Car is slow...
Car is slow... I been to the strip and best I can get so far was a 12.60@108 on motor and with the mods I have should be 3-6 tenths faster. Pcm4less took a look at my dyno sheet and said wasnt room for improvement except maybe alittle torque. I think the hp numbers are to low too. Seems to run ok, but just alot slower than it should be. Anyone have any ideas, this has me stumped...
My mods are:
-fresh 355 ci LT4
-basic ported heads and intake (43.7 hp over stock gmpp lt4's)
-30lb injectors
-52mm tb
-306 cam
-1.6 roller rockers
-forged pistons w/ balanced bottom end
-2800 Vigilante Stall
-3.73 gear
-electric waterpump
-pcm4less tune
-255 fuel pump
-8.5mm msd wires w/ blaster coil
-digital 6 plus msd
-nitrous works wet kit
-pacesetter long tubes coated
-3 in xpipe with spiral flows dumped
-160 stat
-suspension mods
-weld prostars 15x8 and 15x3.5
-granatelli maf
-moroso cai
-trickflow elbow
-Tr6 plugs gaped at .038
-aeromotive adjustable fuel psi regulator
I'd figure it would go faster than 12.60@108. I had a ttop 95z and it went 12.86@107.9 on open ypipe without the electric waterpump, port work, stall, prostars, fuel pump, true duals, 52mm tb, 30lb injectors and aeromotive regulator.. Now I even run a hardtop 95 T/A.
-fresh 355 ci LT4
-basic ported heads and intake (43.7 hp over stock gmpp lt4's)
-30lb injectors
-52mm tb
-306 cam
-1.6 roller rockers
-forged pistons w/ balanced bottom end
-2800 Vigilante Stall
-3.73 gear
-electric waterpump
-pcm4less tune
-255 fuel pump
-8.5mm msd wires w/ blaster coil
-digital 6 plus msd
-nitrous works wet kit
-pacesetter long tubes coated
-3 in xpipe with spiral flows dumped
-160 stat
-suspension mods
-weld prostars 15x8 and 15x3.5
-granatelli maf
-moroso cai
-trickflow elbow
-Tr6 plugs gaped at .038
-aeromotive adjustable fuel psi regulator
I'd figure it would go faster than 12.60@108. I had a ttop 95z and it went 12.86@107.9 on open ypipe without the electric waterpump, port work, stall, prostars, fuel pump, true duals, 52mm tb, 30lb injectors and aeromotive regulator.. Now I even run a hardtop 95 T/A.
Last edited by Meen95z; Aug 23, 2006 at 12:28 AM.
TECH Addict
iTrader: (8)
Joined: Sep 2005
Posts: 2,401
Likes: 0
From: The beautiful Kingdom of Bahrain
Same exact thing kinda happened with my setup. Thats why the motor is apart now to ENSURE theyre no mechanical reason. Also check your converter. I traced a HUGE part of my issues to a bad 3500 stall converter.
TECH Addict
iTrader: (8)
Joined: Sep 2005
Posts: 2,401
Likes: 0
From: The beautiful Kingdom of Bahrain
I think you need more stall also where did your setup stop making power on the dyno? Who ported the heads? Did you get a flow sheet? Was the cam degreed in? Did you get any datalogs? What was your total racewieght?
The max hp was at 5600, but pulls solid till 6400. The heads and intake was ported by Doug Goebel and tested on the flow bench, so I do have flow sheets. And dunno what the race weight is. 3600 about. And the cam was degreed at what it called for.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo I dont think they out flow LE heads. They are just the basic LT4 heads from gmpp with a port match intake and exhaust, clean up around guide bosses and 3 angle valve job. I didnt do to much to them, but he said a 43 hp gain over what they was.
Originally Posted by Meen95z
I dont think they out flow LE heads. They are just the basic LT4 heads from gmpp with a port match intake and exhaust, clean up around guide bosses and 3 angle valve job. I didnt do to much to them, but he said a 43 hp gain over what they was.
Now the three "C's"....Compression, Cam and Converter......What's the real SCR and DCR...."Cam" is Ok but a custom grind would help torque and horse power....Now, "Converter" is way to small for that cam especially in a 355 inch... I would use a 3600 minimum and really a 4000 stall would be better...(for example, I use a PI 3200, but in my stroker it flashes to 4400 on the launch). On your 355, the verter rating you see are pretty much on unless your making big power.
By the way, I'm assuming you dynoed sense you know max horse power vs. rpm. What was it SAE corrected? and 5600rpm peak is way early on a large cam on a 355 inch engine....something is not right...I usually see peaks of 6300-6500 carrying to 7K rpm with cams that size with good heads and the right compression to run it....
Oh yeah, almost forgot..Just because your heads flow more doesn't mean you'll actually see more power out of them...Trust me on this one....
