Bog or delay under wot?

[Olive1970]

I have had this issue with my newer engine that I put in. If I put the gas to the floor it will bog or not have the same response as above say 3500rpms or so? After that it will come alive and just wrap the rpms up, where as before 3500rpm the delay is obvious on the tach.

The truck has HEI, Holley 650 spreadbore, built TH350 with 2200 stall converter.

The engine is: 350 bored 40 over, flat top pistons, 1.94/1.60 valves, double roller, weiand intake, z28 springs, bunch of new factory parts, and a pretty rough cam int exh
dur@.050 234 244
valve lift .488 .510
lobe sep 107 117

I am thinking this is a distributor advance issue? Maybe time to swap springs or make some other mods to the advance? Or time for a different dist?

Thanks all, spring is coming

[Longhorn 70]

Too much squirt?? Just a guess

[TBONE1964]

How does it idle just sitting in park? You have a good idea checking the mechanical advance springs and also it sounds like it may be wanting more fuel in the secondarys. If I remember correctly the spreadbore holleys are double pumpers. Is the secondary accelerator pump working?

Have you run this carb on a different engine and how did it work?

[Olive1970]

Originally Posted by TBONE1964

What are you running for a transmission? If it is an automatic, do you have a stall converter. With that cam, I would want at least a 2800 - 3000 stall.

How does it idle just sitting in park? You have a good idea checking the mechanical advance springs and also it sounds like it may be wanting more fuel in the secondarys. If I remember correctly the spreadbore holleys are double pumpers. Is the secondary acceletor pump working?

Have you run this carb on a different engine and how did it work?

The trans is a TH350 that is rebuilt with upgraded clutch pacs and a shift kit, etc. I have a 2200 stall converter. Just sitting in park it idles fairly well but have it bumped up to 1000rpms for the drop when putting into drive or reverse.

This is the first time running this carb on this engine. It is only a single feed for the secondaries. I ran a squarebore Holley 600 before but it was struggling to run with that, just about maxed out. The only thing I haven't messed with is the distributor.

I am running 18* initial timing and 36* at 3k rpms but of course I dont know how well the response is when setting the timing.

[TBONE1964]

That truck should light up like the forth of July with your combination of parts. I would try (like you suggested) stiffer mechanical advance springs. It may be pulling everything to full advance way before it needs to. If that does not work, I think I would consider a true dual feed double pumper carb with mechanical secondarys. I have never been a huge fan of transfer tube vacuum secondary holley carbs for the very reason of the problem you have.

[Olive1970]

Originally Posted by TBONE1964

That truck should light up like the forth of July with your combination of parts. I would try (like you suggested) stiffer mechanical advance springs. It may be pulling everything to full advance way before it needs to. If that does not work, I think I would consider a true dual feed double pumper carb with mechanical secondarys. I have never been a huge fan of transfer tube vacuum secondary holley carbs for the very reason of the problem you have.

I was hoping that the truck would, but know that something is missing here. As far as the advance springs, would I want to go stiffer so it comes in later? I would have thought to go with a lighter spring with my issue, could be way off though.

I have considered a 750 dual feed double pump. Holley has a new one with electric choke but at a hefty price tag. Maybe sell the two used ones I have and go from there also, try something with distributor first.