Is it a good or bad idea to put 350 heads on my 305 tpi? Is it possible?

I guess my 1988 305 tpi with a th700-r4 tranny has what you guys call a "peanut cam", will it help to install 1.6 roller rockers?

 

It would lower your compression.Thats not good. The 1.6 rockers are a better idea than the heads even though they bolt right up.The heads need work to help out the 305.

 

So will the 1.6 rockers do much difference?

 

Yes they will make a diffenece,but will do better with a cam and other mods. The rockerarms will be a great investment espeially on down the road.

 

350heads have a larger chamber. It will lower your compression ratio.
Y not just upgrade your 305 heads to 350status with larger 350sized valves and some home port work. the stock ports are the same on both heads.

Don't be a wimp....

If you want a larger cam, get one. There ae many bolt in hi perf cams to choise from that are designed to upgrade your 305 tpi motor. You have a hyd roller setup. You can reuse your stock roller lifters.
You'll need a cam, new valve springs and likely a new timing chain and gear set.
1.6 rockers will only get you about 2 to 5 hp with the peanut cam. You're not going to notice the gain. Don;t waste your time or money on this one. Buy a real performance cam and keep your 1.5:1 rockers. We're talking 50 hp here, with the right cam. not 5.

And you'll end up with more lift.

 

I am sure there is a thread on this in hear somewhere talking about valve shrouding . Or something like that .


measure the width of the combustion chamber on the heads ..... bigger than the 305 bore I think . Someone will probably chime in on this ( hopefully) . SOmething about how it hampers the flow into the cylinders . So any gain you get in the head flow #'s ....is lost by the sharp redirecting needed to get the charge in the cylinders




...... I ain't no authority .....I wanted to do that to my 305 ....and read that thread somewhere. Makes sense to me .

 

Even if you don't deshroud the 305 head after installing larger valves, it will out perform the stock head.
this is especially true on the TPI 305 head (081).
The width of the chamber is not where the deshrouding is needed. The flow is not concentrated there. the chamber needs to be deshrouded near the plug boss not at the side of the chamber.
get a head a squirt some water with the garden hose through the port and watch where the flow is.
You only need to widen the chamber just enough to slide the now larger valve in so it clears the chamber wall.
Some one needs to do a tech article on modding 305 heads cause there is a lot of disinformation and bull^&^% floating around.

 

They didn't make any noticable difference on my '86 305. The only benefit they provide is that the roller tips reduce valve tip friction and stem side loading.

For the money you'd spend on a decent set of 1.6:1 rockers, you'll almost have the price of a camshaft covered.

 

Like I said 1.6 rocker arms with a cam and other mods.Just rocker arms with no intent to do anything else really is a waste of money.And it would be good if someone did do a tech article on 305 heads, but not on l03s.

 

oppps I feal I have used the wrong words .....what I ment .......


the 350 heads ......don'y they kinda overlap the cylinder bore(exposeing the head gasket to the combustion ? ) ......so they impead the flow ? I am actually going to have my 081 castings " hogged out " by a person you recomended on an email ( or PM I can't remember ...twas a while ago ) ...... I am a believer of the 305 heads........... Just the guy who started this was gonig to put the 350 heads on his 305 ...... so that was what I was commenting about .


is it a good idea to put 350 heads on a 305 ?


thanx

 

Not its not a good idea. The chamber is bigger and would hang over the 305's bore.

Lower cr too.

 

Here are some 305 cylinder head modifications: Lowering the chamber volume will yield you higher compression, you will gain one compression point from every 5.5cc reduced from the chamber. BEFORE you spend alot of time porting and polishing you need to match the intake and exhaust ports together using the gasket as a template. Blend a 1/2 inch in from the port with a grinder and 1/2 inch under the valve into the pocket. Enlarging and matching the ports with the gasket will give as much if not more power than a port and polish. This is because blending and enlarging the intake ports will help with volumetric efficiency which will in turn add more torque, which is what we drive with in town. Try to have the exhaust ports shot with beads to help suspend the mixture.
Porting will usually only help with top end breathing and a increase in flow potential will not always lead to increase in horsepower.
1.6 roller Rockers will help out with your engine. It will, as said before, reduce friction and wear and add additional valve lift. Some people have it in thier minds that just because something doesn't make you go alot faster it must be a waste of money.
If you decide to buy a camshaft, and it is daily driven, try to get a shorter duration with a high valve lift. You'll have a good idle with plenty of low end response without having to chirp the tires to get the car going. More duration does not always mean more performance, effective timing and valve lift are just as important. Make sure that you get new shot-peened and hardened push rods to avoid premature camshaft wear. You'll need new matching valve springs unless you can make sure that they would match up with the new cam's profile. To stiff and they can lead to premature wear, to loose and you will get valve float.
Tibo

 

Thanks fpr all the answers , i think i will only change to roller rockers for now but im hopping for a new cam, but idont have a clue how to change cam, is it hard???

 

Hard?? no not really. A lot of work, yes.
Will take you all day.. Alll day to do a cam swap.

You'll need a Harmonic balancer puller to remove the harmonic balancer. Some auto parts stores have a loan- a- tool program
where as you can borrow specialized automotive tools like this.

A balancer installer is a good idea too.
You will have to remove and replace the intake manifold, valve covers, water pump and timing cover gasket and front seal.
So you'll need these gaskets in a "cam change gasket set"

 

Its possible to do this if i remove the front, radiator and all that stuff, right???

 

Yes the radiator, air conditioning condenser and a body brace or two needs to be removed to allow enough room infront of the motor to slip the camshaft out.

 

There's also a special tool to take the cam out of its little nest. Forget the name, but its important too. I did this, it took a weekend because my friend and i were lazy. Wish i had done rockers too...

~Matt

 

No special tool needed to remove the cam. Just take the chain loose pop the gear on with one finger tight bolt and your GTG.

 

Really? My friend's dad had a special tool for pulling out the old cam and putting the new one in. I forget the name, but I think maybe it was more important for installing the new one than getting the old one out. Can't remember...

~Matt

 

What cam should i buy?

 

I'd suggest a comp cams XE, but i'm no expert. It all depends on what you want and what other mods you have planned.

~Matt

 

Call the cam manufacturers up and tell them exactly what you have and what you want. here are their phone numbers. I recomend Crowler Cams.

Crane 888-432-2381
Crowler 619-422-1191
Comp 901-795-2400
Tibo.

 

Thanks Tibo, i can use those numbers too.

~Matt

 

Would changing the cam require retuning the computer? I already have a Hypertech chip in my 91 305 TBI.

 

I don't know about the aftermarket chip, but i installed a new cam and just adjusted the timing and the rockers. I didn't touch the computer, although I wish I had taken it out along with all my emissions crap

~Matt

 

the only heads that'll fit the 305 are the 8113/alum. L98 heads, and the sr. torquer 305 heads. i haven't found any other heads for the 305.