As the title says I'm building a mild 355 on a BUDGET. i will be retaining the Tbi, set up since I live where emissions are present. I have a GMPP performer tbi manifold,(contains egr) and i found a good deal on low mileage 906's ( if it goes through)
Build specs; Lt-1 cam, bored .30, dual relief flat tops, i'll be using my factory lo3 roller set up. This is where the question comes in. Since I'm going to be running vortec's, will my factory lo3 (1991) pushrods work? I don't recall if they will or not due to they aren't self aligned. or made for guide plates, if so, ill just have to order guided ones. Thats the main question. Then after that I'm going to run the 1993 Caprice cop car ecm/chip. That will allow me to have the speed limiter delete and have more fun. As for the second question. To feed the 355/lt1 Instead of getting 65lbs injectors, I can maintain my 55lbs ones if I bump of the regulator correct? If so, whats the formula to do that? I saw it somewhere in the tbi stickies. And to tune it all I;m going to use the adl cable and a moates Ostrich 1.0. Any advice or information is much appreciated!! I have some of the items needed, but require a few more. Thoughts and constructive criticism is loved.

 

ANYTIME you swap components around, it's essential to determine the proper pushrod through valvetrain geometry (VGT) testing. Same heads different block, new heads old block, lifter swap, etc will all effect the VGT to some degree.Chances are you'll be ok. The Vortecs are an OEM and it's going to an OEM block with an OEM lifter package. However the time it takes to mock the engine up and run a quick pattern may pay off large in the long run.

 

Okay thats what I was wondering. And the lt1 cam is pretty good for EOM max lift as well,but I'm am going to try and go beehive, just to freshen up the springs and then later go with a bigger cam.

 

The Comp 26918 or 26915 are an excellent choice for the Vortecs. There are others as well but my experience lies with the Comp products. Keep in mind that at some point you may find yourself limited by the pressed in rocker studs. I ran a smallish cam in my first iteration (218 @ .050, .454" lift) and found the limit of the stock valve springs. From there I stepped up to a screw-in stud and the 26918s.

 

The Alex Spring set works pretty well and you don't have to auction off your first born to pay for it.

 

The LS6 springs are also a good lower cost alternative used with Comp 787 retainers.The Alex beehives are currently unavailable & have been for some time.The other drop in spring from Alex's appears to have the retainers ground flush with the bottom of the locks.They do work well tho.

 

The alexs ones appear to be drop in, not changing of the valve seat correct?

 

That is correct,but,you may need to ck availability on them.They were not available a few days ago.The LS springs are about $60 a set.You can find em cheaper on EBay sometimes.The Comp 787 retainers are about $50,or,Alex's has beehive retainers for 11/32" valves for about $40 a set including 7* locks.The LS spring will give you approx 90# seat psi if set up @ 1.800.IIRC,up to .550 lift.No machining of the heads.They are comparable to the Comp 26915 spring but much cheaper.

 

Pardon me, i mean the ls6 springs.

 

GM part# 12499224. You may wanna consider screw in studs,or,@ least pinning yours if going over .500 lift,or,a very aggressive lobe profile.

 

I am upgrading an L31 with:
- LT4 hot cam
- 1.52 self-aligning rockers (drilled head holes to allow 1.6s)
- screw in studs, machined to allow guideplates in the future, with hardened washers taking their place for now.
- 0.015" head gaskets. Bumping compression from 9.4 with 0.036"-ish toward 9.8:1
- machined valve guides (just to guarantee clearance)
- GM LSx beehives (last year's blue painted springs)
- Comp 787 retainers.
- I added +0.050" locks.
Installed spring height with the 787s and stock locks was only 1.725", vs the 1.800" spec for the springs, hence the +0.050"s. From 1.775" installed, this bumped the seat pressure a little vs 1.800", and still gave at least 0.575" lift before spring bind.
Searching threads here on TGO, this seems to be the hottest, budget, streetable, emissions combination going.

