experienced engine builders chime in

Cclaro

Member
Aug 1, 2020
45
6
18
20
FL
Alright I’ve been putting this off for a while because I’d like to not have to think about doing some more extensive work to the car but I’m ready to start really looking at things critically once again. I have a 10:1 compression 357w with the following set up:

Stock crank
Flat top pistons
Scat H beam rods
Custom cam with duration in the 230s intake and 240s exhaust. Lift sits at .600 for both.
205 11r 66cc heads
Super Vic intake
1000cfm throttle body
1 3/4 long tube headers with a 2.5” exhaust and hooker max flow mufflers
Ignition is all msd
Holley terminator x
48lb/hr injectors
Some morrell high rpm sbf lifters
Power sent through a t56 with 3.73 gears out back

here’s the issue/speculation:

took it to get tuned on the dyno about a month back and it made 376hp and 350 rwtp to the 295/55/r15 mt et streets sitting on the rear which apparently is low to many. Car makes peak power from around 5700 rpm to 6700 rpm if I remember correctly I’ll try to find the graph in a second to post it up and have it looked at for some second opinions. After the dyno I drove it quite a while, pulled the intake, had some oil in the runners so I replaced the gaskets and hopefully solved the issue. Well for the secojd time in a row there’s a slight weep of coolant coming through the from driver side of the head on top of the gasket and it seems saturated, I can almost guarantee there’s going to be oil on the runners as well if I remove the intake once again. The block was decked, I can’t tell you how much sadly but I know this will have an effect on intake fit from time to time however the bolt holes and the ports line up fine and with the gaskets in place there’s a solid .200-.250 gap on the China rails. My question is, do I try to find the power that’s apparently missing? Should I check timing chain alignment? I degreed the cam to the cards specification so I’m not sure if there’s a possible mistake. Some say this combination should’ve made well north of 400 to the tire but I’m not sure if that’s just internet talk or if I should’ve really comb over everything again.
 
  • Sponsors(?)


Cclaro

Member
Aug 1, 2020
45
6
18
20
FL
8d4114d3-23db-4159-a431-baf0536ee2ff-png.1077749
 

Hoytster

I don't dare do that to my Knob
15 Year Member
Dec 30, 2002
1,067
725
164
39
Cornwall, PA
Alright, I wouldn't call myself an expert engine builder or anything...

But looking at the info you supplied on your combo, the first two things that stick out are to me is that intake and the camshaft specs. That intake's power band is more in the 6000+ on your cubic inch. I would also expect to see more toward a mid 240 on the intake and low 250 on the exhaust if your planning on pulling 6700 ish.

What's the camshaft centerline and was it degreed? How does that engine feel on the bottom end of the rpm range? I would expect it to be a little lazy.

Edit:. Forgot to say, I don't think 376 is to far off for most of your combo, but I would expect to see closer to max 410ish hp and over 400lbs from that combo.
 

manicmechanic007

Active Member
Sep 26, 2017
569
146
53
62
With 10 to one it is hard to get to 400 hp
You are almost there
.600 is a ton of lift for 10.0 to ones too
I think you may have a bit too much cam but I would also like to see the cam card
I would like to view overlap and centerline specs
With the right cam you can raise the effective compression ratio by the scavenging effect
Reversion is a thing with the sbf and so is spark knock
If you are burning coolant that is no good
You are close
Run what you brung is the old saying
 

Cclaro

Member
Aug 1, 2020
45
6
18
20
FL
Alright, I wouldn't call myself an expert engine builder or anything...

But looking at the info you supplied on your combo, the first two things that stick out are to me is that intake and the camshaft specs. That intake's power band is more in the 6000+ on your cubic inch. I would also expect to see more toward a mid 240 on the intake and low 250 on the exhaust if your planning on pulling 6700 ish.

What's the camshaft centerline and was it degreed? How does that engine feel on the bottom end of the rpm range? I would expect it to be a little lazy.

