TA

Recently I installed a new 383 in my 91. I decided not to do a step by step build thread as there's been enough of those recently. Long time members here might be familiar with my car as it was probably one of the better running stock heads/cam TPI cars. It had run a best 1/4 mile of 12.49 at 108 and consistently ran high 12's with the old engine.

Even though the car was still running good it was starting to get up there in miles (130k) and I was looking for a bit more power so I decided it was time for a new engine. I had a few things in mind when deciding which way to go with the build. I wanted it to be reliable, obviously make more power, and done with a relatively low budget in mind. For a few reasons I decided to go with a TPI set-up, even though I knew this would severely restrict my HP numbers. I already had decent TPI parts on my old set-up (AS&M runners, Accel intake, ported plenum) which would help the budget. I already knew my old combo ran pretty well, so I thought, if ever there was TPI set-up that might work well, this was it. Finally I had this inherent curiosity to see how low I could go (1/4 mile) with a TPI set-up. I decided to go with a 383 because I thought if I was already doing a build, a few extra cubes certainly wouldn't hurt.

If you followed WW7's epic 383 build (http://forums.corvetteforum.com/c4-t...-w-photos.html) you'll remember that Pete K was the builder. Pete used Shane Wolfe (engine builder on the forum) to do his machine work. Shane has a great engine building background as well and I got in contact with him and had him build me a 383 short block. The parts and set-up are identical to WW7's short block. I can't say enough good things about Shane. His work is outstanding, reasonably priced and he stands behind his build. He even made a two hour trek to my house after I made a bone head move and installed the crank sprocket in the wrong key hole. The trip actually worked out very well, as he spotted my error in seconds and degreed the cam while he was there.

I decided on a used set of TPIS ported 113 heads that I bought from a member here on the forum. Again I had the budget in mind and I really didn't think I benefit that much from a better flowing head considering the TPI. I chose a LPE 219 cam simply because its proven itself well as a decent cam for similar applications.

Over the last couple months I pulled the old engine and installed the top end on my new engine. It took a lot longer than I expected, but this was working on it a few hours at a time. I finally got it in a couple weeks ago and I was happy that it seemed to be running pretty well. I was a little concerned since the tune was a mail order one from PCMforless. I got it on the dyno yesterday and I gotta say I'm pretty happy with the results (318 hp/401 tq). The dyno chart (as well as a few misc build pics) is below. The blue numbers are from my old engine and the red are the new one. The torque drops off pretty rapidly, just like the old engine, but the HP really surprised me. You can see that with old engine the HP drops off pretty quickly with the torque (as expected with a TPI car). The HP with new engine is MUCH flatter than I expected and was over 300 from 4000 RPM all the way until he cut it off at 6k. The overall peak increase isn't that great, but if you look at specific RPMs (especially at the top) the increase is pretty substantial. I wasn't expecting that at all. You can also really feel the car pulling up top, which was obviously absent with the old engine.

Looking at the A/R ratio it appears I still have some tuning issues to work out as it's very rich when it gets in the upper RPM bands. Overall I'm very happy and I'm looking forward to getting this thing to the track when I get the tune worked out.












**EDIT** I added a video of the car

I'll add a another vid when I get the new chip back and get it back on the dyno.

GREGGPENN

Yes...very good numbers -- especially for an automatic! Even more impressed by the top-end run-out. How did you install that LPE219 cam? straight up or a couple degrees retarded?

Pretty amazing to see the dyno vs prior build. If someone only saw the difference between peak numbers, they'd have no idea how dramatic the difference really is!

All the way into the 6k rpm range...wow. Seriously, how'd you install that cam?!

TA

The cam was installed straight up

mcm95403

I'm very curious to know your mods prior to the build that got you into the mid 12's at 108 with a stock cam and heads. I'd love to duplicate that on my 91

TA

First I did all the simple things that in reality don't do all that much. Stuff like cutting the air filter lid, low-temp fan switch, cat-back exhaust, etc. then I went into the things that made a more significant impact. I freed up the exhaust from front to back (long tube headers, 2.5" duals with an X-pipe, no cats and 2 chamber Flowmasters). I added AS&M runners, an accel intake, ported plenum, 1.6 RRs, 24lb FMS injectors, an AFPR and a custom tune. I added a 2500 stall converter and also messed around with several rear end ratios.

We all know that TPI cars fall on their face on the top end, but make a decent amount of torque off the line. So to make a TPI car turn respectable times you need to focus on the things that it does well. Its essential to get off the line quick, so you need to get your 60' times down. TPI cars respond well to intake an exhaust mods. Intake, exhaust, a torque converter and drag radials will make your car decent performer at the track. The problem is that all those things cost a decent amount of money. Money that could be going toward a decent set of heads and a cam. I did go from running 14 flat at 100 (when it was stock) to the time you mentioned, but in hindsight there was probably much easier ways of getting there

GREGGPENN

Any chance your runners are siamesed at the bottom of the runners and/or in the intake base?

Any chance of a really big intake manifold leak?!

TPI's just don't run out that far. Maybe the siesmometer "stick" on the dyno stuck!!!

WW7

Congratulations on a great job Tom...Glad to hear your up and running. That motor sounds like it's a screamer.. Can't believe it revs to 6,500 with a tpi, you must have some magic in those hands...Can't wait to see what it does at the track......WW

TA

The dyno operator told me he cut it off at 6k and the rest was some sort of run-out. If you look at the HP curve my guess is he actually cut it off at about 5600 as the graph seems to be trending downward at that point and that has an unexplained uptick. Even taking that into consideration, its making power north of 5k which is impressive.


