Okay guys, i have a question for all those who know about cylinder heads. I need some suggestions. Would it be better to just take my L98 heads and machine them out to 1.60/2.02 and a set of 1.6 rockers arms thrown on or buy some heads from Summit or whatever. My question is i want to run a 9.8:1 compression ratio, so these heads are like that anyway. But would it be less expensive to do the CNC work on them or just buy new aluminium heads.

And as far as my rotating assembly goes, what does the plus or minus cc on the pistons means? So if like I buy a piston with +7.00cc, does that raise my cc chamber to 71cc? please help guys.

 

It depends on the shop and what all is done to the head, but after a thorough clean up, valve job, valve resizing, etc, your looking at probly near half the cost of a good set of cylinder heads. Depends on how much you have done tho and what the shop will charge.

Now its gonna depend on your motor build plans tho. How much power you looking to make and what size motor is this going on? stock L98 or mild 350-355 builds may be ok with fresh L98 heads. However, hot 355-383+ motors will want more flow and larger runner heads adn the L98 is not a good choice.

If you ever plan to upgrade down the road, its best to get the heads now so fork out the cash for a decent aftermarket set.

if you go aluminum heads now, bump compression up for sure, in the mid 10's is always nice. Aluminum heads need compression to make same power as iron since aluminum dissipates heat faster than Iron.

+ or - cc's of pistons usually refer to dish or dome pistons. its confusing as some places call +7cc a dome but others call it a dish. Some places call -7 a dish.

Either way, a flat top with valve reliefs will always have more total volume in the cylinder so therefore it has less compression than say a dome piston. Compression is just a ratio of volumes. For mid 9's to 1 on a 64 cc head you will want around a 12cc dish piston. flat tops in the 5-7 range usually bring compression closer to 10.0-10.3 to 1 on a 350-355 and thats abit high for Iron heads

 

After reading posts by Orr89RocZ for years now, I'll concede he certainly knows more than me, but I wanted to clarify something that might be missed. Orr, by all means correct me if you disagree:

BUT....the OP mentions only machining to accept the larger valves. Essentially NOTHING would have improved except for the larger valves. First off, L98 heads aren't real great to begin with, and without additional work, (which hasn't been mentioned) I think the larger valves do nothing but slow down airflow since the heads don't flow enough to keep up velocity.
Doing that additional porting work on iron heads will QUICKLY run the bill up.

My two cents is that iron L98 heads are either stock....or boat anchors. Yes, ultimately goals and budget will tell, but it's just my opinion. When I upgraded to my ZZ4 cam, I just couldn't afford new heads. I had the stock 1.50/1.94 valve job and valve train done, and that was it. Budget dictated that was all I could do, but never again would I do a head swap and NOT do new heads. In hindsight, the additional cost, for all my wrenchin' that had to be done anyway....would've SOOOOO been worth it.

 

Okay this is useful. Now, i want to run a mild built 350. My mech keeps telling me to do a stroker and i dont want to. Can someone please recommend me a good bottom end kit and heads. I just want my ****ing firebird back and now its pissing me off, cause hes had it since the begging of january and didnt do the tear down til the beggining of this week.

Things I Need to know/have:

1. Will my block be okay for a mild 350 build, or he said for 150 I can have his 4-bolt main 1-piece rear seal block.
2. A good rotating assembly for a mild built 350
3. Heads, something that will keep me in the comp ratio range and allowing me to use pump 89-91 octane (if thats possibly)
4. A cam with good mid range and some top-end power (1800-5500 powerband)
5. A GOOD 330-350 hp @ the wheel motor.

Can you please recommend me some products, im so ****ing pissed off its not even funny.

PS. i will be getting a BBK 58mm dual throttle body and slp runners. Oh and the price range of parts if we could keep them below 2800-3000 that would be awesome.

 

Yes. 2 bolt mains are just fine unless you start to get crazy. Not saying 4 bolts mains aren't better, and the 1 piece seal is nice too, but you're on a budget, so I'd say no to the additional cost.

Stock replacement. You don't need anything forged or crazy like that. Do you actually NEED a new rotating assembly? What happened?