Edit:. Forgot to say, I don't think 376 is to far off for most of your combo, but I would expect to see closer to max 410ish hp and over 400lbs from that combo.
cam is on a 111 ICL, overlap is 8 degrees (intake open 4.5BTDC exhaust close 3.5ATDC), engine feels a tad bit lazy under 3000 but freight trains after that until 7000 which is where im shifting around. camshaft was degreed as well. was thinking of dropping it down to a vic jr but im not too sure, cam was specced around the intake.
 

revhead347

Apparently my ex-husband made that mistake.
15 Year Member
Jun 14, 2004
8,945
1,548
214
41
Acworth, GA
So, if you have coolant on top of the gasket, then most likely it blew a head gasket. Do not look for water in the oil, because it doesn't always blow between a water passage and an oil return. Most of the head gaskets I have blown never got water in the oil.

One of the funky things you run into when you deck the block is then correcting the intake. It is entirely possible that your intake was not machined to match the deck job on the block. This causes two problems. First off, the intake and head ports don't align properly, which causes power loss. the other part, is that the intake acts like a wedge, pushing the heads apart when it is torqued down, leading to blown head gaskets.

A proper engine builder wants as much of the engine to work with from the beginning when they machine the engine. So when the engine was built, the engine builder should have assembled the engine with spacers, and measure the intake gap. Then milled the intake on each of the mating surfaces so that it fit properly with a block that head been decked.

The engine is definitely down on the power, but I would recommend making sure it's mechanically correct first. The rest is probably tuning issues.

Kurt
 
  • Like
Reactions: 1 user

Cclaro

Member
Aug 1, 2020
45
6
18
20
FL
So, if you have coolant on top of the gasket, then most likely it blew a head gasket. Do not look for water in the oil, because it doesn't always blow between a water passage and an oil return. Most of the head gaskets I have blown never got water in the oil.

One of the funky things you run into when you deck the block is then correcting the intake. It is entirely possible that your intake was not machined to match the deck job on the block. This causes two problems. First off, the intake and head ports don't align properly, which causes power loss. the other part, is that the intake acts like a wedge, pushing the heads apart when it is torqued down, leading to blown head gaskets.

A proper engine builder wants as much of the engine to work with from the beginning when they machine the engine. So when the engine was built, the engine builder should have assembled the engine with spacers, and measure the intake gap. Then milled the intake on each of the mating surfaces so that it fit properly with a block that head been decked.

The engine is definitely down on the power, but I would recommend making sure it's mechanically correct first. The rest is probably tuning issues.

Kurt
How would I check for a head gasket leak
 

Shawn_Mc

Member
Oct 1, 2021
33
8
18
59
Anahiem
If you didnt end up with a positive deck number, I doubt they decked the block enough to throw the head to intake alignment. But, if it's not parallel and square to the crank line...that's a different issue. But again, the OP said the bolt holes lined up ok. I'll agree that the cam profile and compression ratio are a bit of a mismatch, which is why it's a little lazy below 3000. The 111 ILC is a little retarded for that compression ratio and that cam. Once you figure out the leak. Id advance that cam timing, to like 105, that will build cylinder pressure quicker and pull the RPM range down a bit and you may end up making 400 hp, but it'll be signing off at 6200ish, but it'll pull harder at 3000, too. With that much cam, you'd be better off with 11.5/1 CR, if you can keep the detonation away. What's the lobe separation number on the cam? if youre at 108, there wont be a lot you can do with it. If it's in the 110-112 range, advancing the timing will help quite a bit.
If you can do a leak down test on it, that will tell you what you need to know about the head gaskets.
 

Cclaro

Member
Aug 1, 2020
45
6
18
20
FL
If you didnt end up with a positive deck number, I doubt they decked the block enough to throw the head to intake alignment. But, if it's not parallel and square to the crank line...that's a different issue. But again, the OP said the bolt holes lined up ok. I'll agree that the cam profile and compression ratio are a bit of a mismatch, which is why it's a little lazy below 3000. The 111 ILC is a little retarded for that compression ratio and that cam. Once you figure out the leak. Id advance that cam timing, to like 105, that will build cylinder pressure quicker and pull the RPM range down a bit and you may end up making 400 hp, but it'll be signing off at 6200ish, but it'll pull harder at 3000, too. With that much cam, you'd be better off with 11.5/1 CR, if you can keep the detonation away. What's the lobe separation number on the cam? if youre at 108, there wont be a lot you can do with it. If it's in the 110-112 range, advancing the timing will help quite a bit.
If you can do a leak down test on it, that will tell you what you need to know about the head gaskets.
It’s on a 114 Lsa
 

