What do you think of these heads?

http://cgi.ebay.com/ebaymotors/SBC-C...QQcmdZViewItem

what about on a 305 TPI motor converted to 4 barrell carb w big HR cam and shorty headers?

 

Too much for a 305.

 

What would be a good head for a 305 spinning to 6500?

(can a 305 spin that high?)
(I saw 5k in the 305 in my boat in neutral yesterday)

 

Just cause you have seen your boat rev up to 5k dosent mean much. If you have a stock 305 I wouldnt try to doing 6500 or even 5500 for that matter. Unless you built the ***** out of the motor you have and your going to drag race it all the time and most of the engines life will be that high of an rpm I wouldnt waste my time look for heads to support it. Just go for some low buck after market iron heads and you will be fine.

 

Depends on the heads/cam combo. If you only make power to 5k why spin beyond it?

 

You need to make the combination work together. Those heads on a 350 would require a cam and intake that goes to about 6500 RPMs. On a 305, 6500 would be minimum, and you'd have absolutely no low end - it would be horrible to drive around town.

What 305 do you have? You don't give squat info on your car or engine. "Big HR cam" means absolutely nothing - need specs. Ditto headers - if you've got Flowtechs, that's a completely different story vs., say, SLP 1-7/8" shorties. Need info here.

Rods will be the problem with spinning a 305 to 6500 - specifically rod bolts. If stock, you're pushing it. With ARP rod bolts and resized rods, good balancing, 6500 is a piece of cake. Of course, the next question is why you'd spend that kind of money on a 305 - to be "different"? That's the typical misguided motivation.

416 or 081 casting heads, ported with 1.94"/1.60" valves, very good valve springs, a Comp XE274 cam or something similar (not a "Summit special"), Performer RPM intake, 1-5/8" primary shorty headers with a good 3" exhaust on back, will be a good performing 305. You'll need stall/gears to go with it, of course.

 

This is really good info here because despite having (paid for shops to have) built several big roadrace motors I have never done a street motor so I have a warped frame of reference
I'm used to motors that spin to 7500 rpm and can stay there all day, (377s) and 415 strokers that shift at 6k.

I appreciate the reality check and appreciate your help to bring this concept into line.

What I'm starting with is a bone stock 1991 305 TPI motor.
My first project is to swap the 700R4 and put in a T5, second project is a 3.42:1 disc brake rear that I have in storage, (unfortunately, in a diffferent state). I will also be adding SFCs wonderar, stb, 4/6 boint roll bar, prokit, shocks, possibly replace front bushings, sway bars, adj LCAs, (My 10 bolt has LCA relocation brakets, it's off my 3rd gen racecar) PHB eventually camber plates... etc

I'm 43 years old and don't much bother with driving stupid around town, I have owned and successfully raced a couple of Chevy road race cars and will be taking this car for hot lapping at the west coast tracks from SIR down to Laguna Seca and that is where I want the performance to show up when the rpms never drop below 2500 rpms, even if it dogs a bit around town.

**The goal is to find the power curve that fits this motor and will make me happy for a while with minimum cash outlay, until I build my next exotic motor.

my performance expectations is based on a mild build up 355 with SR torker heads and a big flat tappet cam, power band from 2500-6500. there was zero performance, total dog at 2450 rpm and at 2500 it'd go ZING to the redline. the trick was never letting the RPMs drop on the track.

First queston.
I have read that the post 86, one piece rear seal block is called the roller block.
Does that mean that 1991 305 TPI motor came with a roller cam, or is that not at all accurate?
The XE 274 cam you reccommended is a flat tappet cam so it brings my above notion into question.

I don't want to go into the bottom end or pull the motor out of the car any further then to pull the timing cover and swap the cam in.
I have no noble plan to build a 305 to be different, I'm looking for the best cheap parts to make it come to life and act like a Chevy V8 and be fun to drive for a year or so until I'm ready for a real motor.

