OK, so I've been reading many of the threads concerning engine builds. I have a specific set of parameters, but have lots of questions. The car is a 2nd-owner 1991 L98/700R4 Formula with 97K miles. It serves as a nice-day commuter since my round-trip is only 12ish miles.

I want it to remain rather docile, but get a decent bump in power. I'll probably take it to the track once in a while, but it will be primarily a street car. It has a CAI, full-exhaust and tune and did 216rwhp/280ish rwtq.

The engine is probably nearing freshening time, so I figured that I'd give it a few exra HP while in there. I'd like to keep the TPI, so my first question is whether extrude-honing is worthwhile? Secondly, would a 383 be worth the extra coin over a 355 when under a TPI intake? I'd love the weight saving of aluminum heads, but would a good port/polish job on the stockers be worthwhile? Roller rockers worth the coin on a mild build? What is a well-behaved cam that produces a little more HP with TPI?

Any input/experiences would be greatly appreciated! Thanks!

 

Heads and TPI are going to limit all out power on a 383 but you still have 30 more ci and a lot more bottom end torque over a 355

If doing a full rebuild; only cost difference is the cost of the stroker crank ( $170 ) and some labor for clearancing the block.
Often offset from cost of having to get the old crank reground

 

Yah, but this won't be a max-effort engine anyways, so the TPI bottle-neck isn't a big deal. I'm tending to agree with you that the extra cubes are worth the extra coin...thanks for the input!

 

I agree on upgrade to 383. Non forged nitrous kits are relatively cheap. Stock TPI will be a limit but we know from "ten times torque article" that it will give you around 400 hp and 500 ft-lbs. You could always upgrade to larger runners if you wanted a little power boost a few years down the road. Will be a fun 12 mile daily commute

 

How's the FIRST working out for you? I got sent all over the globe too much to take advantage of the group buy, but appreciated all your input/advice. I would possibly still go with a FIRST if it was hassle-free...

Anyways, I'm leaning towards the 383, so what cam/heads would work well for a solid build? Again, this won't be a race engine...

Thanks for your help!

 

What are ur specifics exactly? a daily driver with a cam that has good manners with an auto ?

 

Yup...you pretty much nailed it. Nice manners, good throttle response, fun/usable power and reliable. Not a track car by any stretch...I have a cammed Z06 for when I want to go fast. Just something respectably quick 0-100 that will start every morning and make my drive enjoyable...

The tranny has to have a previously installed shift-kit...it hits hard. Forgot to ask the prior owner about that. If I do a stall, it will be a mild one.

 

Do you guys think some cheap(er) aluminum heads like the Summits, or some Corvette 113s would be worth the expense? I like the idea of saving weight... Anyone use the Summits?

 

I'm interested too.

 

170 cc version for 995 they flow 500 lift: 242 intake, 175 exhaust
.600 lift: 245 intake, 191 exhaust

 

seems like a good buy for the 200cc if you know what mfg made them they .Heads flow, @ .600" lift, 28" Intake 261 cfm
Exhaust 176 cfm

 

When I started my motor build I was looking at the Summit 170 heads I had them even orderd already the person that was helping me pick out a cam Ect told me I would be happyer with a longer intake runnes.

The lonnger runner will give you more Over Rev than the 170 the 170 is more for a truck type motor set up for max TQ Towing when you never rev thew motor pass 4000 RPM's the 190 to 200 will let the motor breath & rev more up on the big end.

I went with Trick Flow 195.

And after reading more in to it most are sayin 190 runners are a great runner size for a prefomance Street car.

While 170 are not much bigger what stock heads have now I think the are 166 something like that.

The Price diffrence between Summits $999.00 for a pair I think I paid $1100.00 For my Trick Flows.
But The TF I end up getting have the .480 max lift 62 cc heads If iwas goine to buy them again get the larger lift just I case you ever want larger lift cam,

 

yeah i would say trickflows are a better buy but I got my 180cc afr for 1350 shiped to my door and the spings can handle up to .600 and they shimmed them for me to control the aggresive lobes of the xfi 268. and my 180s are 261 int and 209 exh @.5 but if your just trying to make a daily driver you dont need alum heads put that money toward your exhaust

 

One more thing I found out the hard way the temp swicths that screw in to the aftermarket heads willn't fit the new heads have next size larger holes in them all you have to do to get around this go down to the local harware store and go to the plumbing section pick up a couple Bass adapters.

I think they cost $2 or $5 a each. cheep fix.

I read yes and no on useing teflon tape on them I didn't use any so far there don't leak,

DONT use telflon on the Anti knock sender either.

 

I would prolly stay in the 180-195cc range for the heads...if I need them at all. Good tip on the 170s not being much more than the factory, but then again the 113s aren't any better either, correct?

So far...budget 383 bottom end and extrude-honed TPI or FIRST intake. I'd still like opinions on a cam and possibly budget heads (if needed). Thanks for the input and hope everybody is having a great Holiday Season!

 

Yes

You will need Heads that flow you are making a bigger AIR pump with out a good set of heads it will not able to breath and take Avantage what the 383 can do. you be choking the motor.

Mite as stay with the stock motor than that motor need more air and fuel.

You going to have to get a chiped burned anyways mite only do it once.

Between more cubes (Bigger air Pump) Larger cam for the bigger Air pump need some head so it can Breath a Intake sytem and some Larger injectors so it wont choke the motor they all go hand and hand.

If not might as well put a stock motor back n the car.

Power cost motor and on the 1980's car it cost to get them to work.

 

If anything put a plug in the head and put the temp fan switch in front of the aftermarket manifold. Usually there are three holes in front. Use the one on the left.

