[10secbird]

I'm curious what my ported 48s flow. Going from running a best of 11.86 with mostly stock 670 heads and a Crane Fireball cam, to running a best of 10.87 with the main changes being the ported 48 heads and a large Cam Dynamics flat-tappet camshaft. Thats a 1 second gain changing to ported heads and a bigger camshaft. It seems like everyone knows what their heads flow and having them flow-tested is pretty common these days...so what can I expect to pay to have my heads flow tested. What is the common process when checking a set of heads? How many ports do they flow check ...or do you just pick a sample port

[mgarblik]

Most competent race shops around here, (Ohio) charge a shop rate of $75.00-$90.00 per hour. If you are just trying to get a baseline of flow for your heads, I would just flow 1 head, and do an end cylinder and a center cylinder. They do vary a little. The process of changiong the head on the bench, especially if they don't have a slider set-up and a Pontiac flow plate is what takes most of the time, not the actual flow test. If they have all the Pontiac stuff they should be able to do this in an hour or less. If they don't have the specific fixtureing, it could add an extra 1/2 hour easily. It is also important to have a properly calibrated bench and consistant intake flow guides if you ever go to another bench at a different shop. Just the differences in fixtures, calibrations, and bore diameter flowed through can vary your results by 10-15%. That said, if you stay with the same shop, people and bench, the raw numbers mean nothing more than bragging rights as long as you continue to improve as you work on the heads. On my bench, I an almost always flow within 1-2 % of the published flow specs. I get from a company like AFR. Edelbrock heads test 3-4% lower than what they publish on my bench. That along with constantly checking the bench with the calibration flow orifices, keeps my bench as good as I can get it.

[Tom Vaught]

X2 on above.

Buying a set of Flow Calibration Plates from Bruce at this link:
http://www.flowbenchtech.com/forum/ is well worth the money IF you are doing more than one set of heads in your lifetime.

Once you have the plates you can have the shop test them on their bench before they install the Pontiac flow fixtureing stuff and get ahn idea of where the bench is vs other benches. Just get the numbers from the plates at 28" of test pressure and don't say anything about the bench being high or low.

That was you can judge the offset vs other benches you might use.

Tony B always thought his bench was "not that close" but after checking using the plates found out it was pretty accurate. He used to never state numbers.

Tom Vaught