After buying a bbs header and talking to orr on the subject. I am going to be using a 355 instead of a 406. I will be using the summit 224 cam and for compression im shooting for under 8:1. I will be using aluminum heads also for intake it will be a single plane topped with a blow through carb.

What turbo will have less backpressure and which one has better power capabilities? I will be changing the rear gears from the 4.88s to either a 3.23 or 3.42?

Thoughts and opinions are greatly appreciated

If you want it to be quality out of the box, and last, the MP.

Whats your thoughts on the turbonetics 7868 turbo? Its only 720 through summit racing

Honestly I cant seem to find a good compressor map for it worth a damn, that being said looking at the HP76 wheel map, with a 355 it would be at the bare edge of hitting choke line on the top end, so i'd expect the HP78 wheel to be just a bit better, and for the money probably not a bad choice at all.

Thanks for the insight, it should come together quickly now

th gt45 has a solid reliability track record, there are hundreds of ppl using them for years with 0 failures on the turboforums

the gt45 has a 76/106mm compressor wheel , and iirc a 83mm turbine wheel
the gt45 will have less backpresure then a mp76 unles su opt for the large turbine wheel and housing

one of the site sponsors on the turbo forums sells the gt45 for 300 shipped with a warrenty on it

as far as which one is better what exactly are ur power goals and intended use of the car

Im looking for about 600 to the tires and i want a car that can be driven to and from the track... closest one is over an hour away

Hook me up with a link to these ones. I am likely going to use one for a remote mount on my ls1 car. I thought these were 69mm comp tho? 76 is bigger than i wanted for 500 whp

thanks for pointing that out orr i totally typoed that the ebay gt45 is

69.5-70mm inducer/106 exd the inducer measurement all depends on whos measuring it
im poretty sure its vs racing on ttf that sells the gt45's to be sure just check the gt45 thread in the diy section

the gt45 in rmt might be a lil laggy with its .105 ex housing and large turbine wheel one of the members here actually ran 2 of them in a rmt configuration on his race car theres a thread in here on it

the gt45 isnt going to do 600 to the tire but it would be close

I seen a mustang make near if not at 700whp with a single mp t70. I was shocked! I run 2 and was only in that range haha.

My ls1 is just bolt on with 320whp na. 3200 stall. I know a p trim t70 is gonna be full boost by 3200 lol. That may be too much. Q trim be better. Gt45 may slow things down too much but hard to say. Ls flows alot of air for what it is and 10 to 1 comp. i will find out hehe. Can you get a divided housing in those? I can partly block 3/4 of it all to speed things up.

I saw that rmt thread. Those are big turbines for a sbc to spin. My beastly 400 could spin 2 p trim .96's by 4500 full boost. Starts spooling by 3600. I figure one will be full spool by 3000 or sooner if all 8 cyl were breathing into it. So a q trim or the 80's mm turbine may help get it back up into the 3500-4000 rpm range. I shift by 6300

they all come with divided housings, most guys with pretty stock sbc's who use them say it starts to spool around 3k in a regular aplication , obviously rmt would slow it down some

Oh good cuz the ls1 is superior to stockish mild sbc's so i should have little issue. Only problem is the longtubes and 3" exhaust. Will need cast mani's for better heat wrap and really wrap the exhaust. Not sure if i should go back to 2.5", may try as is with boatload of wrap. Thanks

Sorry for offtopic

600 whp is a stout build. Good 355 with 76mm will do it. Depends on wheel. Gt45 could get close i imagine

gt45 would prolly do around 550-575 rwhp , i know it will deff do 500rwhp

Being so cheap i would be scared to push it so hard to reach the higher limit. Blades would be spinning something fierce

theres a guy making over 1200 to the tire with a pair of them on a big block so im not sure if 600 would really be pushing them.

with the size of the compressor wheel it should be capable of it
the gt45 is a pretty stout unit, big shaft big bearings, i think u would be hard pressed to actually kill one, infact i dont think anyone has been able to kill one yet,except for the typical seals goingout cause of incorect oil feed and drains