OK, we're starting to creep over into the "if you're gonna do this, ya might as well do that" category. ...Dangerous waters are these....
I'm not gonna recommend a head, since there are an unbeleivable amount of choices from mild to wild, cheap to outrageous, etc. etc, and so much of it is preference. I've been reading and wrenching for well over 10 years now, and every choice has a "but" attached to it. Are you planning on future upgrades? Plan of selling the car or engine ever? Are you gonna stay TPI, or go with another EFI intake? Not trying to overcomplicate it, but there's really no way any of us simply give you a part number and be "right"

Similar issue here. Sooooooo many variable. Keeping with the mild/budget theme, I personally chose the ZZ4 cam. I knew it could be used without reprogramming the computer, I bought it cheap with about 1 hour on it since it's common for guys to take 'em out of their stock ZZ4 crate motors, and I knew it was "good enough" to justify doing. No point swapping in something hardly any bigger than what you have, right?

We'll get back to this one....

The 58mm throttle body is too big for what you're looking to do, don't waste the money. You'd be just fine with your stock 48mm. Either way, it's an EASY upgrade later. No need to do it now if you're on a budget and looking to get the car back up and running ASAP. The SLP runner are good, but like almost every other part, they're only as good as the whole package. The runners really need a better manifold like Edelbrock's or TPIS large port TPI manifold. No sense getting better airflow through the runners, only to choke the airflow at the manifold. ...and IF you decide to do a new manifold, then you could buy a vortec TPI manifold and open up new head options. See, this is the "if you're gonna do this, might as well do that" thing I was talking about. Me and my friends typically start talking about changing oil, and next thing you know, 3 guys are all greased up and the whole top end is pulled off. It's just the way it is.

OK, there are a thousand options, but I'm gonna walk you through what I'm planning. I'm making NO such recommendations to you, but I'll explain why I'm planning on doing it, and you can take it for what you will.

First of all, I LOVE the look of the TPI. It's NOT the best by any means, and there are cheaper and better options. I like it, so I'm keeping that long runner style. Plus it's relatively easy to upgrade since fuel rails, vaccum lines, nut bolts EGR, wires, etc. don't need to be re-arranged. OK, so I KNOW that at least for ME, I'm keeping the LTR (long tube runner) TPI.

Second, I know I want it to flow better, so that means runner and a manifold. Best outta the box, and most costly is TPIS. Cheapest, and highest flowing once ported is probably SLP. Also look at Accel or edelbrock. All are better than stock. I can choose a Scoggin Dickey/Edelbrock Vortec TPI manifold that allows better airflow, AND allows me to use Vortec style heads. (vortec heads need vortec manifolds). Vortec heads are pretty darn good heads and pretty cost efficient. Not the BEST heads ever, but darn good bang for the buck.

Cam. Well I wanna go a little bigger than the ZZ4 I have now, but not by a ton. I like that it's easy to tune, sounds good, runs and drives good etc. etc. I'll go a little bigger, but I haven't picked one yet.

So. I'm gonna use my stock 2 bolt main block, have it machined .030 over, I'm gonna get some vortec heads (not sure which yet) a vortec TPI manifold with TPIS runners since they look closest to stock, and then find me a cam similar to a ZZ4 cam.

SUPER rough numbers from the Summit catalog in front me show a Blueprint Engines 355 2 bolt shortblock for $1500. You're probably lookin' a good bit less from your mechanic to get to the work done.
Vortec heads: $800 ish
Cam: $200 ish
Manifold $450 ish
Runners (slp) $350 ish
Keep in mind these are just estimates, and of course no labor, and shop supplies like fluids, hardware, gaskets, etc. etc. etc. .....this project ain't cheap.

...and unfortunately, this won't get anywhere NEAR low 300 HP at the wheels. The TPI intake is just too restrictive. Yes, you can throw great heads and a big cam and some tuning at it, but it'll still be underpowered compared to what a different EFI intake could do PLUS you're looking at more cost. PLUS, more power strains all the other stock parts too. I blew my trans in under 500 miles.

Man, there's just no easy answer. I feel your frustration, and I wish I could be more help. Good luck. Keep us informed and READ READ READ. TGO is one of the best tools you can use.

