I have aquired a 1991 truck 350. Does anyone know what compression, hp, head quality or anything about these motors? I think it is a roller motor and probably a four bolt main. After that, I don't know much.

 

you need casting numbers (rear of block and also near the valve springs) the block should be good but, the heads are often swirl ports = junk

 

are my stock 305tpi heads that swirl type.

 

It's a flat tappet, hydraulic cam, stock FWHP is 210@4400 or so, torque is 300 @ 2800 or so. Good place to start.
Tim sends

 

I thought they were roller motors. Do you know if those are swirl heads on my stock firebird 5.0 tpi like they say are on these 350 heads

 

They have roller blocks but are not roller motors. You can however use any type of roller set-up you want in that block without a retrofit. The heads on the truck are swil port 8.x compression garbage. The cam is also garbage. TPI heads are not swirl ports and are far superior to the TBI heads.

 

I am wanting to build a 355 with about 350-375 flywheel hp. This is a street car mainly. It will never be a daily driver, but I want to retain my upper 20,s fuel economy. I am running a 95 model six speed with a 4.10. I will run a mostly stock tpi system other than some port matching and smoothing.

 

acctually not all truck blocks are "roller ready blocks" I have come across afew original 350 tbi trucks that have the newer 1pc rear main seal center bolt heads but, lack the raised lifter bores and raised spiderplate holes. (this needs a visual check)


as stated above the tpi 305/350 heads are fine. I have been using tpi 305 heads for years on a 350/400 eng.s (they do have there limits but, are still better than the TBI-swirlports) it does help if you have casting numbers though

 

Yes you are 100% correct and I completely forgot to mention that disclamer. Most of the later TBI truck motors were roller but the eary varied. His '91 should be roller but a quick check will tell for sure.

 

thanks for the help. I'll tear it apart and get some casting numbers and we'll chat again.

 

www.mortec.com should help with the numbers when you get them.

 

great info, thanks again

 

You don't need to "tear it apart" to get the casting numbers.

The block casting number is visible behind the driver's side head, cast into the top of the bellhousing.

The head casting numbers are under the valve cover. You have to remove the covers, but you don't have to "tear it apart".

 

Pull the intake off, and look to see if you find a big "spider" looking thing holding the lifters down. If you do, its a roller block. If you don't see it, but you see three tall bosses sticking out of the center of the block without any bolt holes in them, you can make it a roller block.

By the way, I'm not sure if your intending to stick a tpi setup on there, but if thats what you are looking to do, you won't get anywhere near 350 to 375 hp. 300hp would be generous. You should get good fuel economy though.

Also, if that was a TBI motor, you can throw the heads away because they are junk, as previously mentioned. If you take the time to do the work yourself, you can get decent flow numbers (almost as good as vortecs) out of your 305 heads with some porting. Then you just enlarge the chamber slightly so you bring your compression down to where you want it, as I believe they have 58cc chambers.

If you want to look into the head porting thing, look up some old posts regarding the 416 castings. They may or may not be the ones you have, but are very similar. Sitting Bull, Vader, and a couple of others have some pretty good posts in regards to portwork.

 

I was thinking that a stock tpi 350 came with 240 hp. If you pump the compression about half a point, do some nice head and tpi porting, put a well matched cam, and adjust your fuel pressure I don't think 300 is a generous number at all. Just my opinion.

 

The truck engines came with trashy factory dished pistons. If you get rid of those in favor of a set of flattops, and use almost any hyd roller, and a set of 64cc heads, you'll have your 300hp.
Used LT1 hyd rollers are very affordable, and some used 64cc iron heads should be easy to find a good deal on as well. If you're on a budget and can't afford expensive pistons, cast flattops are about $70 a set.

Good luck

 

you'll have to get new rings as well wouldnt you?

 

Some cast iron rings would add about another $25 to that.

 

Not trying to start anything here, just want to point something out which I think a lot of people overlook, since it seems like your trying to build this engine with a certain hp figure in mind.

