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77- stroker engine build

T

the_mule

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Augusta, ga
Ok I'm finally prepared to bore everyone with my own build. haha. Some backround, 77 Blazer, I bought it without a front driveshaft (2 wheel drive mode) took it out anyway, broke the rear driveshaft and stuck it in the ground which then ripped a hole in the floor and the h pipe. Ordered a rear and front driveshaft from Tom Woods. Fixed the driverside and passenger side floor (standard sheetmetal plate for both have pic if anyone is interested) rino lined the inside from firewall to the tailgate, replaced the clutch and started messing with the carb as the truck had no power. Did a compression test and it took 4 compression strokes for the compression to build up to around 150. Decided it needed a motor but wheeled it for a few months anyway as had to wait for the money to build the d**n thing (the cam lobes are probably worn down ) It also has some rod knock. Anyway on to more interesting things. It is getting a motor the point of this thread.

Picked up a bare block from craigs list (a guy bought out the inventory of a machine shop going out of business in Tampa so got the block for 75.00)

Block is from a 90 truck 2 bolt mains, 1 piece rear, cast for a factory roller cam.
Just got the block back from the machine shop had them hone it and install the cam bearings, so it is still a 4 inch bore.

Parts so far:
Block
-Eagle rotating assembly, stroker 377 (not 383 because of bore size)
-Vortec heads milled to accept higher lift and tapped for screw in rocker studs
-screw in rocker studs
-pushrod guides
-comp cams 162 cam
-edlebrock performer intake
-harland sharp roller rockers (for intake)
-comp cams gold race roller rockers (for exhaust)
-all the gaskets and break in lube ETC...

Also some stuff for the truck as well
-ORD body mounts and 1" lift
-ORD steering box brace

Started taking the truck apart today, as there is some corrosion i want to clean up and I am working by myself I decided to pull the front clip and inner fender wells to make it easier to pull the motor.

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Need more info on this motor if you really want to run the vortecs. Like pistons, rod length, internal or external balance on crank. CompCams 162? You might need to explain this one.

Here's the 383 I'm building now.

010 4 bolt block bored .030 over
Scat 3.75 internal balance crank
Scat 6" rods, bushed for floating pins
KB hyperuetectic pistons with 7 cc valve reliefs, 1.13 compression height.
Comp Cams XR274R solid roller
Set of nothing special stock heads, pocketed ported and cleaned up to flow 240 cfm at .600 lift
And the rest of the associated performance parts

Every engine simulator I have put it through gives me around 500 hp @6000 rpm and 5000 ft-lbws of torque @ 5000 with almost 275 available just off idle. Post up some details and I'll run it through a simulator I have.
 
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Its a 3.75 inch crank, with 5.7 inch rods the piston pins are 1.425, so the piston is .025 in the hole on a standard deck, the heads have a 64 cc combustion chamber, with a 4.125 head gasket at .039 compressed thickness, I have a compression ratio of 9.609, which I want because I still want to run pump gas, haha I actually usually run 93 but want the ability to run 87 if need be.

It is an internally balanced assembly already balanced. Hyperuetectic pistons with a 12 cc d shaped dish, bushed for floating pins.

The rotating assembly comes with everything needed, but it was hard to find I actually called to try to get a scat assembly but they don't make one with a standard piston and I needed a balanced assembly because the local machine shop doesn't have a balancer.


I meant 262 because the grind is XE262H-10 sorry.

The cam is Comp cams part number 12-238-2
specs: Lift intake .462
Lift exhaust .469

Duration @ .05 intake 218 exhaust 224
lobe seperation 110.0

I don't know what the vortec heads flow but will find out.
 
You won't be running 87 octane with a 9.6:1 compression. It is carbed right?
 
Actually he could run a static compression ratio of 9.6:1 on pump gas if he chose the right cam. However, this motor will not run on pump gas. With the cam he chose he ends up with a dynamic compresion ratio of 8.45:1. Dynamic compresion ratio takes into effect the rod length and the cam timing.

The Vortec heads are a great simple bolt on for most engines to gain some power. But they really are not what they are cracked up to be.

A DCR of 8.25:1 is the absolute max that most people can run on pump gas. At 8.45:1 with a the piston .025 down the hole, this motor with be especially prone to detonation. It will probably destroy itself in a short order.

Let me run some numbers and I'll get back to you.
 
Here's what I reccommend you do. This is if your set on using the Vortecs.

KB102 18cc D cup piston. This will leave the piston .017 down the hole.
Get a set of copper head gaskets at .021 thickness.
Step up to a cam in the 270 range.

THis would get you around 375 hp @ 5000 rpm and 425 Ft-lbs @ 2500 rpm and will run on pump gas. It's right at the ragged edge for pump gas, but it will run on it.

My 383 has a static C.R. of 9.8:1, but because of the cam I chose the dynamic C.R. is only 8.1. Will happily live a long time on pump gas with gobs of power.
 
When I calculate the dynamic compression ratio I get 8.04 :1 or 8.159 depending on the calculator. The Intake opens 25 degrees Before Top Dead Center and closes 57 degrees after bottom dead center, the exhaust opens 69 degrees before bottom dead center and closes 21 degrees after top dead center. Am I missing something ? I really dont want to blow this thing up.
 
Didn't get much done today finished getting the motor out and managed to dump water all over the garage so after cleaning that up it was time to quit for the day. Tomorrow will tear apart the old motor should be interesting to see what shape it is in.

