I've been thinking about this lately, and I'm sure someone else has gone through this before. My current 305 TPI is a roller of course, but I have access to a free complete flat-tappet 350, pre-85. I don't want to take the easy way out and stick a carb on it and call it done, because it's still a cruise around car. I also have all the Moates tuning equipment for it.

So here's what I'm wondering. Since naturally I'd be using the flat-tappet heads to go with the block, will my TPI intake come close to bolting up? I'm not at all interested in doing the retro flat-to-roller swap, as that would probably cost me more than going out and finding a roller block. If possible, I'd like to use the 350 motor I have, since it's free, and I know what it's been through. But I'd also like to keep my TPI.

This is the last obstacle for me swapping to a 350. New knock sensor, ESC, injectors, and a chip burn are no problem. Thanks for the help, I'll continue searching in the meantime.

 

Why?

 

Correct me if I'm wrong, but I recall reading somewhere that the heads wouldn't bolt up the same. Also because I didn't think roller heads would work with a flat-tappet cam.

If my 305 roller heads will bolt right up to the 350 flat-tappet block and work with the cam, then by all means, I'll do that. I was just under the assumption that option was out because of the different cam styles, without retrofitting of course, but like I said, I want to stay away from that path.

 

Use the LB9 heads, IF the 350 has dished pistons.

 

Consider yourself corrected on both counts.

Yes your heads will bolt right up. No retrofitting necessary. Only thing to watch out for is self-aligning vs push-rod-hole-aligning rockers.

 

According to my dad, they're flat top pistons. Where does that leave me? Also, which should I be aiming for, self-aligning or push-rod-hole-aligning? I'm assuming self-aligning, but doesn't hurt to make sure. Will the stock 1.5 LB9 rockers work? I'm not sure what they came as factory. But just to clarify, the 350 block is pre-85.

 

Don't forget the pushrods are a different length.

 

Use whatever is on whichever heads you use. One, AND ONLY ONE, alignment system must be in effect; IMO it's not real important which, as long as all the parts are in agreement.

Push rods themselves go with the cam type... since roller lifters are MUCH taller than flat ones (roughly .400"), the push rods are correspondingly shorter.

 

So if I use roller heads, roller lifters, and roller push rods, I assume I'll be using a roller cam. That brings me back to using a roller cam in a flat tappet block. Isn't that retrofitting? Also, since the pistons are flat topped, where does that leave me? Thanks so much for the input!

 

Your confusing yourself. If U use 305 heads and 350 everything else,
Rockers will depend on the head or rocker itself.

I personlly wouldnt waste the time swaping (unless its a roller 350) because you most likely wont gain enuff to make it worth it, unless you upgrade the cam and stuff.

 

No such thing ; the heads don't know what cam is/was being used
As stated all you have to do is correctly match up the components;
cam ,lifters ,pushrods and timing set when swapping from one style to the other

 

I am still somewhat considering looking for a roller 350, but it pains me to let this one go to waste. It's literally a free complete motor, and it's 100 ft from my Firebird as I type this. The fact that it's available and I know what's been done to it is a HUGE factor for me.

I am planning on upgrading the cam, along with porting the heads, runners, plenum, and intake. Anyways, when you say use 305 heads and 350 everything else, does that include a flat-tappet cam aswell? I only bring this up because you mentioned 350 everything else. I am indeed confusing myself

Now that I think about it, what sort of a compression ratio am I looking at with LB9 heads and flat top 350 pistons? Is it too high? I ask this since Atilla said use the LB9 heads IF the 350 has dished pistons.

 

So use it.
You are just confusing the issue by talking about cam types when all you do is use the cam type that is in the engine you want.
End of story
Your heading implied you were wanting to change cams in a certain engine ; not complete engines

Read my lips
the heads don't care what cam you use.
Only relationship between the heads and cam is if the valve springs are suitable for the cam lift you want to run ( when you upgrade the cam )

 

My first post I stated pretty clearly I was swapping in a 350 in place of my 305, hence the post under Engine Swap. I do want a cam upgrade (ofcourse) in the near future, but this was about getting the motor swapped first. But thank you, that really cleared up a lot.