 

well lemme me tell you, i to also love the look of tpi and it came factory on l98s so im staying with it.... I have a fully hogged out aftermarket tpi system that pulls all the way to 6 grand with stock unported iron l98 heads and this was on a 350 engine..granted i had a 2032 cam but its only a minor upgrade from the stock cam... almost superram like abilities but in a stock appearing package.. 48mm is plenty enough for what you wanna do cause im still using my stock 48mm TB....SLP runners to me are the best on the market because you can hog them out pretty good... mine are so siamesed and ported that i can fit most of my hand down them. i also did some serious work to the plenum, terrible blockages behind the TB that need attention.. i also siamesed and opened up the runner passages. the edelbrock manifold is a must to complete the package...... i really didnt mess with this too much but its been ported a little bit to compliment the runners.... one last thing i had was the slp cold air intake.. its really the only cold air intake for our cars and its a major step up from the trash factory intake that GM gave us firebird owners.. The only downside is that you need to relocate your canister which is no big deal really.... but i think they discountinued this item.....when i had my stock tpi it stopped pulling around 4500-4800 but this unit.... man it pulls freakin hard till 6 grand but i spent close to 1300 for all the parts and porting which i dont think you would want to spend that and thats why many people choose the hsr because its alot cheaper and still flows better..... and because my intake flows well i went with the GM HOT cam..... i only went to a forged crank and rods because i wanted a strong dependable bottom end... its more than likely a bit overkill for my setup but i know i have something that will last....

 

Okay, about my engine. I pretty much blew every main seal bearing in it, because i started burning to much oil and i didn't notice it. So if that answers your question about the rotating assembly, then do i need a new one? yes or no?

Second, i also LOVE LOVE LOVE the way my TPI looks!!!!I would hate to change it, but i understand that restrictions of air flow limit horsepower unfortunately.

Lastly, i don't really wanna bore my engine UNLESS it is completely necessary. IF it is then fine, ill bore it 0.30+ and call it a day. But couldn't i just tell my mech to stock rebuild it, then when i have another amount of decent cash, i can come back and do the heads, cam, and EFI/manifold? Plus wouldnt i need to start running some sort of exhaust? Or should with the money i save go do exhaust that way when i come back to the top end ill have it already done?

Thanks, 3rd

 

i would get a rotating assembly it if was me since your down there... stock like assemblies are not that expensive around 500-700 dollars... this is what you need if you wanna stock rebuild
http://tpiparts.net/inc/sdetail/9143


its says external last time i checked there was a kit exactly like this that was internal balance... but this comes with everything you need except freeze plugs and cam bearings.. this kit has 9.3 compression which is right around stock compression for our cars and is rate up to 500 horsepower... and eagles cast crank is stronger than the factory cast crank....
..... if you wanna tpi to flow to 5500-6000 its gonna cost you some healthy amount of money, more than the rotation kit to be honest.... you may not need a .30 overbore.... it may clean up with a .10 or .20 overbore... that needs to be checked so you know which overbore kit to get...

 

Do you suggest me boring it over anyways? And what exactly does overboring do to a car? I saw a kit, http://store.summitracing.com/partde...3&autoview=sku. Is this overkill, or could i run this and then like use everything you suggested to get it back up and running?

 

well i bored my engine .30 over because that was the lowest oversize they offered... but overboring is cleaning up the cyclinder walls it also increases your cubic inches but not alot... someone else needs to chime in because im not a expert at this.... but
that was the exact same kit i was looking at about two months ago... but i later found out that the kit with 64cc heads which your l98 are 64cc will give you 10.3 compression which is a little to high for iron heads..... i went with this kit

http://www.cnc-motorsports.com/produ...roup5513=10450

its got 9.6 compression and its interal balanced kit...this is the perfect kit to get.... i got the internal balance option and i requested a 4340 forged crank which will require different bearings,the crank option cost me 435 extra dollars... in all this kit cost me 1320 which is way more bottom end then i will eva use....

 

So with this kit i can still run my stock heads, and intake for now. I can pretty much have my mech rebuild the engine and then go back and put on a vortec manifold, heads, cam and intake later, or do i need to so some other upgrades to make it work?

 

yes im using that kit with stock l98 heads for now.... next summer im going to switch over to getter heads... that kit basically its the perfect kit... it gives me 9.6 compression with 64cc heads which means that its pump gas friendly, its internally balanced just like factory, its a 1 piece seal and its comes with premium parts and not weak parts like the factory gives you.... if you do get this kit make sure you get the balanced option is only 110 dollars extra.. a balanced engine gives off less vibrations and friction at higher rpms and allows that engine to run smoother which means it will last longer and can take a little more abuse..... the last time i checked it would cost 190 here to balance a kit at my machine shop so i saved 80 right there.... this will go right in if your rebuilding your l98.... i just got the special crank and bearings so i can pound on the car from time to time without worrying about breaking parts.....

