Hey everyone, I'm finally making the switch from TBI to TPI. I'm running a 305 TBI LO3 right now and am to install an TPI system from a 89' LB9. I was thinking of getting some better stock style heads. Are the heads between the LO3 and the LB9 the same? And if they are can they be ported to flow?

 

LO3 heads are terrible. get a set of LG4 or L69 or LB9 heads, install 1.94 intake valves and port them. the valve job will need done at a machine shop, but you can port the heads. do a search for sittingbull, he has articles and has explain what to do.

 

i would get a set of lb9 heads they are the better of the 3 mentioned,, if you look at the compression ratio on the 1986 engines it goes like this lg4 305 8.6.1 lb9 305 9.5.1 1985 1986 both had the 9.5.1 cr after that it dropped to 9.3.1 ,,i don;t really no what caused it to drop, i'm still learning

 

that will make a nice power difernce over the LO3 heads(at least from 25-40hp)

also see if you can have them milled to bring it to 9.5:1 compression

i was gonna find a set of 86LB9 heads and have them worked but then was told that if i mill my heads down that i can make 9.6:1 compression

 

The LB9 heads are the same as the L69 and LG4 heads. 85-87 305's all had the same compression ratio cause they used the same pistons throughout those years and the heads were the same cc size.

As for heads, try to get your hands on a set of 87-92 LB9 heads. That way you don't have the hassle of having the middle intake bolts at the incorrect angles.

 

ia m an owner of a 1986 305 tpi trans am and i can tell you from my pontiac owners manuel that the lg4 had 8.6.1 cr,,i'm not here to argu but thats the fact

 

Ok thanks for the fact.

Go open some 85-87 LG4's look at the pistons and get back to me. We'll see how the 'facts' add up.

 

i would get a set of vortec 350 heads and have them milled to 58 cc chambers and get the sdpc baseplate which will need to be milled also.

 

what are the valve sizes on the lg4 1.74 compared to the 1.84 on lb9 engines ,wouldn't that be enough to change compression

 

Every LG4 that left the assembly line came with 416 heads with 1.84 valves, same as the L69 and early LB9. Period.

As for compression ratio, it's generally regarded that GM lied about the low compression ratio in the 85-87 LG4s. The early ones used dished pistons, but by 85 GM started using the same ones in everything. Pretty sure this has been verified numerous times, but with the search down, nothing i can do.

 

ed would putting 1.94 valves on my 305 tpi wake the car up

 

yes but you should also have them ported, 3angle vale job, shot pended, mangafluxed, and new springs and retainers. also have them milled so you can get a little more compressionwith stock pistons.
that along with a cam and headers will make a sweet 305tpi.
and runners new base and all the little mods would be a killer 305tpi.

 

really ? what is the deffination of a Killer 305 , cause I got most of them parts sitting here waiting to go in ( except the heads) ..... pick a close E/T

...... sorry man ...been couped up to long this winter , you got me dreaming about what my new combo is going to push

 

my guess is 13.70's @102 thats if u can get her to hook up good.(60'=under 2.0)
but my guess is 13.90's @99
also you will need to get some lca's and a panhard rod, these will make the car hook up in 1st gear.
making a 275-315hp is useless unless u can put it where it to the concrete. thats about 250rwhp and that should give you some nice #'s. you should eat up 350's ever now and again. nuttin better than beatin a350 wit a 305 they allways are like when u tell them its a 305, u also have to get some 3.73's in that rear

 

whoa! 13's! no way... i plan on the same thing... ZZ4 cam, SR heads, hooker headers and cat back, afpr. and if i get a really good job, hi flow intake and runners. if i go LT1 intake, im gunna go with the corvette alum heads.. then next summer im gunna go with a tranny rebuild, 2400-2600 stall, and 3.23's or 3.42's with a new posi unit... also a number of suspension upgrades... wow, if i get into the 13's with that, ill be happy... then ill have to save up for a roll cage.

 

i don't think 13's are as hard to reach as everybody makes it out to be. i wanna hit 13.9999, and i'm happy. i'm not saying he will hit 13.90's with just heads.
he gonna need-
cam, lifter, rockers, new base+runners,port plenum, pulleys, free mods, headers, high flow cat, cat back, lca's, panhard rod, relocation brackets, custom burnt ecm, heads reworked(1.94 valves, major porting and 3 angle valve job, along with milling for a litle more compression), a new perfromance 700R4, also make sure nothing else is wrong with the car, also some 3.73's and some sticky tires. good lanuchs(60' of 2.1) and i think 13.9 is possible.

 

those are not a good choice for the 305 ...... ya 58 cc is important but the combestion chamber is toooooooo big( too wide ) for a smaller bore ...... not really gaining what you think out of the heads

 

To run 13's with a fairly stock suspension you'll need to be trapping at 100mph +

 

thanks guys, one more question which cam would you go with 212-218 or 218 224 made from comp ,, remember it a86 305 tpi auto thanks again

 

That second one will be pushing the limit for a street car . What is the LSA's ? But I am going 208/221 duration @ .050", .474/.510 lift, 112 deg on my 305 so....... I haven't run this yet . I am told I can run it .....so I'm gonna . Let me know how THAT cam works for ya , and I'll do the same

 

hey guys some quick advice on cams. i am runnin a LPE 214/224. it is kinda rough. i am installing a converter becasue the stock one is a little tight. that is why i run a 14.82 @94mph with a 2.2 short time. the motor comes on strong at about 2000 till 5500 or 6000. i am portin my heads too. i like this cam alot, i think it makes great power, but i would not advise a cam any larger on a tpi car. if you got a carb, live dangerously. the 208/221 cam would be a great cam. i have messed with that on desktop dyno. my cam makes more power by a few horse, but the other cam woudl be a little better for off the line grunt. you may even be able to run your stock converter with that one. bottom line is, my cam is great if you got a converter. if you are gonna stay with your stock converter, i dont advise any more than that 208/221 listed above.

 

the 212 - 218 cam has 112 lsa ,,, the 218 -224 has 114 lsa,, this cam you need to change your chip ,heads and gears so it says in the comp article,, i think i'll go with the 212 -218 with the 112 lsa thanks guys