What I have
Comp 54-454 (227/243, 6.14/6.23 113 LSA)
BTR Platinum 660
springs, Chromoly pushrods.
Heads are 799�s being sent to Wilkes Performance.
This is going on a 310ci engine @around 13.1 compression.
I�m looking for any advice as far as light valves in stock 2.0/1.55 sizes.
Also would like to run stock rockers with upgraded trunnions. I�d be interested in hearing recommendations on the trunnions too.

I�m also interested in critiques on what I have for use in future development on this combo.
For example I may have a custom grind built dropping the LSA down to 109-110 to try and boost mid range.

 

What is this a 4.8 bored for 5.7 pistons? Why are you limited to 310ci? If you want to boost tq build a bigger motor

 

A rules restriction is why the 310ci

boosting torque is relative to within that 310ci restriction.

5.7 bore L33 block with 4.8 crank

 

Even at 13:1cr I just can't get my head around those cam specs at that displacement with the short stroke. It's going to be quite useless below 5k rpm and even then the top end won't be optimal at all with that cam. You'll need a custom grind and I'd start with something with far less overlap and duration. I'd go for less static compression, and I'd try to push the dynamic as high as possible with a shorter duration cam that helps to crutch that short stroke of your combo

 

What is your intended rpm range and shift points?

A lot of what I dislike about that cam is the exhaust side. It looks like a ls3 nitrous cam.

 

4000-as high as I can rev it

its not really going to be shifted other than once From 1st to second with a 1.66 2nd gear and a 4.56-4.88 rear gear

 

Do you care about idle?

 

no not at all

 

233/237-113+3. .653/.638 lift. Add five degrees to both sides of you go solid roller (highly recommended for rpm)

Run LS6 sodium filled intake valves turned down. Manley stainless exhaust valves.
Manley nextek springs.
11/32x .105 pushrods.
Bronze guides.
C5R chain.
Pick a roller rocker.

Should pull strong to 8500 in that 310

 

This was a 4.8 with a 224/232 .590/.590 114 LSA

My intended setup will be .3L bigger, 3+ full points of compression higher and similar heads.

450 to the wheels is what I�m shooting for but that�s with a drivetrain with very little losses

 

LS6 intakes would fit without turning but hard to find
Why bronze guides?
I�m hoping to be able to make the power I�m after at a max of 8000 (to stick with hydraulic)
With that said that�s something I�d look at in the future.

I�m going to have to fool with Intakes on this combo too.

 

bronze has natural lubricity vs powder guides. I would recommend finding an intake with more plenum. Fast 90 would do great.

 

I appreciate your feedback.

In that dyno I posted above that was a 4.8 that Richard Holdener ran. It had a Fast LSXRT manifold.
That quick drop at the tail end of the run......is that because of the manifold or the cam?

Ive gotten tons of mixed feedback on manifolds and I was almost convinced to go with a Holley Sniper (tall version). Knowing this was going to hurt mid-range I was skeptical but I�ve gotten quite a bit of feedback saying that even on a small engine it�ll stop breathing at 7k

Im far from knowledgeable on this so it�s frustrating

 

I know you aren't going to listen to me but you should just get your car swap running with a completely stock 4.8L first and then modify that with a small low lift cam of your chosen duration after you get it running on the stock cam so you can see the difference that will have yourself. Then when the time comes and you have this engine put together all you will have to do is a simple long block swap.

 

Was the cam in that holdener dyno the same cam in your OP?

manifolds are a whole other topic. I don't think the LSXRT ran out of breath up top so much. The runner length plays a huge factor in what RPM the engine will do its best. Long runners will bring the rpm band down. You can cheat it with cam up to a point, but eventually the intake dynamics will take over. In my own testing, I had a fast LSXR long runner on a 5.7 that hit 6300 rpm and carried clean to 7000, but the power peak was at 6500, and it was very flat. I put a MSD on, and the peak power moved to 6900, and the power carried out to 7500. But i was down on torque below 6400 rpm.

BUT -- a smaller engine with the same top end will generally make the same power at higher RPM, which is what you see in that dyno -- it peaked at 7200. More often than not, when I see a sharp drop after peak power, it comes down to two things:

1. overlap - overlap helps carry power past peak. At nine degrees of overlap, on a 310 CI motor, it should have plenty.
2. valvetrain stability -- valve float, lifter pumping delays, flexion in the pushrods, all these things contribute. As RPM goes up, the weight of that valve goes up exponentially. At 8000 rpm, that valve instant weight can exceed a ton, and it's being supported by that rinky-dink steel tube and a tiny spiring under the lifter cup with an assist from oil pressure. Don't fool yourself about the oil pressure. it maintains zero lash, but it's not overcoming 1-ton of force. This often collapses lifters that are not designed for the RPM and valvetrain weight.

Regarding overlap, i really do think there is enough in either cam to help carry the power past peak. Valvetrain stability is the main reason I like solid valvetrains. You take the lifter pumping out of the equation. Run a beefy pushrod, and you eliminate flexion - or at least move it to a higher RPM. both allow you to run higher springs for increased stability.

Another way to compensate for the lifters is to run something like johnson 2126 short travels. These will take you to 8K while staying hydraulic. you'll have excellent valvetrain control.

Sorry, that post was longer than I meant for it to be when I started.

 

im probably going that route actually.
I have a bunch of oddball to me systems that I�d like to work out with the JY 5.3 I have. The diy dry sump, for one, getting it running with a TerminatorX is another.

 

No that dyno was with a 224/232 .590/.590 114LSA cam.
The one in my OP was recommended by him to get at the power I�m hoping for with a 4.8 (a little bigger @5.1 in my case)

On manifolds......Against the judgement of most for this kind of engine I�ve considered a TBSS intake even.
I thought it may actually be �OK� on this small engine in those upper RPM�s.
The FAST is on the radar for sure and the bright side is it seems used units sell for almost new prices.....If it doesn�t work like I�d hope I can always get most my money back.

I needed a lifter recommendation. I�ve search for �short travel lifters� and I just don�t know what is what as far as the better parts

 

My go to lifter for high rpm hydraulic performance is the Johnson ST-2126-LSR.

 

I actually like the premise of your build ! I would do a LS1 + 20 over bore 3.918 For valves LS3 turned down to 2.04 and a good tulip exhaust valve . As for the cam only I believe Jake Fusion , iirc has run some thing similar to that , he could tell you what to expect as results. If you are going to run the TBSS intake have a radical port done ,it will help up on top end .

 

Is there any reason that I�m not seeing for not running a 3/8 pushrod?
seems they almost fit based on what I�ve read. Just open things up a bit and should be good.

Even the cost isn�t bad