I bought a holley 58mm and im pleased widht the preformance gain.
Did a test before and after i installed it (same day) and i gained 0.5 sec from 62-105mph, Got the same time in 84 degrees now as i did earlier in 48 degrees

I did a few test runs before i bought the holly, a couple at wot and a couple between 90-97% tps, and at the 90-97 tps run it was 5-9 kpa lower map readings.
So widht that cam and heads im sure youre in need of a bigger TB, and way not go 58mm?

 

Hey Lisa I guess you had to port out the intake so that it matched up with the TB?? What exactly is involved in that?

 

I filled the intakemanifold widh rags so i had 1 inch clearence to the 2 ports. Had a friend hold a vacumcleaner beside the grinder when i ported the holes up to 58mm, after that i vacumed the plenum and pulled out the rags and vacumed again thats it.
If it should be a few "filings?" left it doesnt matter they wont hearth the engine

 

thanks for the details Lisa33, one more question, how did you measure the holes so that you knew you had reached 58mm when you were porting them?

 

I used the gasket that came widh the TB.

 

I wouldn't go through the trouble of porting the intake for a throttlebody or porting the intake period (unless you gasket match your heads if they're ported), a 52mm will be just fine....there were some people who purchased 58mm tb's that had idle problems. If you do a search you'll see those problems listed....there were a good many people too.

Joe

 

GM uses a 48mm on the 502 ramjet. If its big enough to feed a 502 a 48mm should be fine on anything but highly built motors.

 

Check it out.....almost everyone here agreed that you would have no more gain than with the 52mm. They say "why not the 58". "For 50 bucks more". My thinking is why spend the extra 50 bones and go through with that intake porting for nothing?????????? Just to spend more money and put shavings in the motor? Shavings could darn well hurt your engine. I got my whole motor in pieces plenum sitting right here on the ground I didnt even bother porting the plenum, just bought the HOLLEY 52 and its going on my 383.

Dunno just my thought.

 

The aluminum shavings will not hurt the motor....if that was the case someone would've had a problem by now. As far as throttlebodies...no downside to 52mm...58mm you have to port the manifold and could have idle problems (I think split blm's and the idle takes forever to fall back to normal speed).

Joe

 

The aluminum shavings will not hurt the motor....if that was the case someone would've had a problem by now. As far as throttlebodies...no downside to 52mm...58mm you have to port the manifold and could have idle problems (I think split blm's and the idle takes forever to fall back to normal speed without modifying the idle air passage).

Joe

 

I did a research before i ported the intake holes and the answers was that it shouldnt be a problem if a FEW shavings would be left/missed in the plenum.
About 58 or 52, The 52mm should properbly been enough but as im going S/C soon so i vent for the 58mm.
Havnt seen any problem with split BLMs or the idle.
But thats no garanti that it should be so for everybody else.

 

You're actually supposed to shove a rag in the intake to catch the majority of the shavings.

Joe

 

Better check your pricing again. Seems to me that since a 52 is just a reamed out 48 and a 58 is a whole new TB that the 52 would be quite a bit less expensive since you only need to send in your core for the 52 and for a 58 they donn't take cores.

I picked up a used 48 and sent it to AS&M for their 52. Kept my stocker.

The AS&M bolted right up and no problems whatsoever. JMHO

 

The BBK/Edelbrock throttlebodies do not require a core as they are new and I like mine just fine (no problems either). I think it was $299.

Joe

 

I believe the 52s are $279 and the 58s are $479.

I recommend going with the AS&M (just send in your core.)