 

Its not the TPI intake that wont get 300+ RWHP, its the cam and heads. ZZ4 cams and long-tube runners are good for around 270-280 RWHP. You need something bigger like aftermarket heads and an XFI268HR-113 or LT4 HOT cam to get 300+. I had 318 RWHP with ported Corvette heads and a hot cam, and long tube runners, but stick shift. Another SoCal member just got 321 RWHP with those same heads ( I sold them to her ) and a hot cam, with long tube runners, thru an automatic. Another member made 303 RWHP with a CompuCam 2032 and a SuperRam with an automatic. But a cam that big requires a custom computer chip.

 

Now what im saying is can i just use my stock cam, intake, heads, for right now, because i dont know what combo to go with then come back and do all those three at once. All i need is a functioning car for right now.

 

how much are you willing to spend to rebuild your bottom end... that kit at cnc motorsports i showed you can get you that nice balanced kit for under 900 shipped... just get that, freeze plugs and cam bearings and your set....

 

also i really dont know why alot of people underrated the tpi.... it can make great power if you know what your doing.... most people aren't willing to spend the cash on highflow tpi parts... for intsance... just the slp runners and edelbrock intake alone will cost you a good 750 at full price... at that price you could get a hsr that flows beyond 6 grand with over 100 left to spare.. but to take full advantage of them they need to be ported which isnt cheap.... i stuck with tpi and it paid off for me... its like having a superram flow.....

 

well i was hoping on spending less than a grand on my bottom. I also want something that will last as well. But my mechanic still wants me to run a stroker motor. I tried today telling him i don't want to anymore. I think ima pull my car out and start doing some more research. Like Kevin said, many people here have built 350's that will do circles around 383's. I did like your idea about the 355 but he laughed and said why not a 383. I dont know whats going on anymore.

 

Believe me, I know abit here and there, but i'm no expert

My basis is from work done by Rhuarc30. He had done a 4 phase L98 head porting project that turned out to be very impressive but would have been costly for most ppl to do if they didnt do alot of work themselves

Stock Stage One Port
Lift Intake Exhaust Intake Exhaust
.1 53.9 41.6 63.5 41.2
.2 111.2 95.2 115.2 87.7
.3 157.3 112.4 163.2 122.7
.4 182.0 116.6 198.2 151.6
.5 192.0 116.9 224.8 161.3
.6 193.6 117.6 228.6 170.7

Thats after a mild port job on stock heads with stock valves. So you can gain ALOT from a mild clean up job that normally would run 300-400 bucks from most shops as its only 2-3 hrs of work for the pair.

With valve job done on stock 1.94 valves and more detailed port work
Lift Intake Exhaust
.1 63.8 41.4
.2 120.6 88.2
.3 178.9 124.1
.4 215.2 154.3
.5 240.1 171.8
.6 241 180


Cut for 2.02/1.6 valves and he got around 270 on the intake and a bit over 190 on the exhaust

Thats on a heavily ported head tho but i'm willing to bet cutting valves on stock port with mild clean up will yeild good results. However the price of that vs sticking with stock valves and doing a detailed clean up on the heads may not justify the larger valves. The flow on a mild port job with stock valves is enough to make plenty of power.




Now back to your issue 3rdgenred, if your on a budget then just keep stock block, freshened up and do get it bored as you will need fresh round bores with new pistons for best sealing or else you'll have lots of blowby and never properly break in the rings

Any cast rotating assembly will be fine to 500hp if you keep rpms under 6500 or so. I'd build the bottom end as strong as you can now so you can upgrade later.

With vortec heads, SLP runners/aftermarket base with a hotcam and such, you can get near your 300 or so whp as stated above by Kevin. They are the TPI experts i've seen here and have some very impressive setups running right now.

If you go that route, keep compression down in the mid 9's. If you want aluminum heads, keep compression up in the mid 10's.

You could run stock L98 heads and a mild port job on them with stock size valves with a 3angle job and still make decent power. I made near 260whp with bolt ons on stock heads. A cam should net 280-290 depending, and porting could easily break 300whp mark

 

But what do you mean by building the bottom end as strong as you can now? Does that mean not going cast but forged?

And i was planning on getting different heads i guess, cause all that porting work would be about the same as some decent aluminum heads.

 

well honestly if it was me i would get the best kit i could afford... trust me you dont wanna go down there again because you "cheaped out"....

 

Get the best parts you can afford for your goals. if you want something down the road in 2-3 years that needs forged internals, you should get them now.

But sounds like you just need a mild setup. you might beable to get away with new rods and pistons with stock crank reconditioned. But new crank is only 200 bucks or less. Definately have to get teh assembly balanced tho. I'd go for internal balanced so you have greater options for balancers and flexplates

 

okay, well i don't want forged internals, that's just a little bit to much for me. Something like this maybe, http://tpiparts.net/inc/sdetail/9143.