Any info on the CR of LB9 heads on 350 flat top pistons?

 

"Flat top" pistons cover ALOT of ground.

How many cc's are the valve reliefs? How far "down in the hole" are they at TDC? Stock, they were .025" below the deck; virtually ALL cast, MOST hypereutectics, and ALOT of forged, add .020" to that... the pstons are .045" or more below the deck at TDC. I guarantee, if you leave that out of your "calculations", no "calculator" in the world will EVEN GET CLOSE to reality.

There's no such things as "roller heads". Heads are just a chunk of cast iron. Nothing in there to roll.

 

I honestly have no idea about any of the measurements on the 350. It'll be a few weeks before I have the space to tear into the motor. Just looking for a ballpark figure I guess. As long as I can use pump gas, whether it be 93, 89, or 87, I don't mind, It's not a daily driver. Still in the planning stages to see if this 350 will actually work, then I'll really dive in and get to work once I have the space.

 

What got completely lost here is what heads are on the pre-'85 350. Most factory 350 heads are performance junk. Get the casting numbers from the heads (located under the valve covers) and post them. Check both heads - not uncommon for engines over 25 years old to have a head changed on it. It's a fair bet yours will end with 882 or 624 - guess what - large chamber, crack-prone junk.

Some other details not covered:

'89 TPI will have the center two intake base mount bolts on each side at 72 degress. '86-earlier factory heads had all intake mount bolts at 90 degrees.

'89 will have 1-piece rear main seal, which has a different bolt pattern than '85-earlier 2-piece rear main seal. You'll need a 153-tooth 2-piece RMS flexplate (simple solution - get one for '82-'85 f-body V8).

'79-earlier SBC's had the dipstick on the driver side. Not a problem if you have headers, but stock exhaust manifolds and the dipstick tube try to occupy the same space with earlier engines.

And, since you didn't say how much earlier than '85 the engine is, '68-'74 350's didn't have hardened exhaust valves and seats for unleaded gasoline.

AND, one last consideration - casting and machining quality on 70's and early 80's 350's sucked. It's practically a given that 1-piece RMS era engines are higher quality than 2-piece versions.

 

Putting protect-a-boot's on my wires today, I'll pull the valve covers and look when I do, I'll edit this when I look.

This is what I was worried about in the first place, but if I use the 305 heads, I won't have a problem. If when I post the casting numbers and the 350 heads are better, then I'll tackle this obstacle.

Did not know this, I'll look into getting one after I get the head cast numbers.

No worries here, as I have Hooker 2055s.

I don't believe it's quite that old, my guess would be early 80s. I'll look into this aswell.

Along with this, it would be much easier with a roller block anyway. I (hopefully) wouldn't have to post if I had a roller block, as a knock sensor, esc, injectors, and a chip are fairly straight forward. But just because it's free this way and I know it hasn't been beat on, you know I have to try this route first. If all else fails, I can pick up a 350 roller from a junkyard, but why do that if I have one sitting in the garage?

Thanks so much for all the help five7, nobody even mentioned the flexplate before. Little things like that are what worry me about this swap.

 

Last three digits of the 305 head casting numbers are 081.
Last three digits of the 350 head casting numbers are 882.

Researching these gave me 58cc, 1.84/1.5 valves for the 081, and 76cc, 1.94/1.5 valves for 882.

Also, the dipstick is on the driver side, so it is earlier than 79.

So assuming I go with the 882 heads, how would I solve the issue of the two center intake bolts at 72 degrees?

 

If the 350 is stock, I would bet the dollar bill in my pocket that the 305 has way better buttt-meter results.

 

The 305 heads are not ideal, but they are WAAAAAAAAY better than the 882s.