Last edited by jimbob; Aug 23, 2006 at 02:26 AM.
that cam loves 4.10s and 3500+ stall.
depending on your altitude,DA etc. you should be able to run 11.60s,you did not mention the type of tire you were on,unless i missed that!if you ran that on radials you are really in for a suprise when you put a sticky tire on!
depending on your altitude,DA etc. you should be able to run 11.60s,you did not mention the type of tire you were on,unless i missed that!if you ran that on radials you are really in for a suprise when you put a sticky tire on!
I dead hook on the street and track, got a set of bfg drag radials. I usually get about a 1.75 60ft. This is more of a daily driver so didnt wanna run to big of a converter. And it only put down 347 rwhp and 336 tq on a mobile dyno. What do you think the problem is with max power being so low in rpm?
Last edited by Meen95z; Aug 23, 2006 at 08:37 AM.
TECH Addict
iTrader: (8)
Joined: Sep 2005
Posts: 2,401
Likes: 0
From: The beautiful Kingdom of Bahrain
Originally Posted by scrmnws6
Flow numbers! Thats funny. They dont mean much.
Originally Posted by Meen95z
I dead hook on the street and track, got a set of bfg drag radials. I usually get about a 1.75 60ft. This is more of a daily driver so didnt wanna run to big of a converter. And it only put down 347 rwhp and 336 tq on a mobile dyno. What do you think the problem is with max power being so low in rpm?
I will do you one better though.....If your running basically stock compression height/quench and your pistons are 4-8cc dish a cam change to something on the order of Mid 220's Intake/Mid to low 230"s Exhaust on a 10X LSA will do wonders for your time with that small of converter....I bet you would pick up 2-3 mile an hour, and maybe more on your time. What you have is to low of horse power at your shift extension causing it to run low mile an hour/trap speed for the horse power it does make. Talk with either Bret Bauer/Lloyd Elliott or Joe Overton (if he still does cams) and Ai can help too.
Now for the rpm being so low at max hp, that could be a lot of things...My guess heads and cam combo problem...(that's just a guess though and could be wrong)....With just stock Lt4's I would think you would peak atleast over 6k rpm's with that size cam....Remember though LT4's have bigger combustion chamber cc's then LT1's even though they were rated less. I believe they were some where in the 56-58cc's actuall. Your compression might be less then you might believe "These are just some ideas as to the problem, so take with a grain of salt"
Hope this might help you....
well the trans is out right now, so would I gain more from a bigger converter or changing cam? They say the 306 is 2500-5800 rpm range. So I figure 2800 im coming into the cam? Id hate to change the cam cause this winter I'll prolly sell the heads for afr 227's. So would a bigger converter help? And Im leaving the line at 2k rpm. I think the the intake was 238 cfm at 28" and exhaust 191 on the heads..
Yes, a bigger verter would help....!!!
Also, a cam to feed those bigger heads would be way different....However, that's some very big heads on a small cubed engine. You'll be running right up there in rpm to make good power out of them 7200 rpm (if your paticular computer will rev that high)....I would suggest a custom cam a way bigger stall with those heads..."It's all about the combo"...and it looks like you may be going to the other extreme of the power range....Personally, I would have those LT4 heads ported (someone who knows heads) have bigger valves installed for them. You would keep the horse power up in the midrange (auto extension) over what your planning. Now if you had a stroker totaly different recommedation might be needed. By the way Ed Wright uses LT4 castings...He's in the 10.1-10.2 area with them...So, when done right they can support big power...
Also, a cam to feed those bigger heads would be way different....However, that's some very big heads on a small cubed engine. You'll be running right up there in rpm to make good power out of them 7200 rpm (if your paticular computer will rev that high)....I would suggest a custom cam a way bigger stall with those heads..."It's all about the combo"...and it looks like you may be going to the other extreme of the power range....Personally, I would have those LT4 heads ported (someone who knows heads) have bigger valves installed for them. You would keep the horse power up in the midrange (auto extension) over what your planning. Now if you had a stroker totaly different recommedation might be needed. By the way Ed Wright uses LT4 castings...He's in the 10.1-10.2 area with them...So, when done right they can support big power...
Originally Posted by Meen95z
well the trans is out right now, so would I gain more from a bigger converter or changing cam? They say the 306 is 2500-5800 rpm range. So I figure 2800 im coming into the cam? Id hate to change the cam cause this winter I'll prolly sell the heads for afr 227's. So would a bigger converter help? And Im leaving the line at 2k rpm. I think the the intake was 238 cfm at 28" and exhaust 191 on the heads..
Well the heads were 1300.00, then dumped another $700 in them or the little work I had done, is it worth to keep going or just sell them and get afr's? And what kind of converter (size) would I need?