 

But what are the mid lift flows like?
Lots of the cheaper heads have impressive flows at valve lifts most are not going to see
and very ordinary (weak ) flows @ lower lifts compare to a better quality head

 

Hi Ben, glad to see your back home. I had some free time this past spring/summer and decided to polish my FIRST unit. Big pain that I wouldn't recommend. Initially was going to throw it on stock motor. Changed my mind and will be giving car the full treatment (new engine, rebuilt trans, aftermarket rear end, paint). So putting intake together is a little ways away. Only thing that looks tough is getting all aftermarket fuel fittings and hoses figured out. You also need to by a different style EGR valve as stock wont bolt up. Other than that unit looks pretty straight forward. Extrude hone costs $$$ for the base and runners. By the time you get aftermarket base, runners and throttle body, FIRST is not that much more expensive and is capable of more. I started a thread about TPI sizing calcs that you should take a look at. I am going to port my runners some to match up with engine size and cam better. This intake is my white whale. Feel like it will never be done.

I think aftermarket aluminum heads are still worth it even for a daily driver. Improvements over stock are significant. Trick Flow 195's seem to best at lower price point. AFR's are nice especially if you can find them a few hundred cheaper. Others like Darts or the new profilers.

Even stock TPI with decent aftermarket heads on 383 will produce lots of power. Although it won't be a perfect matched system, it may satisfy you. If you get an itch, cans always upgrade intake later on.

Seth

 

He has stated above at this stage he wants to run the stock TPI so won't be a problem
Engine will rev to 4K and he will kill everyone in the stoplight to stoplight race on account of the torque

 

OK. I guess I'm wondering if the heads would be worth anything more than weight-savings on a mild LTR 383. Essentially, I am not trying to build a screamer...just a matched power combo. If the 383 is too much for the LTR set-up, then I'm back to a 355 and pocketing a few hunderd bucks.

I have a very good tuner locally, so that's not a problem.

 

Hey Seth,

Actually was in TX until just recently, but then my father passed away, so now I'm home, but who knows for how long...

Wish your FIRST was all hooked up/running...would love to have your review. I'm sure your car will be totally bad-azz when done, so keep me posted...

The FIRST would be the only other intake I'd consider as it looks fairly stock and has similar (although enhanced) power-production characteristics. However, with some extra cubes, the other intakes might be more viable, but then that snowballs into a full-effort build.

I like the idea of the Al heads to feed a 383 and the weight savings, but dunno if worthwhile on a upgraded daily-driver that uses LTRs.

Haven't even gotten to cam questions yet...geez I'm a pain in the azz.

Thanks for input and Merry Christmas to everyone! Ben

 

Yessir...you are spot on in that assesment. No need for a 6500rpm engine here...5000rpm with a great curve would be great!

 

LOL thats how I ended up with a 357 also I wanted a 383 to start with I went 357 to save a couple hundred to put somewhere else in the motor.

And Heads and cam even on a stock 350 will make night and day diffrence you can do the intake latter if you want. thats intake job is a day job.

 

I think I'd be OK with spending the extra $$ on the 383...a few hundred seems worth it for the giggle-inducing TQ. I'd even consider some 113 heads with some cleaning up and better springs... Which leads to: "What cam would work best with a mild 383?"

Thanks for all your help!

 

Impressive results on L98 iron heads if you have the time
Read from part 1
https://www.thirdgen.org/forums/tpi/...d-project.html

One thing to consider is 113 Vette heads have smaller 58cc chambers.
You need to decide what head you are going to run before buying pistons as both factor into the final compression ratio

 

Yah...If I went 383 anyways, I could pick pistons to cooperate with the 113s...or any aftermarket head. That's why I'm trying to nail down the general game-plan now. I like the idea of porting the factory irons, but that 40+ lb weight-savings is sooooo alluring. Thanks for the tips and I'll check out the link...

 

Sorry to hear that your dad past away.

From what I've read a comp cam XFI 268 or 280 seems to work well for built TPI's. I looked at excel sheets I made for stock TPI intake. It simply has too small of runner diamater to support a 383. Even with that we know you can make good power from the ten times torque article. As you mentioned, always the balancing act of how much you want to spend for more performance. Maybe you can keep stock intake now and keep searching on this site, ebay or craigslist for aftermarket intake. Seems like people are always selling them. From what I recall reading online, stock TPI runners are biggest bottleneck. More than stock base and 113 heads.

 

Seth,

Thanks for the condolences on Dad.

The small TPI port will restrict HP, but the velocity should make for some great TQ and throttle-response...especially feeding a 383, correct? The problem is that I don't want to build the engine twice, so matching the parts is vital and why I am bugging everyone for opinions.

This is just going to be a fun street car that if I go to the track once in a while and bang out a mid/low 13...great! No drag suspension, no huge TQ convertor, leaving the 3.23s in place out back and reliable.

I'm going to make a hypothetical "build list" off Summit for you guys to critique. I'm also going to talk to the guys at VA Speed, but I'll bet they suggest a LS1 swap...

Thanks again for all the help!

 

If you want to run in the low 13's you don't need a 383. IMHO a 383 is good for if you're gonna do a lot of track racing other wise it's a waste of money. A stock L98 and L31 can run 13's with just a head/cam swap and a better breathing intake.

 

"but the velocity should make for some great TQ and throttle-response...especially feeding a 383, correct?"

Yes it will up to the point that it runs out of air. That will come quite quickly and then it will flat line and finally nose over powerwise.

 

Here you can have a close look https://www.thirdgen.org/forums/tech...ads-clean.html

They raise the intake manifold around 4mm over stock. Kinda "vortec hybrid" head.