The rotating assembly won't ship until 12/1 so I should be seeing it late this week the heads should have shipped late last week. So they also should be here this week.

Oh yeah the motor mounts are for sale, first come first serve so put in your bids early. :waytogo:

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I get the same, If you don't mind what does your horsepower simulator show, I might order another head gasket to boost the ratio.

Go with a 4 or a 4.030 gasket and .021 compressed as the one I have now is 4.125 and .039

Also do think there are any downsides to using a head gasket that is that much larger than the bore, if it matters enough to change the volume and the compression ratio then the mixture is filling the tiny gap between the head and the block and burning, that can't be good for the swirl of the mixture.
 
I had a software glitch I had to work through. I worked up a solution for you and trudt me, you may want to rethink the cam choice you have since you have a factory roller block. I'll get it all up tomorrow evening when I get home from work.
 
the_mule said:
I get the same, If you don't mind what does your horsepower simulator show, I might order another head gasket to boost the ratio.

Go with a 4 or a 4.030 gasket and .021 compressed as the one I have now is 4.125 and .039

Also do think there are any downsides to using a head gasket that is that much larger than the bore, if it matters enough to change the volume and the compression ratio then the mixture is filling the tiny gap between the head and the block and burning, that can't be good for the swirl of the mixture.
Click to expand...

What do you consider much larger? Technically there could be minute efficeincy losses because of unburned fuel in the gaps, but you probably wouldn't notice. However, I wouldn't use a 400 gasket, as it will be very thin between cylinders, and include steam holes, and blow out easier than a 350 gasket. You probably won't have a problem, but I would just find the gasket you need. If you use a thin gasket, make sure you mill your heads perfectly flat, and your block too, or you will get a leak. You can check with a straight edge and a feeler gauge, for a thin gasket, I would want .002 thousands or less warpage. Normal tolerance is ~ .005".

Felpro makes a rubber coated steel (cometic type) gasket that is only .015" thick.

Also, if you have a factory roller block there is no way I would put a flat tappet in there. Annoying breakin risk, and also you are giving up decent power gains without the roller cam.
 
I will be upgrading to a roller cam later but I already have this cam (bought the cam before the block, so I didn't know I was going to have a roller block) and want the truck to be back together, because if it sits to long it will never get back together the "might as wells" are already hitting pretty hard. So it needs to be assembled, before I tear the whole thing apart. haha
 
Sorry, had to work a double shift tonight.

folkehealth covered the part about the gasket and block. With the piston .025 down the hole and a .015 gasket you'll end up with a quench area behind the valves of .040. .035 to .038 is considered optimal.

However, if you would use a KB102 piston with an 18 cc dish and a comp high of 1.433 you would end up with both a optimal quench of .037 you would also be able to bring the DCR down to a reasonable range of around 8.1:1 which will run happily on pump gas.

this will put you around 375 horse with a cam in you have picked. However, a hydraulic roller cam will put you in the 450 range easily. Now you see why I said you'll want to think about your cam choice.

If work lets up this week, I'll get a full range of cams done for you. I'm not sure if it will or not, we have a guy out on family medical leave.
 
Now I am really looking at propane injection kits. haha like I don't have anything better to do. Then I could use an even higher cr but would need to call and get the order changed on the rotating assembly. What are the popular thoughts on propane injection?
 
For the street, I wouldn't even bother with the propane unit. It really isn't worth the grief of finding fuel.

I ran some sims earlier and even with the recommendations I gave you, the cam you have will not work on pump gas. You will have to step up to something in the 270 range to get the DCR down to pump gas levels.

I'm going to run the sims on a roller cam you should run with this combo and post it up here shortly.
 
OK, I gonna have quite a few post her in a short amount of time, but I am posting the numbers as I run them.

Engine steup:

377 4.00 bore 3.75 stroke
L31 vortecs no porting work
XR264HR cam
8.0:1 DCR
Standard dual plane high flow intake
750 carb
Large tube headers, mufflers W/ no cat
383.1 hp @ 5000 rpm
465 ft-lb @ 2500 rpm

This is wuth a roller cam close to what you have now.
 
I found this for you.

Comp Cams 12-414-8 X4280HR

With the setup you want with the Vortecs

410.3 hp @5000 rpm
441 ft-lbs @ 4000 rpm

Has a torque curve as flat as the great plains and will run on pump gas.

Get your butt to the local wrecking yard and find a good set of hydro roller lifters.
 
still no rotating assembly

I still don't have a rotating assembly, now summit is saying the 12/28/10 they will receive it, so while I'm waiting....... I decided to build a front bumper for it and later this week put the new body bushings and 1 inch pucks in, because I can't stand doing nothing.

First are the pieces I started with then some mock up then the final bumper. The front clip is just sitting in there and the trip is lightly set in on it. The lift has not been installed on the rest of the truck yet so the fenders will move up about an inch or so. The front clip is sitting on the lift pucks but not bolted in.

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Still no rotating assembly

So today I installed the OFD steering box frame support, then started on the 1 " body lift and the new bushings (only to find out I have to drop the gas tank ):doah: The tank is full so I decided to be lazy and went to lowes for a transfer pump and 5 five gallon buckets, Finally go the tank out and decided to quit for the day. Forgot to take pictures of the tank out but will take some tomorrow. Below of the before and after for the steering box brace.

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