First dyno run...yesss....could it be my cam....oh noes....

[JESSE]

dyno

i agree with pontiacgp...

on my set up i went with the beehive springs, retainers and keepers that matched to the cam, heads,intake,carb.... i used comp cams to get the right combo and it all works as advertised... 😀

hey pontiacgp, hows things going???

 

[pontiacgp]

Hi Jesse....going good I think, I'll let you know after tomorrow. I'm lookin forward to another long nite in the shop to get the race car finished for testing tomorrow...how about yourself?

 

[megaladon6]

vortecs can be easily and safely modified to take .510 lift and will flow perfectly fine with that cam. yes a bigger head would release more HP, but you should be good with what's there.

what is the A/F with the new jets? what octane are you running?

according to camquest you should have about 340hp which would work out to 300hp, assuming a 12% loss through the drivetrain.

heres a stupid question, could 305 vortec heads bolt up to a 350? that would explain the power loss!

 

[SeeMy355]

vortecs can be easily and safely modified to take .510 lift and will flow perfectly fine with that cam. yes a bigger head would release more HP, but you should be good with what's there.

what is the A/F with the new jets? what octane are you running?

according to camquest you should have about 340hp which would work out to 300hp, assuming a 12% loss through the drivetrain.

heres a stupid question, could 305 vortec heads bolt up to a 350? that would explain the power loss!

That's a good question...

I never thought about them being 305 vortec heads, although I did ask what vehicle they came off of...

I'm running 93 octane...

My A/F is 18:1 at about 4250 RPM and held steady through conclusion of the test at 6000 RPM...

 

[SeeMy355]

You also may have too much torque converter for your set up. 3000 is a little high for a street car and your valve train could be the other cause too. That's why I went with a 442 lift cam instead of going larger because once you go with say the cam you have, your bound to run into problems. I would go get a second opinion from another mechanic cause it sounds like your running into too many problems with your current mechanic.

Probably not a bad idea...

It's worth looking into...

 

[megaladon6]

My A/F is 18:1 at about 4250 RPM and held steady through conclusion of the test at 6000 RPM...

and there's your problem you are WAYYYYYY too lean. you want about 12:1 at WOT and no more than 16:1 ever. if you just want max power i think you don't want to go past 14:1 and want more like 11:1 at WOT (that's with a holley q-jets are a bit more variable and can run rich at WOT and slightly lean at cruise/idle). you need to go to larger jets. right now the engine and carb are pulling plenty of air so nothing needs to go larger but the fuel delivery. remember, a larger carb means more air capacity.
the dyno guy should have known that it was too lean, maybe he has a carb he wants to sell you.

 

[jrm81bu]

I don't think i would have finished the run with a ratio like that.

 

[SeeMy355]

My A/F is 18:1 at about 4250 RPM and held steady through conclusion of the test at 6000 RPM...

and there's your problem you are WAYYYYYY too lean. you want about 12:1 at WOT and no more than 16:1 ever. if you just want max power i think you don't want to go past 14:1 and want more like 11:1 at WOT (that's with a holley q-jets are a bit more variable and can run rich at WOT and slightly lean at cruise/idle). you need to go to larger jets. right now the engine and carb are pulling plenty of air so nothing needs to go larger but the fuel delivery. remember, a larger carb means more air capacity.
the dyno guy should have known that it was too lean, maybe he has a carb he wants to sell you.

Well, thanks for the information...

You did a better job of explaining the issue than the mechanic did...

All he did was advise me to buy a bigger carburetor. He didn't really explain A/F ratios and what ratio is ideal. He just told me to get a Holley 750 Double Pumper with mechanical secondaries...

I've already decided that I'm going to upgrade the carb, but since this is putting the health of my engine (and invested money) at risk, I'm thinking I should move the carb up to the top of the priority list, instead of paint and body...

My other option is just purchasing the larger jets for the 670 Street Averger that's already on the block...

Any suggestions?

Thank you all for your assistance...

 

[SeeMy355]

I don't think i would have finished the run with a ratio like that.

Believe me...

If I would've known better I wouldn't have done it either...

This is my first rebuild, so I've done a lot of learning and this is another notch in my belt...

I'm just glad I haven't damaged anything...

 

[megaladon6]

is this a street car or a drag car? street car-just replace the jets it's alot cheaper and you don't need absolute max top end power. if it's a drag car, the 750 will give you some more top end power, but not a major increase in numbers. is it worth another $300+?