FireInMe17

I have a 1990 Camaro RS with just a pitiful 3.1L V6 in it right now, but not for long. I bought a 305 TPI out of a 87 Camaro IROC-Z that I'm going to swap into the car. I have the springs for the whole suspension, so I have that covered. I've tracked down a computer and a harness for a TPI setup too so I'm good on those fronts. What I don't know about, or need help with, is all the engine stuff.

Now, I'm not going to just be swapping in the engine and driving it that way, I want to spice things up a bit. And I know that a 350 would be the best thing I could do to a 305, but I want to build the 305.

I'm getting brand new Vortec heads for it, those from a 96-02 long block crate engine for a fullsize truck, and the cam to go along with it. I can't find the specs for the cam that I want just to know the duration, but I know that a cam like that would give me low-end torque which is a good thing for me, and thats what I want, but I want to know what the specs are for it, and what the implications of using that cam in a 305 would be.

Next comes the Vortec heads. I can't seem to find any CFM flow numbers for the heads, and I know that the heads, being from a 350, will need to be milled down to keep good 9.3:1 compression that a 305 runs stock in TPI form. I know that the heads have a 64cc combustion chamber stock, but I don't know what it needs to be, and how much milling would need to be done. And I know that I need to get the Vortec TPI intake manifold to make it work with a TPI setup.

From there, I have headers for the stock heads on a 305, but, will they work on Vortec heads? I know that the old heads have circle shaped exhaust ports, and some of the newer Vortec heads have D-shaped exhaust ports. I don't have the heads yet to know if they would work or not, so I'm wondering if I need to look at getting new headers.

I plan on running a full 3" American thunder exhaust with the 3" collector headers that I have, and I'm also getting that soon, next weekend. So the engine will be able to breathe, and its going to sound pretty good too I think.

The heads that I'm getting are fully assembled and have never been used before, they are right off the crate engine, but the engine itself has never been fired, same with the cam, and thats why I feel alright buying a cam thats already been installed. But fully assembled means that I have my valves and guide seals and springs, rockers and the whole nine yards. BUT, I want to get 1.6 roller rockers if it would work, and I was even thinking about LT4 springs, but I know that with using 350 Vortec heads on a SBC 305 that I need to watch my valve clearance. This is where most of my questions are, because I have no idea about this kind of stuff never doing any of this work before.

I know that 305's are known to have valvetrain problems, and when I tore down my 305 to the heads it had 4 bent pushrods so I want to get the best parts that I can for it to make sure that I wont have any problems with it in that respect.

Beyond that, I don't really have much planned for it, but I figure that with the computer I'm getting for it and with everything that I want to do to it, I should be pushing at least 260hp and 350ft/ilbs if I do it right, and or course I'm going to tune it up the best that I can get to get the most out of the computer.

The only mods the guy I got it from did was put 24ilb injectors on it, so thats what I'll be running.

What I want out of this engine is well, SBC power, and I'll get that with what I'm doing, but I LOVE low end torque for getting the car up off its feet quick, so thats why I think a truck cam will be great because thats what trucks are for, hauling stuff. I don't really like or want high RPM power, so again this cam should be good for it. The 24ilb injectors should give me a little boost, but will only be good if I can tune the computer for them, and get more use of them versus the 19ilb injectors that come stock with the engine. MPG isn't really important to me with this car, just as long as I can get 17 or so from it on the highway I'll be a happy camper.

So I know I've asked a lot but I would really really appreciate any help or insight to my plans, and I'm going to need it to properly build a 305 Vortec TPI, so any and all help is great guys. Thanks in advance!

Car as it sits:

FireInMe17

Anyone?!?!?

vetteoz

iTrader: (13)

Why would you go to the extra expensive. If you get a cam with the right lift you don't need 1.6's.
They are only for guys who what more lift and don't want to swap cams
Vortec heads are limited to .480 lift without mods


A 350 makes more power with 22's , some guys have 24's in TPI 383's
Why do you think you need 24's in a 305?

