first off this isnt a corvette, its a 1967 tahiti jet boat that came with a corvette 327 hypo and had a corvette steering wheel and emblems. i want to keep the boat completely original so im sticking with the 327. im building it myself in my engine class and i need advise on a good engine kit, and i was thinking of running the summier K1107 cam. i need an *** load of power between 4000-5500 rpm, and a decent amount around 3000-4000 rpm. any help would be greaty apreciated-scott

 

Does "327 hypo" mean it's basically a L-79 350 HP 327?

What are the block and head casting numbers?

What are the details of the exhaust and inlet configuration?

The cam is the LAST thing you select once you've got a handle on the rest of the configuration and have established a reasonable torque bandwidth goal.

Duke

 

yes its a 1967 350 hp 327, i will be giving the camel hump heads a 3 angle valve job as well as porting and polishing them, 10-1 compression, the HIGHEST the engine will rev to is 5500 rpm and thats my goal. theres not really any intake or exhaust restrictions, i will either rup an rpm air gap or a single plane manifold. my goal is to have lots of power between 3000-5500 rpm.

 

Go to The C1/C2 discussion and search all posts by user "Dave McDufford". Build your engine EXACTLY like he did. (I was the system engineer.) Note that his peak torque is at 4500 and peak power is at 6500, which is higher than your intended rev range.

Dave decided to go with the LT-1 mechanical lifter cam because he wanted to rev to 6500, but since you will not see greater than 5500, you can stay with the hydraulic lifter L-79 cam. Power up to 4000 is about the same for both. At 4000 the LT-1 cam begins to pull a slight advantage, but the biggest increase is above 6000, which would not be useable for your application.

The '67 rods are better than the '65 rods, but still marginal for sustained high revs. I still recommend the Crower Sportsman, but I understand they are hard to find. Try to stay close to the OE rod weight, which was one of the nice features of the Crowers.

I recommended to Dave that he install the big pan and windage tray from the mechanical lifter 327s. He decided against this because he wanted to have his car NCRS judged, which was okay as he won't be spending much time over 4000 - just occasional short duration bursts.

For a boat I highly recommend the big pan and windage tray setup since you will see sustained high revs, and like racers in the sixties, you can run it a quart over full - 7 quarts total with the cartridge filter.

DO NOT cut metal from the crankshaft, heads, or block unless ABOLUTELY NECESSARY. If you grind the crank the surface Tufftride treatment is removed, which will reduce crankshaft durability.

Prior to block disassembly measure the deck clearance on all eight cylinders VERY CAREFULLY. This will tell you if the decks are parallel to the crank and is a dimension you MUST HAVE to compute compression ratio. If the measurments show the decks are parallel to the crankshaft axis, the engine can be bored with equipment that indexes off the deck. If deck parallelism is off by more than about 3-4 thou, find a shop that has boring equipment that indexes off the crankshaft axis. If one side is a few thou higher than the other you can have it cut down. If it's the right side you may want to leave it alone to preserve the stamped ID numbers. Dave's left deck was five thou higher than the right, so he had it cut five thou. In the vintage Corvette world, only the OE broach marks and stamped numbers on the right side are important.

As with Dave's engine, you should end up near 10.25:1 with a .038 composition gasket and typical OE deck clearance, which is okay for premium fuel. The OE (Federal Mogul, ex TRW) forged pistons are very durable and will live if installed at the proper shop manual clearance, which is about .003".

Other than the rods, everything in Dave's engine is OE or OE equivalent from major manufacturers like Federal Mogul. It has NO "hotrod" parts.

I recommend you do the same if you want a reliable engine that will make an honest 350 HP SAE gross. As built your engine is closer to an honest 300 and the key to getting the full 350 is the head work.

The biggest restriction in yours (and Dave's) engine with reworked heads is the OE inlet manifold. A LT-1/Z-28 manifold (or equivalent aftermarket) will be good for 15-20 horsepower at the top end without a significant loss of low end torque. For the rev range you are operating in, DO NOT install a single plane manifold. A single plane will produce LESS average power in the 3000-5500 range. A single plane is only an advantage if the engine is intended for sustained operation from 5000 to 7000 and beyond - like a road racing engine where you are shifting at 7000 or above.

Duke

 

i was thinking of using the rpm airgap manifold and a 750 edelbrock carb, i would use holley but the edelbrock just seems a lot easier to run.

