Please check this combo

[dmaaero]

Guy"s could you check this combo for miss matched parts. I am seeing way to many engines on the internet with over 400hp, they have less compression and a smaller cam. I"m thinking maby the old intake is not as good as i thought it would be, an maby i need a different cam? I would like to see more hp and torque out of this engine, what would i need to change.
355 sbc
dart pro 1 heads 180cc runners an 72cc chambers 2.02/1.60
holley contender dual plane intake
.125 dome pistons yielding 10.1-1 compression
comp cams xe 284h =507/510 lift 240/246 duration @ 50 lsa 110
holley 4779 750dp
hooker 1 3/4 sidepipe headers with 4"sidepipe sts baffles
on a side note, the 1-7 bank is .022 in the hole an the 2-8 bank is .028 in the hole (did not remove matching numbers) how bad did that hurt me? engine dynoed at 276 rwhp and 316 torque, thanks david

[lun40119]

What trans...gears, rearend, and car is it in. Could be a crappy converter too.

[dmaaero]

It"s in a 74 corvette, M20 4-speed, 3.08 gears

[lun40119]

How new is the combo. Have you done a leakdown?????

[dmaaero]

engine"s about 1 1/2 years old, most likely less than 10,000 miles. I have not did a leak down test.

[lun40119]

I would do a leak down first and see what you have got. Could need rings, or possibly a valve job. Do the leak down and get back. I think it is down on power, especially for a stick car.

[want-a-be]

How thick is the head gasket you are running? I'm betting you aren't running the compression you might think you are. When the block was honed,...was a torque plate used? What kind of initial are you running on the timing? When the timing totally comes in where is it at? imo...you should have had both sides decked the same. I realize you wanted the numbers to stick around. That side should have been decked first the the other matched. But you could compensate with the head gasket.

When the cam was installed,...was it degreed in or just lined the dots up? What kind of valve spring pressure did you have when you installed the cam?

You'll appreciate a valve job right now if you installed those heads new. I'm not familiar with the intake you're running but I'd consider the air gap type. Dart has a good one and so does Edelbrock. If you have the room,..run a 1" open spacer under the carb. Might also consider cutting about 1" out of the devider if it isn't already done. Do some research first.

It's my opinion that your cam might be too big for the application. I don't think you have enough compression to support the cam of choice. I've made more hp/tq with a lot smaller cam and a lot less unported stock head out of a 355.

At what RPM was the peak tq and peak hp at? How high do you wind this thing up? What were the fuel numbers off the dyno?

Don

[dmaaero]

My first leak down test, i used cheap harbor freight guages. I got 14% but those guages only use 15psi not 80-100psi. I"ll get another set of guages an try again. . Only place i heard air, was coming from under the valve covers. Checked compression an it"s 200 lbs on every cylinder.

Head gasket is a victor 5746 .026 compressed. Pistons are +3.5cc
I have no idea about the torque plate i could go back to the machine shop an ask.
Timing is 17* inital an 34* total all in at 2000rpm (it pings at 36*) I also run vacume advance. Did not deck either side of block, tall side has the #"s. I did not degree the cam, an i did not check any spring pressure. Only pressure i know of is what came with my heads,1.437 135lbs seat 330lbs open 1.800 tall installed. Dart did the springs for me, i just told them what cam i was going to use.

Torque was over 300 the entire pull except dropped to 280 around 3000rpm, peak hp was at 5000 thats all we turned it. a/f ratio was 13-13.5

A quick note when this dyno was done i had only 2 hours on this engine. Also had3933 short reach plugs in it, they were black. Have since gone to ngk bcpr5es .750 reach, they look fine now.
Thanks for your time so far guys, david

[lun40119]

sounds like its leaking.........

[dmaaero]

I think i got it now! I put 100lbs air to a cylinder an the guage dropped to 98lbs. I do not hear any air from the valve cover hole, but i do hear it from the carb. I"ll do the other 7 cylinders an make notes what i hear. This takes a while but i"ll be back middle of the afternoon with some results. thanks jake

[lun40119]

Now I am confused.......the way that mine works is to turn the dial until I get to 100psi, and read the second guage from there. And then listen to where it is going. If it is coming out the carb, you have a valve job issue. I have had the same thing happen to me. Spring pressure drops, valve starts to float beats the hell out of the seat, and the valve, and you have leak. And it really kills hp.

[dmaaero]

I just used it like a single guage, use the regulator to set the guage to 100lbs an hook it to the cylinder. It drops 2lbs, disconnect it, an it goes back to 100lb. it does the same on every cylinder, drops 2 lbs of pressure. Is that ok to do it that way? david

[lun40119]

Did you buy a leak down tester, or a regulater. I am not sure what you are using???????

[dmaaero]

I bought a leak down tester, but it said open the regulator till the % guage reads zero. Well it reads zero at 15lbs of presssure on the pressure guage. With no pressure the % guage reads 100% I didn"t think 15psi was enough. So i just opened the reg. till i had 100lbs on the pressure guage. Then i hooked it to the cylinder, it lost 2lbs........hope you understand. david

[lun40119]

i guess it does, but I am not familiar. Ours is different. So what do you figure you are leaking???????????? And where is it going?

[dmaaero]

I would think 2psi out of 100psi would be 2%. It"s not much air coming out, but if you put your ear to the carb you can hear it, also to the valve cover hole you can hear it. Can"t really tell through the side pipes.

[dmaaero]

I didn"t feel comfortable with the 2% readings i got today, so i ordered a new leak down tester. Give me a couple of days till it comes, an i"ll do it again. :o

[want-a-be]

I have a Snap on leak tester. It's been pretty good to over the years. Not bad for the money.

Don

[dmaaero]

Got the new leak tester, have no air what so ever coming from the carb or from the exhaust. Only place i hear air is from under the valve covers. I have 6% leakage on all cylinders. This test was done with all the plugs out. I think thats why no air was heard from carb this time,

[Awesome Bill]

Your combination is not the problem even if it leaked 30%. If it does not have a ton of blow by, or a hole out of compression completely or something stupid like that, your most likely in the ball park. You did not mention your carb size? Also those spark plugs you used on the dyno pull were wrong and way cold. Should of been AR3935 or AR135. You do not have enough compression to use them. With the gear you have, I would not put anything larger than a 600cfm carb on it if that. You have no gear and a heavy car. The large 650-750 carbs is junk on this application. If it pings @ 36°, you should pull it back to 32-33°. Check you fuel supply also. Stock fuel pumps and lines are only good to 400hp @ best. Ton of things you can do but start here. The 3.08 gear is really whats happening!

[dmaaero]

Bill,
Couple years ago on the old forum you told me to use something in the 5 heet range, that was right on perfect for this engine!!!!!! I went with ngk"s. I do have a 750 carb, but like you said it has took a ton of time to get it to work on this engine. I"ll work on a electric pump an new fuel lines. Hopefully this summer i will put a 5 speed with a 1:1 fifth gear in this car. :) Still researching those..... thanks for your reply along with others that contrubited, your advise is much appericated. thanks guys, david

[Awesome Bill]

Just keeping it for real. loose the 750 and get something smaller, you won't believe the power that will just fall into your pedal foot.