FireInMe17

Why not compliment a cam with better rockers? And I think I need 24ilb injectors because thats what the engine came with when I bought it, and I don't plan on getting the 19ilb injectors its supposed to have.

The cam I'm getting has a 191/194 duration or 414 intake and 428 exhaust, its for a full size truck, so its going to make all of its torque at low engine speeds which is great. Especially with a TPI only being good to make power up to 4500RPM, in a 350 this cam puts out its max torque at 2800RPM, and thats great for what I want.

zraffz

I'm confused... I understand what you are trying to do but if I was building a 305 I'd build a screamer instead of giving up all my top end power to gain the low end grunt of a larger motor. 305 instead of a 350 you are sacrificing more torque then you are horsepower; you're trying to gain back that torque but you're not going to see any more top end power. I guess it's all you can do to have fun in a streeted TPI 305 though.

That cam sounds good, what is the overlap on it? As far as 1.6 rockers, why not just go with a bigger cam and save the money? It's going to simulate a 10% gain over those cam numbers, you can run a larger cam and do the same thing.

FireInMe17

To be honest, I don't like top end power, I hate needing 5000RPM in my Camaro with the V6 to get going if I want to, I love driving my S10 Blazer with a 4.3L and only ever needing MAYBE 3000RPM to get going fast. My Blazer has that low end grunt that I like without needing to wind the engine up. Winding the engine up leaves something more to be wanted when I drive the Camaro the way it is now.

I don't know what the overlap is on the cam, but I'm using it with the heads its supposed to be with on a truck. Using the Vortec heads from what I've seen gives 40-50 more horsepower to a smallblock V8, and the torque numbers are up a good 30-40 ft/ilbs too.

So the way that my 305 was when I tore it down, it made 195HP and 295ft/ilbs. Hopefully with just the heads it will make 235-245hp and 325-335ft/ilbs, and the cam will up those numbers a bit more. Then I have headers and a full 3" exhaust to put on it to get me even more power.

All in all if I do this right my numbers will be close to a 90-92 350 TPI, if not better. But I think my edge will come from the Vortec heads and their superior flow rates over stock TPI heads.

I'm not really trying to gain back what I'm going to lose going with a 305 versus a 350, I just want to build a 305 to be a bit faster than all of my other friends that have 305's, and my one friend who has a 302 Mustang who says hes still gonna spank me, HA!

I guess I'll just forget my rockers and springs and go with the ones that the heads are coming from, that way I know it will all work right with the cam and not have to do any second guessing.

But what I still need to know, is with using 350 Vortec heads on a 305, if I just bolt them on I'm going to have low compression, so either I need to mill the block, or the heads, or possibly use a thinner head gasket. Stock, my combustion chambers are 58cc, and the Vortec heads have 64cc chambers. Do you think I could get away with just using a thinner head gasket?

five7kid

iTrader: (14)

That starts with valve springs. While I don't know the specifics of your engine's history, bent pushrods usually means the valves have been floated, which is caused by inadequate valve springs.

I guess I don't understand where you are getting these Vortec heads, but you said "new", and without any further information, I assume with factory truck valve springs. If that is the case, they are as bad or worse than stock 305 springs. They are the first thing I'd change on Vortec heads.

FireInMe17

Alright well that's good to know. I've heard that LT4 springs are good to get, would those be good? And by new I mean new off a crate engine that's never been fired.

vetteoz

iTrader: (13)

On a 350

Plenty of online CR calculators to work out difference

FireInMe17

Vortec heads added 40hp and 30ft/ilbs to the 4.3L in the Blazer in 1994.