What quench and static compression are you aiming?
- Quench: 0.035"-0.045" is optimum quench.
- Compression is dependent on cam timing to aim for 8.0:1 - 8.5:1 dynamic compression. A bigger cam will bleed off more static compression than the LT1 cam.
The LT4 HOT has intake closing at 38.5* ATDC @ 0.050" and 68.5* @ 0.006". And using the KB calculator 38.5* @ 0.050" + 15*= 53* gets me to 8.5:1 DCR. Or +25*=63* per the wiki article gets 7.93 DCR. So, not quite a concrete answer, but in the target ballpark.

 

With double flat top reliefs pistons at +6 cc, with the 64 cc heads itl be right around 10.27 : 1.. Give or take the size of the gasket i use. And are you running .575 lift with a computer? if so is it tpi of tbi?
i am mostly sticking with the lt1 cam because I already have it, and i dont want to blow up my wct5. Keeping a nice budget power'd motor and not blowing up my trans is ideal.

 

Your 0.040+ overbore adds 0.15:1, and the 6cc pistons adds about 0.4:1 to the SCR vs my L31. Did you have the block decked? How far in the hole will determine which head gasket thickness to use. Typical are 0.010" increments: 0.015, 0.25, 0.36, 0.045"-ish. Using deck+gasket of 0.040", I concur with your 10.3:1 SCR. FYI: going to 0.050"-ish deck+gasket drops SCR to 10.07:1.

The LT4 HOT cam has lobe lift of 0.328" = 0.499" w/ 1.52s = 0.525" w/ 1.6s. So, even if I used 1.6s to get 0.525" valve lift, springs with 0.575" to bind leaves me enough clearance to be safe. I went with 1.52s a) to give more safety margin, and b) the extra 0.499-0.525 lift range isn't THAT beneficial on factory vortec heads.

It's not so much the valve lift that trips up the computer, but longer duration, more overlap and reverse pumping into the intake, all of which drops idle vacuum. From this thread:
LO3 = 178/194 @ .050, .350/.385 lift, 109* lobe seperation installed at 112* intake centerline. (either that lift is TINY w/ 1.5s or is wrong)
LT1 = 203/207 @ .050, .447/.459 (w/1.5), 116* LSA on a 112* ICL
LT4HOT = 219/228 @0.050 (272/281@.006) .328/.328 lobe lift 112* LSA
While a big step up from 178* to 203*, that LT1 cam WAS a factory stock EFI cam. Even the 219* of the LT4 should be OK. Closer to 230*@0.050" and larger durations really needs a good tuner.

I am running TPI. But for purposes of computer considerations, there isn't really any difference than TBI.

Blowing up your WCT5 is more a matter of how hard you abuse it... Factory LO3, side step the clutch at 5k (especially paired with sticky tires), and you'll blow it. Upgrade to 300+hp and feather the clutch, it should last a good long time.

 

yes, the duration was my worst fear. I'm going to be practicing tuning on my lo3 before i tune that 350, I wanted a decent duration so the computer wouldn't go bat**** crazy, and me and tuning I can already see will be a tussle.

No block decking, just .30 overbore, with dual relief flat top with +5 or +6 cc dish, and .025 compressed gasket, along with the lt1 cam... My goal is right around 10:1. perfect for cast iron. 9.4 would be better, but eventually i wanna run afrs...... Aluminium heads with hi compression 383. But for now, thats the engine build.

 

No you aren't wrong, the lo3 was the definition of peanut cam. It's unfortunate that GM decided that they could make the "fuel efficient" car have any fun. Even like a 200/200 duration at .50 with like .410/.410 would be nice. my friend 1987 k5 blazer motor have 185?/195? at .50 with a .420ish lift both sides. And that engine would do 100+ ft long burnouts with the one tire fryer open dif. with the 700r4.

 

And that was a tbi engine, although he had a 1406 on it.

 

The Alex springs and the Comp Beehive are two different animals. In the OPs case, either would work well with the economical side of it probably going to the Alex springs (although I'm not sure of their cost but I'm guessing it's less than that of a 26918).

 

Don't lose sight of the fact that despite a 10:1 static compression ratio, a cam with a 210 @ .050" duration will produce effective compression pressures far greater than a cam with a 230 @ .050" duration. So much so, that detonation could become a problem. I've been there and done that.