hello i am new here but i love this place its really cool and everyone seams cool. maybe some of you guys can help me out i have a 88 trans am i am building a 400 4 bolt that i got out of a blazer . i dont know what all i want to use first off i dont know if i should use mass air or speed density anyone have any suggestions on that. i took the 400 block and drilled taped and grind the block so i can use the factory hyd roller cam that came in the 87 and up cars and i am thinking about using either vortec heads or gm fastburns and i dont know what cam to use i was thinking about the zz4 cam but i also heard that tpis has alot of good grinds i think they have a zz9 cam i was lookin at. and the intake will be a tpi setup the base is stock but it is ported huge and i siameised the runners in the base down to the length of lt1 runners cause i had a camaro 4 years ago i used 2 race it had a 383 tpi and i siameised the runners cause it was dead at 4500 rpm. so i still have the intake and i will use that i want 2 either get a set of slp runners and fully siameise the runners or take some stock ones and siameise them. the injectors i have now are 24.75 lb lt1 injectors but i might try 2 get a bigger set the throttle body will either be a 58mm or a 54mm. the car is a 5 speed it has t tops and i got the jegs torque arm if anyone has any suggestions or advice i would appericate it thanks WADE

 

Your are going to need all the air you can get. So go with the speed density route. Of the two heads you have named I would go with the Fastburns. However they have 62cc combustion chambers. So you will have to be carefull on which pistons you use or your compression will go to the moon.

Neither of the cams will provide the air for high performance in a 400 motor. I would go with something on the order of 230 degrees on the intake side and as much lift as the Fastburn heads will take. The Compcams 230degree XFI cam would be a good choice if the heads will take the lift. Do not go cheap on the valve train componets.

I can assure that a bored out stock TPI manifold is not big. You need to go after market with one such as the Edelbrock and then have it opened up. JerryWho has done that with his 400+ cubic inch motor and the first impression are real good. Can't wait to see the dyno numbers. I would not siamese the runners in the base in your situation.

I would go with the 58mm throttle body as it is the same price as the others and you will need all the air you can get. You will also need a custom cold air intake that you can do yourself.

Also you will need a good custom exhaust system. I can recommend the 1 3/4" one sold by Dyno Don who hangs out on the Southern California board. You will not find a better pair on the market and a custom wye pipe can be furnished.

 

I forgot to say that you will need a minimum of 30# injectors maybe 36#.

 

i was looking on comp's website i found the xfi cams but it doesnt have the specs on them. well at least i couldnt find them. but i wanted to know why you said not to siameise the base intake also i have injectors out of a grand national and i was told they were pretty big the guy i got them off of told me he thought they were 36#. i dont know what the g/n came with stock.

 

ok i got a question what do you think about this i have a 86 transam i just got 305 tpi auto has bad motor but i have a good tpi motor out of a 86 iroc that i rebuilt it has new rings and bearings, high volume oil pump. a the slp cam 204/214 .420/.442 using comp cams 1.52 roller tip rockers, fully stock ported tpi heads, and tpi intake, 52 mm throttle body also hypertech stage 2 and it has all the little tpi tricks done to it so i was thinking about trying to use them lt1 injectors on it but do you think they will be to big i think they are 24.75# also the car has a holley ignition system i think it is a hp-100. so what do you think about using them injectors

 

I have a SD car with a 412ci, AFR 195comp port heads, HSR on top and a XFI292 cam, T-56 trany and 3:73's, works pretty good in my opinion.

I run 30# SVO injectors and have plenty of play left in them and a Holley 58mm TB

 

Consider the intake manifold and runners to be an extension of the intake runners in the head. There are a number of factors that play into the optimum design of the intake runners for your motor. Some are the rpm requirements of the motor, the heads and subsequent air flow along with the cam. You need to do some research on intake manifolds.