I'll try to get some video of it running also. I was pleasantly surprised at how lumpy the 219 cam sounded

88BlackZ-51

Tom,

These are the threads that I like. The LS swaps are cool and all, but the good ole' SBC 1 stuff is still where its at for the C4's imo.

I havent been feeling well as of late, but I have a bit of energy so I'll give this a thought.

First off I see Gregg got his nose in the thread pretty quick, but not suprised since he loves the long tubes. Say Gregg, Tom made pretty much the same power as you if you calculate the drivetrian loss for the automatic. What's up with that?

I will say that I am suprised that you didnt make a bit more tq over the stock cubes. I expected another 15 rwtq, but maybe it will come with tuning, but in saying that the peak numbers almost mean nothing. Looking at say 4000 rpm's and the amount of tq increase you made with the 383 is HUGE over the 350.

I guess I am getting to be one of the members who have stayed with the C4 over the years, and have been advised of many of Tom's modifications and the results.

I know Tom wanted to do the 383 on a budget, and he certainly did that. Not sure if my calculator is right but given 20% loss that would but that 383 in the 400chp/500tq range which isnt too shabby, and enough to get that white beast into the 11's foresure. I would imagine with that power an LS3 wouldnt be getting away from TA.

I hear about guys saying they have $5000 to spend etc....

Maybe take a good long look at this build, and do your best to copy it. I am not a pro, but I would assume it would be a very fun motor with 500 ft/lbs and more rpm to work with then a stock 350 with mods.

Enjoyed reading this. I am guessing another 7-8 more mph, but time will tell.

Good job Tom!

GREGGPENN

It would be more accurate to say I like what I own and prefer building on the theme of the car. If I had an LT, I'd have stuck with short-runner.

You misread any post/intent here. I am not saying anything about overall power-levels and peak#s. (In fact, I said good job in post #2!) My only reference is to the area above 5k rpms and Tom addressed that.

Edit: Really my intent was in line with personal debate to swap my cam config (to a straight-up or retarded alignment.) I put it in on a 108ICL.

1985 Corvette

Nice results, TA. Your build is the route I would have gone if I decided to reuse my two piece block. That will be really fun on the street for sure. On a track though, do you think the TPI will have you looking for more air intake at some point?

Impressive numbers and a stock look, I love these kinds of builds! Any plans to tinker with intake options in the future?

88BlackZ-51

Gregg,

I was merely joking, but I guess you thought I wasnt. I would never want to ruin a thread like this. Maybe you missed the smile face.

TA

I made an interesting discovery tonight while tinkering under the hood. I put about 250 miles on the car prior to the dyno and during that time I drove it verrrry easy. I decided that after the dyno I could start hammering it a bit. Over the past couple days I was noticing the car seemed to be shifting pretty sloppy. I was thinking the trans was starting to slip or the TC was having issues.

I decided I should make sure the TV cable was adjusted properly before I became too concerned. Well damn if I didn't forget to attach the TV cable when I was finishing up the engine. You can even see it if you look at the "after" picture above. I re-attached it and suddenly the shifts are nice and firm again. So I put about 350 miles on the car (including a dyno run) with the TV cable unhooked. I checked the fluid and it looks fine. Any chance I hurt the trans? Any were the dyno numbers affected by the unhooked cable? Anybody have any idea?

GREGGPENN

No and no.

TA

mcm95403

Being in CA I can't do much with exhaust - I'll have to be content to go about it other ways like better heads and a good cam. I don't think I'll be doing converter unless the trans dies although I may do deeper gears.

Thanks for the info

Vic'89

Hey Tom, nice addition !

Everything looks real good.

The HP on the dyno graph doesn't look like a TPI motor HP graph.
It is real flat.

Will you make a Corvette Challenge race soon ?

Vic

cv67

I wouldnt bother with retarding/advancing most cams especially smaller ones waste of time. Leave it as is.

GREGGPENN

IMO, that's bad advice. The stock 89 is installed retarded and it runs out better than you'd (and I'd) expect.

My 383 cam is installed advanced. You won't believe the front-end responsiveness. IMO, there's considerably more difference between my current car, the stock version, and even an LT4. IOW, it's way more responsive than accountable by the CI increase.

I can also tell be comparing my dynos vs other straight-up installs. (Though, as pointed out by Vic, the top end of this one is misleading for a TPI. Again, I want to reiterate it's not a slam. I've just seen to many of them. If we found out there was extra base/runner siamesing, that would be huge to point out -- if the same dyno could be duplicated in another run/build.)



BTW...You should see the difference modeling an advanced vs retarded cam in EAPro! And, EAPro is a very good predicter compared to freebie applications. AND....it could make a measurable difference in performance for ZF6's in 6th on the hwy. Or puttering around the parking lot. For racers, the top-end is most important. I would easily consider 2-4 deg retarded for a TPI cam installation. I can't remember for sure, but I believe the stock 89 cam had even more retard built-in than that. It' created the low-rpm response thru a wider LSA.

cv67

Bet they are installed retarded for emissions purposes.

+1,2 deg either way wont make an iota of difference when you turn the key imo. Unless you have some humungo (or the wrong) cam its fruitless in search of power better off changing the stick period. Just my (bad) .02