I don't know about cam specs but I do know about driving them.
I was picturing moving the RPM band up to 2000-2500 on the bottom to get up to 6500 on the top. I don't know where peak torque would be but that's where I shift when I'm on the track.

I don't typically race around town, I drive very conservative in traffic and don't mind lugging at 2000 rpm and when I need to get up and go, downshift and stuff the peddle.

Soo I can't give you cam specs because I don't understand them, I' ma driver, not a wrench but I can swap the cam and heads, I just cant time or fine tune anything.

My plan was to put in a hydraulic roller cam tha twould move the RPM range up higher but if 6500 rpm is unrealistic on a stock bottom end then tell me what is realistic?
I had planned on going to a Wieand stealth dual plane which really do work up to 6500 rpm with a 650 carb but if we are moving the RPM range down much it might work to keep the TPI.
What is a doable RPM range on a stock 305 bottom end?
I will probably use Pacesetter midlength headers w 1 5/8 primary and 3" out since they retain use of the smog pump and I want this motor to be smog legal for a year or so until WA figures out it's new smog laws

Maybe add a 16 lb flywheel with a dual friction centerforce clutch when swapping trannies.

So what is the common name for the head you described?
Is it a stock ported head from this motor or like an L98 AL head ported? what is the common name for that casting?

With your heads and a HR cam range that fits the usable RPM range of the motor w stock rod bolts etc, where does that put the HP and RPM range? Where is peak torque?

Thanks
Evan


So

 

The T5 is a pretty weak transmission. It won't last long under hard driving conditions. In 86, chevy went to a 1 piece rear main seal. In 87, the blocks went roller.

TPI is 20 year old FI technology. It sucks. Don't use it.

 

In the original post you said you're going carb. I'll assume that's still the case.

A T56 is highly superior to the T5. Take a look at that before you spend any time/money on a T5. The LT1 T56's bolt to the Gen I engines.

Get a factory roller lifter style cam. Something in that 260-ish to 270-ish duration range. Port your stock 081 heads, have 1.94" intake valves installed (and 1.60" exhaust it you feel like it), Performer RPM manifold, 600 double pumper Holley, I think you'll be happy.

 

I would also recommend reworking your stock TPI heads. I;d go with a 1.94" intake valve and a 1.5 or 1.55" exhaust valve. They will need a full porting job not a "pocket porting. Another good head to rework and use on a 305 is the L-98 ZZ4 350 aluminum corvette TPI or ZZ4 crate engine head. the stock valves are fine. needs full porting.

Another very good head is the GM L31 350vortec head (requires a vortec manifold) should be milled to reduce the chamber volume. A little exhaust porting is nice.

A Isky Hyd roller #RR265/272 PN#211265/272 combined with a split 1.6/1.5 rocker set would work very well with what you have planed.
The GM "LT-4 HotCam" w/1.6 rockers would be a good choice also.


I would cc the heads and mill to reduce the chamber size and combine with a thin head gasket to get the measured cr as close to 10:1 as possible.

With a overdrive trans like the T5 or T56 I would use a 4.10:1 rear gear.
use a 750cfm carb. Use a manifold with a fully divided plenum.

 

THis is all very good advice and I appreciate it very much.
I used to road race fender to fender with a T5 behind a 355 ci race motor and very comfortable with thier abilities and limitation.
Since their is no launching I think we will be ok for a while. In hotlapping the key is to be smooth and not upset the car so a ginger tranny is not too much trouble.
also Since the car is a 700R4 swap I need all the stock swap conversion parts and it's a cheap way to start. The 3.42 rear is already paid for so it's a start also. When the trannny breaks I can get a T56 or TKO 600.
Rear end should be fine, maybe need a new posi unit.

I will olook to have the stock heads worked as suggested above and work w the cam reccomendations.

So, ya'll think carb over TPI still?
What RPMs would the above package spin?

Thanks
Evan

 

Fully divided plenum? Care to share why? I'm always here to learn.