This is a good set up that will be able to handle a good head (180cc) and a good cam right? I know i wont be hitting over 500hp and i know i want a power band that is lower than 6000 rpm.

Just gimme your 2 cents please.

 

yeah that will work just fine but its external balance not a big deal tho......

 

yeah i'm not a fan of the external balance but i have no reason for it other than i just like neutral/internal balanced setups. they have alot of good neutral balance flexplates and harmonic balancers out there so it makes it easier to go internal balance.

They make another kit like that in a internal balance option. i do believe scat and eagle have some options.

 

hey guys i spoke with my engine builder and he stated that he has built multiple vortec headed engien with over 10-1 compression ans zero decked blocks and that what he is gona due to my block he stated he has had no pining problems with them what due you guys think?

 

ive got a question and thought why not ask here instead of starting new thread about tpi and head choices.

Ive a chance to pick up a set of World product heads(sportman II) for cheap...they are pretty much brand new and shop owner wants 475 for the assembled pair. My question is can i use these heads with tpi and maybe a HSR later?

The motor is a fresh rebuild 327 with summit 1103(for now), 083 heads and a 91 SD tpi setup right now with a tune

now maybe a go WP heads+327+HSR+LT4 hot cam?(i know i have to run retro-fit roller rockers)

 

You could use those heads, but they have a large intake runner for a 327. They are better suited for a 350+ motor unless you plan to really rev that motor up to the high 6000 rpm range. Then i'd use an HSR on that setup

 

The Sportsman intake runners are up over 200 right?

 

sportsman II's are sitting at 200cc.. thats pretty big for a sub 350 motor

 

my 327(really a 333ci)

was built/blueprinted/balanced to 7500rpm


and yes a HSR is on its way. ive got a 3300rpm stall in front of a mild 700r4

my biggest thign now is to decide on a gear ratio

My plan is to run this setup until i can get another motor built. Im going to be building a 355 roller motor

Lastly, the WP heads are 200cc im getting. $450 for the pair is a steal from im hearing.....brand new stainless valves/ported/polish/upgraded springs/screw in studs/guideplates

 

Okay guys so I have thought really hard about what I'm going to do. I'm going to pull the car outta the shop tomorrow. I know it's weird after all this talk but I'm done with. I'm so fed up with this bullshit it's just like I want to get rid of it and not even deal with it. Apparently my dad says he knows some guys who rebuild engines if you give them the core. Well see.

It's sad that I've grown this dislike for my firebird. I just want it gone.

 

Dont give up on it, you can make that motor pretty strong without too much money or trouble.

 

Now I am confused.. If they are internally balanced at the factory, then why do they use couterweights on the flex-plate. I haven't taken 1 apart yet that doesn't use these weights. My new built engine is internally balanced and required an internally balanced flexplate that doesn't use any couter-weights.

 

L98 is actually both external and internal. uses small counter weights on flexplate. Neutral front balancer tho

For new motors, you get your assembly internally balanced when they use bobweights to simulate rods/piston weight and dont add on flexplate or anything like that to the crank. I think its the best way to build motors as there are alot of nice neutral balance stuff like flexplates and harmonic balancers

 

Yep, its just sitting in front of my house, with no engine. Ugh f*** my life guys.

I'm actually thinking about just starting fresh and saving for like......ever. Nah ill probably start to tackle it after my birthday and tax return, so some time around May/June. This is also when i get out of school so ill be working then to so i can really get nitty gritty then.

Im actually thinking about just like trying to figure it out myself, i mean how hard is it to build a engine? If I buy a stand, cherry picker and the "How to build a 350 SBC" book, you think ill be able to do it?

OR, what im thinking about doing is actually doing a LS1 swap. That was my original plan for this car in the future, so yeah? Like if i buy the stuff from Spohn (Tubular k-member, trans crossmember, motor mounts, a-arms) does that stuff just bolt in or are there some mods that need to be done to put it in (welding or fabbing). If not, i have a Haynes manual, and i think i can figure it out right?

Just give me your two cents guys, i mean its not going any where really fast and it doesnt need to be done til like the end of this summer. Thanks.

-3rd

 

Haha basically what i did. It sure does work. You'll be fine if your mechanically inclined and have alittle bit of basic wrench work skills

Suspension and stuff isnt all that hard either. Just unbolt stuff and bolt it back the way you took it off.