 

You elongate ( slot ) the holes in the intake manifold just like the aftermarket intakes do ( so that one intake part # fits both style heads )

 

What evryone is trying to tell you is, ditch the smogger 350 idea. Your going backwards if you use it.

 

From a sticky in the Engine Swap forum:
I realize that this combination is not ideal, but it's what I have to work with. Of course I'd like to go out and buy a roller block and a good set of heads. But that takes money. It doesn't grow on trees. By using this pre-85 block, I've so far totalled $44 in cost, being flat-tappet specific. Of course it will cost more with injectors, gaskets, knock sensor, esc, etc. But those will cost me money regardless of what block I use. $44 for a brand new flexplate, compared to a few hundred for a roller block that I have no idea what's been done to it. That's quite a difference in my opinion.

I'm not trying to make a monster here. This isn't a full blown race car. I'm shooting for maybe 12.80s at best? Time and time again I've heard "pull that 305 and drop a 350 in there, you'll be much better off," and now "you're going backwards by putting a 350 in there." Really?

I know the heads aren't ideal. But I'm working with what I have. I already have plans to port them along with my runners, plenum, intake. I also plan on a cam and a decent gear out back. I appreciate the help that a few people have gave, especially five7kid, but I don't appreciate posts that say "it's a waste of time" without offering an alternative.

 

There is a difference however. That 305 you have and that 350 are not near exact twins with a simple matter of displacement. If you said it was a 84 flat tappet 305 and you were replacing it with a 84 flat tappet 350 then go for it. Otherwise, skip.

 

I hate to say it andrew but the more research I do, I personally think that if you want to make positive power and have the $ and patients, build up that 305 or get a 350 Tpi bottom. Don't always fall for the Cubic inch rule as there is ways arround it. I proved that. I just would hate to see you put $$ in that 350 and not get where you'd like to be in the 1/4 mile. 12's are not as easy as they seem. 13's were easy in my car, but my 12 second goal is costing more and more $$ to get there. Its still cheep in the read world but for us young (weekend) gearheads it adds up. But this is all your choice to make. Ill help man as much as I can when you start tearing into it. Its your car not anyone elses so keep that in mind. Do what you want and don't let other stray you off. People dogged me many times about building a V6 up and $1k later im pushing 300hp. I literly rasied my Horsepower level by over twice the baseline power and im not done yet! I just took what I had in front of me. A little 3.1L V6 and gave it what it wanted. People still down me for what I did but oh well, I love what I did. And when you decide what to do, do it, then have fun in the car, you will feel great that you did what you wanted (just hopefully you make some power gains that are very noticable since it will be engine swap)

Im no V8 guy so Im sure others know that but if your aiming for a goal look at all the possibilities to get to that point. I personally went with just building the motor I had and just making HP to get there as it was logically easier for someone like me to get the power I wanted. You know my little car has some power considering. So just look at all your options. I know you don't plan to get into the work till this winter so you have plently of time. Reasearch and research some more. Took me about 1 full year of reading here and there to able to commit to what I did with my car. For alot of us this is a hobbie and not a job related skill. The last thing you want is to be stuck in deep on a project and get lost along the way. I know your already doing research so just keep at it buddy and you will know what you want and what your capible of come fall. No worries.

Consider building the engine of your choice(be the 305, the 350, or a different 350), but also the suspention in the process, that is something I didn't do and which I would have done first. Getting the power down and having that trans put out good torque manipulation is a wounderfull thing.

Just my 2 cents on the thought in general. Sorry its just talking and not much info really, but I personally don't know much of anything about chevy V8'sAnd I just wanted to chime in.

 

I am not sure what you were saying to me? I was not saying a flat tappet bigger cubed motor was faster, I was saying I bet it was slower. Bigger cubes but being an identical twin yes. In other words.... Roller 305 > flat tappet 350 and roller 350 > flat tappet 350.

 

Im sorry man I ment, andrew as in phoenixfirebird, Thats his name as well. He's a good friend of mine.

 

[quote=PhoenixFirebird;5316[/quote]

leaves you around 11.5:1