Just woundeing why, the 5.3L with 317 heads make a T76 feel like a slug off the line but pickup top end?

 

ur lowering the compression way beyond what ull actually need. ive seen 5.3s with ls1 head making fantastic results

 

^^^^ What he said. It lowers compression.

 

What compression? If it's super low then turn up the boost. Low boost and low compression makes a car sluggish... 9.5:1 cr will give decent drivability while not in full boost..

 

yea dude 317's on a 5.3 is extremely low compression.

 

317's are 71cc chamber so it drops a 5.3 down to 8.5:1cr. Stock 5.3 862/706 are 61cc and 9.5:1cr

 

depends on the 5.3 also. The L33 uses flat top pistons instead of dish.

 

What engine with 8.6:1 compression isnt a slug? People are under the impression that turbos need low compression. Probably true if you are trying to run 30psi on pump gas.. But if you had a turbo to achieve that and you are running a stock 5.3 odds are it would fly apart well before that...lol. So no need to lower the compression to prepare an engine for something it will never see. I did this also....it sucked. lol.

 

An 8.5 5.3 without a turbo is like a 150-200 hp combo... so there's your sluggish right there.

Do you have data that says a lower static 5.3 with more pressure is more efficient then a 10:1 5.3 with a t76? What makes you think it will "pick up top end"?

 

not only that, but it is also usually paired with a cam like a ls6 or 224r, where your dynamic compression is down in the low 6s or high 5s. THAT is the real problem

 

It makes is a slug when NOT in boost, which for a street car is 98% of the time unless you're Vin Diesel

 

GN's are v6 with 8.5 CR and are not sluggish when not in boost(well not that much) and only rated at 245hp in boost

Convertor stall
Rear end Ratio
Ar. of exhaust housing..

 

As previous owner of 2 turbo Regals, I beg to differ. They feel real sluggish when not under boost. Fortunately they spin up pretty quick.

 

can you elaborate on this a little more?

I'm going with a ls6 cam w/317 heads, ls9 head gasket on a 347 with -2cc valve relief flat tops..

I would like 9.5 compression

 

that equals out to 9.45 compression and 7.08 dynamic compression.

 

ok so let me see if i get this right... i got a 5.3l with 317 heads, ls6 cam, and flat pistons.. which should be 9.5:1 comp right?? should i swap into ls1 heads for better results or turning the boost up at lower rpms should even it out??

 

Actually I used the Ls1 bore for that. Your combo is
9.05 cr
6.75 dynamic cr

That is why they are such dogs. That is a 200whp at best N/A. I would run 241s myself over 317s which is
9.55 cr
7.15dcr

 

Grr, can you explain the dynamic CR and how you calculate the DCR and STR? Thanks

Also, I understand the significance of STR, but what is an ideal DCR for a street vehicle and how does that play into driving or response. Im sure Im not the only one who would find this info useful

 

i see. understand why prior of the turbo build it only dynoed 329/321. what kind of boost could them 241s hold?

 

ok I looked it up and understand now. Now I just need to figure out when my intake valve closes lol. Would that be on the cam card?