FireInMe17

I'd love to use the online calculators to do the math myself, but I don't know all the specs to properly fill out the forms in the calculator. When I try to do it I get 22.5:1 as a compression ratio, and thats not even close haha

vetteoz

iTrader: (13)

But a 4.3 is 3/4 of a 350 ,
it has same 4.00" bore / 3.48" stroke so efficiency of chamber is same as a 350
305 has smaller bore

vetteoz

iTrader: (13)

So your a expert on how much HP it SHOULD make with a head swap
but you don't know the basic specs of your engine ( like what head gasket you are going to use)

In any case you are only looking for the CR difference between the two chamber sizes so ballpark figures will work to give percentage change in CR with larger head

http://www.csgnetwork.com/compcalc.html

FireInMe17

I have pretty much everything figured out except the cc of the pistons in the engine and the deck clearance. That's it and that's all that's holding me back from finding out my Cr.

vetteoz

iTrader: (13)

Std SBC is 0.025 deck height.
Just use a flat top (zero cc ) piston for doing the calc, you are only looking for the relevant difference between the two chamber sizes

Then do the 64cc head calc with a lower deck height to see how much you need to cut the block to get the CR back to same as 58cc head

FireInMe17

Ok thanks, that was a big help. I got .075" to remove to have a 9.35:1 CR, that will be good, but would it be easier to mill the block or the heads? If I mill the heads, wouldn't I have to mill the intake by the same amount too so it will seal right on the heads?

Mud

Someone check behind me on this. But if you mill the block, it would lower the heads. If you mill the heads, that will lower the heads too. I would think too that that would affect the overall valve lift too. I'm not sure, but .075 just seems to be a bit much to take off. I could be wrong. Also, I personally have never heard of anyone milling the intake to make up for the milling of the heads or block. I would think that would make the intake narrower, making the port facing further away from the head ports. My guess, is that you would need to have the intake ports matched and ported to the head ports after the heads were milled down.
Just my opinion. --Thanks

five7kid

iTrader: (14)

Uh, valve lift is determined by the cam lobe, not the distance between the cam and the rockers.

It may affect valve/rocker geometry, though.

Mud

You are right, what I meant to say was that by using the original length pushrods, then the valves would start lifting sooner and may not completely seat. I would think that milling the heads .075 would require having the pushrods shortened by the same amount.
just using some logical thinking.

five7kid

iTrader: (14)

Well, that is still illogical, because the rockers are adjustable. You would just screw them down .075" less.

As stated already, though, this may mess with rocker geometry, so that should be checked before assuming stock length pushrods will be adequate.

vetteoz

iTrader: (13)

Done all the time

http://www.practicalmachinist.com/vb...09/#post984014

http://www.chevelles.com/forums/showthread.php?t=38273

Exactly what you want because the distance between heads is reduced when block or heads cut.
If intake not machined, it is too wide and sits high on the heads so ports no longer line up
Also gap on the china wall at each end is too large to seal

vette9190

iTrader: (2)

You would have to have the intake side of the heads angle milled to to keep the proper angle to mate with the intake manifold

Mud

That makes sense. The reason I never heard anyone doing that before is because I don't have any peers that have custom engine work done to their cars. I took automotive repair classes 20 years ago and I guess I forgot some of that stuff. I am just now getting back into my love for cars and performance. Back in the late 80's and early 90's I had a nicely built '77 Camaro 350 until I wrapped it around a tree, and soon after that I started driving plane Jane cars. LOL. Man, I sure do miss that car.

Thanks for correcting my inputs, I defidently don't want to look like a dumba$$ when giving my opinion on motor work and all, but I guess its a little too late for that. I'll try to stifle myself unless I know for sure what I'm talking about.

Cheers

vetteoz

iTrader: (13)

Famous old saying

" 'tis better to appear a fool than open one's mouth and remove all doubt. "

88gunmetalgta

iTrader: (1)

The intake side of the heads would need to be milled only if the heads were angle milled. (likely, if the heads are to be angle milled, your machinist will correct the intake face too.)

I may be wrong, and someone will correct me I'm sure

Just something to keep in mind.


What TPI base will you be using?