 

For a 5500 RPM 327 use about a 600 CFM rated carb.

The engine's air demand is only about 470 CFM, which is only 0.9" depression on a 600 CFM carb, and the smaller carb will provide better part throttle metering and throttle response.

Duke

 

If you want to be sneaky and REALLY have a bundle of torque, cut down the mains on a 350 (3.48" stroke) or a 400 (3.75" stroke) crank shaft, for some non-visible cubic inches.

RACE ON!!!

 

this is the cam ive chosen http://store.summitracing.com/defaul...h.asp&x=39&y=8 im gonna run it with an rpm air gap intake and a 650 edelbrock.

 

By time you cut the mains on a 400 crank down to small journal the oil holes will end in the radius of the journal this even will happen on some 350 cranks when turning them down to small journal.

 

im definitely keeping the 327 crank.

 

Uh oh..Duke...I think you lost him!

He's gone the "Voodoo" route!

Actually doesn't look too bad.....Harold's cams are pretty interesting designs.


327's are sweet little engines. A buddy has one in his '65....it's a strong runner with pocket ported SR Torquers, an old Tarantula intake and a 750 DP. We used a small circle track solid lifter cam and it flys!

We used the stock type TRW 11.0's too and they have lived with stock rods. But man are those things heavy! Next time around we'll be using much lighter stuff.

I'm with Duke on oiling system improvements for a boat though. Keep stock pump....use a HP spring in it..or just order the Z-28 setup. Use the windage tray. Boats run at constant higher rpm
and get beat on a lot, so insurance here is good.


JIM

 

you do have a good point that boat engines take a beating, which is how i know the 327 was one hell of an engine...38 years in my boat being abused with no problems until now when it just got too old and tired. i went with the voodoo cam because of price, im 21 in school and i have a dodge charger to take care of...not much money to spend after the car is FINALLY running good. the next cheaper cam were the summit ones, but they seemed too cheap to be any good....i am running 10-1 compression so i think the 750 will be too big, im leaning towards a 650 double pumper. i start taking the engine apart tuesday so i get to see what 38 years of abuse has done to this engine

 

The relationship between compression ratio and the need for air flow is nil.

RACE ON!!!

 

750 will be fine...I'd use it in a heartbeat!

The Voodoo's were designed by Harold Brookshire, previous owner of the old Ultradyne cam co. He was working for Lunati for awhile. His cams always feature assymetrical lobes and he uses very quick opening and very soft closing ramps. Of course there are some factory cams the same way.....

The Summit cams are pretty basic.....not too wild at all. Not sure who's they really are, but I'm sure similar ones are sold by Elgin etc. But I've seen a few good perfroming engines that used them..just have to pick the right one.

JIM

 

haha 750 it is!! im goin with the cam that builds power to 6200, that way ill maintain good power at 5000 and when i hook up that 100 shot of nos the cam will still have room to breathe man i cant wait to feel a 16' jet boat accelrate with 500 hp!!

 

what should i look for in a cam to make my engine handle higher compression without detonation. im trying to run 10.3-1 compression on 91 octane. it is in a boat so the heads stay a bit cooler then in a car, the water comes out of the intake at 130 degrees...which usually meens the oil is running at 180-200. ive been told to look for lots of valve overlap.

 

I would love to do that

 

You need a cam with a late closing inlet valve, which will cut dynamic compression. You also want minimal overlap unless you have headers. With manifolds, more overlap leaves a larger residual of hot exhaust gas in the cylinder, which will increase the tendency to detonate, and this also reduces VE since fresh charge is replaced by exhaust products.

Guess what cam meets the above requirements?

Duke

 

let me guess...the L-79 hydraulic cam so comp cams and lunati should be out of the question now?

 

The L-79 cam has about the right amount of overlap for exhaust manifolds (aftermarket cams of similar duration have too much) and should be okay up to about 10.5:1 with the production ignition advance map.

The LT-1 cam has a little more overlap, and a much later closing inlet valve, so it will handle 10.5:1 okay, and can probably run a more aggressive ignition map.

With typical production deck height, the OE type forged, domed pistons, and a typical composition head gasket, the CR should come in at no more than about 10.5, but you HAVE TO MAKE ALL THE MEASUREMENTS TO COMPUTE TRUE CR, and make any adjustments as required.

This starts with measuring piston crown-deck clearance on teardown.

Search on "compression ratio" or "CR" for more info.

Duke