Sounds good. My 4l60e wont like more power as it is. Neither will the ls1 stock bottom


355 if this is the first turbo build you have attempted, cant go wrong with doing a gt45. 500-550 whp is a mid 10 sec car

This build is going to stretch over the next couple months and since i have to buy crank, rods and pistons wouldnt it make sense to build a 383car and go with maybe an 88mm? But the 355 i found pistons that will be 7.5 to one with 76cc heads

if you have aluminum heads you wont need to go below 8 to 1 for your goals. 9 to 1 in a good chamber is better for the goal.

Alright then, do you run head studs or arp bolts? And what headgaskets do you run? The last thing i want is a blown hg.

i run cheap head gaskets , this way they are the first thing to let loose if something happens.dont recoment cheap gaskets with aluminum heads though as if the gasket goes u stand a chance of torching the head which can be a couple hundred to fix if the damage is severe

studs will make it hard to get the heads off in the car, id go with arp head bolts

im also a fan of right around 9.0-1 cr

Studs arent that hard to get heads off. Harder than bolts but mine came off just fine with studs in car.

Id run bolts at that power level and any regular gasket. I run mls style gaskets for best seal but the motor is built around it and should support all the chamber pressure as long as i dont go lean and melt it down. A regular gasket is safer because it may blow before the motor does. If you get forged crank rods pistons and a fresh decked block just go mls and be careful with tuning process. Its the risk you take with forced induction

ive never used head studs in a 3rdgen so wasnt sure, ive used them on other cars and the only way to get the heads off would be to pull the studs out then lift the head off

For fueling ill be using the carb shop so it should be close out of the box and should hold

I have a set of motown 220 heads laying around, how is 8.3 to 1 compression and these iron heads sound? Along with the summit 224 cam and the ebay gt45? How much boost would be a safe figure assuming i have timing right and 91 pump?

that sounds pretty damn good , can u get e85 in ur area , if u can and u buy an e85 carb u could really crank up the boost and make tons of power

I do have e85 in town there is only one station that sells it though and its across town but would 12 to 14 lbs be reasonable with a btm box pulling out 1degree per psi? On 91 pump or is that too much?

Also before i forget i have a built 700r4, what would happen to overdrive if i put a manual valvebody in it? Im looking to make it as streetable as possible

I cut the whole harness out of the car so will it need any electrical connections if i put it in?

Hard to say but you shouldnt have a problem getting 14 psi on that setup. It should make the power you want.

Sounds great, hopefully this will be fast enough for me, this will make the 4th engine in the car in the past 5 years ive owned it

I like the GT45 for what it is. The quality is right up with the MP.

You can get them cheaper through Huron Speed. Turbonetics also has the new 7675 and 7875 midframe turbos they just released. They should spool the same as the TC78 with less backpressure, and make more power on less boost. Only a little bit more money too.

Yes it will. The thing that hurts the GT45 is its small inducer on the compressor but it will still do 600 rwhp.

Is this a rear mount build?

For a good budget bulid I would use the GT45. This turbo has made 630 rwhp on LQ4's but it is maxed out. The specs are close to the same as the MP with a much cheaper price. Why such low compression? That thing will be a dog out of boost. Run a 3.23 gear. Whats the LSA on the cam? EVO plays a huge role in spooling a turbo and can make or break a build.

GT45 or a TC78 will do ya.

a buddy of mine has a 351 mustang with a ebay gt45. carbed setup. No real tuning yet. Just street romps watching the wb02 and jet changes , etc..

1st time out at the track. foot braking and pushing thru the beams , only pulling 1.73 60fts ran 10.15@137

Im running such low compression because motown 220s are iron heads.

Camshaft lsa is 114

Im leaning more towards a 3.42 gear as i have a powerglide with a brake laying around and that gear would probably be a better choice to help get out of the hole faster with the 1.76 gear