. That way it would flow a little better.

Raylar Engineering

Changing roller rockers will not have any effect on the detonation (ping) these motors are known for, they only add horsepower by reducing valve train friction. These motors ping because they have poorly designed iron cylinder heads. The combustion chambers were designed with very little attention to performance. Take a look at this image:


The green areas are the changes we made in the combustion chamber to allow for a more even burn without detonation (ping). By switching to aluminum heads, you can increase compression, run more boost and most importantly gain the velocity / airflow that produces the power you're looking for.

Kerr

I had to use oil dry, a shovel and trash bag with 01 motor, swapped it out for a 06 out of a salvage yard and cant tell one bit of difference.. got the entire motor, wiring harness ect bla bla bla, unpluged, pulled it out, put new one in, plugged up the connectors and BAM.... runs like it did stock. lol..

xx_ED_xx

iTrader: (17)

only difference i would see is better pcms and more cats, that and the early ones didnt have 4 02 sensors

yooperLS6

hog, thanks for the history lesson on the 8.1L I picked up an 04 YukonXL to use as dedicated trailer tower and really couldn't find much info on the 8.1 other than marine application.

Egarms

I have a question for you raylar eng! How much is the most power in hp/tq you have ever made out of an 8.1l with your heads, 540ci crank, rods, pistons and with twin turbos? I want to know how much the block will take before it pukes?

Kerr

A lot,

Just single turbo on my 8.1L i went 13.2 @102 my sububran is 9300 lbs.. with a hurt trans

Id say the block will live, i think he told me rod failure is around 900 hp, pistons will depend on the tune, well it all depends on the tune to be honest..

Raylar Engineering

Short answer: We haven't / don't know.

There is only one vehicle on earth running the 540 kit for the 8.1L engine, and it's still naturally aspirated, running our 203 cam and ported stock heads. The 540 kit has only been available for about a month at this time. Lots of guys on the marine side are running our forged bottom ends with the Whipple blowers and putting out 800hp all day long at about 8-9lbs of boost. Assuming the same efficiency at 540cid, you should see about 870hp.

While not our engines, Nelson Racing loves to put forged 4.5 / 4.75 rotating assemblies into their Dart Big M blocks and run them up to 22-25lbs of boost. To give you an idea, those engines routinely put out around 2000-2500 horsepower without problems - Tom Nelson repeatedly says in every video the engines are very drivable and practically boring before the boost kicks in. Our "tiny" 540cid displacement won't put out as much as a 632, but it gives you an idea of whats really possible in a BBC with boost. To see those ridiculous videos, check out NRE tv, its always a good kick in the pants.

I would imagine that a twin turbo 540 Vortec would casually put out around 1300hp+ at mild boost levels, but we have yet to see anyone run one yet.