Its pretty rare (not necessarily impossible) to achieve 300 + hp at the wheels from a stock TPI setup (even with portwork). Now, people use the term tpi loosely sometimes. Just to be clear, I am not talking about the MiniRam, Superram, Stealth ram, etc...They are technically not TPI setups. Take a look at madmax's post ...

https://www.thirdgen.org/techbb2/sho...amese+manifold

Stupid link button isn't working right now, so just copy and paste that into your address bar.

He has 10.3 compression, ported L98 aluminum heads, 224/232 cam with about a half inch of lift, siamesed tpi, and headers. Something similar to what you have in mind I think. Take a look at his hp and torque figures. Hp falls short of 300 by a significant amount. Do a search, and you'll notice everyone has similar results.

Heres a popular thread with a Tuned Port 383....

https://www.thirdgen.org/techbb2/sho...threadid=84340

I'm not trying to say that its a bad setup in any way. Hell, look at my sig, I have something along those lines as well. My short block was originally a 350 TBI motor as well. I just think you should look a little more into how you want to reach your 350 to 375 flywheel hp figure, because the long tube runner design won't make it (unless you have a f.i.r.s.t. setup or something, but thats a different animal). A carb will make it for you, but forget about the driveability and bottom end grunt of a TPI setup. Maybe you should look into a Holley Stealth Ram. If you do decide to go with fuel injection though, it would be a good idea to start reading up a bit around the DIY prom board if you haven't already. There is a lot to be done inside a $3 chip.

Do whatever you prefer, I just wanted to point this out to you.

 

How could I imagine there'd not be confusion between RWHP and crank hp??

I was thinking that based on the factory 300hp 350 with 4bbl, 10.2:1 CR, and 929 cam, the addition of an LT1 roller cam would put it above 300 at the crank.
...Just to clarify things

 

Here are my general plans as I currently have a mostly stock 91 305 tpi formula with a t56 and 4.10 rear and love the performance. I plan on building this 350 truck motor with either 9.5:1 or 10:1, but no higher. If it does not have a roller cam in it now, it will. I have aquired a set of 86 tpi 305 heads as these 350 heads, I'm told, are swirlers. I also bought an entirely stock but complete 86 tpi setup. I may be overly optomistic, but I think I can push 350 at the flywheel without too much trouble. this is a street car and a highway cruiser. With my t56 and 4.10 I will still only be turning 2100ish at 80mph. That should keep me right where I currently am at about 26.5 mpg on avg.

 

Where did I confuse rwhp with hp at the crank? I'm not following you. I've labeled the type of hp (crank or at the wheels) that I am talking about each time I've mentioned something about it.

Look at the ZZ430 crate engine. 430 hp with a carb. Go stick a TPI setup on it. You have basically an L98 motor with the LT4 cam. Do you see anyone with 430 hp on a cammed L98? No.

Technically, the factory 300 hp 350 you are talking about won't work with the LT1 cam because it wasn't a roller block. For a moment though, assume that you can just slide it in. You'll certainly gain something, and I have no doubt you can achieve 300 hp at the crank with a setup like that. Heres the thing though... your talking about a 4 barrel carb, and hes thinking of a TPI setup. They are two completely different induction setups with completely different flow characteristics.

Do a search and look through other people's dyno results. Stock TPI doesn't get you very far. Do you see anyone running AFRs or similar flowing heads and a stock TPI setup? I never have, and its for the same reason I am telling you.

 

In my first post I was referring to crank hp, based on the specs of the 30 yr old 300hp 4bbl.
Later 92blue referred to 300rwhp and said it probably can't be done with TPI. I'll go along with that.
Originally I guessed that tubage was referring to crank HP, because he made a reference to crank HP in the 7th post on this thread. So I threw out the 300hp figure based on the factory 300hp 350, just for reference purposes.

I haven't see any dyno charts showing crank HP #s for TPI. But it seems like with some basic mods including a mild roller cam, and flattop pistons, headers, and some headwork it would be possible to gain 90hp over the 210hp flat tappet low compression truck engine.

I'm not trying to start anything either, I'm just clearing up the confusion. I hope.

 

I agree it can be done. I'll just have to keep you all posted. Thanks for all the input.