Shawn_Mc

Member
Oct 1, 2021
33
8
18
59
Anahiem
Might have to get the degree wheel out to play then
Just watch the piston to valve clearance on the intake side. As you open and close the intake sooner, you get closer on that side. As you advance it, you'll make more space on the exhaust side. My personal experience with advancing and retarding the cam timing follows the basic rule of advancing it creates more bottomed power, retarding it stretches it out over the top end. I just went back through your posts. In one spot youve got the LSA at 111 and then 114 and while 3 degrees doesnt seem like much, it is when you start hanging the valves open at 230+/240+ @.050". EFI likes those wider LSA's, but when you get bigger in the grinds, things get more dramatic. What youve described is within a gnats eyelash of a Comp 289DHR-12.

As a side note where did the final total timing end up?
 

Cclaro

Member
Aug 1, 2020
45
6
18
20
FL
Just watch the piston to valve clearance on the intake side. As you open and close the intake sooner, you get closer on that side. As you advance it, you'll make more space on the exhaust side. My personal experience with advancing and retarding the cam timing follows the basic rule of advancing it creates more bottomed power, retarding it stretches it out over the top end. I just went back through your posts. In one spot youve got the LSA at 111 and then 114 and while 3 degrees doesnt seem like much, it is when you start hanging the valves open at 230+/240+ @.050". EFI likes those wider LSA's, but when you get bigger in the grinds, things get more dramatic. What youve described is within a gnats eyelash of a Comp 289DHR-12.

As a side note where did the final total timing end up?
Lsa is 114, intake center like is 111. Timing is at 29° Any higher power dropped off
 

Shawn_Mc

Member
Oct 1, 2021
33
8
18
59
Anahiem
And honestly, looking at the graph, the power is as flat as a pool table from 5700-6700 which looks more like it ran out of overlap.
 

Shawn_Mc

Member
Oct 1, 2021
33
8
18
59
Anahiem
Which I’m presuming is a variable I can’t change
Not without a cam change. There's enough cylinder head and intake to pull a little longer, but the way it flattens out, it's just odd.

You know what that cam really wants? A turbo. With 5-6 lbs of boost, you'd be knocking at the door of 650 hp at the wheel.
 

Cclaro

Member
Aug 1, 2020
45
6
18
20
FL
Pictures of what may be contributing, full throttle on the pedal is about 83%. Second picture is me holding it wide open.
 

Attachments

  • 37B2648A-CAC1-404C-BA39-32B96F886280.jpeg
    37B2648A-CAC1-404C-BA39-32B96F886280.jpeg
    484.8 KB · Views: 13
  • 149F275B-DB5E-49F3-AFB4-0FFDB67E8E2E.jpeg
    149F275B-DB5E-49F3-AFB4-0FFDB67E8E2E.jpeg
    495.6 KB · Views: 13

Shawn_Mc

Member
Oct 1, 2021
33
8
18
59
Anahiem
Pictures of what may be contributing, full throttle on the pedal is about 83%. Second picture is me holding it wide open.
dude, original sin!! I think youre being generous with the estimation of 83%. It's worth some more dyno time just to make sure the map you guys wrote works with the throttle WFO.

Fix your coolant leak. Your hp will be there when you get that throttle opened up all the way. That explains your flat power curve.
 

Cclaro

Member
Aug 1, 2020
45
6
18
20
FL
dude, original sin!! I think youre being generous with the estimation of 83%. It's worth some more dyno time just to make sure the map you guys wrote works with the throttle WFO.

Fix your coolant leak. Your hp will be there when you get that throttle opened up all the way. That explains your flat power curve.
You really think on a throttle body this large that it’s gonna make that significant of a change?
 

Shawn_Mc

Member
Oct 1, 2021
33
8
18
59
Anahiem
Absolutely!! I bet that body wasnt even flowing 750CFM at that setting. When the blades are cocked over like that, the disruption in the laminar flows are giant. You've probably got some power on the table too. It'd be worth testing a 1 and 2" spacer beneath the TB. @5700rpm, the engine (357ci) is pulling roughly 500-520cfm @ 85% efficiency, and I'd gotta think you're better than that. As flat as that graph is, it's running out of air, which is why I was thinking it wanted more over lap or something.
Did you guys have a vacuum sensor connected?
At full throttle, top of the RPM range, you only want about .8-1" of vacuum. With that throttle position, I bet you were closer to 5-7" of vacuum.