Hey guys, I have a 331 stroker that i bought off someone. He said it was his spare motor and was ran for one night of racing to test it.
Anyway, i did a compression test on the motor and came up with the following: 1-100psi, 2-90psi, 3-90psi, 4-90psi, 5-90psi, 6-60psi, 7-80psi, 8-90psi.
This is the first time i have done a compression test, i took 1 plug out a time and did the test, will i have different readings if i take them all out first. Engine was at 145 degrees.
Engine should be making 467 HP as per the dyno sheet i was shown, however i canot get out of the 13 secound zone.
did you turn the engine over, tell the compression stabilized?
Seams very low to me....
usually your hoping for them to all be withing 10% of eachother.
Hey guys, I have a 331 stroker that i bought off someone. He said it was his spare motor and was ran for one night of racing to test it.
Anyway, i did a compression test on the motor and came up with the following: 1-100psi, 2-90psi, 3-90psi, 4-90psi, 5-90psi, 6-60psi, 7-80psi, 8-90psi.
This is the first time i have done a compression test, i took 1 plug out a time and did the test, will i have different readings if i take them all out first. Engine was at 145 degrees.
Engine should be making 467 HP as per the dyno sheet i was shown, however i canot get out of the 13 secound zone.
Any help is appreciated.
first of all the compression looks low....
i saw your mods in your mods in you profile....
"It has a 331 stroker, stock heads with bigger valve,1.6 roller rockers, victor junior intake, holley 750 douple pumper, msd ignition, 1 5/8 headman headers, powerglide trans and 3:73 gears. "
i find it a stretch for the combo to make 467 hp with a stock head 331....just curious what cam is in that motor
you say can't break out of 13's.....
based on the horsepower....that car should flat out fly....
i highly recommend you get a complete build sheet on that motor
Here are number based on rear wheel horse power of 467
Your ET / MPH computed from your vehicle weight of 3300 pounds and HP of 467 is 11.18 seconds and MPH of 119.86 MPH.
ok now lets say it was an engine dyno with 20% parasitic drivetrain loss that would net 375 wheel horsepower...
Your ET / MPH computed from your vehicle weight of 3300 pounds and HP of 375 is 12.03 seconds and MPH of 111.41 MPH.
something is not right......
__________________
Reggie
Real Racers Don't Street Race
PERIOD.......
'88 LX Hatch With A Little Of This & A Little Of That...... 10.39 @128 MPH Soon to be faster....
I cranked the engine for 7-8 compression strokes (about 7 secounds).
Getting a build sheet on the motor is impossible, the guy i bought it from moved out of state. He had stated the following: Scat crank, JE rods and pistons, stock heads with bigger valves, All forged internals.
I replaced the cam that was in the motor with a new comp cam, i will look at the card when i get home this evening and post which one.
The motor was originally built for a open wheel modified stock car, it had a two barrel carb on it.
I plan on taking the heads off this weekend to measure the pistons and see if it has been bored over or not, i also plan on checking the cc of the heads and what type of pistons are in the motor (supposed to be 12:1 compression)
All your help is appeciated, I am new to drag racing and building motors.
Thanks
I cranked the engine for 7-8 compression strokes (about 7 secounds).
Getting a build sheet on the motor is impossible, the guy i bought it from moved out of state. He had stated the following: Scat crank, JE rods and pistons, stock heads with bigger valves, All forged internals.
I replaced the cam that was in the motor with a new comp cam, i will look at the card when i get home this evening and post which one.
The motor was originally built for a open wheel modified stock car, it had a two barrel carb on it.
I plan on taking the heads off this weekend to measure the pistons and see if it has been bored over or not, i also plan on checking the cc of the heads and what type of pistons are in the motor (supposed to be 12:1 compression)
All your help is appeciated, I am new to drag racing and building motors.
Thanks
that's cool we were all new at one time
i hope you got what you paid for if not well ....lesson learned
but just keeping asking the question.... i personally will try to help you out as well as so many others here....
keep us posted of the result of the tear down......
GOOD LUCK....
Maybe one of the mods can move this to 5.0 tech to get more exposure & opinions.....thanks
__________________
Reggie
Real Racers Don't Street Race
PERIOD.......
'88 LX Hatch With A Little Of This & A Little Of That...... 10.39 @128 MPH Soon to be faster....
getting that kinda power with a stock casting head is possible, but the only thing someone would use to do it, would be the casting its self. Do you remember how the exhaust port looked? by dropping a header, and peeking in the exhaust port, it should be EASY to stop something done...
Squirt about a teaspoon of oil into each cylinder (one at a time) as you try another compressing test...if the compressing goes way up, its more than likely the rings, if not much or any differance, a valve job may... MAY....do wonders, or may do nothing, but its worth a shot.... a rebuild will need a head job anyway, so its not like it would be a waste of to much.....
Hey guys,
Thanks for the help. I decided to pull the motor and tear it apart. I fund that he pistons had a lot of play in them. I will be boring engine over to 40 thousands and will be puttin on a new set of edelbrok performer heads.
Thanks for the help and will post when i have it back together.
Well many things make up the comp. numbers. Mostly camshaft. The proper way to check it is to crank it over about 6 or 7 times with the throttle blades open and no plugs in it. But the numbers do seem low. But if you don't know what it is the numbers don't mean much. Meaning if its a dish piston motor and the camshaft is wrong the numbers are going to be low. Your better off doing a leak down test. Fill the cylinders with air and see how much past by the rings. It talkes a leak down test gauge set-up to do it but thats your best bet right now.
We almost need a sticky on what to buy used vs what to buy new.
I would be really nervous buying a complete motor from anyone unless I could hear it run first. I also would be nervous buying a tranny, a rear end or even a computer that looked like it had been opened.
On the other hand, should be no problem to buy used valve covers, wheels, trim pieces, intakes, exhaust etc.
Just my 2 cents
__________________
Quarter Pounder
'93 LX Coupe; 2.3L swap
COBRA CLONE: GT40Ps, 1.7 rollers, Explorer intake & TB; 24 pounders, long tubes; X pipe; dumps; pullies; filter etc.
331 stroker compression 
buying a complete motor from anyone unless I could hear it run first. I also would be nervous buying a tranny, a rear end or even a computer that looked like it had been opened.
