hotrodf1

Hey all,
I haven't been on here in a while. Hope you all are well.

I have blown up my Fastburn 385 motor (ZZ4 lower end) in the last race at Barber. Block and all is toast, and heads are about $700 to fix (the fastburns). Pretty bummed but trying to figure out what the best plan is.

Firstly, budget it important. All the stuff I have is for SBC, so the LT1 would also work (headers, power steering, T56, twin disc race Quartermaster race clutch, etc). Otherwise I would entertain the LS swap.

The goal is to make 335HP at the tires, but have a wide powerband (think most area under the curve). The fastburn (with custom cam) was WAY over that number, but I used a two barrel carb and restrictor plate to detune. The result happened to be a really flat HP curve from 4500 to over 7000RPM.

The plan with the LT1 would be to utilize the stock alum. heads, but upgrade valve springs to the comp beehives from the wrecked fastburn heads, and then put a cam in the LT1 too.

Other part of this is I would potentially swap over to the GMPP carb intake and utilize my MSD dist. programmable ignition too for simplicity at the track. Seen so many EFI guys stumped with who knows what going on under the hood.

So, is 335HP / 355tq easily achievable with the stock alum heads using the GMPP carb intake, headers, etc.? Anyone hazard a guess on cam selection? Need something not overly aggressive on valvetrain - it has to live with a beating for a while. I have a ZZ4 cam, but thinking it wouldn't be enough. (208/221 I believe they are).

Other option is a $100 short block from 96-00 Chevy vortec truck and fix the heads and put all back that way it was. (though the ZZ4 was forged crank and I don't believe the vortec truck crank is).

Would certainly appreciate any feedback out there!

Injuneer

Appears you were using a Gen 1 SBC. Which version of the T56 did you run - LT1 or LS1? Pusher clutch or the LT1 pullback design? LT1 heads have d-port exhaust, do the fastburns also have d-ports for the headers? No idea if you can reuse the PS pump, given the significant difference between the front of an LT1 block and a Gen 1.

hotrodf1

Yes, was a Gen I. T56 was LT1 style, but with Quartermaster throwout bearing unit (kinda like a LS1) that goes over the input shaft.

Fast burns had basically the same D-port as LT1, raised from center, so headers are modded accordingly to center pipe over the port. In fact, the LT1 header gasket fits the fast burns perfectly.

I'm friends with Billy Godbold over at Comp, and he's not so sure the LT1 is a great idea for road racing.

I'm thinking it's not bad, since the stock GM parts would probably be enough to make my HP goal, and the are pretty available, since everyone now wants an LS (also makes the LT stuff cheaper).

I can't seem to find any comparison of EFI vs. GMPP carb manifold. Have seen folks that claim to have made 500 and in one case 580 fwhp using that carb manifold. I'd guess it's probably not too bad then!

Injuneer

The LT1 block is no slacker. The guys that built my engine also did several 1,000+ HP forced induction LT1's. That was 16 years ago. Before they even tried to go over the 1,000 HP mark, they spent a lot of time measuring and evaluating the block. In their opinion, it was very similar to GM's Bowtie block. I know my buddy's setup made 1,125 HP (flywheel) with 20+ PSI boost, spinning well in excess of 7,000 RPM.

We both ran EFI with the stock Opti using only the optical cam position module, feeding a MoTeC aftermarket ECU, and their 8-channel ignition driver, 8 LS1 coils. Unfortunately I don't personally know anyone that ran the GMPP dual-plane carb intake, so I can't comment on it's capabilities. But your goals, assuming you mean flywheel HP and torque, should be easy to attain. If there's a weak point in the LT1 with regard to operating for extended periods at high RPM, it's the oil pump drive stub and the plastic retainer. But running a distributor would seem to eliminate that issue.

And I don't think you need to run anywhere near 7,000 RPM to reach your goal. That would be stressing the stock rotating assembly and 2-bolt mains (unless you find a Corvette engine with 4-bolt mains).

DrewHMS97SS

If he is doing any block work, wouldn't the 2-bolt block be a better option to allow a splayed 4 bolt modification?

Injuneer

The LT1 block was designed to have 4 "straight" bolts. GM put the extra meat in the webs, knowing that some of the engines would use straight 4-bolt mains.

I asked for Pro-Gram splayed 4-bolt mains, which I got, but the shop guys told me it was not necessarily stronger than the straight mains. The 1,125 HP LT1 was built on a Corvette straight 4-bolt main block, with no block fill. After the owner decided that was not enough HP, and decided to go to a Dart Iron Eagle Gen 1 block, he sold the LT1 engine to yet another buddy. The shop tore the LT1 down and found that even after being exposed to the huge HP and RPM loads, it was still in excellent condition.

9.04-second, 155.33 MPH, 3,800# 30th SS convert.....

DrewHMS97SS

That is awesome. So moral is on the LT1 there is little difference between 4 bolt straight and 4 bolt splay. Good to know

hotrodf1

The HP I'm talking about is at the tires, sorry should have been more specific. I guess that would translate to about 375 or so at the crank. I wouldn't be opposed to some home porting work if there are some known areas to focus on without getting too crazy. The LT intake seems to flow well until you hit .400" lift, then the flow doesn't increase beyond about 205cfm.

I wouldn't think I'd have to spin over 6300 or so to get there 335rwhp. Haven't played with D dyno too much. I might throw the LT head numbers in there and see what kind of cam it might want. Not sure how to model the intake though.

I also didn't realize that the LT has some special features for the timing set / water pump drive.

Injuneer

Good article on LT1 vs. Gen 1 SBC.

Rebuilding the Chevrolet LT1 Engine - Engine Builder Magazine

Good MATCHED LT1 stock ported head, ported LT1 intake and cams.... custom cam profiles available, specific to you needs.

http://elliottsportworks.com/

Ported LT1 EFI intake will support 290 CFM.