EFIDynoTuning Forum

I am going to weigh in a little on this post. The cam # you posted is a Extreme Marine cam with only 218 int./224 exh duration @.050, with what I would call mild lift 0.495 int./0.503 exh. on lobe separation of 112 degrees (didn't see lobe centerline listed). Also an "rpm range" of 1200-5200. Pretty mild camshaft if you ask me even for 302CI, hence the "marine" statement, this cam should work well right off idle to a moderate rpm range in a boat, truck or mild heavy street car.

You state I from what I understand is, this is 460 CI "small block" engine using a A9L processor. And only 6.5 lbs of vacuum, I assume in gear! The cam is really mild for 460 CI, - comp cams says its an "aggressive grind" but (for what a 302 or small CI in a heavy boat trying to turn a prop) without seeing all the grind spec's I don't know the amount of overlap ground into the cam, to give much of opinion on the effect on engine vacuum. Which if it's really only 6.5 lbs at idle in "gear" (which leads to why exactly - mechanical reasons or vac leaks, cam not degreed) and yes a lot of efi systems won't like "low vacuum" per se.
If there is an issue with vacuum assisted power brakes due to "low vacuum", that is a separate issue. This cam should produce more vacuum than 6.5lbs vac. from 460 CI, which concerns me as to why. For example; I am running a custom grind in a 351W Turbo F150 combo with 238/242 degrees @ .050 and .565/.575 lift, it holds 13/14lbs of vacuum at 875 rpm in gear with 2400 converter. The 460 CI are "big block" displacement territory and should have a head/intake/cam combo to support that displacement.
You will see generic statements on camshafts listings saying EFI or Carb, NOS, Supercharger or Turbo grinds, which is more of a marketing tool than anything. All cams work "well" in a boosted application etc, just some will be "better" based on the rest of the engine etc.

Lobe separation, Lobe centerline and actual valve events will help cams to work "better" in certain applications. Low vacuum is an issue for speed density and stock programming in mass air systems and will cause idle and low speed driveabilty issues that have to be addressed via tune changes and possible torque converter changes, gearing etc to aid in drivability.
A 112 degree and higher lobe separation usually aids in better idle stability and will help raise the rpm that peak torque/horsepower is produced over a 106/110 LS range on a otherwise same cam grind (valves open overlap). And not by huge amounts either.
But, your seat of the pants dyno may not be able to tell much difference (other than idle/low speed issues) due to so many other factors. Good running (again subjective) engine combo's are just that - a well selected group of parts that complement each other and fit within a specific budget/rpm range.
Just as aa example: I have currently a high compression 408" NOS fogger carb foxbody, Turbo 351W F150 under 15lb boost Fuel Inj, higher boosted supercharged 302 2V Mustang FI, GSXR 750 FI all have had camshafts changes designed for the engine/vehicle application and would not use the same cam profiles.
Hopefully this info helps some as to camshaft selections, which all the cam manufactures have tested and their tech support is a good source of information for general applications. Of course, a custom grind is better (not everyone is qualified in that) and costs accordingly too. Catalog "shelf" cam grinds are for general applications and work OK for the masses.

I understand, I have found the information. Due to how the injection driver circuit reacts between 13 - 14 volts the battery offsets are that typically used were causing inconsisitent part throttle/decel fueling that no amount of "traditional" change would have corrected. Holley gave me the information. I am back on track now.
Thx for trying to assist!

Yes and no, I have had some issues in the past that actual AFR where not matching commanded AFR. This is a fairly high boost (25lb) on E85 application. I just wanted to remove that possible variable.

Hello everyone,
Does anyone have published injector data for Delphi/Lucas 96lb low impendance injectors? Same injector that is rebranded and sold by TFS, Accel/Holley, and they are not responding to my request currently.

Thanks,
M. Miller

























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